Secondary protection on step up transformer

[philly]

I have an application where we will be installing a 1.5MW 480V backup gen-set which will be connected to a 480V-4.16kV step-up transformer in order to supply backup power to a 4.16KV SWGR lineup through an existing 4.16kv breaker. The gen-set will have a breaker as well as a switchboard on the LV side of the step-up transformer where the gem-set will connect.

With this arrangement would there be a requirement for a secondary MV fused switch on the secondary of the transformer other than the breaker at the switchgear which it is feeding?

Furthermore this gen-set is being added to an already existing backup system which consists of a backup utility transformer with 4.16kv secondary and a 4.16kv fused switch which then feeds into the 4.16kv swgr breaker referenced above. The idea when adding the gen-set would be to connect the gen-set transformer secondary to the line side of the existing utility transformer secondary switch (Kirk key gen-set breaker and utility switch) and utilize the existing feeder cable between the utility transformer secondary switch and the switchgear.

For this arrangement would the existing switch be able to serve as any required secondary protection for the new step-up transformer? Are there any tap rules that would come into play with taping this seconds gen-set feed onto an existing feeder?

 

[jim dungar]

I think you need to provide a one-line. I am confused how you are proposing to make these connections.

It sounds like you are going to connect your gen set to the load side terminals of the backup utility transformer secondary side switch. How do you plan to isolate your transformer-gen set when the backup power is from the utility?

You do not mention it but I hope you have confirmed if your transformer must be a 4160Y/2400 output.

 

[Hv&Lv]

I agree that a one line is needed to fully understand what’s going on.
will the isolation/bypass switch be supplied by the utility or will you provide it?
who is responsible for the step up XF? The terminations And connections?
we have a setup like I think your talking about now, it’s a 1MW 4160.
that one doesn’t have fuses, it has a Westinghouse breaker.
It’s loud and the spring winding will definitely get your attention.

this one is soft loading. We actually load tested this one by back feeding a circuit all the way back to the substation some years back.