Distance Protn Carrier Scheme Rev 1

DISTANCE PROTECTION CARRIER SCHEMES

By

Y. k. Pandharipande.


NEED FOR TELE-PROTECTION CHANNEL Conventional 3 Zone Distance Protection results in delayed

Zone 2 trip for end zone faults (last 20%)

Faults hanging up to Zone 2 time may cause instability.

Non-simultaneous tripping at near and far end precludes the possibility of applying high speed auto-reclosing, which further aggravates system stability.

Simultaneous tripping can be achieved by inter-locking both end relays through a signalling channel (PLCC, Micro-wave, Pilots, Fibre Optic). Information transmitted can be:

Trip Order (for internal faults) Block Order (for external fault)


3 ZONE DISTANCE PROTECTION


PERMISSIVE UNDER REACH TRANSFER TRIP (PUR)

AIDED TRIP LOGIC FOR FAULT AT F1


PERMISSIVE OVER-REACH TRANSFER TRIP (POR)



PERMISSIVE OVER- REACH TRANSFER TRIP (POR)


IDEAL BLOCKING SCHEME



PRACTICAL BLOCKING SCHEME



COMPARISON OF INTER-TRIP & BLOCKING SCHEME.

1. INTER-TRIP SCHEME

Signal Attenuation, being sent on a faulted line. This can be over come by inter-phase or inter-circuit coupling.

No intentional delay.

POR schemes are suitable for short lines tied up to weak sources, where S.I.R. (Zs/Zl Ratio) is low. Also suitable for Series Compensated Lines.

2. BLOCKING SCHEME

No attenuation since signal sent on a healthy line.

Aided trip is intentionally delayed to allow signal transmission time for blocking signal to be received on external fault.


WEAK INFEED SCHEME OPTION (FOR POR SCHEME)

WEAK INFEED LOGIC FOR FAULT AT F1


ZONE 1 EXTENSION SCHEME (NO CARRIER)

Contact from A/R to reset Zone 1 Extn to Zone 1 during Dead Time.

Distance Protn Carrier Scheme Rev 1

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