NLDC 1

SCADA-Functions

Author, Vineeta Agarwal

Place PSTI, Bangalore

Date 29-4-2011

NLDC 2

Responsibilities of RLDCs

Operation, monitoring and control of Regional Grids.

Control of Central Sector Transmission System.

Allocation of Central Sector Generation.

Data Exchange with SLDCs.

Data exchange with NLDC

NLDC 3

Responsibilities of SLDCs and Sub-LDCs

SLDCs Operation, monitoring and control of state owned power

system. Data Exchange with Sub-LDCs. Data exchange with RLDC

Sub-LDCs Responsible for Operation, monitoring and control of power

system data in its area Data Exchange with SLDCs.

NLDC 4

ULDC Scheme

Unified Schemes for all regions for compatibility Three level hierarchical SCADA along with EMS More than 2,100 km of Optic fibre network More than 3,000 km of microwave network More than 10 lakhs sq. km geographical area

NLDC 5

Scada Supervisory Control and Data Acquisition

SCADA is the system responsible for gathering, processing, and displaying information about the state of a monitored system. From a SCADA control center, operators and application programs can oversee and change the operating state of monitored devices.

NLDC 6

SCADA FUNCTIONS

TO SUPPORT REAL TIME MONITORING AND CONTROL

Data Acquisition Supervisory Control Data exchange Data Processing Alarms, Flags SOE, Generalized calculations Disturbance Data Collection (HDR) Historical Information Storage & Retrieval (ISR)

NLDC 7

Data Acquisition

Data Acquisition process samples real world physical conditions and convert the samples into digital numeric values for use by computer. Components of Data Acquisition System

Sensors/transducers that convert physical parameters to electrical signals.

Signal conditioning circuitry to convert sensor signals into a form that can be converted to digital values.

Analog-to-digital converters A Scada system to process this digital data.

NLDC 8

SCADA Host Functions

Primary task is to maintain SCADA databases.

Performs other functions: Converts raw data to engineering units.

Performs limit checks.

Processes alarms.

Processes calculations.

Manages communication devices.

NLDC 9

Data Processing The major function of the data processing module is to

place data from RTUs into the database.

Status Points Analog ValuesPulse Accumulators

Retrieved valueschecked for anystatus changes

Retrieved valuesconverted toengineering unitsand placed indatabase.

Last retrieved value isconverted to floatingpoint and scaled.

Points then checkedfor a defined “normal state”

Engineering valuechecked againstoperational limitsand rate of changelimits.

Conditionally, differencewith respect to previousvalue is computed, withadjustment if valuenegative (counter wrap-

around)

NLDC 10

TELEMETRY FOR ULDCTELEMETRY FOR ULDC

P Q

V

O

SS

DS

DC

MW MVAR

VOLTAGE

TAP POSITION

SINGLE STATUSISOLATOR POSIITION, PROTECTION,

LOSS OF VOLTAGE

DOUBLE STATUS CIRCUIT BREAKER POSITION

DIGITALCONTROLCIRCUIT BREAKER CONTROL

F FREQUENCY

THE PARAMETERS ARE MONITORED FOR FOLLOWING STATIONS :

•Substations 220 KV and above

•132/110KV AC Interstate Tie lines and in loop of 220 KV transmissions system

•Generating Station above 50MW capacity.

•Significant stations identified by constituents

P Q

DS DC

SS

SS

V F

DS

SS

SS

O

P Q

SS

DS

P Q

P Q

DS

DS

SS

SS

SS

SS

Q

DS

V F

SS

SS

SS

SS

SSSS

SS

NLDC 11

Data types

SCADA processes and stores three different types of data:

analog, status, and count data.

NLDC 12

Analog Data

Analogs are numeric values representing the state of variable-state devices, such as power lines, transformers etc

In the monitored system a physical variable is usually

measured by a transducer, and the output of the transducer is passed through an analog-to-digital (A/D) converter in the RTU .

NLDC 13

Transducer

linear Conversion

NLDC 14

   Status Data

Status values represent the state of devices, such as circuit breakers, tap changers, LOV,BPT

NLDC 15

Digital Data

Potential free contacts are used to transfer switch position to control centre.

NLDC 16

Data flow from RTU RLDC NLDC

NLDC 17

Data polling method

Analogs are defined as periodic/Cyclic data . The periodicity varies from 10 seconds to 15 seconds

depending upon the quantity of data and available bandwidth .

Digital input state changes are to be reported spontaneously .

The Digital input data have higher priority than Analog values.

NLDC 18

Data Flow

NLDC 18

NLDC 19

Supervisory Control

In Scada systems control actions are performed by RTU or PLC.

operator of the control room can override or adjust normal PLC (RTU) controls

NLDC 20

ALARMS

NLDC 21

ALARMS

ANALOG DIGITAL

NLDC 22

Alarms-analogs

Normal limit-Range of limits which device is considers to be operating normally

Reasonability Limit-range of values that SCADA uses to determine whether the value retrieved for the analog is realistic.

Forbidden Limit-Range of values that SCADA considers violated when the analog point fall within that range

Dead band Limits-On a pair of low or high limits if it is violated the value must rise above the limit by at least the dead band amount before the SCADA consider s the analog to be back within normal limits .

NLDC 23

Normal Alarms-analogs

MW/MVAR/MVA/FREQ/VOLTAGE ALARM LIMIT-OPERATIONAL ALARM LIMIT-ALARMING ALARM LIMIT-EMERGENCY

NLDC 24

Alarm Limit -Mw

ALARM LIMIT-OPERATIONAL+/- 1.05*(1.732*V*I*O.8) ALARM LIMIT-ALARMING+/- 1.10*(1.732*V*I*O.8) ALARM LIMIT-EMERGENCY+/- 1.15*(1.732*V*I*O.8)

V-NOMINALVOLTAGE I-NOMINAL CURRENT

NLDC 25

Exception Displays

Abnormal digital status points and analogs displayed in chronological order

Abnormal digital status points and analogs displayed as per category.

Abnormal digital status points and analogs displayed per location

Failed (LDC) sites displayed in chronological order

Failed substations and devices in chronologically order.

NLDC 26

Exception Displays

NLDC 27

Priority Alarms

Alarms are categorized in 8 category Priority 1 -Emergency threshold overshoot and status point alarms

of controllable switching devices, ICCP links and other ICCP data exchange related alarms)

• Priority 2 -Point alarms of non-controllable switching devices. • Priority 3 -Protection trips and substation alarms • Priority 4 -Alarms relevant to RTU’s, communication lines, and

alarms of “unreasonable” category • Priority 5 - “configuration management” alarms, i.e. hardware

failures (mimic board, printer, etc.) and software failures • Priority 6 –All Network alarms-state estimator , contingency

analysis) and the alarms detected by the generation applications (AGC and LF)

• Priority 7 -Scada topology alarms •Priority 8 -HDR, Tagging, Limit Replacement.

NLDC 28

Flags Gives Source and Quality of data

Source of data RTU -----------Telemetered ENTERED-----Manually Entered EXTERNAL----Always to be entered manually INTERSITE-----Data from other site CALCULATED—Calculation tag

Quality of data GARBAGE-The data is unreliable. The flag appears when data

is uninitialized. SUSPECT-Data is labelled suspect when there is one or more

of this flag (OLD, BAD, OVER and RESUSP) REPLACED-Data is labelled replaced when MANREP,

ESTREPor REMPL) GOOD-Data is labelled GOOD when it is not GARBAGE,

SUSPECT and REPLACED.

NLDC 29

Flags

NLDC 30

Flags Unit: - uninitialized. Old:-Could not be retrieved in the last scan Telemetry failure:- communication with RTU failed BAD: - when RTU returns one or more standard test values in the

RTU outside the allowed limits. Either Transducer is faulty or there is an RTU malfunctioning.

Over Range: - Raw Value Received from RTU is outside the expected Range.

Unreasonable:-The converted value has crossed the reasonability limit.

Anomalous:-Basically not a data quality Flag .State Estimator considers the above measurement not fit for the solution.

Manually replaced:-Replaced by operator

NLDC 31

Flags State Estimator replaced:-Value for an analog is

overridden, or replaced, by state Estimator on operator request.

Generalized Calculation: - Value replaced through generalised calculation.

Maintenance mode: - The Device has been placed in maintenance mode.

NIS:-device not in service. It will not allow scanning or calculation to update the record which is marked NIS

Alarm Inhibit: - Alarms for this device inhibited. Remote Suspect:-The value is suspect at source control

centre. Remote Replaced:-The value has been replaced by

source control centre

NLDC 32

Sequence Of Events Sequence of events provides milli secs accurate

time of status changes for devices monitored by Remote Terminal Units .

The RTU clock is synchronized periodically by the control center clock .

Reading its internal clock when a SOE status point changes state .

Time stamped digital data stored in RTU buffer and transferred as file or Digital data with time stamped is transferred for SOE

NLDC 33

Historical DATA Recording Historical Data Recording (HDR) function allows you

to preserve a time series of any set of analog, status, and accumulator measurements . HDR functions

Saves the SCADA measurements in disk files called Historical files.

Keeps track of the Historical files that have been created and allows you to delete them.

The Database Reconstruction functions allow you to reconstruct or create a Data History listing from the data in the Historical files.

The reconstructed database can be moved to the network database for use by other applications.

NLDC 34

Trend Displays

Real Time Trend Display Digital, analog or counter value can be viewed

simultaneously in different displays. The information is usually sampled cyclically, stored in

memory on a circular buffer and plotted on a window against time.

Historical Trend Displays To trend the value (digital, analog counter) with archived

data

NLDC 35

Trend Displays

DISPLAY OBJECT

TRACK

NLDC 36SCADA-EMS GROUP NRLDC 36

MODIFYING TRACK ATTRIBUTES

AXIS DIRECTION Whether the X axis is horizontal (the default) or vertical

Grid lines Whether grid lines are visible or not (the default) in the display area

SCALE TO OBJECT All display objects are scaled to the currently selected display object's scale

AUTO SCALE set automatically based the historical maximum and historical minimum

FULL DATE STRING Whether the date and time is displayed or just the time.

NLDC 37

Tagging

Tags are free formatted text, which provide critical information to next shift operator .

Tags can be provided over digital, analog and counters data-points.

Operators can insert, edit or delete any number of tags, if they have privileges to do so.

Some operators may only be allowed to view tags. These operations can be done from graphic displays by

selecting a dynamic object or from a system list of entities.

NLDC 38

Types of Data Outages

All data became suspected.

All the data pertaining to your organisation is out.

All the data pertaining to other organisation is out.

Data only from a one or some of the substation is out.

NLDC 39

Trouble Shooting

All the data on display have become

suspected

1. Both Data server of this control center are out.

OR

2. Master Data Server failed and standby data server

has not taken over.

NLDC 40

Trouble Shooting

All the data pertaining to your organisation

is not updating.

1. Both ICCP server of this control center are out.

OR

2. Master ICCP Server failed and standby ICCP server has not taken over.

All the data pertaining to other organisation

is not updating.

NLDC 41

Trouble Shooting (contd.)

Some Data is not updating on display

or it is marked as suspect

Is RTU reporting to this control

center.

Check CFE Route

Check ICCP Route

Find out from which RTU it was coming.

Is this RTU belongs to

your organization.

Yes

No

No

Yes

NLDC 42

Does the bad data belongto your organisation.

Yes

Find to which Sub-LDC this RTU reports.

Are both servers OK.

Communication link between Sub-LDC and SLDC is out.

Data is interrupted due to outages of servers at Sub-LDC

NoYes

Checking ICCP Route

Are the ICCP Servers of RSCC OK.

Communication between RSCC & this SLADC not OK.

Yes

Data is interrupted due to outages of ICCP servers at RSCC.

No

Are the Data Servers of RSCC OK.

Data is interrupted due to outages of Data servers at RSCC.

NoYes

No

NLDC 43

DATA BASE

SCADAMDL for the SCADA database

NETMODEL for the Network database

GENMODEL for the Generation database

DTSMODEL for the DTS database

COMMUNICATION database

NLDC 44

Network Database

Network Modeling

NETMODEL How Network Components are electrically connected?

The Parameters used to model them.

NLDC 45

Network Database

THE NETWORK DATA

The topology of power network A description of every component in the system An equivalent model Schedules Tables A load model Operating limits

NLDC 46

Thank you !!