115 kV Substation Switching Scheme 1

[rrivas]

I work for a private generator that wants to interconnect with the local utility grid. I'm proposing to open an existing 115 kV transmission line (in and out) and interconnect the generator step-up transformer with a 3-breaker ring bus. Is there a better substation switching scheme to use (cost, reliability, etc.)? Any information would be greatly appreciated. Thanks.

rrivas

 

[SidiropoulosM]

The scheme you are proposing is a good one. There is a lower cost scheme, which is to provide one breaker only at the tap location, which will disconnect your generation from the 115 kv line. The disadvantage of this scheme is that your generation will be tripped for a fault on either section of the 115 kv line. This may or may not be acceptable to you, depending on the length of the line, its outage record etc.

 

[dpc]

The ring bus is a good workable solution. It will be expensive at 115 kV and require some land. Utility may want something more elaborate, but ring bus should be more than adequate.

 

[busbar]

In ANSI regions, standards to thumb through might be…

C37.113-1999 …Protective Relay Applications to Transmission Lines
C37.95-2002 …Protective Relaying of Utility-Consumer Interconnections
C37.91-2000 …Protective Relay Applications to Power Transformers
C37.102-1995 …AC Generator Protection
C37.101-1993 …Generator Ground Protection

The design needs to be coordinated with the line owner, his protection scheme and possibly varied operational modes.