CSC-211
Multifunction Protection IED
Technical Application Manual
CSC-211 Multifunction
Protection IED
Technical Application Manual
Compiled: Jin Rui
Checked: Hou Changsong
Standardized: Li Lianchang
Inspected: Cui Chenfan
Version V1.01
Doc.Code0SF.451.085(E)
Issued Date2012.8.31
VersionV1.01
Doc. Code: 0SF.451.085(E)
Issued Date2012.8
Copyright owner: Beijing Sifang Automation Co., Ltd
Note: the company keeps the right to perfect the instruction. If equipment does not agree with
the instruction at anywhere, please contact our company in time. We will provide you with
corresponding service.
is registered trademark of Beijing Sifang Automation Co., Ltd.
We reserve all rights to this document, even in the event that a patent is issued and a different commercial proprietary right is registered. Improper use, in particular reproduction and dissemination to third parties, is not permitted.
This document has been carefully checked. If the user nevertheless detects any errors, he is asked to notify us as soon as possible.
The data contained in this manual is intended solely for the IED description and is not to be deemed to be a statement of guaranteed properties. In the interests of our customers, we constantly seek to ensure that our products are developed to the latest technological standards as a result it is possible that there may be some differences between the hardware/software product and this information product.
Manufacturer: Beijing Sifang Automation Co., Ltd.
Tel: +86 10 62962554, +86 10 62961515 ext. 8998 Fax: +86 10 82783625 Email: [email protected] Website: http://www.sf-auto.com
Add: No.9, Shangdi 4th Street, Haidian District, Beijing, P.R.C.100085
Preface
Purpose of this manual
This manual describes the functions, operation, installation, and placing into service of IED CSC-211. In particular, one will find:
Information on how to configure the IED scope and a description of the IED functions and setting options;
Instructions for mounting and commissioning;
Compilation of the technical specifications;
A compilation of the most significant data for experienced users in the Appendix.
Target audience
This manual mainly face to installation engineer, commissioning engineer and
operation engineer with perfessional electric and electrical knowledge, rich
experience in protection function, using protection IED, test IED, responsible
for the installation, commissioning, maintenance and taking the protection
IED in and out of normal service.
Applicability of this manual
This manual is valid for CSC-211 multifunction protection IED.
Technical support
In case of further questions concerning the CSC family, please contact
SiFang compay or your local SiFang representative.
Safety information
Strictly follow the company and international safety regulations. Working in a high voltage environment requires serious approch to
aviod human injuries and damage to equipment
Do not touch any circuitry during operation. Potentially lethal
voltages and currents are present
Avoid to touching the circuitry when covers are removed. The IED contains electirc circuits which can be damaged if exposed to static
electricity. Lethal high voltage circuits are also exposed when covers
are removed
Using the isolated test pins when measuring signals in open circuitry. Potentially lethal voltages and currents are present
Never connect or disconnect wire and/or linker to or from IED during normal operation. Dangerous voltages and currents are present.
Operation may be interrupted and IED and measuring circuitry may
be damaged
Always connect the IED to protective earth regardless of the operating conditions. Operating the IED without proper earthing may
damage both IED and measuring circuitry and may cause injuries in
case of an accident.
Do not disconnect the secondary connection of current transformer without short-circuiting the transformers secondary winding.
Operating a current transformer with the secondary winding open will
cause a high voltage that may damage the transformer and may
cause injuries to humans.
Do not remove the screw from a powered IED or from an IED connected to power circuitry. Potentially lethal voltages and currents
are present
Using the certified conductive bags to transport PCBs (modules). Handling modules with a conductive wrist strap connected to
protective earth and on an antistatic surface. Electrostatic discharge
may cause damage to the module due to electronic circuits are
sensitive to this phenomenon
Do not connect live wires to the IED, internal circuitry may be damaged
When replacing modules using a conductive wrist strap connected to protective earth. Electrostatic discharge may damage the modules
and IED circuitry
When installing and commissioning, take care to avoid electrical shock if accessing wiring and connection IEDs
Changing the setting value group will inevitably change the IEDs operation. Be careful and check regulations before making the
change
Contents
Chapter 1 Introduction .................................................................................................................. 1
1 Overview ..................................................................................................................................... 2
2 Features ...................................................................................................................................... 3
3 Functions..................................................................................................................................... 5
3.1 Protection functions ..................................................................................................... 5
3.2 Control functions .......................................................................................................... 6
3.3 Monitoring functions ..................................................................................................... 6
3.4 Station communication ................................................................................................ 6
3.5 IED software tools ........................................................................................................ 7
Chapter 2 General IED application ............................................................................................... 9
1 Display on LCD screen ............................................................................................................. 10
1.1 LCD screen display function ...................................................................................... 10
1.2 Analog display function .............................................................................................. 10
1.3 Report display function .............................................................................................. 10
1.4 Menu dispaly function ................................................................................................ 10
2 Report record ............................................................................................................................ 11
3 Disturbance recorder ................................................................................................................ 12
3.1 Introduction ................................................................................................................ 12
3.2 Fault recording ........................................................................................................... 12
3.3 Wave recording .......................................................................................................... 12
3.4 Sequence of event record.......................................................................................... 13
3.5 Operation record ........................................................................................................ 13
4 Self-supervision function ........................................................................................................... 14
4.1 Introduction ................................................................................................................ 14
4.2 Self-supervision principle ........................................................................................... 14
4.3 Self-supervision report ............................................................................................... 14
5 Time synchroniation function .................................................................................................... 16
5.1 Introduction ................................................................................................................ 16
5.2 Synchronization principle ........................................................................................... 16
5.2.1 Synchronization from IRIG......................................................................................... 17
5.2.2 Synchronization via PPS or PPM .............................................................................. 17
5.2.3 Synchronization via SNTP ......................................................................................... 17
6 Setting ....................................................................................................................................... 18
6.1 Introduction ................................................................................................................ 18
6.2 Operation principle ..................................................................................................... 18
7 Authorization ............................................................................................................................. 19
7.1 Introduction ................................................................................................................ 19
Chapter 3 Overcurrent protection ............................................................................................... 21
1 Overcurrent protection .............................................................................................................. 22
1.1 Introduction ................................................................................................................ 22
1.2 Protection principle .................................................................................................... 22
1.2.1 Time characteristics ........................................................................................... 22
1.2.2 Inrush restraint function ..................................................................................... 24
1.2.3 Low voltage component ..................................................................................... 24
1.2.4 Direction determination feature .......................................................................... 25
1.2.5 Logic diagram..................................................................................................... 26
1.3 Input and output signals ............................................................................................ 28
1.4 Setting parameters .................................................................................................... 29
1.4.1 Setting list ........................................................................................................... 29
1.5 Reports ...................................................................................................................... 30
1.6 Technical data ........................................................................................................... 31
Approx. 0.95 at I/In 0.5 ................................................................................................... 31
Chapter 4 Earth fault protection ................................................................................................. 33
1 Earth fault protection ................................................................................................................. 34
1.1 Introduction ................................................................................................................ 34
1.2 Protection principle .................................................................................................... 35
1.2.1 Time characteristic ............................................................................................. 35
1.2.2 Inrush restraint ................................................................................................... 36
1.2.3 Direction determination feature .......................................................................... 37
1.2.4 Logic diagram..................................................................................................... 39
1.3 Input and output signals ............................................................................................ 41
1.4 Setting parameters .................................................................................................... 42
1.4.1 Setting list ........................................................................................................... 42
1.5 IED reports ................................................................................................................. 44
1.6 Technical data ........................................................................................................... 44
Approx. 0.95 at I/Ir 0.5 .................................................................................................... 44
Chapter 5 Sensitive earth fault protection .................................................................................. 47
1 Sensitive overcurrent protection ............................................................................................... 48
1.1 Introduction ................................................................................................................ 48
1.2 Protection principle .................................................................................................... 48
1.2.1 Time characteristic ............................................................................................. 48
1.2.2 Direction determination feature .......................................................................... 49
1.2.3 Logic diagram..................................................................................................... 52
1.3 Input and output signals ............................................................................................ 53
1.4 Setting parameters .................................................................................................... 54
1.4.1 Setting list ........................................................................................................... 54
1.5 IED reports ................................................................................................................. 56
1.6 Technical data ........................................................................................................... 56
Chapter 6 Negative-sequence overcurrent protection ............................................................... 59
1 Negative-sequence overcurrent protection ............................................................................... 60
1.1 Introduction ................................................................................................................ 60
1.2 Protection principle .................................................................................................... 60
1.2.1 Protection function description ........................................................................... 60
1.2.2 Logic diagram..................................................................................................... 61
1.3 Input and output signals ............................................................................................ 62
1.4 Setting parameters .................................................................................................... 62
1.4.1 Setting list ........................................................................................................... 63
1.5 IED reports ................................................................................................................. 64
1.6 Technical data ........................................................................................................... 64
Chapter 7 Thermal overload protection ...................................................................................... 67
1 Thermal overload protection ..................................................................................................... 68
1.1 Introduction ................................................................................................................ 68
1.2 Protection principle .................................................................................................... 68
1.2.1 Function description ........................................................................................... 68
1.3 Input and output signals............................................................................................. 70
1.4 Setting parameters .................................................................................................... 70
1.4.1 Setting list ........................................................................................................... 70
1.5 IED reports ................................................................................................................. 71
1.6 Technical data ........................................................................................................... 71
Chapter 8 Current overload protection ....................................................................................... 73
1 Current overload protection ...................................................................................................... 74
1.1 Function description ................................................................................................... 74
1.1.1 Logic diagram ..................................................................................................... 74
1.2 Input and output signals............................................................................................. 74
1.3 Setting parameter ...................................................................................................... 75
1.3.1 Setting list ........................................................................................................... 75
1.4 IED reports ................................................................................................................. 75
Chapter 9 Overvoltage protection ............................................................................................... 77
1 Overvoltage protection .............................................................................................................. 78
1.1 Introduction ................................................................................................................ 78
1.2 Protection principle .................................................................................................... 78
1.2.1 Overvoltage protection principle ........................................................................ 78
1.2.2 Voltage connection ............................................................................................. 79
1.2.3 Logic diagram ..................................................................................................... 80
1.3 Input and output signals............................................................................................. 81
1.4 Setting parameters .................................................................................................... 81
1.4.1 Setting list ........................................................................................................... 81
1.5 IED reports ................................................................................................................. 82
1.6 Technical data ........................................................................................................... 83
Chapter 10 Undervoltage protection............................................................................................. 85
1 Undervoltage protection ............................................................................................................ 86
1.1 Introduction ................................................................................................................ 86
1.2 Protection principle .................................................................................................... 86
1.2.1 Protection function description ........................................................................... 86
1.2.2 Voltage connection ............................................................................................. 87
1.2.3 Depending on the VT location ............................................................................ 88
1.2.4 Logic diagram ..................................................................................................... 89
1.3 Input and output signals............................................................................................. 91
1.4 Setting parameter ...................................................................................................... 92
1.4.1 Setting list ........................................................................................................... 92
1.5 IED reports ................................................................................................................. 93
1.6 Technical data ........................................................................................................... 93
Chapter 11 Displacement voltage protection ............................................................................... 95
1 Displacement voltage protection............................................................................................... 96
1.1 Introduction ................................................................................................................ 96
1.2 Protection principle .................................................................................................... 96
1.2.1 Displacement voltage input ................................................................................ 96
1.2.2 Protection description ........................................................................................ 96
1.2.3 Logic diagram..................................................................................................... 97
1.3 Input and output signals ............................................................................................ 98
1.4 Setting parameter ...................................................................................................... 99
1.4.1 Setting list ........................................................................................................... 99
1.5 IED reports ............................................................................................................... 100
1.6 Technical data ......................................................................................................... 100
Chapter 12 Circuit breaker failure protection.............................................................................. 103
1 Circuit breaker failure protection ............................................................................................. 104
1.1 Introduction .............................................................................................................. 104
1.2 Protection principle .................................................................................................. 104
1.2.1 Protection description ...................................................................................... 104
1.2.2 Current criterion evaluation .............................................................................. 105
1.2.3 Circuit breaker auxiliary contact evaluation ..................................................... 105
1.2.4 Logic diagram................................................................................................... 106
1.3 Input and output signals .......................................................................................... 107
1.4 Setting parameter .................................................................................................... 108
1.4.1 Setting list ......................................................................................................... 108
1.5 IED reports ............................................................................................................... 108
1.6 Technical data ......................................................................................................... 109
Chapter 13 Dead zone protection ............................................................................................... 111
1 Dead zone protection ............................................................................................................... 112
1.1 Introduction ............................................................................................................... 112
1.2 Protection principle ................................................................................................... 112
1.2.1 Function description .......................................................................................... 112
1.2.2 Logic diagram.................................................................................................... 114
1.3 Input and output signals ........................................................................................... 114
1.4 Setting parameter ..................................................................................................... 115
1.4.1 Setting list .......................................................................................................... 115
1.5 IED reports ................................................................................................................ 116
1.6 Technical data .......................................................................................................... 116
Chapter 14 Synchro-check and energizing check function ......................................................... 117
1 Synchro-check and energizing check function ........................................................................ 118
1.1 Introduction ............................................................................................................... 118
1.2 Function principle ..................................................................................................... 118
1.2.1 Synchro-check mode ........................................................................................ 119
1.2.2 Energizing check mode .................................................................................... 120
1.2.3 Override mode ................................................................................................. 121
1.2.4 Logic diagram ................................................................................................... 121
1.3 Input and output signals........................................................................................... 122
1.4 Setting parameter .................................................................................................... 123
1.4.1 Setting list ......................................................................................................... 123
1.5 IED reports ............................................................................................................... 124
1.6 Technical data ......................................................................................................... 125
Chapter 15 Autoreclosing function ............................................................................................. 127
1 Autoreclosing function ............................................................................................................. 128
1.1 Introduction .............................................................................................................. 128
1.2 Function principle ..................................................................................................... 128
1.2.1 Auto-reclosing initiation modules ..................................................................... 128
1.2.2 Autoreclosing logic ........................................................................................... 129
1.3 Input and output signals........................................................................................... 132
1.4 Setting parameter .................................................................................................... 134
1.4.1 Setting list ......................................................................................................... 134
1.5 IED reports ............................................................................................................... 136
1.6 Technical data ......................................................................................................... 137
Chapter 16 Unbalance protection ............................................................................................... 139
1 Unbalance protection .............................................................................................................. 140
1.1 Introduction .............................................................................................................. 140
1.2 Protection principle .................................................................................................. 140
1.3 Input and output signals........................................................................................... 146
1.4 Setting parameter .................................................................................................... 147
1.4.1 Setting list ......................................................................................................... 147
1.5 IED reports ............................................................................................................... 147
Chapter 17 Under current monitoring ......................................................................................... 149
1 Under current monitoring ........................................................................................................ 150
1.1 Introduction .............................................................................................................. 150
1.2 Protection principle .................................................................................................. 150
1.2.1 Function description ......................................................................................... 150
1.2.2 Logic diagram ................................................................................................... 150
1.3 Input and output signals........................................................................................... 151
1.4 Setting parameter .................................................................................................... 151
1.4.1 Setting list ......................................................................................................... 151
1.5 IED reports ............................................................................................................... 152
Chapter 18 Load shedding protection ........................................................................................ 153
1 Low frequency load shedding protection ................................................................................ 154
1.1 Introduction .............................................................................................................. 154
1.2 Protection principle .................................................................................................. 154
1.2.1 Function description ......................................................................................... 154
1.3 Input and output signals........................................................................................... 155
1.4 Setting parameter .................................................................................................... 156
1.4.1 Setting list ......................................................................................................... 156
1.5 IED reports ............................................................................................................... 157
2 Low voltage load shedding protection .................................................................................... 158
2.1 Introduction .............................................................................................................. 158
2.2 Protection principle .................................................................................................. 158
2.2.1 Funciton description ......................................................................................... 158
2.3 Input and output signals .......................................................................................... 159
2.4 Setting parameter .................................................................................................... 160
2.4.1 Setting list ......................................................................................................... 160
2.5 IED reports ............................................................................................................... 161
3 Overload load shedding protection ......................................................................................... 162
3.1 Introduction .............................................................................................................. 162
3.2 Protection principle .................................................................................................. 162
3.2.1 Fucntion description ......................................................................................... 162
3.3 Input and output signals .......................................................................................... 163
3.4 Setting parameter .................................................................................................... 164
3.4.1 Setting list ......................................................................................................... 164
3.5 IED reports ............................................................................................................... 164
3.6 Technical data ......................................................................................................... 165
Chapter 19 Fast busbar protection scheme ............................................................................... 167
1 Fast busbar protection scheme .............................................................................................. 168
1.1 Function description ................................................................................................ 168
1.2 Input and output signals .......................................................................................... 169
1.3 Setting parameter .................................................................................................... 170
1.3.1 Setting list ......................................................................................................... 170
1.4 IED reports ............................................................................................................... 170
Chapter 20 Secondary system supervision ................................................................................ 171
1 Current circuit supervision ...................................................................................................... 172
1.1 Function principle .................................................................................................... 172
1.1.1 Function description ......................................................................................... 172
1.1.2 Logic diagram................................................................................................... 172
1.2 Input and output signals .......................................................................................... 172
1.3 Setting parameter .................................................................................................... 173
1.3.1 Setting list ......................................................................................................... 173
1.4 IED reports ............................................................................................................... 173
2 Fuse failure supervision VT .................................................................................................... 174
2.1 Introduction .............................................................................................................. 174
2.2 Function principle .................................................................................................... 174
2.2.1 Three phases (symmetrical) VT Fail ................................................................ 174
2.2.2 Single/two phases (asymmetrical) VT Fail ....................................................... 175
2.2.3 The fourth voltage U4 VT fail ........................................................................... 175
2.2.4 Logic diagram................................................................................................... 175
2.3 Input and output signals .......................................................................................... 177
2.4 Setting parameter .................................................................................................... 177
2.4.1 Setting list ......................................................................................................... 177
2.5 IED reports ............................................................................................................... 178
2.6 Technical data ......................................................................................................... 178
Chapter 21 Monitoring function .................................................................................................. 181
1 Switching devices status monitoring ....................................................................................... 182
2 Self-supervision ...................................................................................................................... 182
Chapter 22 Station communication ............................................................................................ 183
1 Overview ................................................................................................................................. 184
1.1 Protocol .................................................................................................................... 184
1.1.1 IEC61850-8 communication protocol ............................................................... 184
1.1.2 IEC60870-5-103 communication protocol ........................................................ 184
1.2 Communication port ................................................................................................. 185
1.2.1 Front communication port ................................................................................ 185
1.2.2 RS485 communication ports ............................................................................ 185
1.2.3 Ethernet communication ports ......................................................................... 185
1.3 Technical data ......................................................................................................... 185
1.4 Typical substation communication scheme ............................................................. 188
1.5 Typical time synchronizing scheme ......................................................................... 188
Chapter 23 Hardware ................................................................................................................. 189
1 Introduction ............................................................................................................................. 190
1.1 IED structure ............................................................................................................ 190
1.2 IED module arrangement......................................................................................... 190
2 Local human-machine interface .............................................................................................. 192
2.1 Introduction .............................................................................................................. 192
2.2 Liquid crystal display (LCD) ..................................................................................... 192
2.3 LED .......................................................................................................................... 193
2.4 Keyboard ................................................................................................................. 193
2.5 IED menu ................................................................................................................. 194
2.5.1 Menu construction ............................................................................................ 194
2.5.2 Operation status ............................................................................................... 196
2.5.3 Operation status ............................................................................................... 197
2.5.4 Operation configuration .................................................................................... 197
2.5.5 Settings ............................................................................................................ 197
2.5.6 Report............................................................................................................... 197
2.5.7 Communication configuration .......................................................................... 198
2.5.8 Testing .............................................................................................................. 198
2.5.9 Device setup .................................................................................................... 199
2.5.10 Device information ........................................................................................... 200
3 Analog input module ............................................................................................................... 201
3.1 Introduction .............................................................................................................. 201
3.2 Terminals of analog input module ........................................................................... 202
3.3 Technical data ......................................................................................................... 206
4 Fast binary Input & Output module ......................................................................................... 208
4.1 Introduction .............................................................................................................. 208
4.2 Terminals of fast binary input & output module ....................................................... 208
4.3 Technical data ......................................................................................................... 210
5 Fast binary output module ...................................................................................................... 212
5.1 Introduction .............................................................................................................. 212
5.2 Terminals of fast binary output module ................................................................... 212
6 Binary input & output module .................................................................................................. 214
6.1 Introduction .............................................................................................................. 214
6.2 Terminals of binary & output module ....................................................................... 214
7 CPU module ............................................................................................................................ 217
7.1 Introduction .............................................................................................................. 217
7.2 Terminals of CPU module ....................................................................................... 217
7.3 Technical data ......................................................................................................... 219
8 Power supply module ............................................................................................................. 221
8.1 Introduction .............................................................................................................. 221
8.2 Terminals of power supply module .......................................................................... 221
8.3 Technical data ......................................................................................................... 223
9 Technical data ......................................................................................................................... 224
9.1 Type tests ................................................................................................................ 224
9.2 IED design ............................................................................................................... 227
9.3 CE certificate ........................................................................................................... 228
Chapter 24 Appendix .................................................................................................................. 229
1 General setting list .................................................................................................................. 230
1.1 Setting list for CSC-211 M01 ................................................................................... 230
1.2 Setting list for CSC-211 M02 ................................................................................... 237
1.3 Setting list for CSC-211 M03 ................................................................................... 244
1.4 Setting list for CSC-211 M05 ................................................................................... 250
1.5 Setting list for CSC-211 M6 ..................................................................................... 255
1.6 Setting list for CSC-211 V01 .................................................................................... 259
1.7 Setting list for CSC-211 C01 ................................................................................... 262
1.8 Setting list for CSC-211 C02 ................................................................................... 268
2 General report list ................................................................................................................... 275
2.1 Event report list ........................................................................................................ 275
2.2 Alarm report list ....................................................................................................... 277
3 Typical connection .................................................................................................................. 282
4 Time inverse characteristic ..................................................................................................... 304
4.1 11 kinds of IEC and ANSI inverse time characteristic curves ................................. 304
4.2 User defined characteristic ...................................................................................... 304
4.3 Typical inverse curves ............................................................................................. 305
5 CT Requirement ...................................................................................................................... 317
5.1 Overview .................................................................................................................. 317
5.2 Current transformer classification ............................................................................ 318
5.3 Abbreviations (according to IEC 60044-1, -6, as defined) ...................................... 319
5.4 General current transformer requirements .............................................................. 320
5.4.1 Protective checking current .............................................................................. 320
5.4.2 CT class ........................................................................................................... 320
5.4.3 Accuracy class ................................................................................................. 322
5.4.4 Ratio of CT ....................................................................................................... 322
5.4.5 Rated secondary current .................................................................................. 323
5.4.6 Secondary burden ............................................................................................ 323
5.5 Rated equivalent secondary e.m.f requirements ..................................................... 323
5.5.1 Definite time overcurrent protection and earth fault protection ........................ 324
5.5.2 Inverse time overcurrent protection and earth fault protection ........................ 325
Chapter 1 Introduction
1
Chapter 1 Introduction
About this chapter
This chapter gives an overview of SIFANG Multifunction
Protection IED CSC-211.
Chapter 1 Introduction
2
1 Overview
CSC-211 series are selective, reliable and high speed multifunction
protection IED (Intelligent Electronic Device), which are able to be applied
for protection, control and measurement for following applications:
Applicable in subtransmission network and distribution network with
solidly earthed (grounded), low-resistance earthed, isolated or
compensated neutral point
Protection of feeders, capacitors, distribution transformers, bus
coupler, etc.
Used as backup protection IED for lines, transformers, reactors and
busbar
Providing control and monitoring functions of the circuit breakers,
disconnector, etc.
Supporting all functionalities required for automation system
Chapter 1 Introduction
3
2 Features
Extensive multifunction IED including protection, control and
monitoring functions
Three pole tripping required in sub-transmission and distribution
network
A complete protection functions library, include:
Overcurrent protection (50, 51, 67)
Earth fault protection (50N, 51N, 67N)
Neutral earth fault protection (50G, 51G)
Sensitive earth fault protection (50Ns, 51Ns, 67Ns)
Negative-sequence overcurrent protection (46)
Thermal overload protection (49)
Overload protection (50OL)
Overvoltage protection (59)
Undervoltage protection (27)
Displacement voltage protection (64)
Circuit breaker failure protection (50BF)
Dead zone protection (50SH-Z)
Synchro-check and energizing check (25)
Auto-recloser function for three-phase reclosing (79)
Unbalanced current or voltage protection
Undercurrent protection (37)
load shedding function
Chapter 1 Introduction
4
Voltage transformer secondary circuit supervision (97FF)
Current transformer secondary circuit supervision
Fast overcurrent/busbar protection scheme using IEC61850
GOOSE-message
CB status supervision
Self-supervision to all modules in the IED
Complete and massive reports recording, trip reports, alarm reports,
startup reports and operation reports. Any kinds of reports can be
stored no less than 40 items, and be memorized in case of power
disconnection
Up to two electric /optical Ethernet ports can be selected to
communicate with substation automation system by IEC61850 or
IEC60870-5-103 protocols
One electric RS-485 port is able to communicate with substation
automation system by IEC60870-5-103 protocol
Time synchronization via network(SNTP), pulse and IRIG-B mode
Versatile human-machine interface
Multifunctional software tool CSmart for setting, monitoring, fault
recording analysis, configuration, etc.
Chapter 1 Introduction
5
3 Functions
3.1 Protection functions
Description ANSI Code
IEC 61850
Logical Node
Name
IEC 60617
graphical
symbol
Current protection
Overcurrent protection 50,51,67 PTOC
3IINV>
3I >>
3I >>>
Earth fault protection 50N, 51N, 67N PEFM
I0INV>
I0>>
I0>>>
Neutral earth fault protection 50G, 51G
Sensitive earth fault protection 50Ns, 51Ns,
67Ns
3INE>
3INE>>
Negative-sequence overcurrent
protection 46
Thermal overload protection 49 PTTR Ith
Overload protection 50OL PTOC 3I >OL
Voltage protection
Overvoltage protection 59 PTOV 3U>
3U>>
Undervoltage protection 27 PTUV 3U<
3U
Breaker protection and control function
Breaker failure protection 50BF RBRF
3I> BF
I0>BF
I2>BF
Dead zone protection 50SH-Z
Synchro-check and energizing check 25 RSYN
Auto-reclosing 79 RREC OI
Three-pole tripping 94-3 PTRC
Capacitor bank protection
Unbalanced current protection 46NI
Chapter 1 Introduction
6
Unbalanced voltage protection 46NU
Undercurrent protection 37 I<
Load shedding function
Low frequency load shedding function 81U
Low voltage load shedding function 27
Overload load shedding function
Secondary system supervision
CT secondary circuit supervision
VT secondary circuit supervision 97FF
Other functions
Fast busbar protection using reverse
interlocking
3.2 Control functions
Description ANSI Code
IEC 61850
Logical Node
Name
IEC 60617
graphical
symbol
Circuit breaker, disconnector and
other switching devices control
3.3 Monitoring functions
Description
Position of circuit breaker, disconnector and other switching device monitoring
Circuit breaker status supervision
Auxiliary contacts of circuit breaker supervision
Self-supervision
Fault recorder
3.4 Station communication
Description
Chapter 1 Introduction
7
Front communication port
Isolated RS232 port
Rear communication port
0-1 isolated electrical RS485 communication ports
0-2 Ethernet electrical/optical communication ports
Time synchronization port
Communication protocols
IEC 61850 protocol
IEC 60870-5-103 protocol
3.5 IED software tools
Functions
Reading measuring value
Reading IED report
Setting
IED testing
Disturbance recording analysis
IED configuration
Printing
Chapter 1 Introduction
8
Chapter 2 General IED application
9
Chapter 2 General IED application
About this chapter
This chapter describes the use of the included software
functions in the IED. The chapter discusses general application
possibilities.
Chapter 2 General IED application
10
1 Display on LCD screen
1.1 LCD screen display function
The LCD screen displays measured analog quantities, report ouputs, menu
and logic linker status.
1.2 Analog display function
The analog display includes measured Ia, Ib, Ic, 3I0, Is0, Ua, Ub, Uc, U4, Mea
Ia, Mea Ib, Mea Ic, Mea Ua, Mea Ub, Mea Uc, Mea Uab, Mea Ubc and Mea
Uca.
The Mea means that the measurement analogue quantity, for example, Mea
Ia, means the measurement current for phase A.
1.3 Report display function
The report display includes tripping, alarm and operation recording.
1.4 Menu dispaly function
The menu dispaly includes main menu and debugging menu, see chapter
Chapter 23 for detail.
Chapter 2 General IED application
11
2 Report record
The report record includes tripping, alarm and operation reports. See Chapter
24 general report list for detail.
Chapter 2 General IED application
12
3 Disturbance recorder
3.1 Introduction
To get fast, complete and reliable information about fault current, voltage,
binary signal and other disturbances in the power system is very important.
This is accomplished by the disturbance recorder function and facilitates a
better understanding of the behavior of the power system and related primary
and secondary equipment during and after a disturbance. An analysis of the
recorded data provides valuable information that can be used to explain a
disturbance, basis for change of IED setting plan, improvement of existing
equipment etc.
The disturbance recorder, always included in the IED, acquires sampled data
from measured analogue quantities, calculated analogue quantity, binary
input and output signals.
3.2 Fault recording
The IED can save the latest 40 fault records (be memorized in case of power
disconnection), which can be read via the IED operation interface or
communication port. The fault record consists of the following information:
Fault time: date and time
Event list: operative element and time
Running data: current, voltage, frequency and phase angle
Operation setting
IED operation mode
3.3 Wave recording
Wave recording function is used to record the analogue data and status with a
pre-defined length after and before disturbance occurs, reshow the operation
track of the protected IED. The recording wave includes at most 12 analogue
channels, 64 binary channels (32 binary input, 16 binary output and 16
GOOSE signal) and time sequence information. IED records the data as the
sample of 20 points in each cycle, accumulated length of each record is up to
Chapter 2 General IED application
13
8 seconds and 20 latest recording waves can be stored. Wave are searched
and called via dedicated software from the RS232 serial port on panel, and be
converted to COMTRADE format for being used by other recording wave
analysis software or fault simulation software.
3.4 Sequence of event record
The IED monitors and records the change of operation event, alarm event,
binary input, binary output and protection linker, records the event occurrence
time, reason and current status, and transfers the information to the station
control center via the communication port.
3.5 Operation record
The disturbance recorder information is saved for each of the recorded
disturbances in the IED and the user may use the local human machine
interface or dedicated tool to get some general information about the
recordings. The disturbance recording information is included in the
disturbance recorder files. The information is also available on a station bus
according to IEC 61850 and IEC 60870-5-103.
Fault wave recorder with great capacity, can record full process of any fault,
and can save the corresponding records. Optional data format or wave format
is provided, and can be exported through serial port or Ethernet port by
COMTRADE format.
Chapter 2 General IED application
14
4 Self-supervision function
4.1 Introduction
The IED may test all hardware components itself, including loop out of the
relay coil. Finding whether or not the IED is in fault through warning LED and
warning characters which shown in LCD and display reports to indicate fault
type.
The method of fault elimination is replacing fault board or eliminating external
fault.
4.2 Self-supervision principle
Measuring resistance between analog circuits and ground
Measuring the output voltage in every class
Checking zero drift and scale
Verifying alarm circuit
Verifying binary input
Checking actual live tripping including circuit breaker
Check setting values and parameters
4.3 Self-supervision report
Table 1 Self-supervision report list
Information Description
RAM Error RAM is abnormal
EPROM Error EPROM is abnormal
Flash Error Flash is abnormal
BO Abnormal Binary output is abnormal
AD Error AD is abnormal
Zero Offset Zero drift is out of limitation
Invalid SetGr Pointer of setting group is error
Chapter 2 General IED application
15
Information Description
Setting Chk ERR Setting value is error
Logic Scheme ERR Logic file and CPU file do not cooperate
Chapter 2 General IED application
16
5 Time synchroniation function
5.1 Introduction
Use the time synchronization source selector to select a common source of
absolute time for the IED when it is a part of a protection system. This makes
comparison of events and disturbance data between all IEDs in a SA system
possible.
5.2 Synchronization principle
Time definitions
The error of a clock is the difference between the actual time of the clock, and
the time the clock is intended to have. The rate accuracy of a clock is
normally called the clock accuracy and means how much the error increases,
i.e. how much the clock gains or loses time. A disciplined clock is a clock that
knows its own faults and tries to compensate for them, i.e. a trained clock.
Synchronization principle
From a general point of view synchronization can be seen as a hierarchical
structure. A module is synchronized from a higher level and provides
synchronization to lower levels.
A module is said to be synchronized when it periodically receives
synchronization messages from a higher level. As the level decreases, the
accuracy of the synchronization decreases as well. A module can have
Chapter 2 General IED application
17
several potential sources of synchronization, with different maximum errors,
which gives the module the possibility to choose the source with the best
quality, and to adjust its internal clock from this source. The maximum error of
a clock can be defined as a function of:
The maximum error of the last used synchronization message
The time since the last used synchronization message
The rate accuracy of the internal clock in the module.
5.2.1 Synchronization from IRIG
The built in GPS clock module receives and decodes time information from
the global positioning system. The module is located on the CPU Module. The
GPS interfaces to the IED supply two possible synchronization methods,
IRIGB and PPS (or PPM).
5.2.2 Synchronization via PPS or PPM
The IED accepts PPS or PPM to the GPS interfaces on the CPU Module.
These pulses can be generated from e.g. station master clock. If the station
master clock is not synchronized from a world wide source, time will be a
relative time valid for the substation. Both positive and negative edges on the
signal can be accepted. This signal is also considered as a fine signal.
5.2.3 Synchronization via SNTP
SNTP provides a Ping-Pong method of synchronization. A message is sent
from an IED to an SNTP-server, and the SNTP-server returns the message
after filling in a reception time and a transmission time. SNTP operates via the
normal Ethernet network that connects IEDs together in an IEC61850
network. For SNTP to operate properly, there must be a SNTP-server present,
preferably in the same station. The SNTP synchronization provides an
accuracy that will give 1ms accuracy for binary inputs. The IED itself can be
set as a SNTP-time server.
Chapter 2 General IED application
18
6 Setting
6.1 Introduction
Settings are divided into separate lists according to different functions. The
setting consists of two parts -setting list and communication parameters.
6.2 Operation principle
The setting procedure can be ended at any the time by the key SET or
QUIT. If the key SET is pressed, the display shows the content of Select.
The range of setting zone is from 1 to 16. After confirming with the setting
zone-key SET, those new settings will be valid. If key QUIT is pressed
instead, all modifications which have been changed will be ignored.
Chapter 2 General IED application
19
7 Authorization
7.1 Introduction
To safeguard the interests of customers, both the IED and the tools that are
accessing the IED are protected, subject of authorization handling. The
concept of authorization, as it is implemented in the IED and the associated
tools is based on the following facts:
There are two types of points of access to the IED:
local, through the local HMI
remote, through the communication ports
There are different levels (or types) of guest, super user and protection
engineer that can access or operate different areas of the IED and tools
functionality.
Chapter 2 General IED application
20
Chapter 3 Overcurrent protection
21
Chapter 3 Overcurrent protection
About this chapter
This chapter describes the protection principle, input and
output signals, parameter, logic diagram, IED report and
technical data used for overcurrent protection.
Chapter 3 Overcurrent protection
22
1 Overcurrent protection
1.1 Introduction
The non-directional overcurrent elements can be applied as backup
protection functions in various applications including line and transformer
protection in systems with radial nature and those which are supplied from
a single source. The directional overcurrent protection allows the
application of the IED also in systems where protection coordination
depends on both the magnitude of the fault current and the direction of
power flow to the fault location, for instance in case of parallel lines or
transformers, or in a loop configuration. Main features of the overcurrent
protection are as follows:
Two definite time stages
One inverse time stage
11 kinds of IEC and ANSI inverse time characteristic curves as well as
optional user defined characteristic
Settable directional element characteristic angle to satisfy the different
network conditions and applications
Each stage can be set individually as directional/non-directional
Each stage can be set individually for inrush restraint
Cross blocking function for inrush detection
Settable maximum inrush current
First definite stage and inverse time stage can be set individually to
alarm or trip
VT secondary circuit supervision for directional protection. Once VT
failure happens, the directional stage can be set to be blocked or to be
non-directional
Undervoltage criteria checking (selectable), blocking of the definite
time stages is possible when the measured voltage exceeds the
threshold
1.2 Protection principle
1.2.1 Time characteristics
Chapter 3 Overcurrent protection
23
The time characteristic for each stage can be chosen as definite time stage
or some type of inverse time characteristic. 11 kinds of inverse time
characteristics are available. It is also possible to create a user defined
time characteristic. Each stage can operate in conjunction with the
integrated inrush restraint and directional functions and operate based on
measured phase current. In addition, an undervoltage control feature is
provided which can be used for definite overcurrent stages.
Furthermore, each stage is independent from each other and can be
combined as desired.
Pickup value for the definite stage can be set in setting value. Each phase
current is compared with the corresponding setting value with delay time. If
currents exceed the associated pickup value, after expiry of the time delay,
the trip command or alarm signal is issued. The dropout value of the
definite stages is approximately equal to 96% of the pickup value for I/In
0.5. The condition for delay time starting is expressed in the following
formula:
Equation 1
The delay time can be set for each definite stage individually in setting.
After the delay time elapsed, a trip command or alarm signal is issued.
For the delay time of inverse time characteristic, which is calculated here
based on the type of the set characteristic, the magnitude of the current
and a time multiplier, both ANSI and IEC based standard curves are
available, and any user-defined characteristic can be defined using
following formula:
K_OC
Equation 2
where:
A_OC: Time factor for inverse time stage
B_OC: Delay time for inverse time stage
P_OC: Index for inverse time stage
Chapter 3 Overcurrent protection
24
K_OC: Time multiplier
By applying setting of these coefficients, the IED calculates the tripping or
alarming time from the measured current in each phase separately. Once
the calculated time has been elapsed, the trip signal or alarm signal is
issued.
1.2.2 Inrush restraint function
The protection IED may detect large magnetizing inrush currents during
transformer energizing. In addition to considerable unbalance fundamental
current, inrush current comprises large second harmonic current which
does not appear in short circuit current. Therefore, the inrush current may
affect the protection functions which operate based on the fundamental
component of the measured current. Accordingly, inrush restraint logic is
provided to prevent overcurrent protection from maloperation.
The inrush restraint feature operates based on evaluation of the 2nd
harmonic content which is present in measured current. The inrush
condition is recognized when the ratio of second harmonic current to
fundamental component exceeds the corresponding setting value for each
phase. The setting value is applicable for both definite time stage and
inverse time stage. The inrush restraint feature will be performed as soon
as the ration exceeds the set threshold.
Furthermore, by recognition of the inrush current in one phase, it is
possible to set the protection in a way that not only the phase with the
considerable inrush current, but also the other phases of the overcurrent
protection are blocked for a certain time. This is achieved by
cross-blocking feature integrated in the IED.
The inrush restraint function has a maximum inrush current setting. Once
the measuring current exceeds the setting, the overcurrent protection will
not be blocked any longer.
1.2.3 Low voltage component
It is possible to set the protection in a way that the definite stages of
overcurrent element would operate only when at least one phase-to-phase
voltage falls below than the corresponding low voltage setting. This
component can be used to prevent any maloperation of the overcurrent
element during reverse charging of electric motors. The low voltage
Chapter 3 Overcurrent protection
25
component can be set for each definite stage by the dedicated binary
settings.
The voltages connected to IED may correspond to three phase to earth
voltages VA-N, VB-N, VC-N or any phase to earth voltage or phase to
phase voltage by using dedicated binary setting. In case of 3Ph V
Connect is enabled, three phase to phase voltages are measured, or any
one phase to phase voltage should be measured.
1.2.4 Direction determination feature
The direction detection is performed by determining the position of current
vector in directional characteristic. In other word, it is done by comparing
phase angle between the fault current and the reference voltage. Figure 1
illustrates the direction detection characteristic for phase A element.
Forward
UBC_Ref
Ph_Char
IA
IA-
0
90
Bisector
Figure 1 Direction detection characteristic of overcurrent protection directional element
where:
Ph_Char: The settable characteristic angle
The assignment of the applied measuring values used in direction
determination has been shown in Table 2 for different types of faults.
Table 2 Assignment of applied current and reference voltage for directional element
Phase Current Voltage
A aI bcU
B bI caU
Chapter 3 Overcurrent protection
26
C cI abU
As can be seen from Table 2, the healthy voltages are used in direction
determination. This guarantee corrects direction determination even if the
fault voltage has collapsed totally because of a single-phase short-circuit
fault. For three-phase short-circuit fault, without any healthy phase,
memory voltage values are used to determine direction clearly if the
measured voltage values are not sufficient. The detected direction is
based on the memory voltage of previous power cycles.
During direction detection, if VT fail happens (a short circuit or broken wire
in the voltage transformer's secondary circuit or operation of the voltage
transformer fuse), may result in maloperation by directional overcurrent
elements. In such situation, directional (if selected) overcurrent protection
will be blocked.
1.2.5 Logic diagram
OR
AND
Ia2/Ia1 >
Ib2/Ib1 >
Ic2/Ic1 >
t <
Cross BLK
Figure 2 Logic diagram of cross-blocking for inrush restraint
OR
OC1_V Blk On
OC2_V Blk On
Uab OCInv 2H_Blk On
< I_2H_UnBlk
AND
OCInv 2H_Blk Off
0
INV A OK
AND
Cross BLK
OCInv 2H_Blk On
OCInv 2H_Blk Off
0
VT Fail
Blk Fun_VTFail
UnBlk Fun_VTFail
Phase A Forward
OC Inv Dir On
Ia Inverse
AND
OC Inv Dir Off
1OR INV A OK
AND
OR
OC Inv Dir Off
1
Figure 5 Logic diagram of inverse overcurrent stage
1.3 Input and output signals
IP1
IP2
IP3
OC1_Trip
OC2_Trip
OC Inv TripUP1
UP2
UP3
Table 3 Analog input list
Signal Description
IP1 Signal for current input 1
IP2 Signal for current input 2
IP3 Signal for current input 3
UP1 Signal for voltage input 1
UP2 Signal for voltage input 2
UP3 Signal for voltage input 3
Chapter 3 Overcurrent protection
29
Table 4 Binary output list
Signal Description
OC1_Trip Overcurrent protection stage 1 trip
OC2_Trip Overcurrent protection stage 2 trip
OC Inv Trip Overcurrent protection inverse time stage trip
1.4 Setting parameters
1.4.1 Setting list
Table 5 Function setting list for overcurrent protection
NO. Default Abbr. Explanation Unit Min. Max.
1. In I_OC1 Current setting for stage 1 A 0.05In 20.00In
2. 0.4 T_OC1 Time setting for stage 1 S 0.00 60.00
3. 1.5In I_OC2 Current setting for stage 2 A 0.05In 20.00In
4. 0.1 T_OC2 Time setting for stage 2 S 0.00 60.00
5. 90.0 U_OC_UnBlk
Low voltage setting for
blocking overcurrent
protection (phase to phase)
V 1.00 120.0
6. 1 Curve_OC Inv Inverse time curve 1 12
7. 0.5In I_OC Inv Current setting for inverse
time stage A 0.05In 20.00In
8. 1 K_OC Inv Time multiplier 0.05 999.0
9. 0.056 A_OC Inv Time factor for inverse time
stage S 0.001 1000
10. 0.02 P_OC Inv Index for inverse time stage 0.01 10.00
11. 0 B_OC Inv Delay time for inverse time
stage S 0.00 60.00
12. 30 Angle_OC Direction characteristic angle degree 0.00 90.00
13. In I_2H_UnBlk Maximum inrush current
setting A 0.25In 20.00In
14. 0.15 Ratio_I2/I1
Ratio for second harmonic
current to fundamental
component
0.07 0.50
15. 0.2 T2h_Cross_Blk Time setting for
cross-blocking function S 0.00 60.00
Table 6 Logical linker list for overcurrent protection
Chapter 3 Overcurrent protection
30
NO. Abbr. Explanation
1. Func_OC1 Enable or disable the stage 1 of overcurrent protection
2. Func_OC2 Enable or disable the stage 2 of overcurrent protection
3. Func_OC Inv Enable or disable the inverse time stage of overcurrent
protection
Table 7 Binary setting list for overcurrent protection
Bit 0 1 Explanation
1.0 OC1 Dir Off OC1 Dir On Enable or disable the direction for
stage 1
1.1 OC1 V_Blk Off OC1_V Blk On Enable or disable the low voltage
blocking for stage 1
1.2 OC1 2H_Blk Off OC1 2H_Blk On Enable or disable the inrush
restraint for stage 1
1.3 OC2 Dir Off OC2 Dir On Enable or disable the direction for
stage 2
1.4 OC2 V_Blk Off OC2 V_Blk On Enable or disable the low voltage
blocking for stage 2
1.5 OC2 2H_Blk Off C2 2H_Blk On Enable or disable the inrush
restraint for stage 2
1.6 OC Inv Dir Off OC Inv Dir On Enable or disable the direction for
inverse stage
1.7 OCInv 2H_Blk Off OCInv 2H_Blk On Enable or disable the inrush
restraint for inverse stage
2.9 3Ph V Connect 1Ph V Connect Select voltage connection way by
single phase or three phase
2.14 UnBlk Fun_VT Fail Blk Fun_VT Fail Enable the function of VT fail
blocking
4.0 OC1 Alarm OC1 Trip Stage 1 of overcurrent protection
alarm or trip
4.1 OC Inv Alarm OC Inv Trip Inverse stage of overcurrent
protection alarm or trip
1.5 Reports
Table 8 Event information list
Information Description
OC1 Trip Overcurrent protection stage 1 issues trip command
OC2 Trip Overcurrent protection stage 2 issues trip command
OC Inv Trip Overcurrent protection inverse time stage issues trip command
Chapter 3 Overcurrent protection
31
Information Description
Inrush Blk Inrush is detected to block function.
Table 9 Alarm information list
Information Description
OC1 Alarm Overcurrent protection stage 1 issues alarm signal
OC Inv Alarm Overcurrent protection inverse time stage issues alarm signal
1.6 Technical data
Table 10 Technical data for overcurrent protection
Item Rang or Value Tolerance
Definite time characteristics
Current 0.08 Ir to 20.00 Ir 3% setting or 0.02Ir
Time delay 0.00 to 60.00s, step 0.01s 1% setting or +40ms, at 200% operating setting
Reset time approx. 40ms
Reset ratio Approx. 0.95 at I/In 0.5
Inverse time characteristics
Current 0.08 Ir to 20.00 Ir 3% setting or 0.02Ir
IEC standard Normal inverse;
Very inverse;
Extremely inverse;
Long inverse
5% setting + 40ms, at 2
Chapter 3 Overcurrent protection
32
Maximum operating time 100s
Reset mode instantaneous
Reset time approx. 40ms,
Directional element
Operating area range 170 3, at phase to phase voltage >1V Characteristic angle 0 to 90, step 1
Chapter 4 Earth fault protection
33
Chapter 4 Earth fault protection
About this chapter
This chapter presents the protection principle, input and output
signals, parameter, logic diagram, IED report and technical data
included in earth fault protection.
Chapter 4 Earth fault protection
34
1 Earth fault protection
1.1 Introduction
The non-directional earth fault elements can be applied as backup protection
functions in various applications including line and transformer protection in
systems with radial nature and those which are supplied from a single source.
The directional earth fault protection allows the application of the IED also in
systems where protection coordination depends on both the magnitude of the
earth fault current and the direction of power flow to the fault location, for
instance, in case of parallel lines or transformers, or in a loop configuration.
Main features of the earth fault are as follows:
Two definite time stages
One inverse time stage
11 kinds of the IEC and ANSI inverse time characteristic curves as well
as optional user defined characteristic
Zero sequence directional element
Negative sequence directional element is applied as a complement to
zero sequence directional element. It can be enabled/disabled by setting
Each stage can be set individually as directional/non-directional
Settable directional element characteristic angle to satisfy the different
network conditions and applications
Each stage can be set individually for inrush restraint
Settable maximum inrush current
Inrush restraint function adopting 2nd harmonic measured phase or earth
current (settable)
First definite stage and inverse time stage can be set individually to alarm
or trip
VT secondary circuit supervision for directional protection function. Once
VT failure happens, the directional stage can be set to be blocked or to
be non-directional
Chapter 4 Earth fault protection
35
Zero-sequence current is calculated by summation of 3 phase currents or
measured from earth phase CT selectable
1.2 Protection principle
1.2.1 Time characteristic
The time characteristic for each stage can be chosen as definite time stage or
some type of inverse time characteristic. 11 kinds of inverse time
characteristics are available. It is also possible to create a user defined time
characteristic. Each stage can operate in conjunction with the integrated
inrush restraint and directional functions and operate based on measured
phase current.
The earth fault protection can operate with the measured or calculated zero
sequence current (zero-sequence current IN measured from earth phase CT
or zero-sequence current 3I0 calculated by the summation of three phase
currents, 3I0=IA+IB+IC). These two types of measured quantity can be enabled
or disabled via binary setting. If setting 3I0 Measured is enabled in the
binary setting, the function will operate based on the measured
zero-sequence current, whereas, the 3I0 Calculated is enabled, the
zero-sequence current is calculated from the summation of three phase
currents.
Furthermore, each stage is independent from each other and can be
combined as desired.
Pickup value for the definite stage can be set in setting value. The measured
or calculated zero-sequence current is compared with the corresponding
setting value with delay time. If zero-sequence current exceed the associated
pickup value, after expiry of the time delay, trip command is issued. The
condition for delay time start is expressed in the following formula
Equation 3
The time delay can be set for each definite stage individually in setting. After
the delay time elapsed, trip command or alarm signal is issued. The drop out
value of the definite stages is approximately equal to 96% of the pickup value