Travelling wave pilot protection of a transmission line based on time synchronization

1. A method for travelling wave pilot protection of a transmission line, the method comprising:

receiving indications of travelling waves from two terminals of the transmission line, the two terminals being time synchronized;

checking whether the indications from the two terminals occur within a short trip window;

confirming, based on the checking, that the indications from the two terminals relate to a same travelling wave; and

making a trip decision based on the confirming that the indications from the two terminals relate to the same travelling wave.

2. The method according to claim 1 , wherein the confirming further comprises:

confirming that the indications from the two terminals relate to the same travelling wave in response to the indications being received within a time distance of each other, the time distance corresponding to the short trip window.

3. The method according to claim 2 , wherein the confirming is preceded by:

time compensating at least one of the indications.

4. The method according to claim 1 , wherein the indications represent a fault along the transmission line.

5. The method according to claim 4 , wherein each indication is provided by synchronized binary information representing at least one of travelling wave polarity, fault direction, blocking signal, unblocking signal, or trip signal for the fault.

6. The method according to claim 2 , wherein a fault is detected in response to the indications being received within the short trip window.

7. The method according to claim 1 , wherein the terminals have a combined time synchronization error less than 0.2 ms.

8. The method according to claim 1 , wherein the short trip window has a length in time corresponding to 2-6 ms.

9. The method according to claim 1 , wherein each indication is an arrival time of the same travelling wave at the respective terminal.

10. The method according to claim 1 , wherein the trip decision relates to whether or not to cause a circuit breaker to trip.

11. The method according to claim 1 , wherein the transmission line is part of a power distribution system.

12. The method according to claim 1 , wherein the transmission line is an alternating current (AC) transmission line.

13. The method according to claim 1 , wherein the transmission line is a direct current (DC) transmission line.

14. The method according to claim 4 , wherein the fault is detected in response to the indications being received within the short trip window.

15. The method according to claim 5 , wherein the fault is detected in response to the indications being received within the short trip window.

16. An arrangement for travelling wave pilot protection of a transmission line, the arrangement having a processing unit, the processing unit being configured to cause the arrangement to:

receive indications of travelling waves from two terminals of the transmission line, wherein the two terminals are time synchronized;

check whether the indications from the two terminals occur within a short trip window;

confirm, based on the check, that the indications from the two terminals relate to a same travelling wave; and

make a trip decision based on the confirmation that the indications from the two terminals relate to the same travelling wave.

17. The arrangement according to claim 16 , wherein the processing unit configured to cause the arrangement to confirm comprises the processing unit configured to cause the arrangement to:

confirm that the indications from the two terminals relate to the same travelling wave in response to the indications being received within a time distance of each other corresponding to the short trip window.

18. The arrangement according to claim 16 , wherein the processing unit is part of an Intelligent Electronic Device (IED) included in the arrangement.

19. The arrangement according to claim 17 , wherein the processing unit is part of an Intelligent Electronic Device (IED) included in the arrangement.

20. The arrangement according to claim 19 , wherein the IED is a protective relay.