Main-Tie-Main Breaker differential protection

[mull982]

Can anyone provide any guidance/recommendations for providing differential protection on a double ended sub with Main, and tie breakers? Both main breakes have CT's and tie breaker has CT's on both sides of breaker. Does anyone know of a good reference for this?

I am also interested in providing 67N directional ground fault protection with main and tie breakers. Can anyone provide a refence for setting up this protection?

 

[templdl]

Maybe this will get you started:
http://www.abb.com/search.aspx?q=differential relay&abbcontext=products
I believe both a differential and pilot wire relays are used depending upon the application.

 

[rbalex]

A main-tie-main with CTs on both sides of the tie is characteristic of a partial differential scheme. Is the tie operated "normally-open" or "normally-closed"?

 

[mull982]

A main-tie-main with CTs on both sides of the tie is characteristic of a partial differential scheme. Is the tie operated "normally-open" or "normally-closed"?

Tie is "normally closed" with one of the main breakers normall open so both sides of the switchgear are running off one utility source. If they loose the one utility source, the tie breaker stays closed and they close the other main (opening the main that was closed) and operate both buses off the other utility source. In a rare case they will open the tie breaker and opeate both sides off its respective main utility source. Boths tie and mains will never be closed at same time.

 

[rbalex]

Since there is always a open breaker in the modes you described, IMO you don't need a bus-differential scheme, partial or otherwise if the breakers are coordinated with downstream overcurrent devices.

The IEEE "Buff Book" (Std 242), Chapter 13 describes most common and a few unusual bus protection schemes. 67N applications are discussed in Chapter 14. Get it quick - it will be disappearing soon.