Power System SCADA

8/10/2019 Power System SCADA

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POWER SYSTEM SCADA

Supervisory Control and DataAcquisition Systems


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POWER SYSTEM


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Used in industrial and en ineerin a lications

To monitor and control distributed systems from amaster location

Solutions across a large variety of industries

Electric power gen. ,trans., & distr. Oil and gas industry metering and control systems

Traffic signals

Etc. Used in US Utilities industry since 1960s


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SCADA (Supervisory Control and Data

Std C37.1-1994 specifications as "a system

o eratin with coded si nals overcommunication channels so as to providecontrol of RTU [Remote Terminal Unit]

equ pmen .


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.

Ability to perform operations at an unattended

Successful carried out the power systemoperat ons can prov e s gn cant cost sav ngs


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.

from time to time, e.g. opening or closingcircuit breakers Cost providing and maintaining operator attended

cannot be justified Delay operation may lengthen an outage and

deteriorate customer service

uneconomically


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Began in the early 1960s as an electronic system

master station and a remote station. The master

station would receive data through a telemetrynetwork and then store the data on mainframe

computers.


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In the early 1970s, distributed control systems (DCS)were developed to control separate remotesu systems an in t e 1 s, wit t e eve opment othe microcomputer, process control could be

enabled DCS to use programmable logic controllers(PLC), which have the ability to control sites without

a ng rec on rom a mas er.


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In the late 1990s, SCADA systems were built with DCSili i n m w r miz n

certain proprietary control features built in by the

designer. Now, with the Internet being utilized moreas a communication tool, SCADA and telemetrysystems are using automated software with certain

.


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control processes but are also used formeasurin forecastin billin anal zin andplanning. Todays SCADA system must meet a

whole new level of control automation whilen er ac ng w yes er ay s o so e e equ pmenyet remain flexible enough to adapt to

.


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Control and Supervision

Term applied to remote operation (control) of such devices as motors or

circuit breakers and signaling back (supervision) to indicatethe desired operation has been effected

Sim le s stems have been used in ower utilitoperations,early systems the supervision was provided by

Red light indicate the device was closed

Green li ht indicate the o eration successfull com leted e. .

opening circuit breaker)


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Wires required for each devices between control pointand controlled devices, therefore Cost and complexity increased directly with number of

devices to be remotely controlled and supervised

Reliability suffered due to electrical noise induced in thecontrol circuit

re c rcu can m n m ze y e use o se ec ve re ays usystem became complex and difficult to maintain, limited inspeed of operation


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Computer based system

equipment

Transmit control messages to remote units Receive information

Displayed on CRT and printed on electric printers

. Online diagrams Wall diagrams


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SCADA

Evolved in parallel with the growth and

Three generations of SCADA First Generation- Monolithic

Second Generation- Distributed

Third Generation- Network


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Monolithic SCADA

systems N w rk n n- xi n

Standalone systems with virtually no connectivity to

other s stems WAN use today unknown that time

Use of two identicall e ui ed mainframe s stems

Primary

Backup (take over when failure detected at primary


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Monolithic SCADA


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Distributed SCADA

distribute the processing across multiple systems M l i l i n nn LAN h r

information in real time

Mini com uter class less ex ensive than firstgeneration

Distributed stations served as

Communications processors-communicate with RTU

Operator interfaces-human-machine inteface with system operator, etc.


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Distributed SCADA


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Networked SCADA

SCADA Prim r iff r n i h n m r hi r

rather than a vendor controlled, proprietary

environment Multiple network systems, sharing master station

functions

Major improvement possible to distribute SCADAfunctionally across a WAN and not just a LAN


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Networked SCADA


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ys ems

communication links between them

Wire circuits

Mi r w v h nn l Or power line carrier channels

System requirements

Availabilit of communication channels

Cost factors


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ys ems

for each remote unit

M R


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ys ems

with one master unit for several remotes but only

R3R1

M

R4R2


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ys ems

-

With several remote units on a single

M

R1 R2 R3 R4


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- uperv sory

he heart of the system System Nerve Center Located in Dispatchers Use to Monitor and Control Power System

Operator initiate operations of an RTU are made through the

Signals between MU and RTU are tones of audio frequency andmessages transmitted by frequency shift technique.

from noise interference


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pe so as e


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Ensure the desired device is selected and correct o erationis chosen, the operator at the master station shouldfollows a procedure

Operator selects the remote station

Remote station acknowled es that it has been selected After receiving assurance that the desired operation has

been acknowledged by the remote unit, the operator

Remote unit the performs the operation and signals back tothe master

uperv sory emo e


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uperv sory emo e

Located at selected stations

qu ppe w t mo ems so t at

Can accept messages from the master Signal back to the master that messages have been

received

Desired operation can be performed

uperv sory emo e


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uperv sory emo e

uperv sory emo e


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uperv sory emo e

Located in the RTUs

to the controlled equipment on command from the

master unit o sense when an operation has been performedso that the RTU can signal back to the master that

.

uperv sory emo e


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uperv sory emo e

Transducer functions , ,

watts and vars to direct current or voltage

proportional to the measure quantity hen by means of A/D converters convert the

quantity to digital form

se y e sys em or ransm ss on rom eremote to the master


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ystem


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. ystem

Various programs incorporated with SCADA

o mprove operat ons

Minimize the manual effort required of powersystem operators

ystem


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. ystem

ystem


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. ystem

Automatic Generation Control (AGC) se e sys em compu er o prov e e

AGC function

at reduced cost


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-In ut/Out

CRT

Data

(primary) ut

Equipme

nttt

Bus

Typewriter Controller

Line

Buffer

s

Mode

ms

RemoteUnits

Line

Printer

To Mop Boardindicating and

Recording

instruments

Computer B

(standby)

Input/Outp

ut

Equipem

nt


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-

Operator

Console MODEMS RTUS

Master

Unit

MOD

EMS

Typewriter

2

CRT

3

4

ommun ca on rcu s

Graphic

Instrument

System Diagram

- ecur y


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ecur y

when provides sufficient info on the conditionsxi in n w r m ADA m r

system

Able to check the limits of loadin and other uantitiesin order to determine whether the system is or at nearan emergency state

Cause an alarm to be sounded to alert systemoperator

- ecur y


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y

SCADA- Static-state


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SCADA Static state

To provide a reliable real time model eve op proce ures or est mat ng t e state o

the system Calculate from available data

he result found is an estimate of the securit

of the system

SCADA- Static-state


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SCADA Static state

SCADA-Steady-state


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SCADA Steady state

Use to determine whether a power system is

lines or equipment without a system

Also used to determined a strategy for

correc ve ac on o res ore e sys em o anormal security condition

SCADA- Online load


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SCADA Online load

actual operating data provided sufficient info is

Such program can predict loadings of the lines

Program also used to calculate the penalty

ac ors ransm ss on oss ac ors nee e oreconomic operation of the system


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Documents

Power System SCADA