3 Phase medium voltage transformers

[electricaljohn]

I understand that 3 phase medium voltage transformers can have an integral fused disconnect switch. This is not a typical installation; typically, they have pull-out bayonet type fuse holders on the primary side and not a disconnect switch. Does anyone have expeirence designing medium voltage transformers with integral disconnects, prefferably an oil-filled transformer section and air-filled 200A fused disconnect section? (15KV primary, 480/277V secondary, 300-750KVA, 150?-220? temp. rise) If so, what is a typical design, oil-filled switch and transformer section, air-filled, combonation, or whatever floats your boat?

Thanks
John

 

[steve66]

I think what you are refering to is typically called a substation. Square D should have some info on their site. Try clicking the products link on their website, and then choosing substations.

Steve

 

[jim dungar]

I understand that 3 phase medium voltage transformers can have an integral fused disconnect switch. This is not a typical installation; typically, they have pull-out bayonet type fuse holders on the primary side and not a disconnect switch. Does anyone have expeirence designing medium voltage transformers with integral disconnects, prefferably an oil-filled transformer section and air-filled 200A fused disconnect section? (15KV primary, 480/277V secondary, 300-750KVA, 150?-220? temp. rise) If so, what is a typical design, oil-filled switch and transformer section, air-filled, combonation, or whatever floats your boat?

Most padmount design transformer use load break elbows instead of a switch, but they are not fused.

The standard rating for 15kV fused switches is 600A which are then cabled to the primary of a "unit substation" design liquid filled transformer.

The standard temperature rise for liquid filled transformers is 65C, low temp are 55C and extended loading are dual rated 55/65C.

 

[electricaljohn]

Jim and Steve

Jim and Steve

Thanks guys for the replies. Jim, I meant to say elbow instead of bayonet and you are correct about the 600A disconnect switch connected to the Unit Substation. This is what I'm looking for. Dover Air Force Base in Delaware wants to have the capability of diconnecteing the new Dorms via switch instead of the hot-stick method. I will have to adjust my spec. a bit... thanks for your input.

John