Breaker vs Motor Operated Switch for Substation Bus Tie

[rockman7892]

I've got an application in a distribution substation where there are manual switches serving as bus ties between several different 13.2kV distribution buses. These bus ties are intended to be used when a transformer on a given bus is out of service in order to supply the bus through tie from adjacent transformer (IE no parallel operation)

We are currently looking to replace the manual switches for a few reasons but mainly in order to provide a status indication to SCADA as well as to be able to open and close remotely via SCADA (remote manual operation not automatic transfer).

Currently there have been solutions proposed to use breakers for these bus ties as well as to just replace the existing manual switches with motor operated switches. I have never seen motor operated switches used as bus ties (or really manual ones for that matter) so was curious if there were significant reasons for not using a motor operated switch. It seems like the switch solution would be the cheaper option and a breaker option a more expensive but proper option but was looking for any feedback from others experience.

 

[dpc]

Switches are pretty common for bus ties in substations in my experience. The switches cannot clear faults of course, so if you want to be able to automatically isolate bus sections, you'll need a circuit breaker. Motor operators don't really change the equation much, other than allowing for SCADA operation. Using circuit breakers would be much more expensive and take more space since they would probably require isolation switches, etc.

 

[System Protection]

We use a main and aux bus with an extra breaker that can be used to bypass any of the other breakers on the bus. It can also be used to tie the two buses together so you can take out one of the transformers.