VT Specs 1

[nightfox1925]

We have phase VTs whose specs is:

Primary Volts: 4200/7280GY
Secondary Volts: 120V
Winding Ratio: 35:1
Freq: 60Hz
ABB Model: VIZ-75, 7525A71G02

The vendor drawing shows that these VTs are connected in Wye grounded/Wye grounded on a 7200V, 3 phase buses.

The way I understand the specs is that each VT will have a 4200V Pri and 120V secondary. Connecting them in Wye-wye (both pri and sec neutral grounded)will yield 7280 phase-phase primary and 208V phase-phase secondary.

Is my understanding correct?

 

[dpc]

Close to that. The key piece of data is 35:1 - that is not going to change regardless of what you hook up to the PTs.

So with exactly 7200.00 V primary, phase-phase, you would have 4157 V or thereabouts phase-ground. 4157/35 = 118.8 V secondary phase-to-ground.

Secondary phase to phase = 118.8 x 1.732 = 205.7 V

Check my button pushing, but you get the idea. The PT doesn't know what is on its nameplate. It just steps down the applied primary voltage by a factor of 35, or very very close to that.