MICOM 546 End to End ISSUE

MICOM 546 End to End ISSUE


ISSUE 

During end to end test,  Micom P546 has issue related to differential stability. Below is the concerned issue:

·   Both the CH-1 and CH-2 are being used for differential communication, dual redundant. While injecting stable current from both ends through GPS, 

       1.When CH-1 is removed from either end, Qurayyah or Doha, the differential remains stable and the relay gives no tripping. The channel is then connected back and differential comm. fail alarm goes. 

       2. Then same is done for CH-2. There is no issue with this test.

·     3.  Once both CH-1 and CH-2 are removed, and any one channel is connected back, either CH-1 or CH-2, the Doha side relay gives differential trip for an instant and then gets back to normal i.e. stable. It should not behave in this manner and give no trip. The Qurayyah side relay gives no trip, which is correct behavior.

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      4. When Qurayyah side relay DC is turned off and made on again, it gives differential trip at Doha side relay. Not the expected behavior. It should not give any trip. But when Doha side relay is made of and on again, then there is no trip at any side.

·       5.  Sometimes CH-1 signal lost signal is coming as 1 and going 0 in measurement-4. CH-2 has no lost signal. But when both channels have no signal lost, that time also same problem is being faced.

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      6. The differential communication is through DVM (fox 515, Optif card). 

7. This all is happening if the setting is set to ‘Dual Redundant’ in Prot. Comm/Im64 at both ends. If the setting is set to ‘2 Terminal’ at both ends, then CH-2 becomes unavailable and relay differential function works on CH-1 only. With this CH-1, relay is behaving normal as it should work. 

8. There is 1 CT (Single Breaker)at Qurayyah side and 2 CT’s (1 and a half breaker scheme) at Doha side.

Analyzation 

1. Check the fiber optic cable loss and it should be -22 to -24 db . Otherwise attenuator should add to reduce 

2. Configuration and setting file send to GE and they decided to upgrade the firmware . GE Engineer come to site and updated the latest firmware both side of relay 

3. But issue not solved. 

4. Finally We put  a setup of 2 relays (Micom P546) at Doha side directly connected through fiber cable with each other to confirm that the issue is not related with communication. When test was done, we faced the same issue of differential stability which was coming before.

5. This confirmed us that there is some issue in relay configuration (PSL) and not communication or setting file of the relay. Therefore, we put a PSL file of another relay (from another station) and configured it with input and outputs as per our scheme for both end relays. This made the relays work fine at both ends.

6.It should be made clear that the existing PSL file at DOHA was in use (energised) and the relay was being used as Stub Protection. On existing PSL, SAS was configured from before. Open loop and close loop were done 100% from before. Now all SAS activity will be revised as well.

7. At Qurayyah End, the default PSL file was used for final setting but had the same problem. So another station relay PSL file was written to it and its working fine now.  

8.We compared the existing PSL with another station PSL but couldn’t find any difference. This is strange.

9.Now the issue has been solved and checked through injection from both ends.