Carrier Aided Distance Protection of Transmission Lines: A Distance Relay Feature!
Question 1: Explain Carrier aided Distance Protection in Distance Relays
Answer: A Conventional 3 Zone distance protection results in delayed (350-500 ms) Zone 2 clearance of end Zone faults (last 20%).
Faults hanging on up to Zone 2 time may cause instability in the system.
Also, for successful operation of Auto-reclose, the line should trip from both ends simultaneously.
Simultaneous tripping can be achieved by interlocking distance protection at both ends through the Signaling Channel.
Relay at Substation B will sense the fault in Zone 1 and so it will send a Signal called ‘Carrier Send’ to the Relay at Substation A.
At Substation A, the Signal received is called ‘Carrier Receive’.
So for a Zone 2 Fault Plus Carrier Receive at Substation A, the Relay will Trip in Zone 1 Time i.e. instantaneously.
So, both end Breakers will trip simultaneously and after the dead time, both ends Relays will send Auto-reclose pulse to their respective CB’s
Question No 2: What are the Settings for Carrier aided Distance Protection in Distance Relays ?
Answer:
Scheme – PUR or PUTT
Carrier Send for Zone 1 only
Carrier Receive Reach is equal to Zone 2 reach
Carrier Send Time- 0.1 sec
Carrier Receive Time- 0.05 sec
Question No 3: How to carry out Testing of Carrier aided Distance Protection in Distance Relays ?
Answer: There following two test we can carryout:
Test 1: Distance Carrier Send:
- Give Single Phase, Phase to Phase and Three Phase Faults in Zone 1, Zone 2, Zone 3 and Zone 4.
- Binary Output ‘Carrier Send’ is used as Test Kit Feedback ( Kit will stop when ‘Carrier Send’ Binary Output will Operate). Please note, the carrier should only be sent for Zone 1 Fault and not for Zone 2, Zone 3 and Zone 4 Faults.
- Note down the timing for Zone 1 Fault and the related LED’s
| ZONE | CARR SEND 1 PH (mS) | CARR SEND PH-PH (mS) | CARR SEND3 PH (mS) | Relay LED |
| Zone -1 | 21 | 19.5 | 21.4 | ✔ |
| Zone -2 | — | — | — | |
| Zone -3 | — | — | — | |
| Zone -4 | — | — | — |
Test 2: Distance Carrier aided Trip:
- Give ‘Carrier Receive’ Signal to the Relay and give Single Phase, Phase to Phase and Three Phase Faults in Zone 1, Zone 2, Zone 3 and Zone 4.
- ‘Three Phase Trip’ Output contact of the Relay can be used for the Test Kit Feedback (When the Relay will Trip, the kit will stop).
- As the Carrier is received, for a Zone 2 Fault, the Relay will trip in Zone 1 time i.e. instantaneously and ‘Carrier Aided Trip’ LED will glow.
| ZONE | 1 PH (ms) | PH-PH (ms) | 3 PH (ms) | Relay LED |
| Zone -1 | 17 | 19 | 21 | |
| Zone -2 | 17 | 18 | 21 | ✔ |
| Zone -3 | 0.717 | 0.721 | 0.731 | |
| Zone -4 | 0.319 | 0.318 | 0.336 |