Double sectioned busbar 110 kV.

[beyond86]

Hi. I hope you can help me to understand this situation. We have SLD double sectined busbar 110 kV. There is simple SLD below. There is island station 110 kV.

When our object was in project stage, project engineers decided to leave one of Bus Couplers at open position and wrote this information in the project philosophy. I didn't work at this company that time.
Now I have a question, why they did it?
If we close breaker Bus Coupler A2/B2, we will improve stability our system in case when bus B1 fault. Because now, if bus B1 fault, our system will divided into independed systems, and generators which stay on buses A1,A2 can't produce enough power and frequency will decrease.
So I think it will the better way to close Bus Coupler A2/B2.

 

[Mbrooke]

If the other 3 are closed, then without question A2/B2 should be closed.

You have selective busbar differential, correct?

 

[beyond86]

You have selective busbar differential, correct?

Yes, we have.

 

[Mbrooke]

Then I see no issue in running all of them closed.

 

[RRaghunath]

Make sure your busbar protection includes four bus zones - A1, B1, A2 & B2 with four bus couplers configured!!

 

[bacon4life]

Seems kind of weird to run with A2/B2 open. Brainstorming a few ideas:
1)Was the original plan to NEVER have all 4 closed? Or was it to have 1 out of 4 normally open while allowing all 4 to be briefly closed during switching?
2)Any issues with sync check equipment between sections?
3)Does closing the loop impact breaker failure protection or stability after a breaker failure?
4)Are all breakers fully rated for fault current in both directions? Breakers with external grading capacitors may have different interrupting capabilities in forward versus reverse directions for close in faults.
5)Are these dead tank breakers with overlapping CT's? Stand alone CTs with live tank breakers might have stub bus protection issues.

 

[beyond86]

1)Was the original plan to NEVER have all 4 closed? Or was it to have 1 out of 4 normally open while allowing all 4 to be briefly closed during switching?

Sometimes we close all 4 breakers for short time.

2)Any issues with sync check equipment between sections?

No, sync check is okay at all 4 breakers.

3)Does closing the loop impact breaker failure protection or stability after a breaker failure?

I checked transient stability by ETAP, but I got result when we close all 4 breaker, we improve stability.

4)Are all breakers fully rated for fault current in both directions? Breakers with external grading capacitors may have different interrupting capabilities in forward versus reverse directions for close in faults.

There are the same breakers with 3150A rated current. Max shortcurrent on busbars is 16kA. I think this rated current enought to open this short current.

5)Are these dead tank breakers with overlapping CT's? Stand alone CTs with live tank breakers might have stub bus protection issues.

This is a GIS. We have two CT at each side.