IEEE standard definition, specification, and analysis of...

ANSI/IEEE C37.1-1987

definition, specification, and analysis of systems used for supervisory control,

data acquisition, and automatic control

SHlW17 JuIy 6, 1987


C37.1-1979) (Revision of ANSI/IEEE

An American National Standard

IEEE Standard Definition, Specification, and Analysis of Systems Used for

Supervisory Control, Data Acquisition, and Automatic Control

Sponsor

Substations Committee of the IEEE Power Engineering Society

Secretariat

Institute of Electrical and Electronics Engineers National Electrical Manufacturers Association

Approved March 22,1984

IEEE Standards Board

Approved December 2,1986

American National Standards Institute

o Copyright 1987 by

The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017, USA

N o part of this p u blication may be reproduced in any form, in an electronic retrieval system or otherwise,

without the prior written permission of the publisher.

IEEE Standards documents are developed within the Technical Com- mittees of the IEEE Societies and the Standards Coordinating Commit- tees of the IEEE Standards Board. Members of the committees serve voluntarily and without compensation. They are not necessarily members of the Institute. The standards developed within IEEE represent a consensus of the broad expertise on the subject within the Institute as well as those activities outside of IEEE which have expressed an interest in participating in the development of the standard.

Use of an IEEE Standard is wholly voluntary. The existence of an IEEE Standard does not imply that there are no other ways to produce, test, measure, purchase, market, or provide other goods and ser- vices related to the scope of the IEEE Styndard. Furthermore, the view- point expressed at the time a standard is approved and issued is subject to change brought about through developments in the state of the art and comments received from users of the standard. Every IEEE Stan- dard is subjected to review at least once every five years for revision or reaffirmation. When a document is more than five years old, and has not been reaffirmed, it is reasonable to conclude that its contents, although still of some value, do not wholly reflect the present state of the art. Users are cautioned to check to determine that they have the latest edition of any IEEE Standard.

Comments for revision of IEEE Standards are welcome from any interested party, regardless of membership affiliation with IEEE. Sug- gestions for changes in documents should be in the form of a proposed change of text, together with appropriate supporting comments.

Interpretations: Occasionally questions may arise regarding the meaning of portions of standards as they relate to specific applications. When the need for interpretations is brought to the attention of IEEE, the Institute will initiate action to prepare appropriate responses. Since IEEE Standards represent a consensus of all concerned interests, it is important to ensure that any interpretation has also received the con- currence of a balance of interests. For this reason IEEE and the members of its technical committees are not able to provide an instant response to interpretation requests except in those cases where the matter has previously received formal consideration.

Comments on standards and requests for interpretations should be addressed to:

Secretary, IEEE Standards Board 345 East 47th Street New York, NY 10017 USA

Foreword

(This Foreword is not a part of ANSUIEEE C37.1 1987, IEEE Standard Definition, Specification, and Analysis of Systems Used for Supervisory Control, Data Acquisition, and Automatic Control.)

This standard applies to systems used for monitoring, switching, and controlling electric apparatus in unattended or attended substations, generating stations, and power utilization and conversion facilities. It does not apply to equipment designed for the automatic protection of power system apparatus or for switching of communication circuits. The requirements of this standard are in addition to those contained in standards relating to the individual devices.

This significantly revised standard was originally a section of ANSI C37.2-1970 which also contained device function numbers. ANSI C37.2-1970 was revised into two standards: ANSI/IEEE C37 .l-1979, Standard Definition, Specification, and Analysis of Manual, Automatic, and Super- visory Station Control and Data Acquisition, and ANSI/IEEE C37.2-1979, Electrical Power System Device Function Numbers. Previous editions were approved by the Standards Institute in 1962, 1956, 1945, and 1937. The original work on this subject was done by the American Institute of Electrical Engineers (now the Institute of Electrical and Electronics Engineers) and published in 1928 as AIEE No 26.

The standard applies to a rapidly changing technology. It is anticipated therefore that frequent revision may be desirable. Electrical Power System Device Function Numbers on the other hand have changed very little over the years. This revision, prepared by the Automatic and Supervisory System Subcommittee of the IEEE Substation Committee, was an attempt to bring the standard up to date and further broaden its applicability with respect to control, supervisory, and telemetering, for greater use in many industries.

IEEE Tutorial Course Text 81 EH0 1883-PWR1 is recommended for those not familiar with Supervisory Control Systems.

The Standards Committee on Power Switchgear, C37, which reviewed and approved this standard, had the following personnel at the time of approval:

C . L. Wagner, Chairman John D. Hopkins, Secretary

W. N. Etothenbuhler, Executive Vice-chairman o f High-Voltage Switchgear Standards W. E. Laubach, Executive Vice-chairman of Low-Voltage Switchgear Standards

S. H. Telander, Executive Vice-chairman of IEC Activities Organization Represented Name of Representative Association of Iron and Steel Engineers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J. M. Tillman Electric Light and Power Group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D. 0. Craghead

R. L. Capra K. D. Hendrix R. L. Lindsey J. P. Markey ( A l t ) D. T. Weston

Institute of Electrical and Electronics Engineers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . H. W. Mikulecky M. J. Beachy ( A l t ) G. Hanks C. A. Mathews (AZt) E. W. Schmunk C. A. Schwalbe G. W. Walsh C. E. Zanzie ( A l t )

National Electrical Manufacturers Association . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. A. Wilson T. L. Fromm R. A. McMaster R. 0. D. Whitt

Tennessee Valley Authority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R. C. St. Clair Testing Laboratory Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L. Frier

E. J. Huber R. W. Seelbach ( A l t )

US Department of the Army. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . John S. Robertson US Department of the Interior, Bureau of Reclamation . . . . . . . . . . . . . . . . . . . . . . . . R. H. Auerbach US Department of the Navy, Naval Facilities Engineering Command. . . . . . . . . . . . . . . . R. L. Clark Western Area Power Authority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. D. Bimey

This publication is available from the Institute of Electrical and Electronics Engineers Service Center, 445 Hoes Lane, PO Box 1331, Piscataway, NJ 088551331.

The membership of working group 77.1 of the Automatic and Supervisory Systems Subcommittee which prepared this revised standard had the following personnel at the time this standard was sub- mitted for approval:

Donald F. Koenig, Chairman

W. J. Ackerman R. Hayner A. Matthey J. D. Betz J. Holladay J . O’Hara W. R. Block D. E. Johannson D. G. Rishworth G. Crask L. W. Kurtz, J r B. D. Russell W. Frisbie K. P. Lau J. M. Thorson D. J. Gaushell C. T. Lindeberg G. L. Unzicker A. Haban M. S. Wadkins

The members of the IEEE Automatic and Supervisory Systems Subcommittees who reviewed and approved this standard were as follows:

A. Matthey, Chairman W. J . Ackerman H. Hales C. T. Lindeberg J. D. Betz D. E. Johannson J. O’Hara W. R. Block D. F. Koenig D. G. Rishworth G. Crask L. W. Kurtz, Jr B. D. Russell D. J. Gaushell K. P. Lau J. M. Thorson A. Haban M. S. Wadkins

When the IEEE Standards Board approved this standard on March 22, 1984, it had the following membership:

James H. Beall, Chairman John E. May, Vice Chairman Sava I. Sherr, Secretary

J . J . Archambault John T. Boettger J . V. Bonucchi Rene Castenschiold Edward Chelotti Edward J. &hen Len S. Gxeyt Donald C. Fleckenstein

Jay Forster Daniel L. Goldberg Donald N. Heirman Irvin N. Howell Jack Kinn Joseph L. Koepfinger; Irving Kolodny George Konomos R. F. Lawrence

Donald T. Michael; John P. Riganati Frank L. Rose Robert W. Seelbach Jay A. Stewart Clifford 0. Swanson W. B. Wilkens Charles J. Wylie

Member emeritus t Deceased

Contents

SECTION PAGE 1 . Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2 . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 . Definitions .............................................................. 3 4 . Functional Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4.1 Typical Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.2 System Functional Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5 . Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.1 Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.2 Electrical Power and Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 5.3 Data and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 5.4 Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

6 . Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 6.1 Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 6.2 Vibrationandshock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

6.4 Lightning Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 6.5 Acoustic Interference Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

7 . Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 7.1 Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 7.2 Maintainability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 7.3 Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 7.4 System Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 7.5 Expandability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 7.6 Changeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

8 . Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

8.3 Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

9 . Tests and Inspections 39 Stages of Tests and Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Interface Tests and Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

9.3 Environmental Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 9.4 Functional Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

System Performance Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Bum-In Tests (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Availability Test (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Acceptance Test (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

9.9 Documentation Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

10 . Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 10.1 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 10.2 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 10.3 Operating Instructions and Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 10.4 Maintenance Instructions and Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 10.5 Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

5.5 ManIMachine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6.3 SeismicEnvironment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

6.6 Electromagnetic Interference (emi) and Electromagnetic Compatibility (emc) . . . . . . . 33

8.1 Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 8.2 Nameplates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 9.2

9.5 9.6 9.7 9.8

FIGURES PAGE

Fig 1 Scada System Data/Control Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Fig 2 Master-Station Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Fig 3 Remote-Station Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Interface Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Data Communication Equipment ............................................ 27

Communication Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Fig 7 Noise Criteria (NC) Curves for Speech Communication ........................... 34 Fig 8 Typical Surge Withstand Capability (SWC) Test Points ........................... 41

Fig 4 Manual. Automatic. and Supervisory Control Equipment

Fig 5 Signal Interfaces Between Equipment Governed by this Standard and

Fig 6 Signal Interfaces Between Equipment Governed by this Standard and

TABLES Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Table 11

Analog Input Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Analog Output Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Digital Electronic Input Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Digital Electronic Output Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Digital Electromechanical Inputs (Status) .................................. 25 Digital Electromechanical Inputs (Accumulator) ............................. 26 Digital Electromechanical Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Operating Temperature and Humidity by Location ........................... 31 Test Stages and Classes of Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 SystemInputScenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Recommended Electrical Graphic Symbols and Meanings ...................... 30

APPENDIX Appendix A Master/Remote Station Interconnections ................................ 47 Appendix B Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

An American National Standard

IEEE Standard Definition, Specification, and Analysis of Systems Used for

Supervisory Control, Data Acquisition, and Automatic Control

1. Scope [2] ANSI X3.1-1976, American National Stan- dard Synchronous Signaling Rates for Data Transmission.

[ 31 ANSI X3.4-1977, American National Stan- This standard applies to, and provides the

basis for, the definition, specification, performance analysis, and application of systems dard Code for Information Interchange. used for supervisory control, data acquisition or automatic control, or both: in attended or unattended electric substations, including those associated with generating stations, and power

[4] ANSI X3.5-1970, American National Stan- dard Flowchart Symbols and Their Usage in Information Processing.

utilization and conversion facilities. [5] ANSI Y14.15-1966 (R 1973), American National Standard Electrical and Electronics This standard does not apply to electomech-

anical or static, protective-relaying equipment. Diagrams (Including Supplements ANSI (See ANSI/IEEE C37.90-1978 (R 1982) [ l l ] ,3 ANSI/IEEE C37.90.1-1974 (R 1979) [12],

Y14-15a-1970 and ANSI Y14.15b-1973).

ANSI/IEEE C37.91-1985 E131 , ANSI/IEEE [6] ANSI 224.21-1957 (R 1971), American C37.93-1976 [ 141, ANSI/IEEE C37.95-1973, National Standard Method for Measurement (R 1980) [ 151 , ANSI/IEEE C37.96-1976 Specifying the Characteristics of Pickups for (R 1981) [ 161, and ANSI/IEEE C37.97-1979 (R 1984) [17].

Shock and Vibration.

[7] ANSI/EIA RS-310-C-1977 (R 1983), Racks, Panels, and Associated Equipment.

2. References

When the American National Standards referred to in this standard are superseded by a revision approved by the American National Standards Institute, the revision shall apply.

[ l ] ANSI X3 TR-1-1983, American National Standard Dictionary for Information Proces- sing.4

?Systems covered by this standard typically use computers in the master station and at times in the remote stations. Such computers provide facilities for incorpo- rating automatic control functions either by the supplier or by the user after the system is installed.

3The numbers in brackets correspond to those of the

[8] ANSI/EIA RS-334-1968, Signal Quality at Interface Between Data Processing Terminal Equipment and Synchronous Data Communi- cation Equipment for Serial Data Transmission.

[9] ANSI/EIA RS-404-1978, Start-Stop Signal Quality Between Data Terminal Equipment and Non-Synchronous Data Communication Equipment.

[ lo ] ANSI/IEEE C37.2-1979, IEEE Standard Electrical Power System Device Function Num- bers.

[ 111 ANSI/IEEE C37.90-1978 (R 1982), IEEE Standard Relays and Relay Systems Associated with Electric Power Apparatus.

[12] ANSI/IEEE C37.90.1-1974 (R 1979), references listed in Section 2 of thi; standard.

DeDartment. American National Standards Institute. IEEE Guide for Surge Withstand Capability 4 . 4 " publications are available from the Sales

14iO Broadway, New York, NY 10018. (SWC) Tests.

7

ANSI/IEEE C37.1-1987 DEFINITION, SPECIFICATION, AND ANALYSIS OF SYSTEMS USED FOR

[13] ANSI/IEEE C37.91.1985, IEEE Guide for Protective Relay Applications to Power Transformers.

[ 141 ANSI/IEEE C37.93-1976, IEEE Guide for Protective Relay Applications of Audio Tones over Telephone Channels.

[15] ANSI/IEEE C37.95-1973 (R 1980), IEEE Guide for Protective Relaying of Utility-Con- sumer Interconnections.

[16] ANSI/IEEE C37.96-1976 (R 1981), IEEE Guide for AC Motor Protection.

[17] ANSI/IEEE C37.97-1979 (R 1984), IEEE Guide for Protective Relay Applications to Power System Buses.

[ 181 ANSI/IEEE C37.100-1981, IEEE Stan- dard Definitions for Power Switchgear.

[19] ANSI/IEEE Std 91-1984, IEEE Standard Graphic Symbols for Logic Functions.

[ 201 ANSI/IEEE Std 100-1984,IEEE Standard Dictionary for Electrical and Electronics Terms.

[21] ANSI/IEEE Std 200-1975, IEEE Stand- ard Reference Designations for Electronics Parts and Equipment.

[22 J ANSI/IEEE Std 280-1985, IEEE Standard Letter Symbols for Quantities Used in Elec- trical Science and Electrical Engineering.

[23] ANSI/IEEE Std 315-1975, IEEE Standard Graphic Symbols for Electrical and Electronics Diagrams.

IEEE Recommended Practice for Seismic Qual- ification of Class 1E Equipment for Nuclear Power Generating Stations.

[25] ANSI/IEEE Std 422-1986, IEEE Guide for the Design and Installation of Cable Sys- tems in Power Generating Stations.

[26] ANSI/NEMA ICs 6-1978, Enclosures for Industrial Control and Systems.

[27] EIA EMC B1-1968, Introduction to EMC Designers Guide.’

[24] ANSI/IEEE Std 344-1975 (R 1980),

5EIA publications are available from Electronic In- dustries Association, 2001 Eye Street, NW, Washington, DC 20006.

[28] EIA EMC B2-1968, EMC Specifications, Standards and Bibiliography .

[29] EIA EMC B3-1968, Testing and Measure- ment Techniques for Electronic Equipment.

[30] EIA EMC B4-1965, Designers Guide on Electromagnetic System Design of Electric Equipment.

[ 311 EIA EMC B5-1964, Bonding of Electronic Equipment.

[32] EIA EMC B6-1967, Grounding of Elec- tronic Equipment.

[33] EIA EMC B7-1966, Enclosures of Elec- tronic Equipment.

[34] EIA EMC B8-1965, Cabling of Electronic Equipment.

[35] EIA EMC B9-1966, Filteringof Electronic Equipment.

[36] EIA EMC B10-1967, Electromagnetic Susceptibility.

[37] EIA IE B12-1977, Application Notes on Interconnection Between Interface Circuits

1969 (R 1981). Using EIA RS-449-1980 and EIA RS-232C-

[ 381 EIA RS-232-C-1969 (R 1981), Interface Between Data Terminal Equipment Employing Serial Binary Data Interchange.

[ 391 EIA RS-363-1969, Standard for Specify- ing Signal Quality for Transmitting and Receiv- ing Data Processing Terminal Equipments Using Serial Data Transmission at the Interface with Non-Synchronous Data Communication Equipment . [ 401 EIA RS-422-A-1978, Electical Character- istics of Balanced Voltage Digital Interface Circuits.

[41] EIA RS-423-A-1978, Electrical Character- istics of Unbalanced Voltage Digital Interface Circuits.

[42] EIA RS-449-1977, General Purpose 37- Position and 9-Position Interface for Data Terminal Equipment and Data Circuit-Termi- nating Equipment Employing Serial Binary Data Interchange.

8

SUPERVISORY CONTROL, DATA ACQUISITION, AND AUTOMATIC CONTROL ANSIlIEEE C37.1-1987

[43] IEC TC 65-1976, Safety Requirements for Mains Operated and Related Apparatus for Household and Similar General Use.6

[44] IEEE Std 525-1978, IEEE Guide for Selection and Installation of Control and Low- Voltage Cable Systems in substation^.^

[45] MIL-HDBK 217D-1982, Reliability Pre- diction of Electronic Equipment.8

[46] MIL-STD 471A-1973, Maintainability Demonstration.

[47] MIL-STD 1472C-1981, Human Engineer- ing Design Criteria for Military System Equip- ment and Facilities.

[48] GAUSHELL, D. J., FRISBIE, W. L., and KUCHEFSKI, M. H. Analysis of Analog Data Dynamics for Supervisory Control and Data Acquisition System, IEEE Paper 82 SM 304-4.

[49] LLOYD AND LIPOW. Reliability, Man- agement, Methods, and Mathematics. Engle- wood Cliffs, NJ: Prentice-Hall, 1962.

3. Definitions

The definitions of terms contained in this standard, or in other American National Stan- dards referred to in this standard, are not intended to embrace all legitimate meanings of the terms. They are applicable only to the subject treated in this American National Standard.

Supervisory control and data acquisition systems may use computers. For standard definition of computer terms refer to ANSI X3 TR- 1-1983 [ l ] .

6IEC publications are available from American National Standards Institute, 1430 Broadway, New York, NY 10018.

IEEE publications are available from the Institute of Electrical and Electronics Engineers Service Center, 445 Hoes Lane, PO Box 1331, Piscataway, NJ 08855-1331.

*MIL publications are available from the Director, US Navy Publications and Printing Service, Eastern Division, 700 Robbins Avenue, Philadelphia, PA 191 11.

Definitions in this standard may also be listed

Definitions in ANSI/IEEE Std 100-1984 [ 201 are used whenever possible; however, sometimes such definitions do not include the meaning associated with the equipment governed by this standard.

alarm condition. A predefined change in the condition of equipment or the failure of equipment to respond correctly. Indication may be audible or visual, or both.

analog device. A device that operates with variables represented by continuously measured quantities such as voltages, resistances, rotations, and pressures.

in ANSI/IEEE C37.100-1981 [18].

analog-to-digital (a/d) conversion. Production of a digital output corresponding to the value of an analog input quantity.

analog quantity. A continuous variable that is typically digitized and represented as a scalar value.

automatic. Pertaining to a process or device that, under specified conditions, functions without intervention by a human operator.

automatic circuit recloser. A self- controlled device for automatically interrupting and reclosing an alternating- current circuit, with a predetermined sequence of opening and reclosing followed by resetting, hold-closed, or lockout operation.

automatic control. See: control, (1) automatic.

automatic line sectionalizer. A self-contained circuit-opening device that automatically opens the main electrical circuit through it after sens- ing and responding to a predetermined number of successive main current impulses equal to or greater than a predetermined magnitude. It opens while the main electrical circuit is de- energized. It may also have provision to be manually operated to interrupt loads.

automatic load throwover equipment (transfer or switchover). An equipment that automatically transfers a load to another source of power when the original source to which it has been connected fails, and that automatically restores the load to the original source under desired conditions.

9


Modem One

DEFINITION, SPECIFICATION. AND ANALYSIS OF SYSTEMS USED FOR

Modem Two

NOTE: The restoration of the load to the preferred source from the emergency source upon re-energization of the preferred source after an outage may be of the continuous circuit restoration type or interrupted circuit restoration type.

(1) Equipment of the Nonpreferential Type. Equipment that automatically restores the load to the original source only when the other source, to which it has been connected, fails.

(2) Fixed Preferential Type. Equipment in which the original source always serves as the preferred source and other source as the emergency source. The automatic transfer equipment will restore the load to the preferred source upon its re-energization.

( 3 ) Selective Preferential Type. Equipment in which either source may serve as the preferred or the emergency source of preselection as desired, and which will restore the load to the preferred source upon its re-energization.

(4) Semiautomatic Load Throwover Equip- ment. An equipment that automatically transfers a load to another (emergency) source of power when the original (preferred) source to which it has been connected fails, but requires manual restoration of the load to the original source.

automatic reclosing equipment. Equipment which initiates automatic closing of a switching device under predetermined conditions without operator intervention.

automatic opening (tripping). The opening of a switching device under predetermined conditions without operator intervention.

availability. The ratio of uptime and uptime plus downtime. (See: 7 . 3 , Availability.)

backup. Provision for an alternate means of operation if the primary system is not available.

backup, degraded. A backup capability that does not perform all of the functions of the primary system.

baud. The term baud defines the signaling speed, that is, keying rate of the modem.

The signaling speed in baud is equal to the reciprocal of the shortest element duration in seconds to be transmitted.

For example, in the following table, the signaling speed is calculated from the signaling element duration. In addition, the distinction between bit rate and baud for two different types of modems is illustrated.

Signaling element duration

Signaling speed

0.833 ms

1200 Bd

Information transmitted per element 1 bit duration

Bit rate 1200 bits per second

2 bits

2400 bits per second

The bit rate and baud are not synonymous and shall not be interchanged in usage. Prefer- red usage is bit rate, with baud used only when the details of a communication modem or channel are specified.

bit. (1) least significant. In an n bit binary word its contribution is (0 or 1) toward the maximum word value of (2"-1).

(2) most significant. In an n bit binary word its contribution is (0 or 1 times 2'" -I)) toward the maximum word value of (2"-1).

bit rate. The number of bits transferred in a given time interval. Bits per second is a measure of the rate at which bits are transmitted.

buffer (buffer storage). (1) A device in which data are stored tempo-

rarily, in the course of transmission from one point to another; used to compensate for a dif- ference in the flow of data, or time of occurrence of events, when transmitting data from one device to another.

(2) An isolating circuit used to prevent a driven circuit from influencing a driving circuit.

bum in. A period, usually prior to on-line operation, during which equipment is continuously energized for the purpose of forcing infant mortality failures.

calibration. Adjustment of a device so that the output is within a specific range for particular values of the input.

cathode ray tube (crt). A display device in which controlled electron beams are used to

10

SUPERVISORY CONTROL, DATA ACQUISITION, AND AUTOMATIC CONTROL

present alphanumeric or graphical data on an electroluminescent screen.

channel load factor. See: 5.4.4

channel, scada. The communication path between master and remote stations. (See: Sec- tion 4, Fig 1.)

checkback message. The response from the receiving end to the initiating end of a coded signal or message.

(1) Partial. Message from the initiating end is mirrored by the receiving end back to the initiating end to verify error-free transmission of the message.

(2) Complete. Message from the initiating end is interpreted by the receiving end. A new message is sent to the initiating end to verify error-free transmission and proper interpretation of the message. (See: 7.4, System Security.)

common equipment. That complement of either the master or remote station supervisory equipment that interfaces with the interconnecting channel and is otherwise basic to the operation of the supervisory system, but is exclusive of those elements that are peculiar to and required for the particular applications and uses of the equipment.

console. That component of the system which provides facilities for control and observation of the system. Examples include operator’s console, maintenance console. (See: panel, control )

contention. An operational condition on a data communication channel in which no station is -designated a master station. In contention, each station on the channel shall monitor the signals on the channel and wait for a quiescent condition before initiating a bid for circuit control.

control. The execution of a system change by manual means, remote means, automatic means, or partially automatic means.

(1) automatic. An arrangement of electrical controls that provides for switching or controlling, or both, of equipment in an automatic sequence and under predetermined conditions.

(2) closed loop. A type of automatic control in which control actions are based on signals fed back from the controlled equipment or sys-

11


tem. For example, remote stations can manage local voltage conditions by control of load tap changers and volt amperes reactive (VAR) control compensation equipment.

(3)open loop. A form of control without feedback. (4) manual. Control in which the system or

main device, whether direct or power-aided in operation, is directly controlled by an attend- ant.

( 5 ) partial automatic. Control which is a combination of manual and automatic control. For example, to cause a voltage reduction the local automatic load tap changing closed-loop control may be biased by way of a supervisory control command.

(6) remote. Control of a device from a distant point.

data. Any representation of a digital or analog quantity to which meaning has been assigned.

data acquisition. The collection of data.

data acquisition system. A centralized system which receives data from one or more remote points. A telemetering system. Data may be transported by either analog or digital telemetering. (See; teleme tering .)

data rate. The rate at which a data path (for example, channel) carries data, measured in bits per second (b/s).

data logging. The recording of selected data on suitable media.

dead band. The range through which an input can be varied without initiating response.

device (electrical equipment). An operating element such as a relay, contactor, circuit breaker, switch, valve, or governor used to perform a given function in the operation of electrical equipment.

digital quantity. A variable represented by a number of discrete units.

digital-to-analog (d/a) coversion. Production of an analog signal whose magnitude is proportional to the value of a digital input.

disable. A command or condition which pro- hibits some specific event from proceeding.


display, graphic. A hardware device (crt, plasma panel, arrays of lamps, or light emitting diodes) used to present pictorial information.

distributed processing. A design in which all data is not processed in one processor. Multiple processors in the master station or in the remote stations, or both, share the functions.

downtime. The time during which a device or system is not capable of meeting performance requirements.

echo. A communication technique assuring that a word received at the termination point in a system is the same as the word originally transmitted. The received word is retransmitted to the sending device and matched to ensure that the original message was received properly.

electromagnetic compatibility (emc). A measure of equipment tolerance to external electromagnetic fields.

electromagnetic interference (emi). A measure of electromagnetic radiation from equipment.

enable. A command or condition which permits some specific event to proceed.

engineering units. A unit of measure for use by operatinglmaintenance personnel usually pro - vided by scaling the input quantity for display (meter, stripchart, or crt).

expandability. The capability of a system to be increased in capacity or provided with additional functions. (See: 7.5.)

event. A discrete change of state (status) of a system or device.

failure. An event that may limit the capability of an equipment or system to perform its function(s).

(1) Critical. Causes a false or undesired operation of apparatus under control.

(2) Major. Loss of control or apparatus which does not involve a false operation.

(3) Minor. Loss of data relative to power flow or equipment status.

failure distribution. The manner in which failures occur as a function of time; generally expressed in the form of a curve with the abscissa being time.

failures. (1) infant mortality. A characteristic pattern of failure, sometimes experienced with new equipment which may contain marginal components, wherein the number of failures per unit of time decrease rapidly as the number of operating hours increase. A burn-in period may be utilized to age (or mature) an equipment to reduce the number of marginal components.

(2) random. The pattern of failures for equipment that has passed out of its infant mortality period and has not reached the wear-out phase of its operating lifetime. The reliability of an equipment in this period may be computed by the equation

where R = e-ht

X = failure rate t = time period of interest (3) wear out. The pattern of failures experi-

enced when equipment reaches its period of deterioration. Wear-out failure profiles may be approximated by a Gaussian (bell curve) distribution centered on the nominal life of the equipment.

firmware. Hardware used for the nonvolatile storage of instructions or data that can be read only by the computer. Stored information is not alterable by any computer program. (See: station, remote.)

function check. A check of master and remote station equipment by exercising a predefined component or capability.

(1) Analog. Monitor a reference quantity (2) Control. Control and indication from a

control-check relay (3) Scan. Accomplished when control func-

tion check has been performed with all remotes (4) Poll. Accomplished when analog function

is performed with all remotes (5) Logging. Accomplished when results of

the control function check are logged

hard copy. A permanent record of information in readable form for human use, for example, reports, listings, displays, logs, and charts.

hardwired. The implementation of processing steps within a device by way of the placement of conductors between components within the device. The processing steps are not alterable except by modifying the conducting paths between components.

12

SUPERVISORY CONTROL, DATA ACQUISITION, AND AUTOMATIC CONTROL ANSI/IEEE C37.1-1987

indication. A light or other signal (audio or visual) provided by the man/machine interface that signifies a particular condition.

inhibit. To prevent a specific event from occurring.

log. A printed record of data.

master terminal unit (MTU). Refers to the master station of a supervisory control system (See: station, master).

mean time between failure (MTBF). The time interval (hours) that may be expected between failures of an operating equipment.

mean time to repair (MTTR). The time interval (hours) that may be expected to return a failed equipment to proper operation.

modem. A MOdulator/DEModulator device which converts serial binary digital data to and from the signal form appropriate for the respective communication channel.

multiplexer. (1) A device that allows the inter- leaving of two or more signals to a single line or terminal.

(2) A device for selecting one of a number of inputs and switching its information to the output.

offset. A predetermined value modifying the actual value so as to improve the integrity of the system, for example, the use of a 4 mA signal to represent zero in a 4 mA to 20 mA system.

panel, control. An assembly of man machine interface devices. (See: 5.5.)

point equipment (point). Elements of a supervisory system, exclusive of the basic common equipment, which are peculiar to and required for the performance of a discrete supervisory function. (See: supervisory control functions.)

(1) Alarm Point. Station (remote or master, or both) equipment(s) that inputs a signal to the alarm function.

(2) Accumulator Point. Station (remote or master, or both) equipment(s) that accepts a pulsing digital input signal to accumulate a total of pulse counts.

(3) Analog Point. Station (remote or master, or both) equipment(s) that inputs an analog quantity to the analog function.

(4) Control Point. Station (remote or master, or both) equipment(s) that operates to perform the control function.

( 5 ) Indication (Status) Point. Station (remote or master, or both) equipment(s) that accepts a digital input signal for the function of indication.

(6) Sequence of Events Point. Station (remote or master, or both) equipment(s) that accepts a digital input signal to perform the function of registering sequence of events.

(7) Telemetering Selection Point. Station (remote or master, or both) equipment(s) for the selective connection of telemetering transmitting equipment to appropriate telemetering re- c eivin g equipment over an interconnect in g communication channel. This type of point is more commonly used in electromechanical or stand-alone type of supervisory control.

( 8 ) Spare Point. Point equipment that is not being utilized but is fully wired and equipped.

(9) Wired Point. Point for which all common equipment, wiring, and space are provided. To activate the point requires only the addition of plug-in hardware.

(10) Space Only Point. Point for which cabinet space only is provided for future addition or wiring and other necessary plug-in equipment. NOTE: A point may serve for one or more of the purposes described above, for example, when a supervisory system is used for combined control and supervision of remotely operated equipment, a point for supervisory control and point for supervisory indication may be combined into a single control and indication point.

polling (data request). The process by which a data acquisition system selectively requests data from one or more of its remote terminals. A remote terminal may be requested to respond with all, or a selected portion of, the data available.

primary. An equipment or subsystem which normally contributes to system operation. See: backup.

programmable equipment. A remote or master station having one or more of its operations specified by a program contained in a memory device.

protocol. A strict procedure required to initiate and maintain communication.

quantization error. The amount that the digital

13


quantity differs from the analog quantity. (See: analog-to-digital (a/d) conversion.)

quiescent supervisory system. (See: supervisory system, quiescent.)

refresh rate. The number of times in each second that the information displayed on a nonpermanent display, for example, a crt, is rewritten or re-energized.

relay, interposing. A device which enables the energy in a high-power circuit to be switched by a low-power control signal.

remote terminal unit (RTU). Refers to a remote station equipment of a supervisory system. (See: station, remote.)

repeatability. The measure of agreement among multiple readings of an output for the same value of input, made under the same operating conditions, approaching from the same direction, using full-range traverses.

reproducibility. The measure of agreement among multiple readings of the output for the same value of input, made under the same operating conditions, approaching from either direction, using full-range traverses.

resolution. The least value of the measured quantity which can be distinguished.

scan (interrogation). The process by which a data acquisition system interrogates remote stations of points for data.

scan cycle. The time in seconds required to obtain a collection of data (for example, all data from one remote, all data from all remotes, and all data of a particular type from all remotes).

serial communication. A method of transmitting information between devices by sending all bits serially over a single communication channel.

station, automatic. A station that operates in automatic control mode. NOTE: An automatic station may go in and out of operation in response to predetermined voltage, load, time, or other conditions, or in response to a remote or locally manually operated control device.

station check (supervisory check, status update). The automatic selection, in a definite order, of all the supervisory alarm and indi-

cation points associated with one remote station or all remote stations of a system, and the transmission of all the indications to the master station.

station identification. A sequence of signal elements used to identify a station.

station. (1) master (of a supervisory system). The entire complement of devices, functional modules, and assemblies which are electrically interconnected to effect the master station supervisory functions. The equipment includes the interface with the communication channel but does not include the interconnecting channel.

During communication with one or more remote stations the master station is the supe- rior in the communication hierarchy.

(2)remote (of a supervisory system). The entire complement of devices, functional modules, and assemblies which are electrically interconnected to effect the remote station supervisory functions. The equipment includes the interface with the communication channel but does not include the interconnecting channel.

During communication with a master station the remote station is the subordinate in the communication hierarchy. NOTES: Examples of station equipments include

(1) Hardwired. Station supervisory equipment which is comprised entirely of wired-logic elements.

( 2 ) Firm ware. Station supervisory equipment which uses hardware logic programmed routines in a manner similar to a computer. The routines can only be modified by physically exchanging logic memory elements.

( 3 ) Programmable. Station supervisory equipment which uses software routines.

(3) semiautomatic. A station that requires both automatic and manual modes to maintain the required character of service. (4) submaster. A station that can perform as

a master station on one message transaction and as a remote station on another message transaction.

sta,tus. Information describing a logical state of a point or equipment.

supervisory control. An arragement for operator control and supervision of remotely located apparatus using multiplexing techniques over a relatively small number of interconnecting channels. supervisory control data acquisition system. A

14


system operating with coded signals over communication channels so as to provide controI of remote equipment (using typically one communication channel per remote station). The supervisory system may be combined with a data acquisition system, by adding the use of coded signals over communication channels to acquire information about the status of the remote equipment for display or for recording functions. supervisory control functions. Equipment governed by this standard comprise one or more of the following functions:

(1) Alarm Function. The capability of a supervisory system to accomplish a predefined action in response to an alarm condition. (See: alarm condition.)

(2) Analog Function. The capability of a supervisory system to accept, record or display, or do all of these, an analog quantity as presented by a transducer or external device. The transducer may or may not be a part of the supervisory control system.

(3) Control Function. The capability of a supervisory system to selectively perform manual or automatic, or both, operation (singularly or in selected groups) of external devices. Con- trol may be either analog (magnitude or duration) or digital. (4) Indication (Status) Function. The capa-

bility of a supervisory system to accept, record, or display, or do all of these, the status of a device. The status of a device may be derived from one or more inputs giving two or more states of indication.

(a) Two-State Indication. Only one of the two possible positions of the supervised device is displayed at one time. Such display may be derived from a single set of contacts.

(b) Three-State Indication. One in which the transitional state or security indication as well as the terminal positions of the supervised device is displayed. Such a display is derived from at least two sets of initiating contacts.

(c) Multistate Indication. Only one of the predefined states (transitional or discrete, or both) is indicated at a time. Such a display is derived from multiple inputs.

(d) Indication with Memory. An indication function with the additional capability of stor- ing single or multiple change(s) of status that occur between scans.

( 5 ) Accumulator Function. The capability of a supervisory system to accept and totalize

digital pulses and make them available for display or recording, or both.

(6) Sequence of Events Function. The capability of a supervisory system to recognize each predefined event, associate a time of occurrence with each event, and present the event data in order of occurrence of the events.

supervisory system. All control indicating and associated with telemetering equipment at the master station and all of the complementary devices at the remote station, or stations.

(1) continuous update. A system in which the remote station continuously updates indication and telemetering to the master station regardless of action taken by the master station. The remote station may interrupt the continuous data updating to perform a control operation.

(2)polling. A system in which the master interrogates each remote to ascertain if there has been a change since the last interrogation. Upon detection of a change the master may request data immediately.

(3)quiescent. A system which is normally alert but inactive and transmits information only when a change in indication occurs at the remote station or when a command operation is initiated at the master station. (4) scanning. A system in which the master

controls all information exchange. The normal state is usually one of repetitive communication with the remote stations.

system time. A coordinated value of time main- tained at stations throughout the power system.

tag. A visual indication, usually at the master station, to indicate that a device has been cleared for field maintenance/construction purposes and is not available for control or data acquisition.

telemetering. (1 ) Transmission of measurable quantities using telecommunication techniques.

(a) Current-Type Telemeter. A telemeter that employs the magnitude of a single current as the translating means.

(b) Frequency-npe Telemeter. A telemeter that employs the frequency of a periodically recurring electric signal as the translatingmeans.

(c) Pulse-Type Telemeter. A telemeter that employs characteristics of intermittent electric signals, other than their frequency, as the translating means.

15

ANSIlIEEE C37.1-1987 DEFINITION, SPECIFICATION, AND ANALYSIS OF SYSTEMS USED FOR

(d) Ratio-Type Telemeter. A telemeter that employs the relative phase position between, or the magnitude relation between, two or more electrical quantities as the translating means. NOTE: Examples of ratio-type telemeters include ac or dc position matching systems.

(e) Voltage-Type Telemeter. A telemeter that employs the magnitude of a single voltage as the translating means.

(2) analog. Telemetering in which some characteristic of the transmitter signal is proportional to the quantity being measured.

(3) digital. Telemetering in which a numerical representation is generated and transmitted; the number being representative of the quantity being measured.

terminal. (1) A point in a system or communication network at which data can either enter or leave.

(2) An input/output device capable of transmitting entries to and obtaining output from the system of which it is a part, for example, cathode ray tube (crt) terminal.

test. (1) certified design. A test performed on a production model specimen of a generic type of equipment to establish a specific performance parameter of that genre of equipment. The condition and results of the test are described in a document that is signed and attested to by the testing engineer and other appropriate, responsible individuals.

(2) data (a) The recorded results of test. (b) A set of data developed specifically to

test the adequacy of a computer run or system. They may be actual data taken from previous operations or artificial data created for this purpose.

(3) point. A predefined location within equipment or routines at which a known result should be present if the equipment or routine is operating properly.

time. (1) response. The time between initiating some operation and obtaining results.

(2) settling. Time required by channel or terminal equipment to reach an acceptable operating condition.

timer, watchdog. A form of interval timer which is used to detect a possible malfunction.

transaction. That sequence of messages between master and remote stations required to perform

a specific function (for example, acquire specific data or control a selected device).

troubleshoot. Action taken by operating or maintenance personnel, or both, to isolate a malfunctioned component of a system. Actions may be supported by printed procedures, diagnostic circuits, test points, and diagnostic routines.

update. The process of modifying or reestablish- ing data with more recent information.

uptime. The time during which a device or system is capable of meeting performance requirements.

4. Functional Characteristics

The equipment governed by this standard may be arranged in various configurations and be required to perform some or all of the functions identified in this section.

Typically, equipment governed by this standard compose a system with at least one master station and one (typically several) remote station. Figure 1 illustrates the data and control flow from field sensors and actuators to and from an operator by way of a master station and remote-station system.

4.1 Typical Diagrams. Diagrams of typical equipment and configurations of equipment governed by this standard are illustrated within this section.

The media between the stations could be any suitable communication channel or channels. The communication protocol typically used requires a master station to initiate message transactions.

For brevity, the terms master and remote de- note master station and remote station.

The functional components of a master station are illustrated in Fig 2. A dual computer station is illustrated, however, a single computer master station may be adequate for some applications. The functional components of aremote station are illustrated in Fig 3. Various interconnections of master and remote stations are illustrated in Appendix A.

The computer system illustrated in Fig 2 as a single box typically includes mass memory and

16

SUPERVISORY CONTROL, DATA ACQUISITION. AND AUTOMATIC CONTROL

- M

E M

A


r

REMOTE - STATION - 0 - PULSE COUNTER

POINTS

B I N A R Y D A T A

POINTS

D A T A DISPLAYS

INDICATION

r CONTROL A N D

INDICATION DEVICES

+~ D /A

CONVERTER

I

1

I N D ICATI ON POINTS

STATION CHECK TR IP-CLOSE

LOWER RAISE CLOSE-OPEN STOP-START

4

r A N A L O G D A T A

COUNTED D A T A B I N A R Y D A T A 4 A L A R M S A N D LJ

STATUS INDICATIONS 1

IP,,,,l

POINTS

Fig 1 Scada System Data/Control Flow

COMPUTER SUBSYSTEM

COMPUTER COMPUTER SYSTEM

COMMUNICATIONS INTERFACE

A N A L O G RECORDERS D I G I T A L D ISPLAYS

I I LRTU FUNCTIONS I

I i

Fig 2 Master-Station Block Diagram

various peripherals. It is common practice to interface remote station communication chan- switch the complete computer system in the nels to the primary computer system. The event of a peripherial or computer failure rather man/machine subsystem is that equipment than attempt to reconfigure a system by switch- used to present information to the operator(s) ing peripherials. The communication interface and to accept inputs from the operator@). subsystem of Fig 2 is that equipment used to

17


I INTERFACE

I I I 1

DEFINITION, SPECIFICATION, AND ANALYSIS OF SYSTEMS USED FOR

I I I I

I

I LOGIC I COMMON 4

( 1 ) STATUS AND ALARM PULSE INPUTS INPUTS FROM

(2) SWITCH POSITIONS ACCUMULATOR' FROM MANUAL ENTRY (WATTHOUR PANELS METERS, ETC)

I

I * I POWER POWER

SUPPLY

TRANSDUCERS RELAYS D/A CONVER I TERS, ETC

I

I I POINT INPUTiOUTPUT LOGIC

( 1 1 CONTACT OUTPUTS TO CIRCUIT BREAKERS,

ANALOG OUTPUTS DISCONNECT SWITCHES, ETC TO SETPOINT (2) CONTACT OUTPUTS CONTROLLERS TO DIGITAL SETPOINT

CONTROLLERS

I

Fig 3 Remote-Station Block Diagram

4.2 System Functional Characteristics. This section provides guidance for helping both sup- pliers and users define the functional capabilities that may be required in a system. Not all of the capabilities discussed below are required in every system. When a function or capability is not required, that fact shall be noted.

Each generic function is addressed in a subsection that follows in terms of the minimum features or characteristics that should be addressed to adequately define the function.

Definition of the system functions is a joint responsibility of the user and supplier. The sub- paragraphs that follow provide a checklist that will help ensure adequate communication between the user and supplier of equipment governed by this standard.

When the feature or characteristic is fixed by the design of the equipment the burden of defi-

nition rests on the supplier (for example, number of inputs/outputs per card). However, variable features (for example, scaling resistors, switch settings, firmware, and software) should be jointly defined by the user and the supplier. 4.2.1 Communication Management. The capa-

bilities to manage communication between the master station and the remote station shall be well defined. The topics to be defined include

(1) Message protocol (2) Number of channels (3) Bit rate (4) Error detection techniques (5) Channel switching (6) Number of remotes per channel (7) Number of retries each attempt (8) Number of attempts per hour (9) Time out value(s)

(10) Communication error reporting

18


(11) Channel quality monitoring (normal and

(12) Loop-back provisions 4.2.2 Data Acquisition. (See 5.3). When data

acquisition is a function to be performed, the characteristics for each data type shall be defined. Ranges of data input, scale factors, rates, and accuracy shall be defined for

backup)

(1) Analog inputs (2) Indication inputs-single bit (3) Indication inputs-multibit (4) Indication inputs-with memory ( 5 ) Accumulator inputs (6) Sequence of events inputs The data acquisition capability for each data

type shall be defined in terms of the following characteristics. Scan Groups. How many scan groups, size of group, inputs in each group. Scan Cycle. Each group (seconds to complete an acquisition from all remotes). NOTE: The communication hardware related performance capabilities used in the calculation of scan cycle shall be defined.

4.2.2.1 Remote- Station Data Acquisition. When the remote station locally acquires data between master-station data requests, the capacity (total inputs) and rate of acquisition (inputs per second) for field data interfaced to remote-station equipment shall be defined for each of the above data types.

The modularity (for example, number of inputs per card) of each data type shall also be specified.

4.2.2.2 Master-Station Data Acquisition. The capacity (total inputs) and rate of acquisition (inputs per second) for local or remote- station data interfaced to master-station equipment shall be defined for all applicable data types.

4.2.3 Data Processing. Data processing capabilities shall be defined for each equipment and data type. Systems with report-by-exception functions shall have the capability to report all data for initialization and periodic update purposes.

4.2.3.1 Analog Data Processing. Analog change detection may be a function included as an alternative to processing every input on every scan. Analog change detection is accomplished by testing to see if the new value for each input is within N digital counts (for example, dead band) of the last stored value for that

input. The new value shall replace the last stored value only if the dead band was exceeded and then the input will be further processed as defined below. When the analog change detection function is included, the following characteristics shall be defined:

(1) Location of processing, remote or master, or both

(2) Range of N-remote or master, or both (3) Applicability of N-remote, card, or point (4) Technique for changing value of N When the analog change detection is imple-

mented in the remote station, its output may be used by an analog data report-by-exception function to save communication of unchanged data from the remote station to the master station. When the analog data report-by-exception function is included the following characteristics shall be defined.

(1)Percent of analog changes per scan that results in the channel load associated with reporting all analog points from the remote terminal unit (RTU).

(2) Description of logic in the master station that can be used to select between using the Analog Data Report-by-Exception function or the Report All Analog Data Functions when acquiring analog data from each remote station.

Filtering of analog data may be provided to smooth such data before it is used by other functions. When this function is included, define the equation used and the time delay introduced by the filtering.

Analog data conversion to engineering units is typically required before analog data is used by the operator, other software, or printed in an alarm message. The mathematical equation(s) used to convert analog values represented by digital counts into the corresponding engineering units shall be defined. Specific attention shall be given to sensor and transducer scale factors that may be provided by the user.

Scaling of analog inputs should give adequate consideration to off-normal operation of the power system (for example, over voltage, emergency load limits).

Techniques that are used to (1) Detect an open input to an analog chan-

(2) Identify reasonable values, or (3) Automatically calibrate an analog chan-

nel, or a combination of these three shall be defined.

nel, or

19

ANSI/IEEE C37.1-1987 DEFINITION, SPEC

Analog data limit checking is typically included to determine if other downstream functions such as alarm management or further processing is required. The number of high or low limits accommodated and associated dead-band processing, shall be defined. Specific attention shall be given to the procedure for user specification and revision of limit and dead-band values.

4.2.3.2 Indication Data Processing. Indica- tion input change detection may be a function included as an alternative to processing every input on every scan. Indication input change detection is performed by testing to see if the current indication is the same as the last stored indication for that input. Changed indications shall replace the last stored value and the point or group of inputs shall be routed for other downstream functions such as indication data report by exception, or alarm management, or both.

When the Indication Input Change Detection function is included, the following characteristics shall be defined:

(1) Location of processing (remote or master) (2) Quantity of data reported when a single

(3) Minimum signal duration When the indication input change detection

function is implemented in the remote station, its output may be used by an indication data report-by exception function to save communication of unchanged data from the remote station to the master station. When the indication data report-byexception function is included, the following characteristics shall be defined:

(1) Percent of indication point changes per scan that results in the channel load associated with reporting all indication points from the remote.

(2) Description of logic in the master or remote station that can be used to select between using the indication data report-by-exception or the report all indication data function when acquiring indication data from each remote.

Indication with memory may be a function implemented in the remote. When this function is included, define the number of status changes accommodated, and legal bit combinations supported by the design.

Define the status data processing options supported. Particular attention shall be given to

input changes

'IFICATION, AND ANALYSIS OF SYSTEMS USED FOR

input validity processing and to the interface between the supervisory control function and the status data processing function.

4.2.3.3 Accumulator Data Processing. When pulse accumulation and pulse accumulator data processing is included the following characteristics shall be defined:

(1) Input circuit (2 or 3 connections) (2) Sources of freeze command (internal/

(3) Ranges of values (remote and master

(4) Nominal and maximum counting rates ( 5 ) Source of memory power

external)

station)

4.2.3.4 Sequence of Events (SOE) Data. When a sequence of events data acquistion capability is included the following characteristics shall be defined:

(1) Time resolution (at and between remotes) (2) Method of system time synchronization (3) Time accuracy between any two remote

(4) Number of SOE inputs ( 5 ) Size of buffers (number of SOE messages

which can be stored) (6) Time (Minimum/Maximum) between suc-

cessive change of an input (7) Method of indicating that SOE data is

available (8) Data filter time constant (for example,

contact de-bounce) (9) Data time skew (introduced by de-bounce

filters) 4.2.3.5 Computed Data Points. When the

capability of computing data or results (that are not directly measured) is included the following characteristics shall be defined:

stations

(1) Location (remote or master) (2) Equations supported (3) Resulting data types (numeric or logical,

or both) (4) Downstream functions (for example,

limit checking) 4.2.3.6 Alarm Management. When the capa-

bility to manage and report alarm conditions is included the following characteristics shall be defined:

(1) Conditions reported as alarms (2) Methods of acknowledgement (single or

(3) Methods of highlighting reports (flash,

(4) Information in alarm messages ( 5 ) Hierarchy of alarms (priority level)

groups )

tone, etc)

20


(6) Size of alarm queue(s) (7) Queue management (for example, time

(8) Alarm limit@) 4.2.4 Supervisory Control Characteristics

(See: 5.3). When the capability to remotely control external apparatus is provided, the characteristics of such a control capability shall be defined.

Definition of characteristics common to all control interfaces shall include

(1) Control sequence description (2)Type of checkback message (partial or

complete) (3) Security of control sequences (4) Immediate operate controls (5) Broadcast controls

ordered)

4.2.4.1 Apparatus Control with Relay In- terface. Control using a relay output shall be described as follows:

(1) Dwell time of relay contacts (2) Number of relays that can be simultane-

ously energized in each type of remote (3) Processing actions (for example, logging,

and alarm suppression) 4.2.4.2 Apparatus Control with Setpoint

Interface. Control using a setpoint output shall be defined for

(1) Resolution of setpoint value (2) Duration of output value (3) Processing actions (for example, limit

check, equation, and alarms) 4.2.4.3 Apparatus Control with Electronic

Interface. Control using a solid-state interface shall be described as follows:

(1) Timing diagram of signals (2) Interface communication protocol (3) Processing actions associated with control

4.2.5 Automatic Control. When the capability to automatically control external apparatus is provided the characteristics of such control capabilities shall be defined

(1) Location of automatic control logic (remote or master)

(2) Control equation@) (3) Frequency of execution (4) Field alterable control criteria (5) Associated logging or alarming

4.2.6 Operator Interface Characteristics. The capability to support data or control interfaces to operating or maintenance personnel at either the master or remote station shall be described.

4.2.6.1 Control of Equipment Functions. When operator controllable functions are included the applicable characteristics shall be defined:

(1) Control output interfaces (a) Enable/disable (b) Tagging (types and uses) (c) Local/remote

(2) Control of data acquisition (a) Enable/disable scan (inputs or stations) (b) Enable/disable processing (c) Manual entry of data (d) Change scan frequency by group (e) Assign/reassign data to a group

(3) Control of data processing (a) Setting date and time (b) Setting input change limits (c) Defining formats (d) Defining conversion data (e) Defining operator override values

(4) Control of alarm processing (a) Enable/disable individual alarms (b) Enterledit alarm limits (c) Enter/edit alarm dead-band (d) Edit alarm to operator assignment (e) Acknowledge alarms (individual/page) (f) Silence audible alarm (g) Inhibit alarms (h) Override invalid alarms

(5) Control of function checks (a) Enable/disable (b) Change frequency

(a) Enable/disable (b) Modify criteria (c) Add/delete control functions (d) Reset to reference level or position

(6) Control of automatic control functions

4.2.6.2 CRT Display Capabilities. When crt formats are supported the applicable characteristics shall be defined

(1) Generation of display formats (a) Format definition capabilities (b) Symbols supported (c) Memory per format (d) Use of colors (e) Use of special features (flash, inverse

(f) Control level of detail (2) Standard formats

(a) Index formats (b) System formats (c) Communication channel format (d) Summary of inhibited alarms

video, etc)

21


(e) Input point profile formats (f) Alarmsummary

(h) Station notes format (3) Control of crt and cursor

(a) Cursor operation (b) Selection of formats (c) Response time (d) Update cycle (from data base) (e) Paging of multipage formats 4.2.6.3 Digital and Analog Displays. When

such display devices are supported the applicable characteristics shall be defined

(a) Numeric range with decimal (b) Update frequency (c) Maximum number supported

(a) Ranges (b) Update frequency (c) Maximum number supported 4.2.6.4 Hardcopy Devices. When support of

hardcopy devices is required such as loggers, strip chart recorders, and crt video-copiers the applicable characteristics shall be defined as follows:

(g) Tag summary

(1) Digital displays

(2) Analog displays

(1) Device assignments (a) Initial (b) Automatic re-assignment (c) Manual re-assignment

(2) Generation of log formats (a) On-line/batch capabilities (b) Symbols supported (c) Spooling capabilities

(a) Standard formats (b) Time for response

(a) Standard events (for example, operator and actions)

(b) System events (for example, computer failover and communication failure)

4.2.7 Computer Backup and Switchover. When primary and backup facilities are provided the applicable characteristics shall be defined as follows:

(3) Demand logs

(4) Logged activities

(1) Data base backup (a) Data residency (bulk or main memory) (b) Frequency of update (by data type) (c) Other uses of backup facilities

(a) Method of failure detection (b) Response time for detection

(2) Failure monitoring

(3) Switchover

(a) Method of switchover (b) Time required for switchover (c) Operator interface response following

(d) Operator actions following switchover 4.2.8 History Data. When a capability for

history data acquisition, archiving and retrieval is provided, the appropriate characteristics shall be defined as follows:

switch over

(1) Number of history files supported (2) Data quantities per file (3) Data intervals per file (4) Number of data intervals per file (5) Method of file management (6) Method of data archiving (7) Method of data retrieval

5. Interfaces

The equipment governed by this standard shall have interfaces as described in this section. The interfaces described consist of those illustrated in Fig 4.

Fig 4 Manual, Automatic, and Supervisory

Control Equipment Interface Block Diagram

POWER SOURCE AN0 GROUNDING

INTERFACES (REFER TO SECTION 5 2)

I

AUTOMATIC

CONTROL EOUIPMENT

I

' DATA AN0 CONTRX ' INTERFACES

(REFER TO SECTION 531

5.1 Mechanical 5.1.1 Enclosures. Equipment located in an

outdoor environment shall utilize enclosures which satisfy the requirements defined for the

22


specified environment by ANSI/IEEE ICs 6- 1978 [26].

Equipment which is housed in a building or other suitable enclosure in which it is protected from the weather shall utilize enclosures meeting the requirements of ANSI/EIA RS-310-C- 1977 (R 1983) [7] .

5.1.2 Special Requirements. The location of access doors, enclosure mounting requirements, cooling requirements, terminal-block type and location, cable entry locations, and special cabling and connector requirements should be specified for individual applications.

When required, electromagnetic shielding characteristics of enclosures should be determined in conformance with EIA EMC B7-1966 [331.

5.2 Electrical Power and Grounding. The electric power and grounding interfaces to equipment governed by this standard shall meet the following requirements:

The alternating current source defined below may originate directly from the station source or from a regulating/unintermptible supply.

Equipment operating on direct current shall not sustain damage if the input voltage declines below the lower limit specified or is reversed in

Equipment governed by this standard shall not ground a floating power source. When grounded power sources are used care should be exercised to ensure ground compatibility.

5.2.1 Master Station. Master-station equipment shall be capable of operating without error or damage with one or more of the following input voltage ranges:

120/240 V ac 210% single phase or three phase at 60/50 Hz +0.5% 208Y/120 V ac 210% three phase at 60 Hz k0.576

polarity.

21to 2 9 V dc (24V dcnominal) 42to 58V dc (48V dcnominal)

105 to 145 V dc (125 V dc nominal) 210 to 290 V dc (250 V dc nominal) 5.2.2 Remote Stations. Remote-station equip-

ment governed by this standard shall be capable of operating without error or damage with one or more of the following input voltage ranges:

120/240 V ac +lo% at 60/50 Hz +1% 21 to 29V dc (24V dcnominal) 42to 58V dc (48V dcnominal)

105 to 145 V dc (125 V dc nominal) 210 to 290 V dc (250 V dc nominal)


5.2.3 Grounding. The equipment shall be connected to an external ground at a single point so that grounded loop conditions are minimized. Caution shall be used to prevent inadvertent ground paths from apparatus such as convenience outlets, conduit, structural metal, test equipment, and external interfaces.

5.2.4 Internal Noise. The electrical noise appearing on the power input terminals that is internally generated (from 1000 Hz to 10 000 Hz) by equipment governed by this standard shall be less than 1.5% (peak to peak) of the external power source voltage as measured into an external power source impedance of 0.1 C2 minimum.

5.2.5 Surge Withstand Capability (SWC). The electrical power interfaces shall be designed to provide surge withstand capability as defined in ANSI/IEEE C37.90.1-1974 (R 1979) [12].

5.3 Data and Control. Data and control interfaces consist of electrical interconnections between equipment governed by this standard and the apparatus being monitored and controlled. Two types of signal paths are defined

(1) Data Paths. Inputs to data acquisition or supervisory control equipment

(2) Control Paths. Outputs from data acquisition or supervisory control equipment.

For each input (data) or output (control) path, various signal characteristics need to be defined to specify the interface between equipment. The range of user application varies widely so that it is not possible to establish a standard for all signal characteristics discussed below. In these instances the user should specify the applicable characteristics. See ANSI/IEEE C37.2-1979 [lo] where the use of function numbers is recommended.

Data and control signal cabling which are external to equipment governed by this standard are not specified. The following recommended practices and design guidelines may be used:

(1) ANSI/IEEE Std 422-1986 [25] and

Tables 1 through 7 address the parameters typically associated with each data or control signal, or both. Class I entries represent higher performance devices than Class 11. The user and supplier can agree to specifications other than Class I or I1 whenever unique conditions sug- gest an alternate interface. NOTE: The user should identify the required expansion (see 7.5) for each type of data and control interface.

(2) IEEE Std 525-1978 [44].

23


Table 1 Analog Input Signals

Specifications

Parameter Class I Class I1 Notes

Nominal input signal range

Maximum input signal range

r l mA

r1.2 mA

f 1 mA or 4-20 mA is acceptable f 2 mA or 3-24 mA

f 5 V with source resistance less than 5 k n

Limited by the transducer to 2 mA

Maximum input signal (nonoperating)

200 V peak 20 V peak dc to 60 Hz

Maximum input signal burden l k 52 6 k n or For current inputs

Conversion resolution, minimum 12 b 1 0 b Binary data format

Maximum error at 25 C fO.1% f 0.25% Percent of nominal input signal range

( inch des overload protection )

(with sign)

(of reading)

300 n

(2 mA) includes offset, scale factor, and calibration errors over 6 month period.

Maximum temperature error* fO.O05%/"C tO.Ol%/"C Percent nominal input signal range (2 mA) Maximum common-mode voltage dc to 60 Hz referred to equipment ground

Minimum common-mode rejection 90 dB 70 dB dc to 60 Hz Minimum normal-mode rejection 60 dB 60 dB At 60 Hz

200 V peak 20 V peak (operating)

*Associated with the operating temperature. See Table 9.

Table 2 Analog Output Signals

Specifications

Parameter Class I Class I1 Notes

Nominal output signal range t l mA

Maximum output signal range Maximum output load 10 k n Maximum error at 25 ' C t0.1%

t1.2 mA

(of reading)

Maximum temperature* error tO.O05%/"C

Conversion resolution, minimum 12 b

Maximum update time 0.15 Output signal isolation Yes Maximum common-mode voltage

Maximum common-mode error iO.1%

(with sign)

200 V peak (operating)

r 1 mA or 4-20 mA

r1.2 mA or 3-24 mA 100 n or 500 +0.25%

r0.O1%I0C

1 0 b

0.55 No NIA

N/A

Constant current into a burden of 0 to 1 0 k n . + 5 V range of voltage output is acceptable

10 k n minimum for voltage outputs Percent of nominal output signal

range (2 mA) includes offset, noise scale factor, and calibration error over six-month period

range (2 mA) Percent of nominal output signal

Binary data format

Seconds

dc to 60 Hz referred to equipment

Percent of nominal output signal ground

range (2 mA)

*Associated with the operating temperature. See Table 9.

24


Table 3 Digital Electronic Input Signals

Specifications

Parameter Class I Class I1 Notes - ~~~

Input data format Specify Specify Application dependent Input signal isolation Yes No Optical coupler or equivalent

0 to +20 v Signal current range O t o l m A O t o l m A Signal data rate Specify Specify Signal duration Specify Specify

Signal voltage range 0 to +20 v

Table 4 Digital Electronic Output Signals

Specifications

Parameter class I Class I1 Notes

Output data format Specify Specify ~ ~~~ ~

Application dependent Output signal isolation Yes No Optical coupler or equivalent Signal voltage range Signal current range Signal data rate Specify Specify Signal duration Specify Specify

0 to 30 V 0 to 50 mA

0 to 30 v 0 to 50 mA

Table 5 Digital Electromechanical Inputs (Status)

Specifications

Parameter Class I Class 11 Notes

External contact format Specify Specify Dry contact. Form A is typical Minimum signal voltage

Minimum signal current

24 V, dc

10 mA 1 0 mA

24 V, dc Station battery may be used. Subject to emi restrictions

Minimum change detection time 2 ms 1 5 ms Maximum change detection time 8 ms 30 ms Maximum contact resistance 100 52 100 n Includes cable resistance Minimum leakage resistance 50 k52 50 k n Includes cable leakage resistance

(at operating voltage)

25

ANSI/IEEE C37.1-1987 DEFINITION, SPECIFICATION, AND ANALYSIS O F SYSTEMS USED FOR

Table 6 Digital Electromechanical Inputs (Accumulator)

Specification

Parameter Class 1 Class I1 Notes

External contact format Minimum signal voltage

Minimum signal current Minimum change detection time Counts per contact cycle Maximum count rate Minimum accumulator count range Accumulator freeze command:

Internal External

Alternate memory power source

Specify 24 V, dc

10 mA 30 ms One 10 9999

Yes Yes Yes

Specify 24 V, dc

10 mA 30 ms T W O

10 Per second 9999

Dry contact. Form C is typical Station battery may be used.

Subject to emi restrictions

= 15 minutes at maximum rate

Yes Yes No

Table 7 Digital Electromechanical Outputs

Specifications

Parameter Class I Class I1 Notes ~~

Output contact format Specify Specify Dry contacts. Two Form C’s is typical

Contact current rating 30 A 5 A Minimum of 1 s

Contact interruption rating 125 V, dc 48 V, dc Resistive load Activation time adjustable Yes Yes

Latched outputs available Yes Yes Contact bounce time Specify Specify

(0.1 to 30 s)

5.4 Communication. Communication interfaces consist of functional, mechanical, and electrical interconnections between equipment governed by this standard and the communication apparatus. Any specific application requires one of the two following types of general signal interfaces.

(1) Signal interfaces between equipment governed by this standard and the data communication equipment (for example, a data modem). This interface occurs whenever the data communication equipment is not packaged as an integral part of the equipment governed by this standard, as illustrated in Fig 5 .

(2) Signal interfaces between the equipment governed by this standard and a communication channel. This interface is illustrated in Fig 6.

Subsequent paragraphs define specific signal characteristics for these above mentioned interfaces. However, two characteristics are common to both types of interfaces and shall be measured regardless of the configuration utilized. These characteristics are:

(1) SWC measured between data communication equipment and the communication channel (see Section 9).

(2)Bit error rate measured between data communication equipment and equipment governed by this standard.

The SWC criteria as defined in ANSI/IEEE C37.90.1-1974 (R 1979) [12]. Supplement to ANSI/IEEE C37.90-1978 (R 1982) [ l l ] shall be used in common mode only and with the channel connected to the data communication

26


A U TOM AT IC OR

SU PER V I SO RY EQUIPMENT (1)


DATA COMMUN CAT IO N COMMUNI CATION - EQUIPMENT ( 2 ) CHANNEL

( d a t a modem) L

NOTES: (1) This equipment is called data terminal equipment (DTE) in ANSI and EIA Standards referenced in this section.

(2 ) This equipment is commonly called a data modem but called data communication equipment (DCE) in referenced standards.

Fig 5 Signal Interfaces Between Equipment Governed by this

Standard and Data Communication Equipment

AUTOMATIC COMMUNICATION CHANNEL ( 2 )

SUPER V l S O R Y

NOTES: (1) Data modem is packaged as an integral part of this equipment.

(2 ) Channel includes microwave, radio, cable, fiber optic, and power-line carrier types.

Fig 6 Signal Interfaces Between Equipment

Governed by this Standard and Communication Channel

equipment. Due to the variety of channel and modem qualities available and in use, an average value of 1 bit error in lo4 bits is recommended for design and analysis purposes. 5.4.1 Interface Characteristics Between the

Equipment Governed by this Standard and the Data Communication Equipment (Modems) When They Are Not Integrally Provided. (1) Interface Signals. As a minimum each interface shall satisfy the requirements as defined in EIA RS-449-1977 [42], Category 1 and EIA RS-

All circuits used shall be implemented with drivers and receivers according to EIA RS-423-A 1978 [41] for unbalanced voltage digital interface circuits. Where modems equipped with digital interfaces according to EIA RS-232-C 1969 (R 1981) [38] are to be utilized, the necessary adapters described in EIA IE B12- 1977 [37] shall be provided as part of the equipment governed by this standard.

(2) Signal Repetition Rate. All rates shall be in accordance with ANSI X3.1-1976 [2].

422-A-1978 [ 401.

(3) Signal Quality. All signals shall meet EIA RS-363-1969 [ 391 and ANSI/EIA RS-404- 1978 [9] for asynchronous DCE and ANSI/ EIA RS-334-1968 [8] for synchronous DCE.

(4)Noise Limits. These are defined in the references given in (3).

5.4.2 Interface Characteristics Between the Communication Channel and the Data Com- munication Equipment (Modem) When the Modem is Provided as an Integral Part of the Equipment Governed by this Standard. (1) Sig- nal Impedance. All inputs and outputs shall be balanced 600 52 +-lo% whenever signal rates require standard voice grade channels.

(2) Signal Level. Input (receive) levels may range down to -30 dB (ref 1 mW) and output (transmit) levels shall not exceed 0 dB (ref 1 mW). The output level and receive sensitivity should be adjustable in at most 4 dB steps.

(3) Signal Stability. All inputs and outputs shall be stable within k1 dB for at least one month without adjustment.

(4) Signal Linearity. The output (transmit) shall be linear within 41 dB over the level range and frequency allowed. Input (receive) linearity and delay distortion are not defined and should be specified for each channel type and data rate required.

(5) Signal Distortion. All inputs and outputs shall not contain rms harmonics that exceed 2% at dBm (ref 1 mW) whenever signal rates require standard voice grade channels.

(6) Signal Carrier. Specify center frequency and bandwidth. 5.4.3 Master/Remote Communication Inter-

face. The data communication between master- and remote-station equipment shall utilize an

27


MESSAGE ESTABLISHMENT

DEFINITION, SPECIFICATION. AND ANALYSIS OF SYSTEMS USED FOR

INFORMATION MESSAGE TERMINATION IDATAOR CONTROL)

orderly communication protocol defined in terms of message standards. Message standards shall be defined in accordance with the general format described below. Message format segments shown below apply to both fixed and variable length message standards.

The message establishment segment includes signals required to synchronize data communication equipment and address station equipment.

The information segment includes signals associated with point addresses, point data values, commands, and other codes that are used by station equipment.

The message termination segment includes signals used for message security and end-of- message purposes by station equipment.

The order of data transmission (least or most significant bit first), the signal states (mark, center, space), and the state values (mark = 0 or 1) shall be specifically defined by the supplier.

To exchange information, one station sends a message to another station, which in turn responds with an appropriate message. If an error is detected in either message, that part of the message, or the message sequence, may be repeated one or more times. A message transmission is complete when both the initial message and reply message have been received without error.

5.4.4 Channel Considerations. The loading of communication channels by equipment govem- ed by this standard shall be calculated as described in 5.4.4.1 to establish the adequacy of the channel configuration. Channel load factor is defined as the percent of channel capacity in bits per second required to support the effective data rate for information exchange (see 5.4.4.1).

It is recommended that for fully expanded remote terminal units the calculated channel load factor for routine data and control transactions be less than 67%, preferably less than 50%, to provide adequate spare channel time for additional control actions, and for future expansion of remote station points. To minimize the frequency of transaction failures due to channel errors, it is recommended that no transactions be used which contain more than

approximately 250 channel bit times. Approx- imately 2.5% of such long transactions will fail when a channel is operated at a bit error rate of one error in lo4 bits. Automatic repetition (that is retry) of transactions which fail may be implemented but should be limited to no more than three consecutive retries. If the transaction is not completed satisfactorily at the fourth attempt the channel, or relevant remote station, should be declared at least temporarily inoperative.

A complete list of all necessary routine data acquisition and control transactions should be prepared for each communication channel. Routine in this context implies repetitive at some fixed time interval; for example, 2 s or 10 s, though transactions which occur at relatively long intervals, hourly or daily, may be ignored. Where report-by-exception data acquisition techniques are employed , realistic assumptions for the average number and length of exception transactions during the routine updating interval shall be made. The total channel time required to service this routine transaction list should be calculated using vendor data concerning the characteristics of the protocol, characteristics of the equipment, the intended channel data rate, and the channel configuration, that is, 2- or 4-wire, dedicated or party-lined.

5.4.4.1 Channel Calculations. The utilization of communication channels by equipment that provide automatic retransmission of messages received in error shall be computed as defined below.

The value of C, should be computed for the actual data at each remote station communication channel (dedicated or party-line). These values can then be compared with the desired polling rate for remote stations to determine the adequacy of

(1) Message format (2) Channel speed (3) Party-line channel configurations

NC C, = - the effective data rate for information

TM bits with a given overhead NH and channel error rate CBE

(Eq 1) To bound the channel utilization for message

standards that support variable length messages, the channel utilization shall be computed for the minimum and maximum length messages.

28


NC + N H TM = TL +-

S

NC +") & TR = total turnaround time on the channel

when a retransmission is required (TR may not equal TL)

TM = mean time required to complete a

C, = effective date rate in bits per second + ( T R c s message transmission

(Eq 2) where

-- 1 - P M

5.5 Man/Machine. The man/machine interface (MMI) is defined as the operator contact with -pp,f + p M 2 + p M 3 + " * + P M N P M

_._ equipment governed by this standard. In this section the standard applicable for the operation of the man/machine interface is defined.

is the sum of the message retransmission prob- abilities.

NOTE

TL

S CBE

= number of information bits contained in the message

= number of housekeeping bits. This shall include the message establish - ment, and message termination bits, the total bits in the response message that indicate a successful or unsuc- cessful transmission and any bits in the information segment that do not carry information

:: A message contains (Nc + N H ) bits.

= channel turnaround time. This shall include the round trip propagation delay, modem turnaround time, and equipment turnaround time by both the sender and the receiver of the message

= data rate in bits per second , = bit error rate of the channel (channel

utilization should be computed for

= probability of error occurring that will cause one or more automatic single retransmissions (depends upon message length and CBE)

various C B E )

(Nc + N H ) CBE - 0.5 (Nc + NH) (Nc + NH - 1) CBE2

MILSTD-1472C-1981 [ 471 is recommended as a reference for use in the design and evalua- tion of the man/machine interface to equipments governed by this standard. Alternative human engineering data may be specified by the user. The man/machine interface for operation concerns standards and recommendations for information displays, control capabilities, colors, and man/machine interaction of equipment governed by this standard.

5.5.1 Information Displays. Characters used by printers, loggers, and illuminated displays shall have unique codes so that their display may be electrically initiated. The uppercase alphanumeric characters and their corresponding codes as defined in ANSI X3.4-1977 [3] shall be used to represent alphanumeric data at the man/machine interface. A minimum set of character graphic symbols is recommended in Table 8.

5.5.2 Control Capabilities. The capabilities provided for operator inputs at the man/ machine interface are defined as the control capabilities. The control capabilities may include a combination of

(1) Keys and switches (alphanumeric or function, or both)

(2) Cursor (track ball, joy stick, or key controlled)

for (3) Light pen (4) Poke points (defined crt displayed con-

trol selections) The operator's input to the MMI equipment

for example, (60 + 40) (60 + 40 - 1)

- 0.5 (60 + 40) shall be recognized and acknowledged (valid or invalid) to the operator within 2 s.

When labeled function pushbuttons are included in equipment governed by this standard, the labels shall be legible from a distance of approximately 1 m in the user specified envi-

PMN = probability of N or more automatic ronment. When lighted pushbuttons are included, the significance of the state of the light

= 0.09595

PM2 = probability of two or more automatic retransmissions

retransmissions

29


Table 8 Recommended Electrical Graphic Symbols and Meanings

Svmbol Meaning Symbol Meaning Symbol Meaning

r e 0

0

CORNER, UPPER LEFT

GENERATOR

OPEN BREAKER

CLOSED BREAKER

OPEN DISCONNECT

CLOSED DISCONNECT

TRANSFORMER

TRANSFORMER

CA PAC ITOR

CAPACITOR

CORNER, LOWER LEFT

LINE, VERTICAL

LINE, HORIZONTAL

LINE, CROSSOVER

L INE JUNCTION

L INE JUNCTION

L INE J U NCTl ON

L INE JUNCTION

LINE/BUS JUNCTION

L INE/BUS JUNCTION

L INEIBUS JUNCTION

L lNE lBUS JUNCTION

CORNER, UPPER RIGHT

BUS

FLOW UP

FLOW DOWN

FLOW LEFT

FLOW RIGHT

BUS

GROUND SWITCH

GROUND SWITCH

GROUND

CORNER, LOWER RIGHT

(on, off, blinking) shall be clearly defined and shall be consistent throughout the system.

Control pushbuttons (for example, raise, lower, trip, open, and close) shall be within convenient viewing distance of the information display that will be used during the control operation.

5.5.3 Color Codes. The standard meanings for colors (for example, crt's, status lights) used at the operator interface to highlight the condition of apparatus monitored and controlled through equipment governed by this standard should be defined by users.

The significance of colors shall be consistent throughout the system.

The color status of an apparatus under operator control shall only change to its new state after the status of the apparatus has changed.

5.5.4 Interactive Dialog, The activity at the rnan/rnachine interface during operational use of equipment governed by this standard shall be clearly described and shall be consistent throughout the system.

5.5.5 Alarms. When alarm conditions detected by equipment governed by this standard are first interfaced to the operator both

an audible (voice, tone, or bell) and visual (flashing light or symbol) annunciation should be presented. It should be possible to silence the audible alarm without affecting the visual annunciation. The visual indication of each alarm condition should remain as long as the alarm condition exists.

5.5.6 Dialog During Control. The selection of a point for an operator control action shall result in a visual feedback at the man/machine interface. This positive feedback to the operator shall signify that the equipment governed by this standard is ready to accept a control action. The results of the control action (check-back-before-operate or direct operate) shall be displayed only after a status change has been received from the remote equipment.

6. Environmental Conditions

This section contains a definition of the environment in which equipment governed by this standard is required to operate.

30


There are unusual conditions that, where they exist, should receive special consideration. Such conditions should be brought to the attention of those responsible for the application, manufacture, and operation of the equipment. Devices and apparatus for use in such cases may require special construction or protection. The user should specify those special physical requirements that apply to specific locations. Examples are:

(1) Damaging fumes or vapors, excessive or abrasive dust, explosive mixtures of dust or gases, steam, salt spray, excessive moisture, or dripping water

(2) Abnormal vibration, shocks, or tilting (3) Radiant or conducted heat sources (4) Special transportation or storage condi-

(5) Unusual space limitations (6) Unusual operating duty, frequency of op-

eration, difficulty of maintenance (7) Altitude of the operating locations in ex-

cess of 2000 m (6600 f t ) (8) Abnormal electromagnetic interference

tions

6.1 Environment 6.1.1 Ambient Temperature and Humidity

Conditions. Ambient temperature and humidity are defined as the conditions of the air sur-

rounding the enclosure of the equipment (or the equipment itself, if it uses open rack construction) even if this enclosure is contained in another enclosure or room.

For temperature and humidity parameters by operating location, see Table 9. Table 9 is a guideline to establish five equipment classifica- tion groups. Equipment designated to be in a specific group shall meet all conditions set forth in that group.

Equipment subjected to temperature and humidity variations outside of the first four group classifications listed in Table 9 will require special consideration. Methods to resolve these problems include

(1) Low Temperature. Use a thermostatically controlled heater strip in the cabinet enclosure or use wide temperature range equipment.

(2) High Temperature. Use asun shield,utilize some other cooling method, or use wide temperature range equipment.

( 3 ) High Humidity. Use heater strips, special shelters, or fungus proof the electronic components. (4) Low Humidity. Use a humidifier to main-

tain acceptable humidity levels. ( 5 ) Temperature Restrictions. If it is neces-

s a r y to use heating/cooling equipment to meet the parameters set forth in Table 9 the equip-

Table 9 Operating Temperature and Humidity by Location

Humidity Temperature Allowable Rate Operating Range Operating of Change of

Equipment Typical Location (Percent Range Temperature Group of the Equipment Relative Humidity) (“C) (“C/h)

In a building with air- conditioned areas

In a building with air- conditioned areas

In a building with heating or cooling, but without full air- conditioning

In a building or other sheltered area without special environmental control

Outdoors or location with wide temperature variations

(5 ) Extremes outside the above

( l ) ( a )

(I)@)

(2)

(3)

(4)

40 to 60 +20 to +23 5

30 to 70 +15 to +30 10

10 to 90 + 5 t o +40 without condensation*

10 to 95 without condensation*

0 to +55

10 to 95 without condensation*

-25 to +60

10

20

20

User to specify User to specify User to specify (see 6.1.1) (see 6.1.1) (see 6.1.1)

*Maximum wet bulb temperature of 35 “C.

31


ment should be so marked by a warning sign and a warning statement in the associated documentation.

6.1.2 Dust, Chemical Gas, and Moisture. Sup- pliers shall be made aware of the presence of atmospheric pollutants, so that special provisions for protection can be made where necessary.

In Groups (l), (2), and (3) of Table 9, all equipment cabinets that are vented should have dust filters. In Groups (3) and (4), equipment that is exposed to moisture, corrosive or explosive gases, or other unusual environmental conditions should have a special enclosure. Available types of enclosures for various conditions are specified in ANSI/NEMA ICs 6- 1978 [26].

Consideration should be given to possible contamination inside the enclosure during storage and transit, and also when the enclosure is opened for maintenance or repairs.

6.1.3 Altitude. The equipment shall be suitable for operation at altitudes up to at least 2000 m (6600 ft).

6.2 Vibration and Shock 6.2.1 Operation. Where equipments governed

by this standard will be subjected to vibration, or shock, the user shall express the local vibration environment as any combination of one peak-to-peak displacement amplitude value and one acceleration value over a specified frequency range.

The relationship of frequency of oscillation f, the peak of acceleration a, and the peak-to- peak displacement s is defined by the formula

Four classes are listed as examples of this relationship in typical locations.

Frequency Acceleration Class (Hz) (m/s2) (e) Location

Level I 1-60, 5-200 5 * 0.5 control rooms

Level I1 5-200, 10-500 10 f 1.0 field Level I11 10-500 20 * 2.6 field Level IV 10-10 000 50 2 5.0 field

Source: IEC TC 65-1976 [43 ] , Operating Conditions, Part 111, Mechanical Influences.

Shock phenomena which may occur during manhandling for operation and maintenance of equipment shall be expressed in terms of an equivalent height of fall.

mm Treatment (hard surface) 25 Light handling 50

100 Normal handling 250 Normal handling, heavy material

Light handling, heavy material (> 10 kg)

1000 Rough handling 1500 Rough handline. heaw material Source: IEC TC 65-1976 [43] , Operating Conditions, Part 111, Mechanical Influences.

6.2.2 Transportation. Special care shall be used in the transportation of equipment. The equipment shall be packaged and braced so as to prevent damage during transit. Items such as swinging panels shall be strapped and blocked to minimize stress on the hinges.

All equipment governed by this standard shall show no degradation of mechanical structure, soldered components, plug-in components, or operation after shipping.

6.3 Seismic Environment. The purpose of this section is to describe the analytical and test criteria for qualification of equipment that are specified by the user to operate in an environment subject to seismic disturbance. The user shall supply during system development information that will allow the supplier to make a seismic equipment analysis and submit an equipment seismic report.

6.3.1 Seismic Equipment Analysis. The user should supply a response spectrum in the form of frequency versus amplitude for the location site of the equipment to be installed. Alter- nately, the user may supply information as listed below on which the supplier is to base the analysis

(1)Earthquake reports, which can be furnished by the California Institute of Technol- ogy, Earthquake Engineering Laboratory, Pasa- dena, CA

(2) Data pertaining to typical foundations and soils

(3) A study of the support structures 6.3.2 Equipment Seismic Report. The follow-

ing information is typically required as part of an equipment seismic report.

6.3.2.1 An outline drawing of the equipment locating the centers of gravity, weights of major components, and the location and size of holddown bolts.

6.3.2.2 The maximum vertical and horizontal forces and the upsetting moments which the foundation shall be capable of re- sisting.

32


6.3.2.3 The portion of the equipment that requires an integral pad, and the portion(s) which may be mounted on independent foundations.

6.3.2.4 An outline drawing of the equipment showing the expected maximum displacement of electrical terminals and other points of interconnection between the apparatus and other equipment.

6.3.2.5 The fundamental natural frequencies and samping data.

6.3.2.6 An analysis and description of the probable modes of failure. Maximum working stresses should also be included in the analytical data furnished.

6.3.2.7 The ductility factors used should be indicated in the analytical data furnished.

6.3.2.8 Satisfactory connections between isolated and nonisolated apparatus should be proposed.

6.3.2.9 A description and results of the dynamic analysis used.

6.3.2.10 A description of the test method that has been used to determine the natural frequencies and results of damping of the apparatus together with the static analysis, when a dynamic analysis is not applicable.

6.3.2.11 A summary of the results of an explanation of the seismic proof test procedures. See ANSI 224.21-1957 (R 1971) [6] and ANSI/IEEE Std 344-1975 (R 1980) [24].

6.4 Lightning Protection. The purpose of this section is to describe design criteria and recom- mend practices that will minimize the adverse consequences of exposure to lightning dis- charges. Effective protection can only be accomplished through a combination of adequate design and proper installation.

6.4.1 Design Criteria. The basic design goal for achieving protection from lightning should be that of keeping any abnormal voltage or current, or both, out of the equipment cabinets.

6.4.1.1 Where data paths are connected to equipment through cables which may be exposed to voltage surges such as induced by lightning surges, protection shall be provided at the cabinet input terminals to reduce the probability of damage to the equipment. A minimal amount of protection may be determined by applying a surge withstand capability test as outlined in ANSI/IEEE C37.90.1-1974 (R 1979)

6.4.1.2 Lightning surges can enter the cabi- P I *

net and cause damage despite the protection provided on inputs and outputs. Equipment failures resulting from such damage should be fail-safe. Logic designs should be such as to minimize the possibility of false or improper operation of field devices. Partial failures which do not disable the equipment but which can reduce or eliminate security features, such as error checking in communication circuits, should be detected and cause the blocking of control outputs to prevent false operations of field devices.

6.4.2 Installation Criteria. The basic installation goal for achieving protection from lightning should be to minimize the exposure of all connecting wires and cables to lightning.

6.4.2.1 Power, signal, and communication circuits provide the path through which lightning surges enter equipment. Circuits totally within a protected building can generally be installed without regard to lightning effects. Circuits that are connected to, or are part of, circuits not within a protected building should be installed in a manner that will minimize exposure to lightning.

6.4.2.2 When installation constraints result in a high degree of exposure to lightning, sup- plementary protection such as spark gaps or surge limiters should be considered. See ANSI/ IEEE Std 422-1986 [25] and IEEE Std 525- 1978 [44].

6.5 Acoustic Interference Limitations. The equipment to be installed in the same vicinity as operating personnel, or in an environment where maintenance personnel will be required to perform their duties, shall not produce any acoustic levels in excess of those specified in this subsection. The acoustic energy shall be controlled to the extent that it does not cause personnel injury, fatigue, or interfere with voice communication. Noise generated by equipment shall not exceed NC-30 for control room installations and NC-45 for maintenance area installations as shown on Fig 7 .

6.6 Electromagnetic Interference (emi) and Electromagnetic Compatibility (emc). Manu- facturers shall design and test their equipment to ensure that emi limits are not exceeded, and users shall design and test locations (environments) to ensure that emc limits are not exceeded. Both manufacturers and users should

33


375 75 150 300 600 I200 2 4 0 0 4 8 0 0 75 150 300 600 1 2 0 0 2 4 0 0 4800 9600

OCTAVE BAND (Hz)

63 125 2 5 0 500 1000 2000 4000 8000

OCTAVE BAND, CENTER FREQUENCY ( H z )

Fig 7 Noise Criteria (NC) Curves for Speech Communication

(Reprinted from MIL-STD-1472 C-1981 [47] )

follow EIA EMC B1-1968 [27], EIA EMC B-2 1968 [28], EIA EMC B3-1968 [ 291, EIA EMC B4-1965 [30], EIA EMC B5-1964 [31], EIA EMC B6-1967 [32], EIA EMC B7-1966 [33], EIA EMC B8-1965 [34], EIA EMC B9-1966 [35], and EIA EMC B10-1967 [36] to aid in specifying and applying various techniques which limit equipment and environmental emissions.

6.6.1 EM1 Limits. Equipment shall not generate radiated emissions in excess of (1 V/m)/MHz as measured 1 m from the enclosure. Manufacturers shall mechanically and electrically design equipments for emission limits by employing attenuation techniques such as isolation, shielding, grounding, gasket- ing, filtering, and bonding.

6.6.2 EMC Limits. Equipment governed by this standard shall be capable of operating in radiated fields as specified by the user. In- formation available to date indicates that the average field strength in substations may run

in the order of (1 V/m)/MHz (see NOTE below). Should the field strength of a proposed installation be excessive the user shall mechanically and electrically design the equipment location for conducting susceptibility limits by using cable shielding and grounding techniques found in

(1) At power generating stations, ANSI/IEEE Std 422-1986 1251 should be followed.

(2) At substations, IEEE Std 525-1978 [44] should be followed.

(3) At other locations, the equipment manufacturer’s guide for site preparation and installation should be followed.

NOTE: The specified value of ( 1 V/M)/MHz refers to broadband radiated fields due to station environment, resulting from such things as corona and switching transients. This requirement is not intended to cover narrowband radiated field sources such as electronic test equipment or portable radio transmitters. Where such equipment may be used, the field strength is properly expressed as volts per meter at a specified frequency, and different emc limits may be required.

34


6.6.2.1 Whenever equipment is to be located in an environment and is susceptible to radiated emissions which are excessive (see NOTE in 6.6.2(3)); then either

(1) The manufacturer should shield from radiated sources with an enclosure which provides the necessary attenuation, or

(2) The user should provide additional structural attenuation. The approach taken should be an economic one which considers the location’s configuration, the signal range of interest, and the amount of additional field strength encountered.

6.6.2.2 Equipment which is extremely sensitive to magnetic fields should be stored in environments that limit magnetic flux density. Typical storage limitations for magnetic tape and disk units are in the range of (50 to 70) T.

7. Characteristics

The equipment governed by this standard shall have the characteristics defined and discussed in this section. The characteristics of concern include reliability , maintainability , availability, security, and expandability . 7.1 Reliability. Reliability is defined herein as a measure of an equipment’s or system’s ability to perform its intended function under specified conditions for a specified period of time. It is a probability figure, based on failure data and length of operating time. The reliability of system components is reflected in their respective mean-time-between-failures (MTBF) numbers. This figure o f merit is used in the calculation of the system availability as defined in 7.3.

The design goals for equipment shall be (1) A single component failure anywhere in

the system should not result in a critical failure (for example, false operation of an external device).

(2) To protect against multiple and cascading component failures.

Reliability models and predictions may be made by the supplier in accordance with the guidance contained in MIL-HDBK 217D-1982 [45] , or in Reliability, Management, Methods,

and Mathematics [49] , or as directed by the user.

Failure distributions show the manner in which failures are distributed as a function of time. The supplier of equipment covered by this standard should maintain failure distribution data for all components, assemblies, and units that by their failures can cause critical or major failure of the system, or both. Failure distribution data for equipment in the posses- sion of the supplier and for those field units for which data are available should be documented and be made available for review upon request.

Manufactured or vendor procured parts, or both, and components that can cause a critical or major system failure are subject to these requirements.

The failure modes of equipment governed by this standard and the effects of failures shall be studied by the supplier. The results of the supplier’s failure modes and effect analysis shall be available for review upon request.

7.2 Maintainability. Equipment covered by this standard shall be maintainable by trained personnel at a service facility and in the field.

The maintainability of equipment is reflected in their respective mean-time-to-repair (MTTR) numbers .

The supplier shall be responsible for provid- ing upon request a list of test equipment and quantities of replacement parts deemed necessary to meet the availability and MTTR requirements. In establishing the number of parts, the supplier shall take into consideration the time required to return a failed component (field or factory maintenance, or both) to a serviceable condition.

The MTTR values used by the supplier in his availability computations should be based to the maximum extent possible upon maintenance experience. MTTR values may include

(1) Administrative Time. The time interval between failure of a component and a call for maintenance service.

( 2 ) Transport Time. The time interval between the call for maintenance service and the arrival at the station of a maintenance technician and the necessary replacement parts.

( 3 ) Repair Time. The time required by a trained maintenance technician having the replacement parts and the recommended test equipment at the station to restore normal operation of the failed equipment.

35


Unless otherwise specified by the user, the supplier shall use the following values in his availability calculations:

MTTR (administrative time) 0 h MTTR (transport time) 0.5 h

When insufficient maintenance experience has been accumulated to provide MTTR values, then the appropriate segments/procedures as defined in MILSTD 471A-1973 [46], may be used.

Provisions to enhance the maintainability of equipment governed by this standard should include

(1) Equipment self-tests, diagnostics, and trouble shooting procedures to localize any failure or malfunction to the lowest field re- placeable unit level.

(2) Readily accessible test or break points, or both, to facilitate fault isolation. The placement of components on cards shall allow access for test probes and connectors.

(3) Suitable grips or handles to facilitate the safe removal and installation of heavy or bulky units.

(4) Physical provisions to preclude interchange of units or components of a same or similar form that are not in fact interchange- able.

(5) Physical provisions to preclude improper mounting of units or components.

(6) Provisions (for example, labels) to facilitate identification and interchange or inter- changeable units or components.

(7) Measures to ensure that identification, orientation, and alignment provisions include cables and connectors.

(8) Positive identification of groundable

(9) Where screwdriver adjustments shall be made without visual aid, mechanical guides for the screwdriver shaft should be provided or the screw should be mounted so that the screwdriver will not move out of position.

(10) Sensitive adjustment points should be located or guarded so that adjustments will not be disturbed inadvertently.

(11) Internal controls should not be located close to dangerous voltages or any other haz- ards. If such location cannot be avoided, the controls should be appropriately shielded and labeled.

(12) The preventive maintenance program should minimize wear-out failures.

parts.

(13) The provision for simulation of equipment that is physically remote from the equipment under test.

7.3 Availability. Availability is defined as

A = uptime/(uptime + downtime) (Eq 3) Downtime in the above equation normally

includes corrective maintenance, preventive maintenance, and system expansion downtimes if such times compromise the user’s ability to operate apparatus normally controlled by the equipment being expanded.

For design analysis and to determine an a priori prediction of availability for subassemblies and units, the following equation utilizing MTBF and MTTR shall be used:

A, = MTBF/(MTBF + MTTR) (Eq 4) where

A, = predicted availability of a component.

The equation for A, and the combinatorial equations9 associated with parallel redundant components (or subsystems) are valid under the following conditions:

(1)The failure of any component within a string or parallel set is independent of the failure of any other component. In other words, component failures do not propagate failures of other components.

(2) Sufficient repair facilities and standby replacement parts are available to handle multiple simultaneous failures.

Because calculations for availability are made with mean values, the sensitivity of the equipments design to variations to MTBF and MTTR should be ascertained. It is recommended that equipment availabilities be computed for +25% and k50% variations in both MTBF and MTTR.

Equation 3 for availability shall be used to compute the availability of installed equipment governed by this standard. The equipment’s operating and maintenance records shall be used to support the computations.

The impact of the outage of each system element or function on the availability of the total system should be mutually agreed upon between the user and the supplier.

9Combinatorial equations for modeling more complex designs should be formulated by the supplier as discussed in 7.1.

36


Availability test results should be calculated separately for major system components, (for example, central computer configuration and data acquisition remotes), because different definitions of downtime are applicable, and these components may have a varying impact on the usefulness of the system as a whole.

Major component downtime should be defined so as to reflect the proportional significance of the equipment that is down. For example, downtime for the data acquisition system could be defined as the sum of the downtime for all remotes divided by the total number of remote stations. At the master station, downtime should not include malfunctions in electromechanical peripheral equipment that do not detract from the functional capabilities of the master station as a whole (for example, line printers, card readers, and punches).

Typical availabilities achievable by nonredun- dant commercial grade equipment range from 99.99% for individual simple devices to approximately 97% for complex, computer-based subsystems. Proper use of redundant equipment configurations combined with automatic failure detection, and fail-over control can provide an overall availability of critical system functions of 99.9%, with average downtimes of less than a few minutes per day.

7.4 System Security. The security of operation of equipment governed by this standard is defined as the ability to recognize an inappropri- ate or undesirable operation or condition in such a fashion that causes an appropriate alarm, a nonoperation, or both.

Security of operation considerations are divided into three areas

(1 ) Operating practice and procedures (2) Communication security (3) Hardware, software, and firmware design 7.4.1 Security features that fall into the op-

erating practice and procedures area include the use of manual or automatic function, or both, and operating checks for each uniquely different function or capability of the system. Function and operating checks may include

(1) Analog function check (0 and 90%) (2) Control function check (loop-back) (3) Scan function check (loop-back) (4) Poll function check (5) Logging function check (6) Queue overflow alarms

(7) Diagnostic aids (8) Calibration checks An alarm should be generated whenever an

event or function has automatically or manually been disabled.

An alarm shall be generated when any device fails. The operation of any automatic or manual switchgear feature shall be logged or otherwise brought to the operator’s attention.

Security features of equipment designed for the control of power system apparatus shall include both a select-beforeexecute man/ machine interface sequence and a checkback- beforeaperate communication sequence. The man/machine interface sequence should provide visual feedback to the operator of the selection, so that he can verify that the system has interpreted his intention correctly before he executes the control function. The communication sequence checkback message should be derived as a minimum from the remote station point selection hardware, and not just a simple retransmission of the select message. In this way, the checkback message not only veri- fies that the communication was error free, but also that the remote station hardware has acted correctly in interpreting the control selection.

The communication checkback sequence can either be performed concurrently with the control selection sequence at the man/machine interface, or it can be performed after the selection sequence has been completed. When performed concurrently, the selection of a point for control should cause the select message to be transmitted to the remote station. Upon successful receipt, the remote station should arm itself for control, generate the check-back message, and transmit it back to the master station. A valid checkback message should generate the visual selection feedback to the operator, who can then choose either to execute or cancel the control function. If status and data scanning of that remote station are interrupted during this sequence, the system should disarm the control function after a specified period and reinitiate scanning of that remote station.

When the man/machine interface sequence and communication checkbacks are performed sequentially, the selection of a point for control should cause the master station logic to inter- pret that selection and generate a visual indication of that selection for him to verify. He may then execute the control function, at which time the status and data scan should be inter-

37

ANSI/IEEE C37.1-1987 DEFINITION, SPECIFICATION. AND ANALYSIS OF SYSTEMS USED FOR

rupted, and a select message sent to the remote station. The remote station should then arm the control function and generate the checkback message. The checkback message should be automatically checked by master station logic and, if it is valid, an execute message should be automatically sent to the remote station. If this message is valid, the remote station should execute the command and return an acknowledgement to indicate that the function has been performed. If the next message received after a valid select message is not a valid execute, the control selection should be disarmed. If the select message results in an invalid checkback, the execute message should be aborted. A variable number of select messages may be tried prior to generating an alarm message.

7.4.2 Security features that fall into the area of communication security include

(1) The design goal of equipments governed by this standard shall be such that an error in a message shall not result in a critical failure of the system.

(2) A positive indication shall be available when a remote station did not receive or respond to a valid message. When an attempt to communicate has failed, the transmitting station should be able to automatically retry the message until a retry count is exceeded. When the retry limit for a particular channel is exceeded, an appropriate alarm should be issued.

( 3 ) Error control shall be applied to digitally encoded message traffic on communication channels between master and remote stations to minimize the probability of undetected errors. Error control in concert with the communication protocol and line discipline should ensure that the probability of undetected bit errors is no greater than 10-lo when the channel is operating within the limits of < 1 bit error in lo4 bits. (4) The proper operation of communication

channels should be verified on a regular basis by normal use or by a test message on the circuit to verify its operating status.

(5)The use of party line or switched communication channels, or both, should be care- fully defined so that two remotes with the same address do not share the same communication channel.

7.4.3 Security features that fall into the area of hardware, software, and firmware design include

(1) Power failure and automatic restart (2) Initialization and reinitialization (3) Equipment self-check capabilities with

(4) Automatic switchover with alarm ( 5 ) Internal (watchdog) timer with alarm (6) Fail-safe operation (7) Nonvolatile station addresses at remote

alarm

stations

7.5 Expandability. The measurement of expandability of equipment governed by this standard is the ease with which new points or functions, or both, can be added to the system, and the amount of downtime required to ex- pand station equipment.

Expandability categories are defined as follows:

(1) Point, Spare. Point equipment that is not being utilized but is fully wired and equipped

( 2 ) Point, Wired. Point for which all common equipment, wiring, and space are provided, but no plug-in point hardware is provided

(3)Point , Space Only. Point for which cabinet space only is provided for future addition of wiring and other necessary equipment.

Expandability limits may include but are not restricted to the following considerations:

(1) A limit for master- or remote-station point or memory capacity (addresses or size, or both) preventing the addition of more main memory or point equipment.

(2) A limit relating to the use of routines, addresses, labels, or buffers so that a modifi- cation reduces system capabilities.

( 3 ) A data rate (for example, communication channel) limit so that the scan or polling cycle is extended when additions are made at the remote stations. (4) Design and environmental limits on

components (for example, analog to digital converters) so that equipment operation is compromised if the interface is modified or the device relocated.

7.6 Changeability. The measurement of changeability is defined as the ease with which existing point parameters or existing remote terminal configurations may be changed at both the master station and remote station. Point changeability is defined as follows:

(1) Point descriptions as presented to the system operator

(2) Analog point engineering unit scaling changes

38


(3) Analog point limit changes (4) Analog point limit dead-band changes (5) Output relay timing changes 7.6.1 Reconfiguration of an existing remote

terminal is defined as follows: (1) Addition of points not originally provided

for within the master-station data base for an existing remote terminal

(2) Rearrangement of types of points within the master-station data base for an existing remote terminal

(3)Make the necessary software changes to relocate a remote terminal such as different communication port addresses, and remote terminal addresses.

7.6.2 Changeability limitations may include but are not limited to

(1) Point parameters that have to be periodically changed reside on permanent type memory devices such as read only memory

(2) Restrictions caused by master-station data

(3) Hardware/software compatibility

(ROM)

base structure

(4) Hardware limitations ( 5 ) Software operating system

8. Marking

The equipment and major

limitations

subassemblies governed by this standard shall be suitably marked as necessary for safety and identification.

8.1 Identification. Each equipment shall be identified so that it can be easily correlated with the documentation. The means of identification shall be uniform throughout the system, and it might include color coding, labeling, and part number. The identification mark shall be permanently affixed to the part that it identifies.

8.2 Nameplates. Each separate unit of the system shall be furnished with nameplates bearing the following information: manufacturer’s name, address, identification reference, rated voltage (ac or dc, or both), rated continuous current, and rated frequency (if necessary). Nameplates shall be legible at a distance of approximately 1 m.

8.3 Warning. Warning signs or safety instruc-

tions shall be applied where there is a need for general instructions relative to safety measures (for example, supply circuit).

9. Tests and Inspections

The purpose of this section is to describe the tests and inspections recommended to ensure that equipment governed by this standard will perform reliably and correctly. 9.1 Stages of Tests and Inspections. The test and inspection process requires that various parameters of the equipment be tested orveri- fied during one or more stages in the production and installation cycle of the equipment. This process can be illustrated as in Table 10.

Across the top of the table are shown the three major classes of tests and inspections: interface, environmental, and performance. The three stages of test and inspections are shown along the left-hand edge of the table, certified design, factory, and field. The specific tests and inspections in each class are listed in the body of the table, below the class heading. Tests that are recommended for all types of applications are listed, without marking, in the stage in which they can be most economically performed.

In some cases (for example, temperature, SWC) it might also be appropriate to perform these tests in other stages. Such tests are listed under the appropriate stages and are marked with an asterisk to indicate that they are optional, to be performed only when specified by the purchaser. Other tests (such as emi, seismic, and availability) are not recommended for all applications, but may be appropriate for some. These are marked with a dagger and are optional.

9.1.1 Certified Design Tests. These are tests performed by the vendor on specimens of a generic type of production model equipment to establish conformance with this standard. The conditions and results of these tests should be fully documented and certified so that they can be accepted in lieu of factory or field test.

9.1.2 Factory Tests and Inspections. This stage includes the inspection and approval of interface drawings prior to fabrication of the equipment, and all functional tests and inspec-

39


Table 10 Test Stages and Classes of Tests

Classes of Tests

Interface Environmental Performance Tests and Tests and Tests and

Test Stages Inspections Inspections Inspections

Certified Power Input Temperature design swc Humidity tests Dielectric Acoustic?

tests and Power Input* Humidity* Communications inspections SWC* Altitude/ Man/machine interface (MMI)

Factory Mechanical Temperature* Point Checkout

Dielectric * Pressure? Special Functions Dust? Acceptance? Electro- Bum In?

Shock and

Seismic$

magnetic?

Vibrations?

Field Point Checkout* tests and Communications* inspections Manlmachine interface* (MMI)

Special Functions* Availabili ty? Acceptance*

*Can also be performed in other stages. $Not recommended for all applications, but may be appropriate for some.

tions performed on the actual equipment to be supplied to the user prior to the shipment of that equipment from the vendor’s facilities. The factory tests should be designed to demonstrate as completely as possible that the equipment will perform correctly and reliably in its intended application. Factory tests may also include tests to verify some or all of the results of the certified design tests.

9.1.3 Field Tests and Inspections. Field tests and inspections are performed on the equipment after it has been shipped from the vendor’s facilities. These include preinstalla- tion inspections and tests to ensure that it has not been damaged during shipment, and post- installation tests to verify that it performs its functions reliably and correctly.

9.2 Interface Tests and Inspections. These tests are designed to demonstrate that the various mechanical and electrical interfaces to the equipment are in accordance with applicable portions of Section 5 , together with other applicable parameters called out in the user’s specifications, and will result in safe, correct, and reliable installation and operation of the equipment. For the most part, these interface parameters can either be demonstrated during

factory tests or accepted on the basis of certified design tests.

9.2.1 Mechanical. Mechanical characteristics (for example, materials, workmanship, dimen- sions, fabrication techniques, and finishes) should be verified through visual inspections and comparisons with applicable drawings.

9.2.2 Electrical. These tests include all those to be performed on electrical interfaces to the equipment, with the exception of those related to the functional performance of the equipment.

9.2.2.1 Power Source. Power inputs to the equipment should be tested to demonstrate that the equipment can operate throughout the range of the specified power source.

9.2.2.2 Surge Withstand Capability (SWC). All inputs and outputs to the equipment exposed to a substation electrical environment, unless otherwise specified, shall conform to

Surge withstand capability shall be verified during the certified design test stage or the factory test stage, or both. See Fig 8.

9.2.2.3 AC Dielectric Tests. The equipment covered by this standard shall be capable of withstanding a high-potential test. The purpose of this test is to verify the dielectric strength of

ANSI/IEEE C37.90.1-1974 (R 1979) [12].

40


POWER S O U R C E

S T A T U S C O N T R O L O U T P U T S

S T A T U S AUTOMAT IC I N P U T S

SU P E R V ISORY EOU I PMENT

I

ANALOG O U T P U T S

N O T E (2 )

N O T E (1)

f f 0 DENOTES I N T E R C O N N E C T I O N C O M M U N I C A T I O N

P O I N T C H A N N E L 0 D E N O T E S T E S T P O I N T

NOTES: (1) SWC for analog inputs is normally provided by the transducer. However, when the transducers are located a considerable distance from the equipment governed by this standard it may be appropriate to test for SWC at the input to the analogmulti- plexor. When tested in this manner, the transducer outputs may be disconnected from the equipment and the input terminated in an equivalent impedance.

(2) SWC on the communication channel is limited to common mode only. If the communication channel is disconnected, the modem terminals should be terminated in an equivalent impedance.

Fig 8 Typical Surge Withstand Capability (SWC) Test Points

the insulating materials used in those parts of the equipment exposed to hazardous voltages.

The test shall be applied between all incoming and outgoing terminals and chassis ground. During the test, communication, power supply, and status and data input and output equipment that are not expected to withstand the test voltage may be disconnected from the wiring leading to the terminals. Control output end elements, such as interpose relays or solid- state switches, should not be disconnected.

Equipment connected to control sources rated 60 V ac or less shall be capable of withstanding a 60 Hz high-potential test for 1 min at 500 V ac rms. Equipment connected to control sources rated above 60 V ac (but not over 600 V ac) shall be capable of withstanding a 60 Hz high-potential test for 1 min of 1000 V ac plus twice rated voltage, within a minumum of 1500 V ac rms.

Unless otherwise specified, the dielectric tests shall be performed during the certified design test stage.

9.2.2.4 DC Dielectric Test. All equipment covered by this standard which is to be connected to a station control battery shall be capable of withstanding a dc high-potential test (1500 V plus twice rated voltage). The purpose of this test is to verify the dielectric strength of the insulating materials used in these devices. The intent is to ensure that failures will not occur in such a manner as to degrade the integrity of other critical equipment, such as protective relays, that utilize the common battery.

The test shall be applied for not less than a minute between all incoming and outgoing terminals and chassis ground. Examples of equipment that shall be subjected t o this test include, but are not limited to, power supplies,

41


status input devices (optical isolators, relays, etc), and control output devices. All devices may be tested on a subassembly basis with supervisory or automatic equipment logic wiring removed. All wiring from the device to the terminal strips provided for user field wiring, and any other devices that may be provided, such as fuses and surge arresters, shall be included in the test.

9.3 Environmental Tests. These tests are designed to demonstrate that the equipment will perform correctly and reliably while exposed to the applicable environmental parameters described in Section 6 together with other applicable parameters called out in the user’s specifications. The results of certified design tests are usually sufficient to demonstrate that the equipment will operate reliably and correctly within a specified environment. The user may require the vendor to perform factory tests on his equipment to demonstrate that it will indeed perform correctly under the specified environmental conditions. Equipment in environmental tests should be operating with realistic inputs and outputs.

The environmental parameters and testing requirements specified by the user should be limited to the worst case conditions that can be realistically anticipated in the location where the equipment will ultimately be installed.

9.3.1 Physical. The equipment should be tested to verify that it operates correctly in the following physical environmental characteristics:

9.3.1.1 Temperature. To test the equipment within the specified temperature range (see 6.1.1), it shall be placed in an environmental test chamber where it can be operated for a specified period at both the low and high ends of the range, and cycled between them. Cali- bration and accuracy checks should be made throughout the range.

9.3.1.2 Humidity. Humidity tests (without condensation) should be performed in conjunc- tion with the temperature test (see 9.3.1.1 ). Humidity test data shall include the humidity ranges tested at each temperature.

9.3.1.3 Altitude (Optional). Altitude tests can be performed by placing the equipment in a pressure chamber and adjusting the air pressure to the equivalent of the specified altitude.

9.3.1.4 Dust (Optional). Testing may consist of inspection to determine whether or not

the equipment is properly sealed to prevent intrusion of dust.

9.3.1.5 Acoustic (Optional). Acoustic interference testing should be done in accordance with the methods outlined in MIL-STD 1472C- 1981 [47]. Equipment should meet the standards set forth in 6.5.

9.3.2 Electromagnetic 9.3.2.1 Electromagnetic Interference (Op-

tional). Tests may be conducted to establish that the equipment does not produce either conducted or radiated electromagnetic interference in excess of the level defined in 6.6.

9.3.2.2 Electromagnetic Compatibility (Op- tional). The equipment may be tested to demonstrate that it will operate satisfactorily in spite of the levels of conducted and radiated interference as defined in 6.6.

9.3.3 Seismic Disturbance (Optional). Tests may be performed to verify functional performance of the equipment during seismic dis- turbances as defined in 6.3.

9.3.4 Shock and Vibration (Optional). Tests may be performed to verify functional performance of the equipment when subjected to shock and vibration as defined in 6.2.

9.4 Functional Tests. Performance tests shall be designed to ensure that the equipment performs its functions reliably and correctly. They are performed during the factory or field test stages, or both. For many applications and types of equipment, successful factory tests will be a sufficient basis for acceptance of the system by the user. For more complex applications or systems, additional tests in the field may be required to fully verify correct and reliable performance.

9.4.1 Point Equipment Checkout. AU point equipment to be supplied shall be tested during factory tests to demonstrate that it performs its functions correctly, accurately, and reliably. These tests should be performed with equipment that simulates the actual equipment to be monitored or controlled. Tests may be included to measure repeatability, reproducibility, and other accuracy related parameters.

9.4.2 Communication. The communication tests shall demonstrate proper operation of all aspects of the equipment’s communication capability, including modems, security checking, and message protocols. The data modems or signaling equipment shall be exercised to verify that they operate correctly and reliably

42


on the type of channel for which they are designed. The tests shall be conducted under conditions that duplicate as closely as possible the specifications for the channel.

The communcation tests shall exercise all message protocols and formats to which the equipment is designed to respond. The tests shall also demonstrate that any error detection or correction capabilities function properly and that the equipment does not respond to erroneous commands.

9.4.3 Man/Machine Interface (MMI). Com- prehensive man/machine interface tests should be performed to verify the correct functional operation of all man/machine interface hardware and software. All indications and displays shall be verified to ensure that they cor- relate with the correct point equipment, and all operator controls shall be checked to ensure that they result in only the correct sequence of operations.

9.4.4 Special Functions (Optional). When the equipment supplied is to perform functions tailored expressly to the user’s application (for example, closed loop control), these functions shall be checked during the appropriate test stage. It is often necessary to perform these tests in the field, after the equipment has been adjusted to the parameters of the installation.

9.5 System Performance Tests. Under various system loading scenarios, the performance of major master station interfaces (for example, commnication, disk, man/machine), and the performance of the central computer should be measured. The CPU utilization should be determined for the worst case scenario.

The loading scenarios should be for (1) Normal activity-initial system (2) Heavy activity-initial system (3) Normal activity-fully expanded system (4) Heavy activity-fully expanded system

and need only continue for a few minutes. Normal activity is defined as in Table l l ( a )

and heavy activity is defined as in Table l l ( b ) . The selection of 3% and 10% changes in scan-

ned data is based upon research and studies of the behavior of power system data [48].

The measurements for performance assume that all functions of the system have been indi- vidually verified by functional tests (see 9.4) and now the total system is to be evaluated.

Measurements should be made with the aid of (1) Cyclic status point stimulator (2) Stop watch and observations at the man/

machine interface (3) A computer program operating at the

lowest priority level. 9.5.1 Data Acquisition Performance. The

status input stimulator should be connected to an input of one remote station. The status point is to be toggled at a rate of 2.1 times the status scan cycle. The alarm associated with the toggled input should appear on the logger with a time tag of approximately twice the scan rate. A system overload causing an extension of the scan cycle is obvious from the printout because one or more status changes is missed.

9.5.2 Man/Machine Interface Performance. Observations (with stopwatch) of the man/ machine response to operator requests for new crt displays under various loadings will define the change in performance at this interface as a function of loading. Under heavy loading the

Table 11 System Input Scenario

Input Cycle Activitv

(a) Each Operator

Status Analog

1 min Scan(s) Scan(s)

1 crt request 0.1% changes

1% changes

Input Cycle Activi tv

15 s 1 crt request (b) Each Operator

Status Scan(s) 3% changes Analog Scan(s) 10% changes

43


response should be consistent with the human decision cycle that the operator/dispatcher has been trained to follow.

9.5.3 Computer and Disk Interface Perfor- mance. The third performance measuring device should be a computer program temporarily added to the system to operate at the lowest priority. The objective of using a low-priority program is to measure what otherwise is unused or idle capacity. Again the impact of various loads on idle capacity is the information that is to be obtained and analyzed. The program should accumulate time for central processor usage and time its disk activity. In addition it should print a time-tagged message every time it is called.

To measure computer usage a count should be advanced for each basic time interval (for example, a millisecond) that the program is using the central processing unit. The basic time interval should be selected based upon the speed of the computer and the size of software modules typical of the system under test.

The basic time interval is one in which some useful computation could be performed. Neither too small nor too large a basic time interval will be of use in performance measurement. The idle time of the computer isassessed by comparing the count of the number of basic time intervals recorded by the program to the total period of the test.

The disk interface should be exercised by this program to access the unused capacity and to attempt to compromise total system performance. If the disk interface has unused capacity the lowest priority program should be able to read/write from/to the disk. Counting the number of completed versus attempted disk access of known size during the test interval will give a measure of the available bandwidth.

The program should also try to dominate the disk interface by writing or reading large blocks of data. Restrictions, if any, used by the supplier in his design should be honored in the design of this computer program. The objective of this test is to see if a low-priority program can delay higher-priority tasks by excessive disk activity.

9.6 Bum-In Tests (Optional). The user may require a burn-in test to expose those components that are prone to infant-mortality failures. Three levels of burn-in tests can be conducted

(1) No functional exercise of the equipment

(2) Periodic functional exercise of the equipment

(3) Continuous functional exercise of the equipment Time accumulated in the performance of other factory tests usually is applicable toward the bum-in period. Typical time for such a test ranges from 100 h to 400 h. Elevated temperature not exceeding the specified range for the equipment may be employed to shorten burn-in time. If tests are conducted at operational temperature levels then the minimum duration should be 168 h.

9.7 Availability Test (Optional). The user may require an availability test to be run after the system is installed and placed in operation (see

An availability test takes place over a specified length of time during which the equipment shall operate correctly and reliably for at least a specified percentage of that time. The length of the test should be sufficient to verify that the equipment can be expected to perform its intended functions reliably and correctly over its intended lifetime.

The availability test shall be run under conditions mutually agreeable to the vendor and the user. In general, the vendor should be responsible for making the necessary repairs. Down- time should not include delays over which the vendor has no control.

Availability tests are typically performed over a period of hundreds of hours following which the number and types of failures, and their effects on system operation, are examined. The test time should be selected so that the total number of device operating hours for each type of system- critical device is representative of the predicted MTBF for that device, to obtain sta- tistically significant failure data. All devices should have passed their burn-in tests so that the availability test evaluates seasoned devices. Specific rules for accumulation of up-time, down-time, maintenance time, and administrative time should be agreed upon before the test. An availability test as short as 400 h can adequately evaluate the availability characteristics of a complex multicomputer system.

7.3).

9.8 Acceptance Test (Optional). The conditions according to which the equipment will be ac-

44


cepted as satisfactory should be agreed upon by the vendor and the user. 9.9 Documentation Verification. The final phase of the testing program is to verify that the documentation being supplied is an accurate description of the equipment, including all cor- rections resulting from the tests. Final issue of completed documentation should be provided as soon as practical after shipment and acceptance of the equipment.

10. Documentation

The documentation for equipment governed by this standard shall consist of the five basic types

(1) Design (2) Installation (3) Operating instructions and records (4) Maintenance instructions and records (5) Test.

In general, all final documentation supplied by a manufacturer shall reflect the actual equipment as accepted by the equipment user, and all subsequent equipment changes should be recorded as document revisions by the user. Records collected by the user following the installation of equipment governed by this standard should be in sufficient detail to support the requirements of Section 7 and should be made available to the manufacturer.

Content requirements for each type of standard document are defined in subsequent paragraphs, and suggested practices for the user of this standard. Style, format, and publication requirements are excluded from this standard. The following references are recommendations for abbreviations and symbols: ANSI X3.5- 1970 [4] , ANSI Y14.15-1966 (R 1973) [5], ANSI/IEEE C37.2-1979 [ lo ] , ANSI/IEEE Std 91-1984 [19], ANSI/IEEE Std 200-1975 [21], ANSI/IEEE Std 280-1985 [22], and

Documentation described below may be subject to user review or approval.

10.1 Design. Design documentation shall consist of all drawings and text developed to define the user’s equipment configuration intended or required initially and its ultimate capability. For example, expansion methods for adding points to hardware assemblies and software programs or tables shall be described and illus-

ANSI/IEEE Std 315-1975 [23].


trated. Block diagrams shall be included to describe equipment governed by this standard and external equipment. Layout and wiring drawings shall also be included to define external interconnection needs at each facility. Text, photographs, and illustrative material shall accompany these drawings in sufficient detail so that functional performance and design may be readily understood. For example, functional block diagrams and explanatory text shall be used to describe each major assembly and software program contained in the equipment configuration.

10.2 Installation. Installation documentation shall consist of all drawings and text required to define

(1) Electrical power, data, control, and communications interface wiring procedures

(2) Floor, rack and shelf mounting, drilling, and bolting methods necessary to secure the equipment in place

(3) Safety precautions or guards (4) Grounding and bonding procedures (5) Clearances for access and ventilation (6) Testing and alignment methods (7) Weatherproofing, dustproofing, and other

environmental procedures (8) Other procedures needed to properly in-

stall the equipment.

10.3 Operating Instructions and Records. In- struction information shall be developed for operating personnel who use the equipment governed by this standard.

10.3.1 Manufacturer Operating Instructions. The manufacturer shall publish instructional information defining the equipment and how it shall be operated. This instructional information shall consist of a general description of the equipment configuration provided and shall state its intended use and its major performance characteristics. Whenever a man/machine interface such as a console, benchboard, indicating/ control panel, or logger is involved, the operational documentation shall detail in step-by-step fashion the operational sequences required to use these interface devices. Adequate illustrative material shall be included to identify and locate all control and indicating devices.

10.3.2 User Operating Instructions. The equipment user should publish operating procedures defining the system and include detailed instructions for and responsibilities of the operator. These user instructions should be

45


based on the manufacturer’s instructional information and the nature of the system being monitored and controlled. Procedural instructions should be included which state routine and emergency procedures, safety precautions, and quantitative and qualitative limits to be observed in the starting, running, stopping, switching, and shutting down of control equipment. Whenever operating procedures or adjustments are to be performed in a specific sequence, step-by-step instructions should be stated. Records including data and information recorded by the operator for all normal or abnormal operations should support the requirements of 7.3.

10.4 Maintenance Instructions and Records. Maintenance documentation shall be developed for personnel skilled at the electronic technician level and shall include the following information: 10.4.1 Performance Information. This infor-

mation shall include a condensed description of how the equipment operates (derived from 10.1) and a block diagram illustrating each major assembly and software program in the configuration. Message sequences, including data and security formats for each type of message, shall be included in the condensed description and illustrated whenever such messages are used between stations or locally at a station. The operational sequence of major assemblies and programs shall be described and illustrated by functional block diagrams. Detailed logic diagrams and flowcharts shall also be provided as necessary for troubleshooting analysis and field-repair actions. 10.4.2 Preventive Maintenance Instructions.

These instructions shall include all applicable visual examinations, software and hardware test and diagnostic routines, and resultant adjustments necessary for periodic maintenance of control equipment. Instructions on how to load and use any test and diagnostic program and any special or standard test equipment shall be an integral part of these procedures. 10.4.3 Corrective Maintenance Instructions.

These instructions shall include guides for locating malfunctions down to the spare parts replacement or field-repair level. These guides

shall include adequate details for quickly and efficiently locating the cause of an equipment malfunction and shall state the probable source(s) of trouble, the symptoms, probable cause, and instructions for correcting the malfunction. These guides shall explain how to use any on-line test and diagnostic program and any special test equipment if applicable.

Corrective maintenance instructions shall also include explanations for the repair, adjustment, or replacement of all items. Schematic diagrams of electrical, mechanical, and electronic circuits; parts location illustrations, or other methods of parts location information; photographs, and exploded and sectional views giving details of mechanical assemblies shall be provided as necessary to repair or replace equipment. For mechanical items requiring field repair, information on tolerances, clearances, and wear limits maximum bolt-down torques shall be supplied. Information on the loading and use of special off-line diagnostic programs, tools, and test equipment, and any cautions or warn- ings which shall be observed to protect personnel and equipment, shall also be included. 10.4.4 Parts Information. This information

shall include the identification of each replace- able or field repairable module. Parts shall be identified on a list or drawing in sufficient detail for procurement of any repairable or re- placeable part, These parts should be identified by their industrial, generic part numbers, and should have second-source referencing whenever possible. 10.4.5 Records. Records, including data and

information recorded by maintenance personnel, for all failures and repair activities should be in sufficient detail to support the requirements of 7 .l, 7.2, and 7.3.

10.5 Test. Test documentation by the manufacturer shall consist of a system test plan, test procedures, and certified test reports on tests described in Section 9. The test plan shall state what equipment configuration will be tested, when it will be tested, which tests will be run, and who will conduct and witness the tests. The test procedures shall define the operating steps and expected results. The test report shall record all test results.

46


Appendixes

(These Appendixes are not a part of ANSI/IEEE C37.1 1987, IEEE Standard Definition, Specification, and Analysis of Systems used for Supervisory Control, Data Acquisition, and Automatic Control.)

Appendix A MastedRemote Station Interconnections

Al . Single Master Station

Al . l . Single Master, Single Remote

MASTER R E M O T E

A1.2. Single Master, Multiple Remotes, Radial Circuit

REMOTE I 1

REMOTE 2 1

R E M O T E N 1 0 . 0

A1.3. Single Master, Multiple Remotes, Party- Line Circuit

M A S T E R

I

A2. Multiple Master Stations (Masters could communicate with one another)

A2.1. Dual Masters, Multiple Remotes, Looped Party Line

[ M A S T E R I + REMOTE I ]

REMOTE 2

R E M O T E N

A2.2. Dual Masters, Single Dual Ported Remote, Radial Circuit

I M A S T E R 2 4

A3. Multiple Master Stations, Multiple Remotes

A3.1. Multiple Masters, Multiple Remotes (Single Ported Remotes)

e c( REMOTE I 1

R E M O T E N I 0 0 0

A3.2. Multiple Masters, Multiple Remotes (Dual Ported Remotes)

M A S T E R I

R E M O T E N

0

A4. Combination Systems

A4.1 Single Master, Single Submaster, Multiple Remotes

REMOTE I

SUB - MASTER

REMOTE N 1 I

MASTER

REMOTE I 1

REMOTE N 1

A4.2. Single Master, Multiple Submasters, Multiple Remotes (Submasters could communicate with one another)

SUB - MASTER I . MASTER 0

SUB-MASTERM

REMOTE I 1

REMOTE N I

47


Appendix B

Bibliography

[Bl ] ANSI C2-1987, National Electrical Safety Code.

[ B2] ANSI C39.5-1974, American National Standard Safety Requirements for Electrical and Electronic Measuring and Controlling In- strumentation.

[B3] ANSI S1.23-1976 (R 1983), American National Standard Method for the Designation of Sound Power Emitted by Machinery and Equipment.

[B4] ANSI/ASTM D775-80, Method of Drop Test for Shipping Containers.lO

[ B5] ANSI/ASTM D999-75, Standard Methods for Vibration Test for Shipping Containers.

[B6] ANSI/IEEE Std 4-1978, IEEE Standard Techniques for High-Voltage.

[ B7] ANSI/IEEE Std 100-1984,IEEE Standard Dictionary for Electrical and Electronics.Terms.

1 O A S T M publications are available from the American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103.

[B8] ANSI/ISA RP-55-1-1975, Hardware Test- ing for Digital Process Computers.l'

[B9] ANSI/ISA S50.1-1975 (R 1982), Com- patibility of Analog Signals for Electronic Industrial Process Instruments.

[BlO] CBEMA/ESC-5/77/29, Limits in Meth- ods of Measurement of Electromagnetic Emanations from Electronic Data-Processing and Office Equipment. l2

[ B l l ] IEC 68-2-6-1982, Test Fc and Guidance: Vibration (sinusoidal).'

pational Safety and Health Standards. l4

[B12] OSHA FR V O ~ 37, Oct 18, 1972, OCCU-

11 ISA publications are available from the Instrument Society of America, 67 Alexander Drive, PO Box 12277, Research Triangle Park, NC 27709.

12 CBEMA publications are available from Computer and Business Equipment Manufacturers Association, 1828 L Street, NW, Washington, DC 20036.

13IEC publications are available from the Sales Department, American National Standards Institute, 1430 Broadway, New York, NY 10018.

14OSHA publications are available without charge from the nearest regional or area office of the US Department of Labor, Occupational Safety and Health Administration.

48

c37 Complete 1987 Edition

The documents in the C37 series include definitions, applications guides, test methods and procedures, requirements, and specifications for circuit breakers, switchgear, fuses, relays, and substations.

Purchased separately, the standards in this book of more than two thousand pages would cost nearly $550. At $75 this is probably the most remarkable standards bargain you can ever expect to encounter.

This collection includes 62 standards, 15 supplements and 17 draft documents. Users of C37 will experience a degree of convenience in utilizing this valuable collection that will save weeks, possibly months, of waiting time each and every time it is consulted.

Draft documents have been included in the format in which they are currently under consideration. They are unedited and may contain errors in spelling and inaccuracies regarding the other documents they reference. Because these draft documents are still under review and subject to change prior to publication, both the draft and the current ANSI-approved standards are included in this collection. Users should be cautioned that both editorial and substantive changes may occur in the draft documents prior to final approval and publication.

Available from American National Standards Institute, 1430 Broadway, New York, New York 10018 Wiley-Interscience, A Division of John Wiley and Sons, Inc. 605 Third Avenue, New York,

Institute of Electrical and Electronics Engineers, Inc., 445 Hoes Lane, P.O. Box 1331, New York 10158

Piscataway, New Jersey 08855-1331

Date post:	26-Mar-2018
Category:	Documents
Upload:	buikhue
View:	226 times
Download:	4 times

IEEE standard definition, specification, and analysis of...

Documents