Max amount of Breakers on 34.5kv bus with no Main Circuit Breaker

[cyriousn]

I'm reviewing a project where there is a 270MVA 161/34.5kv transformer and no main circuit breaker on the 34.5kv bus. (I don't know of any circuit breaker for 34.5kv that is higher than 3000A which is a force air cooled switchgear breaker)

The 34.5kv bus has (8) 600A breakers. (7) of the breakers are connected to PV collector circuits and (1) is connected to a cap bank.

Is there any limit of how many circuit breakers can be on a 34.5kv bus without a main circuit breaker? I used to work in the commercial NEC realm so I keep thinking back to the 6 disconnect rule but I don't think that applies here. Any help here is much appreciated!

 

[RRaghunath]

I have seen many MV stations where there used to be no Incoming breaker, the station relying on upstream breaker for any fault in the incomer as well as in the busbar, also as back up for downstream breakers.
The earth fault protection (connected to transformer MV neutral CT) and other protections in the incomer are wired to trip the upstream breaker.
Thus, there is no compromise on protection of the station in case of a fault. This results in cost saving in substations where the incomer breaker rating is an issue.
If the Overcurrent protection is not provided in the incomer, the transformer also may have to be investigated in case of HV overcurrent protection operation. That is a demerit, though a small one.

 

[bacon4life]

ABB offers up to 4000A at up to 46 kV in the VD4 lineup. At some point dual winding transformers start to make sense to reduce current levels.

 

[wcaseyharman]

I am not aware of any NESC rules that would dictate a main breaker, none of our windfarms have a main low side breaker, although none of our stations have more than five or six feeder breakers per transformer (although with the bus tie we can and have run more than that off one transformer).