Protective Relaying - MIT

8/22/2019 Protective Relaying - MIT

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Title of BookTitle of Book::

ower ys em ro ec ve e ay ngower ys em ro ec ve e ay ng

ByBy::

..BSEE 79 / BSECE 80BSEE 79 / BSECE 80 MITMIT

11STST EDITIONEDITION


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INTRODUCTIONINTRODUCTION

Since the mid twentieth century, electricity has been an essential part of our lives. ElectricitySince the mid twentieth century, electricity has been an essential part of our lives. Electricity

powers, our appliances, office equipment and countless other devices and apparatus that wepowers, our appliances, office equipment and countless other devices and apparatus that we

use to make life safer, easier and more interesting. Use of electric power is something we takeuse to make life safer, easier and more interesting. Use of electric power is something we take

, ,, ,

mans useful resources making our life convenient and relaxing through its various usefulness.mans useful resources making our life convenient and relaxing through its various usefulness.


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22 TIME DELAY STARTING OR CLOSING RELAY.TIME DELAY STARTING OR CLOSING RELAY.

33 CHECKING OR INTERLOCKING RELAY.CHECKING OR INTERLOCKING RELAY.

2121 DISTANCE RELAY.DISTANCE RELAY.

2525 SYNCHRONIZING OR SYNCHRONISM CHECKSYNCHRONIZING OR SYNCHRONISM CHECK

RELAY.RELAY. ..

3030 ANNUCIATOR RELAY.ANNUCIATOR RELAY.

3232 DIRECTIONAL POWER RELAY.DIRECTIONAL POWER RELAY.

3737 UNDERCURRENT OR UNDERPOWER RELAY.UNDERCURRENT OR UNDERPOWER RELAY.


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.

46 REVERSE PHASE OR PHASE BALANCE CURRENT RELAY.49 MACHINE OR TRANSFORMER THERMAL RELAY.

50 INSTANTANEOUS OVERCURRENT OR RATE OF RISE RELAY.

51 AC TIME OVERCURRENT RELAY.

52 AC CIRCUIT BREAKER.

52A CIRCUIT BREAKER UXILLIARY SWITCH NORMALLY OPEN.52B CIRCUIT BREAKER AUXILLIARY SWITCH NORMALLY CLOSED.

55 POWER FACTOR RELAY.

56 FIELD APPLICATION RELAY.

59 OVERVOLTAGE RELAY.


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6464 EARTH FAULT PROTECTIVE RELAY.EARTH FAULT PROTECTIVE RELAY.

6767 AC DIRECTIONAL OVERCURRENT RELAY.AC DIRECTIONAL OVERCURRENT RELAY.

6868 BLOCKING RELAY.BLOCKING RELAY.7474 ALARM RELAY.ALARM RELAY.

..

7878 PHASE ANGLE MEASURING OR OUT OF STEPPHASE ANGLE MEASURING OR OUT OF STEPPROTECTIVE RELAY.PROTECTIVE RELAY.

7979 AC RECLOSING RELAY.AC RECLOSING RELAY.

8181 FREQUENCY RELAY.FREQUENCY RELAY.

8383 AUTOMATIC SELECTIVE CONTROL OR TRANSFERAUTOMATIC SELECTIVE CONTROL OR TRANSFERRELAY.RELAY.

..8686 LOCKING OUT RELAY.LOCKING OUT RELAY.

8787 DIFFERENTIAL PROTECTIVE RELAY.DIFFERENTIAL PROTECTIVE RELAY.


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51N51N RESIDUAL GROUND OVERCURRENT RELAY 0.5RESIDUAL GROUND OVERCURRENT RELAY 0.5 2.5 A.2.5 A.

6363 SUDDEN PRESSURE RELAY.SUDDEN PRESSURE RELAY.

63X63X AUXILLIARY RELAY FOR SUDDEN PRESSURE.AUXILLIARY RELAY FOR SUDDEN PRESSURE.7979 RECLOSING RELAY, 3 SHOT DC OPERATED TIMER.RECLOSING RELAY, 3 SHOT DC OPERATED TIMER.

..

87B87B BUS DIFFERENTIAL RELAY, HIGH SPEED, HIGHBUS DIFFERENTIAL RELAY, HIGH SPEED, HIGHINPEDANCE VOLTAGE UNITINPEDANCE VOLTAGE UNIT

WITH LOW INPEDANCE INSTANTANEOUSWITH LOW INPEDANCE INSTANTANEOUSOVERCURRENT UNIT.OVERCURRENT UNIT.

87T87T TRANSFORMER BANK DIFFERENTIAL RELAY,TRANSFORMER BANK DIFFERENTIAL RELAY,PERCENTAGE, 2 RESTRAINTS.PERCENTAGE, 2 RESTRAINTS.


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87G87G RESTRICTED EARTH FAULT RELAY.RESTRICTED EARTH FAULT RELAY.

..

AA AMMETERAMMETERKWHKWH BILLING KILOWATT HOUR METER W/ DEMAND INDICATOR.BILLING KILOWATT HOUR METER W/ DEMAND INDICATOR.

VARVAR VARMETERVARMETER

WW WATTMETERWATTMETER

ASAS AMMETER SWITCHAMMETER SWITCH

VSVS VOLTMETER SWITCHVOLTMETER SWITCH ,,

GTGT OVERCURRENT RELAY.OVERCURRENT RELAY.

1212 ZONE PACKAGE, MHO CHARACTERISTICS, COMPENSATOR DISTANCEZONE PACKAGE, MHO CHARACTERISTICS, COMPENSATOR DISTANCERELAYRELAY

-- ..

2121 ZONE PACKAGED, MHO CHARACTERISTICS WITH OFFSET OPTION,ZONE PACKAGED, MHO CHARACTERISTICS WITH OFFSET OPTION,ZZ--22 COMPENSATOR DISTANCE RELAY (ZONECOMPENSATOR DISTANCE RELAY (ZONE 2).2).


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2121 -- ZONE PACKAGED, MHO CHARACTERISTICS WITHZONE PACKAGED, MHO CHARACTERISTICS WITH-- ,,

(ZONE(ZONE 3).3).50H50H HIGH SET NONDIRECTIONAL INSTANTANEOUSHIGH SET NONDIRECTIONAL INSTANTANEOUS

OVERCURRENT RELAY.OVERCURRENT RELAY.

22 TOWTOW ZONE TIMING AUXILLIARY RELAY (ATARTINGZONE TIMING AUXILLIARY RELAY (ATARTINGOR CLOSING).OR CLOSING).

2727 UNDERVOLTAGE RELAY, 115 VOLTS.UNDERVOLTAGE RELAY, 115 VOLTS.

SCHEME.SCHEME.

5050 INSTANTANEOUS OVERCURRENT RELAYS.INSTANTANEOUS OVERCURRENT RELAYS.

5050--5151 PHASE OVERCURRENT RELAY WITH INSTATANEOUSPHASE OVERCURRENT RELAY WITH INSTATANEOUS

UNIT 1.0UNIT 1.0 12 A (612 A (6 --14 A ITT).14 A ITT).51G51G TRANSFORMER NEUTRAL GROUND OVERCURRENTTRANSFORMER NEUTRAL GROUND OVERCURRENT

RELAY 0.5RELAY 0.5 2.5 A.2.5 A.


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Part 1:

Power S stem Protection


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Electric Power SystemElectric Power SystemElectric Power SystemElectric Power System

Electricity is generated at a power plant (1), voltage is stepped-up fortransmission (2). energy travels along a transmission line to the area where thepower is needed (3). voltage is decreased or stepped-down, at another substation(4), and a distribution power line (5) carries that electricity until it reaches a home

.


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Power SystemPower System

AB

Delivery

SubstationDeliverySubstation

C

ac one

Looped Lines

Distribution

Radial Lines

Power System Protection


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LEGEND:

Initial

Bus No. 1

INCOMING

115kV LINE 1

INCOMING

115kV LINE 2

115KV Switchyard

Bank #1 Bank #2 Bank #3

83 MVA PXFwith OLTC

us o.

34.5KV Switchyard34.5kV switchgear No. 1

F1 F2 F3 F4

TYPICAL DISTRIBUTION SUBSTATION

F1 F2 F3 F4Bus tie F1 F2 F3 F47.2 MVAR

Capacitor Bank

7.2 MVAR

Capacitor Bank

7.2 MVAR

Capacitor Bank

Bus tie

Single Line Diagram


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What is Power SystemWhat is Power SystemWhat is Power SystemWhat is Power System

Protection?Protection?Protection?Protection?

also known asalso known as Protective RelayingProtective Relaying

ranc o ec r c ower ranc o ec r c ower

EngineeringEngineeringScienceScience,,ArtArt andand SkillSkill in applyingin applying

devices.devices.


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Protective relaysProtective relays are devices whichare devices whichmonitor power system conditions andmonitor power system conditions andopera e o qu c y an accura e yopera e o qu c y an accura e yisolate faults or dangerousisolate faults or dangerous

conditions. A well desi nedconditions. A well desi nedprotective system can limit damageprotective system can limit damageto equipment, as well as minimize theto equipment, as well as minimize the

interruption.interruption.


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Purpose of System ProtectionPurpose of System ProtectionPurpose of System ProtectionPurpose of System Protection

To prevent injury to personnelTo prevent injury to personnel

componentscomponentsTo limit the extent and duration ofTo limit the extent and duration of

service interruptionservice interruption


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Components of Power SystemComponents of Power SystemComponents of Power SystemComponents of Power System

ProtectionProtectionProtectionProtection

RelaysRelays

Circuit BreakersCircuit Breakers

Tripping and Auxiliary SuppliesTripping and Auxiliary Supplies


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Components of Power System ProtectionComponents of Power System Protection

Decides whether system

quantities are normal or

abnormal (Brain of the

Transducers

(PT & CT) Relay Circuit

Breaker

Power

System

* ,

no signal is sent to breaker

* If quantities are abnormal,

signal is sent to breaker to

electrical quantities to

level relays can use, i.e.,

5 amperes, 115 volts


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Sensor (Instrument

Transformers)

Feedback

Signals

Relay

Power Circuit Breaker


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Components of Power System ProtectionComponents of Power System Protection

Transmission

CBCT

Line

Trip Coil

Station

Relay Contacts


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Abnormalities in PowerAbnormalities in PowerAbnormalities in PowerAbnormalities in Power

ystemsystemsystemsystems

OvercurrentOvercurrent (overload, short circuit, open(overload, short circuit, open

Ground PotentialGround Potential (ungrounded equipment,(ungrounded equipment,

,,

Surge VoltagesSurge Voltages (lightning strokes, switching(lightning strokes, switching

sur es harmonicssur es harmonics


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Frequency of Types ofFrequency of Types ofFrequency of Types ofFrequency of Types of

FaultsFaultsFaultsFaults

Type ofFault

%Occurrence

SLG

LL

85

8DLG

3L

5

2 or less


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Equipment % of Total

Overhead lines

Cables

50

10

Transformers

CTs and PTs

12

2

Control EquipmentMiscellaneous

38


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Factors Which Influence DesignFactors Which Influence DesignFactors Which Influence DesignFactors Which Influence Design

of a Protective Systemof a Protective Systemof a Protective Systemof a Protective System

ReliabilityReliability DependabilityDependability

ecur yecur y

SensitivitySensitivity

SelectivitSelectivit

SpeedSpeed

EconomicsEconomics

ExperienceExperienceIndustry StandardsIndustry Standards


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o a ro ec ve ys emo a ro ec ve ys emo a ro ec ve ys emo a ro ec ve ys em

ReliabilityReliabilityThe level of assurance that the rela will function asThe level of assurance that the rela will function as

intended.intended.

Reliability denotes:Reliability denotes: DependabilityDependability -- certainty of correct operationcertainty of correct operation

SecuritySecurity -- assurance against incorrect operationassurance against incorrect operation


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SensitivitySensitivity

that it will operate when requiredthat it will operate when required

Must discriminate normal from abnormal conditions.Must discriminate normal from abnormal conditions.


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SelectivitySelectivityPerformance of rotective devices to select betweenPerformance of rotective devices to select between

those conditions for which prompt operation andthose conditions for which prompt operation and

those for which no operation, or time delay operationthose for which no operation, or time delay operation

..

Isolate faulted circuit resulting in minimumIsolate faulted circuit resulting in minimum

interruptions.interruptions.

Implemented through Zone of ProtectionImplemented through Zone of Protection


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SpeedSpeedRemove a fault from the power system as quickly asRemove a fault from the power system as quickly as

possiblepossible

Classification:Classification:

ns an aneousns an aneous -- no n en ona e ayno n en ona e ay

High SpeedHigh Speed -- less than 3 cyclesless than 3 cycles

-- --


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EconomicsEconomicsMaximum protection at minimum costMaximum protection at minimum cost

the cost of installation, operation, and maintenance ofthe cost of installation, operation, and maintenance of

the protection system which must be weightedthe protection system which must be weighted

service interruption.service interruption.


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ExperienceExperience

be encountered:be encountered:

Actual Relay PerformanceActual Relay PerformanceNature of FaultsNature of Faults

Operation and MaintenanceOperation and Maintenance


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Factors Which Influence DesignFactors Which Influence Design

of a Protective Systemof a Protective System

Industry StandardsThe Institute of Electrical and Electronic Engineers (IEEE) and other.

include specific standards for many applications.ANSI-C37.90-1989 Relays and Relay System

Apparatus

IEEE STD 242-1975 Recommended Practicefor Protection and Coordination

of Industrial and CommercialPower System


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Principles of


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Develo ment of Protective Rela sDevelo ment of Protective Rela s

Electro-mechanical relay

Solid-state relay

Digital relay


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ElectroElectro--mechanical Relay:mechanical Relay:

( 1st Generation )( 1st Generation )

The most commonly usedThe most commonly used

(watthour meter)(watthour meter)

Provides individual phaseProvides individual phaseprotectionprotection


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Time Adjustment:

Operator Rod

ension contro e

Contacts

Sensing Coil

DiscCore


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Critical Components:

Composition of the rotating disc & Coil

.

Rotating & Tripping mechanism

Lubrication & alignments. Spring & tension adjusting mechanism

Fatigue & Temperature dependence.

Design Approach: Periodic re-calibration & maintenance

- .

High burden CT, low sensitivity at higher currents.


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Static Relay:Static Relay:

( 2nd Generation )( 2nd Generation )

Characteristic curve is obtainedCharacteristic curve is obtainedthrough use ofthrough use ofRCRC timing circuitstiming circuits

Used to retrofit electroUsed to retrofit electro--mechanicalmechanical

relaysrelaysFast resetFast reset

Less maintenanceLess maintenance


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Set ValueComparator Timing Output

RC Based Timin

AC - DC

Conversion

From CTs


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r ca omponen s:

RC Timing circuit.

Tem erature de endence

Low repeatabilityV

Time


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r t ca omponents: cont nue

AC/DC Conversion.

Offset roblem

Effects of harmonics & Noise


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Periodic re-calibration & maintenance Draw-out connections.

RC & LC Based filters - Slow tripping actions

Without Filter

With RC Filter


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Digital Relay:Digital Relay:

( 3rd Generation )( 3rd Generation )

ComputerComputer--basedbased--with CPUwith CPUSelectable characteristic curvesSelectable characteristic curves

and protection functionsand protection functions

Metering and control functionsMetering and control functions

ven an or s ur anceven an or s ur ance

recordingrecording

Remote communicationRemote communication

SelfSelf--monitoringmonitoring

All inAll in


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( MicroProcessor Based )( MicroProcessor Based )

Micro-processorCPU

Crystal

Data & Address BusMemory EPROM

ontro e ay ontactsu pu on ro

AC - DCConversion

Current Sampling


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Design Principle:

AC/ DC

Analog to Digital ConversionA to D


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r t ca omponents:

High Frequency Bus

Susce tible to EMI/ RFI.

AC/ DC & Digital Conversion

Effect of Offset/ Harmonics, etc.

CPU

RAMEPROM

A/D Hi-Freq Bus


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r t ca omponents:

High Frequency Bus

Susce tible to EMI/ RFI.

AC/ DC & Digital Conversion

Effect of Offset/ Harmonics, etc.

Noise

A to D


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RC & LC Based filters Slow tri in actions

Shielding & Watch-dog timers

Problem reduced not eliminated May reset randomly

CPU

RAM

EPROM

A/DWatch

DOG


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( MicroController Based )( MicroController Based )

-controller Out ut Control Crystal

Steady state data

AC - DC

Current SamplingB CA E

Conversion


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es gn r nc p e:

Lesser no. of components, hence less chance of failure.

-

More functions can be built in a compact space.

Controller

RAM

Controller

A2D Converter

P C

EPROM Decoding logic

A2D Converter

Output driver

or s

Output driver

i i l li i l l


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es gn r nc p e:

Absence of exposed high frequency bus

- .

Cost effective technology appropriate for MV applications

CPU

RAM EPROM

A/D

Di it l R lDi it l R l


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( Numerical Relay )( Numerical Relay )

-controllerCrystalSerial Port To Outside world

Output Control

Steady state data

Relay Contacts

Current SamplingB CA E

irect

Sampling



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Design Principle:

AC attenuation

Numeric filtering & measurement

A to D



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es gn r nc p e: con nue

Digital Signal Processing concepts

The normal representation i.e. with time in the X axis

The signal is sampled periodically, a different value obtained every

, .

Amplitude

Disadvantages No Phase Angle information.

No Frequency information.

Time

Digital RelaDigital Rela


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es gn r nc p e: cont nue


X Axis now represents frequency, instead of time.

-

.

Amplitude

Frequency

50Hz



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Any signal can be represented by infinite Nos. of Sine waves

ny r rary gna

=

+

Fundamental (50Hz). 2nd Harmonic (100 )



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X Axis now represents frequency, instead of time.

Fourier Analysis

.

Amplitude

Frequency

50Hz 100Hz



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Very quick operation. In-built immunit to DC & harmonics tuned

characteristics)

Possibility of providing additional filtering or

inhibiting actions without sacrificing speed of

response.

oss y o s ur ance recor ng us,

post-mortem analysis of fault & relay behavior.

.

Very less no. of components.



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Additional Features:

Communication to external laptop/ computer.

programmed in a single enclosure, instead of a

combination of multi le discreet rela s.

Possibility of using non-conventional

transducers for input sensing. Eg. Hall effect

Current Transducers. A Bay-level controller instead of just a

pro ec on re ay .

C i f Diff t t f R lC i f Diff t t f R l


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Com arisons of Different t e of Rela sCom arisons of Different t e of Rela s

arac er s c ec ro-

mechanical

a c cro-

processor

based

cro-

Controller

based

umer ca

Speed of response Slow Fast Fast Fast Very Fast

Timing Accuracy Temp.

Dependant

Temp.

Dependant

Stable Stable Stable

Size Bulky Small Small Small Very Compact

Draw-out required Required Required Not required Not required Not requiredCT Burden High Low Low Low Low

Reset Time Very High Less Less Less Less

Functions Single

function

Single

function

Multi

function

Multi

function

Multi

function

Maintenance Frequent Frequent Low Low Very Low

Deterioration due to

frequent operations

Yes No No No No

SCADA Compatibility No No Possible Possible Yes

Zones of ProtectionZones of Protection


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Regions (zones) of power system that can beRegions (zones) of power system that can be

protected adequately with fault recognition andprotected adequately with fault recognition and

remova resu ng n so a on o a m n mum amoun oremova resu ng n so a on o a m n mum amoun o

equipment.equipment.

Re uirements:Re uirements:All ower s stem elements must beAll ower s stem elements must beencompassed by at least one zoneencompassed by at least one zone

Zones of protection must overlap to prevent anyZones of protection must overlap to prevent any

sys em e emen rom e ng unpro ec e no nsys em e emen rom e ng unpro ec e no n

spots).spots).



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52

87B

3 6

50/511

52

50/51

87B

OVERLAPPING ZONESG



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Overlapping zones of protection



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1 - Bus Protection

3

5

1

2 - Generator Protection

3 - Subtrans Line Protection

4 - Fee er Protection

5 - Transformer Protection

G 4

Feeder Protectioneeder Protection


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Fault

Bus Protectionus Protection


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Fault

Transformer Protectionransformer Protection


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Fault

Subtransmission Line Protectionubtransmission Line Protection


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Fault

Generator Protectionenerator Protection


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Fault

Primary and BackPrimary and Back--upupPrimary and BackPrimary and Back--upup


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Primary ProtectionPrimary Protection -- Main protection system forMain protection system for

BackBack--up Protectionup Protection -- Alternate protectionAlternate protection

BackBack--up Protectionup ProtectionBackBack--up Protectionup Protection


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Local BackLocal Back--upup -- Alternate protection at theAlternate protection at the..

Remote BackRemote Back--upup -- Alternate protection at theAlternate protection at the

fails.fails.

Local BackLocal Back--up Protectionup ProtectionLocal BackLocal Back--up Protectionup Protection


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B3B1 B2

B4 B6B5

B7 B8 B9F1

Main: B8,B9, L2 remote protection

Fault F1

Local Backup:

If B9 fails, trips B6 and B3

If B8 fails, trips B7 and sends signal to trip L1

remote protect on

Remote BackRemote Back--up Protectionup ProtectionRemote BackRemote Back--up Protectionup Protection


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B1 B2 B7 B8

F1

F2F3

B4B3

B6B5

B9 B10

Fault F1

Main: B5,B6

Fault F2

Main: B2,B4,B5

Backup: B1,B3,B6 , , ,

Fault F3

Main: B3,B4

Backup: B1,B6

Methods of DiscriminationMethods of DiscriminationMethods of DiscriminationMethods of Discrimination


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Current MagnitudeCurrent Magnitude

20 A60 A100 A

TimeTime

Inst.0.35 sec1.0 sec



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Distance MeasurementDistance Measurement

Z = V/I ohms



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Time

Current



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Zone 3Time

Zone 2

Zone 1

Distance



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87T



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Types Of Protective RelaysTypes Of Protective Relays


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Overcurrent Relays - are operated whenthe current passing to the relayexceeds a preset value. They arenot directional in nature.

Bus

I51


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a a ne ro ec ona a ne ro ec ona a ne ro ec ona a ne ro ec on

CTA

B 52

C

51

51N

Ground

Phase

Relays

e ay



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rec ona vercurren e ays - are opera e

when the current passing to it exceeds areset value but with the addition ofanother condition and that is providedthat the direction of the fault is correct

A B

I @ CB2 I @ CB3


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Directional Overcurrent Relays

I @ CB4

A B1 2 3 4

I CB3

So for a fault just after CB4 a directional over-current

relay at CB3 will see the fault in reverse while at CB4

the fault is forward looking thus i t will trip CB4 only to

isolate the fault

The scheme is now selective and a little secure



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I @ CB4

A B1 2 3 4

I CB3

,directional overcurrent relay of CB2 might see the

fault. Therefore, the scheme is now not secure.

The use of distance relay is preferred.



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s ance e ays

Measures the im edance of the line it beinproportional to the distance of the line fromthe substation hence the name implies.

Widely used protection scheme for Double-Ended Transmission Line from 69 kV up to as

g as y ransco .



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Differential RelayA rela that b its desi n or a lication is intended to

respond to the difference between incoming and

outgoing electrical quantities associated with the

.

Input Output=


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CT

PCB

50/5186T

POWERTRANSFORMER

87T TRIPS AND LOCKS-OUTHS AND LS PCB

151GPCB

CT


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Typical Bus Arrangements:

Single bus

Double bus, double breaker

Breaker-and-a-half

Ring bus


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Bus differential connection sin le-bus

87B

86B

TRIPS AND LOCKS-OUT ALL BREAKERSCONNECTED TO BUS

NOTE: All CTs connected to the bus

differential must have same ratios.BUS

Differential Protection


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Primary Element

CT CT

600/5

600A

600/5

5A 5A600A

Relay 0A

5A5A



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PrimaryElement

Fault

CT CT

600/5

600A

600/5

600A5A 5A

Relay 10A

5A 5A


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Part :

Rela in Philoso h

Power S stemPower S stem


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Delivery

SubstationDelivery

Substation

AB

Looped Lines

(System Backbone)

Power Transformer

Distribution

34.5kV Bus

Standard ProtectionStandard Protection


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Radial Lines

Power Transformer

Capacitor Bank


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ELECTRO-MECHANICALOVERCURRENT RELAY


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OVERCURRENT RELAY

BUS

50 50N

3

TARGET

INST.

TARGET

TIME

51 51NCT

LEGEND:50 INSTANTANEOUS, PHASE OVERCURRENT RELAY

,

50N INSTANTANEOUS, GROUND OVERCURRENT RELAY

51N TIME, GROUND OVERCURRENT RELAY

43R RECLOSER SWITCH

79 AUTO RECLOSER RELAY

52 POWER CIRCUIT BREAKER

CT CURRENT TRANSFORMER

a a ne ro ec ona a ne ro ec on


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a a ne ro ec ona a ne ro ec on

A B CCT

52

single-phase

overcurrent

relays are needed to

protect a feeder

a

Ib In=Ia+Ib+Ic

PhaseRelays

roun

RelayIc


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BUS

21 21G 79CT 85

LEGEND:

21 PHASE DISTANCE RELAY67 67N

CT

43R

21G GROUND DISTANCE RELAY67 PHASE DIRECTIONAL OC RELAY

67N GROUND DIRECTIONAL OC RELAY

43R RECLOSER SWITCH

52

79 AUTO RECLOSER RELAY

85 TELEPROTECTION52 POWER CIRCUIT BREAKER

CT CURRENT TRANSFORMER

METERING

BUS PROTECTION

oope ne ro ec on


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Distance RelaDistance Rela

oope ne ro ec on

A relay that measures the impedance of the lineA relay that measures the impedance of the line

Principle of OperationPrinciple of Operation ZLINE FAULT

VFAULTIFAULT

Therefore: ZLINE = VFAULT / IFAULTZRELAY = ZLINE * CTR/PTR

FAULT FAULT LINE

X

LINE

RImpedance Relay is non-directional

oope ne ro ec on


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oope ne ro ec on

Types of Distance RelayTypes of Distance Relay

ImpedanceImpedance -- Used mainly as a fault detector in most ofUsed mainly as a fault detector in most of--

ReactanceReactance --Needs the supervision of mho to obtain itsNeeds the supervision of mho to obtain its

directionality.directionality.

oo -- os w e y use s ance c arac er s c curveos w e y use s ance c arac er s c curvedue to its inherent directionality.due to its inherent directionality.

QuadrilateralQuadrilateral --Made possible by combining reactanceMade possible by combining reactance

type principle rotated along different axes.type principle rotated along different axes.

CompositeComposite -- Combined mho and quadrilateralCombined mho and quadrilateral


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X X

ypes o stance e ay

Zone 2

Zone 1

R R

REACTANCEMHO


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X X

ypes o stance e ay

R

R

QUAD COMPOSITE

oope ne ro ec on


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p

Mho Distance Relay, 21Mho Distance Relay, 21for phasefor phase--phase or 3phase or 3--phasephase

faultsfaults,, or neor ne-- oo--groun au s ogroun au s o

cover arc resistancecover arc resistance

Phase Directional OC Relay, 67Phase Directional OC Relay, 67backback--up for phaseup for phase--

phase or 3phase or 3--phase faultsphase faultsGround Directional OC Relay, 67NGround Directional OC Relay, 67Nbackback--up for lineup for line--

toto-- round aultsround aults

Teleprotection, 85Teleprotection, 85 -- POTT (Permissive OverreachingPOTT (Permissive Overreaching

Transfer Trip)Transfer Trip)

-- ,, ,,

shotshot

oope ne ro ec on


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Im lementin Distance Rela Characteristic with

Time Graded Scheme also called Step Distance Scheme

Z1

Z2

Time = 1.0 secZ2 Time Delayed

me e aye

Time = 0.0 sec

Time = 0.35 sec

A B C D

21

Relay Location

oope ne ro ec on


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-

21

-

Must under-reach end of the line for selectivity

Typically set for 80-90% of line impedance

oope ne ro ec on


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-

21

.

Must over-reach end of the line

Must not over-reach the Zone 1 of adjacent line

-

adjacent line impedance

oope ne ro ec on


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y

ZL2

ZL3

.

Typically set for 100% ZL1 + 100% ZL2 (longest) +0% - 120% ZL3 (shortest)

impedance.

oope ne ro ec on


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90% of ZL = instant

A B

21 90% of ZL = instant

120% of ZL = 0.35 sWhat if the

On this condition CB B will trip instantaneously via Zone 1 operation whileCB A will trip after

0.35 second via Zone 2. This is not good since the fault has to be cleared

as shown?

.

So there is a need to solve this problem to coverSo there is a need to solve this problem to cover

e pro ec on o e rema n ng o e nee pro ec on o e rema n ng o e ne

Communication-Aided Protection

oope ne ro ec on


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A B

Z2 = 120% of ZL = 0.35 s

21= o = ns an

Z2 = 120% of ZL = 0.35 s

XMTR

A

XMTR

BZ2 Z2TRIP

TRIP

ANDAND

RCVR

ARCVR

B

Communication-Aided Protection

oope ne ro ec on


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= o = nstant

A B

Z2 = 120% of ZL = 0.35 s

21= o = nstant

Z2 = 120% of ZL = 0.35 s

XMTR

A

XMTR

BZ2 Z2No TRIP

No TRIP

ANDAND

RCVR

ARCVR

B

oope ne ro ec on


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6767N

Relay is set at fault at the adjacent bus

67

67N

-

Time is 0.70 second

Instantaneous unit is blocked (distance relay must

No auto-reclosure when tripping initiated by back-up

protection

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With Auto-Reclosing

u -

Zone 1 Tripping

Zone 2 Communication-Aided Tripping

Without Auto-Reclosing Zone 2, Zone 3 or Zone 4 (reverse zone) Tripping

Back-up Protection Tripping

Note: Auto-reclosing is single-shot and 300 msec time

delay to give time for the PCB to extinguish the fault


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Normal maximum working temp. = 95Normal maximum working temp. = 95 CC-- r se w a ve e e o er se w a ve e e o e

transformer.transformer.

vercurrenvercurrenFuses for distribution transformerFuses for distribution transformer

Overcurrent relaying for 5MVA and aboveOvercurrent relaying for 5MVA and above

Characteristics:Characteristics:

Must be below the damage curveMust be below the damage curve

Must be above magnetizing inrushMust be above magnetizing inrush


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DifferentialDifferential -- 87T87T

OverloadOverload -- 5151

BackBack--up Groundup Ground -- 151G151G

OverheatingOverheating -- Thermal RelayThermal Relay

Gas DetectionGas Detection -- Buchholz RelayBuchholz Relay Sudden PressureSudden Pressure -- Pressure Relief ValvePressure Relief Valve


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CT

52

87T

50/5186T

LEGEND:87T TRANSFORMER

CT

151G52 DIFFERENTIAL RELAY

86T AUXILIARY LOCK-OUT RELAY

50 INSTANTANEOUS OC RELAY151G BACK-UP GROUND RELAY

52 POWER CIRCUIT BREAKER


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Differential RelayDifferential Relay

A relay that by its design or applicationA relay that by its design or applicationis intended to respond to the differenceis intended to respond to the differencebetween incoming and outgoingbetween incoming and outgoing

electrical quantities associated with theelectrical quantities associated with theprotected apparatus.protected apparatus.


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Constant Percent Slope Characteristic Differential Relay

K = 25 %

K = 40 %

K = 10 %

OperateI1-I2

Restraint = (I1+I2)/2

Min. Pick-up

Percentage Differential ProtectionPercentage Differential Protection


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g o og o o

Variable Percent Slope Characteristic Differential Relay

OperateI1-I2 Slope 2TRIP ZONE

Slope 1Pick-upNO TRIP ZONE

Restraint = (I1+I2)/2


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Typical Bus Arrangements:Typical Bus Arrangements:

Single busSingle busou e us, ou e rea er ou e us, ou e rea er

BreakerBreaker--andand--aa--halfhalf

breakerbreaker

Ring busRing bus

--


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--

87B

86B

-

OUT ALL BREAKERSCONNECTED TO BUS

NOTE: All CTs connected to the bus differentialmust have same ratios.BUS


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-- ,, --

breaker)breaker)87B87B

TRIPS AND LOCKS-OUT ALL BREAKERSCONNECTED TO

BUS 1

86B

TRIPS AND LOCKS-OUT ALL BREAKERS

86B

BUS 2

BUS 1BUS 2


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-- -- --86B

TRIPS AND

86B

87B

TRIPS ANDLOCKS-OUT ALL

87B-BREAKERSCONNECTED TOBUS 1

BREAKERSCONNECTED TOBUS 2

BUS 1BUS 2


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BUS 1

BUS 2

86B1

TRIPS AND LOCKS-OUT

ALL BREAKERS

CONNECTED TO BUS 1

86B2

87B2

87B1

BUS IMAGING

RELAY

TRIPS AND LOCKS-OUT

ALL BREAKERS

CONNECTED TO BUS 2


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NOTE: No bus differential protection is needed. Thebusses are covered by line or transformer protection.


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Low ImpedanceLow Impedance -- using time overcurrentusing time overcurrent

rela srela s99 inexpensive but affected by CT saturation.inexpensive but affected by CT saturation.

99 low voltage application; 34.5kV and belowlow voltage application; 34.5kV and below

High ImpedanceHigh Impedance -- using overvoltage relaysusing overvoltage relaysthis scheme loads the CTs with a hi h im edance tothis scheme loads the CTs with a hi h im edance to

force the differential current through the CTs insteadforce the differential current through the CTs instead

of the relay operating coilof the relay operating coil.).)..

99 115kV and above voltage application or some115kV and above voltage application or some34.5kV bus voltages which require high protection34.5kV bus voltages which require high protection


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Documents

Protective Relaying - MIT