pilot wire relaying scheme

8/4/2019 Pilot Wire Relaying Scheme

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Pilot RelayingPilot RelayingSchemesSchemes

ByBy

BIKAS RANJAN PANDABIKAS RANJAN PANDA

Roll No: 0401212334Roll No: 0401212334

ELECTRICAL ENGGERINGELECTRICAL ENGGERING

SECTIONSECTION --AA

INSTITUTE OF TECHNICALINSTITUTE OF TECHNICALEDUCATION & RESEARCHEDUCATION & RESEARCH

BHUBANESWARBHUBANESWAR


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IntroductionIntroductionPilot relaying schemes employ a communicationPilot relaying schemes employ a communication

channel in conjunction with protective relays tochannel in conjunction with protective relays todetect a fault in the transmission lines.detect a fault in the transmission lines.

High speed determination of fault locations.High speed determination of fault locations.

There are basically two types of pilot relayingThere are basically two types of pilot relayingschemes.schemes.

1. Blocking pilot protective scheme1. Blocking pilot protective scheme2. Tripping pilot scheme2. Tripping pilot scheme


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Types of channelsTypes of channelsThere are basically 3 types of channels used inThere are basically 3 types of channels used inpilot relaying.pilot relaying.

1. Wire pilot1. Wire pilot-- Twisted pair of copper wires used inTwisted pair of copper wires used inTelephone cables.Telephone cables.

2. Carrier current pilot2. Carrier current pilot-- The pilot signal is coupledThe pilot signal is coupleddirectly to the power line to be protected.directly to the power line to be protected.

(freq(freq-- 500500--700 kHz)700 kHz)3. Microwave pilot3. Microwave pilot-- a radio channel of very higha radio channel of very high

frequency (450 to 10,000 MHz).frequency (450 to 10,000 MHz).


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Protective schemes in useProtective schemes in useThere are basically four different pilot relayingThere are basically four different pilot relaying

schemes.schemes.

1. Directional comparison1. Directional comparison

2. Phase comparison2. Phase comparison

3. Transferred tripping3. Transferred tripping

4. Current differential4. Current differential


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Directional ComparisonDirectional Comparison

SchemesSchemesThe protective relays used at each end includeThe protective relays used at each end include

a set of phase and ground tripping devices.a set of phase and ground tripping devices.

The relays operate only for faults in theThe relays operate only for faults in thedirection of the protected line.direction of the protected line.

The relays used are usually of impedance withThe relays used are usually of impedance withdirectional type or mho type.directional type or mho type.

Applicable to schemes using blocking pilot.Applicable to schemes using blocking pilot.

Not suitable for microwave channels.Not suitable for microwave channels.


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PHASE COMPRATORPHASE COMPRATOR

The cosine type phase comparator has two phasors s(p)The cosine type phase comparator has two phasors s(p)and s(m) it follows the ruleand s(m) it follows the rule

--90


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SYNTESIS OF MHO RELAY USING STATIC PHASESYNTESIS OF MHO RELAY USING STATIC PHASECOMPARATORCOMPARATOR

Arg((ZnArg((Zn--Zr)/Zr)trip

=90,threshold else restrain=90,threshold else restrain


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Phase Comparison SchemesPhase Comparison Schemes


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Phase Comparison Schemes ContdPhase Comparison Schemes Contd...... In these schemes phase angle of the currentIn these schemes phase angle of the current

entering the terminal is compared with theentering the terminal is compared with thephase angle of the current leaving the otherphase angle of the current leaving the other

terminal.terminal. If these two currents are in phase, there is noIf these two currents are in phase, there is no

fault.fault.

If the two currents are essentially 180If the two currents are essentially 180 00 out ofout ofphase then there is a fault in the line.phase then there is a fault in the line.

The carrier channel used is a blocking pilot.The carrier channel used is a blocking pilot.


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Opposed Voltage differential SchemeOpposed Voltage differential Scheme

Applied over only wire pilot channelApplied over only wire pilot channel

Provides no back up protection for faultsProvides no back up protection for faultsexternal to the line.external to the line.


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Transferred Tripping SchemesTransferred Tripping SchemesThese schemes utilize frequency shift audioThese schemes utilize frequency shift audio

tone signals over either wire pilot or microwavetone signals over either wire pilot or microwavechannels.channels.

Under normal conditions continuous guardUnder normal conditions continuous guardfrequency is transmitted.frequency is transmitted.

The contacts of the trip and guard relays are inThe contacts of the trip and guard relays are in

each receiver are arranged so that theeach receiver are arranged so that thecombined action of dropped out guard relaycombined action of dropped out guard relayand a picked up trip relay constitutes theand a picked up trip relay constitutes thereception of transferred trip signal.reception of transferred trip signal.


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Transformer differentialTransformer differential

Transferred Trip SchemeTransferred Trip Scheme


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Problems With Telephone PilotsProblems With Telephone PilotsThe high loop impedance and the relativelyThe high loop impedance and the relativelylow shunt capacitive impedance make thelow shunt capacitive impedance make thediscriminating factor low.discriminating factor low.

Compensation:Compensation:A shunt connected reactor across theA shunt connected reactor across the

terminals at each end.terminals at each end.

Use of directional relays.Use of directional relays.By using replica impedances for the pilot loopBy using replica impedances for the pilot loop

under external fault conditions.under external fault conditions.


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Application Of MicrowaveApplication Of Microwave

Channels For Protective RelayingChannels For Protective Relaying11.Transformer and C.B. Failure Protection.Transformer and C.B. Failure Protection

2. Transmission line protection2. Transmission line protection

Advantages:Advantages:

independent of power line.independent of power line.

No necessity of coupling and trap equipment.No necessity of coupling and trap equipment.

Signal level is not attenuated.Signal level is not attenuated.

Facility for high speed relaying channelFacility for high speed relaying channelequipment.equipment.


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ConclusionConclusionDistiction between tripping protective schemesDistiction between tripping protective schemes

and blocking protective schemes was studied.and blocking protective schemes was studied.

Different relaying schemes were studied.Different relaying schemes were studied.

Finally with the limitations of telephone pilots,Finally with the limitations of telephone pilots,the advancement of microwave channels andthe advancement of microwave channels andrecently discovered optical fibre channels wererecently discovered optical fibre channels were

studied.studied.


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pilot wire relaying scheme

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