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Delta-Wye Transformer Bank Voltages
4

Delta-Wye Transformer Bank Voltages

Delta-Wye Transformer Bank Voltages

(OP)
I have a three transformer Delta-Wye Grounded 13.8kV to 8kV stepdown where we lost a phase on the primary side feeding into the substation.

I would like to calculate the voltages on the secondary side for each of the three phases. Can someone suggest a good reference book for these types of scenarios or provide some assitiance with the calculation.

Thanks!!

RE: Delta-Wye Transformer Bank Voltages

I belive on the secondary one L-N voltage would read 8kV or the rated secondary voltage, and the other two L-N voltages would be 50% of rated or aproximately 4kV depending on which primary phase was opened.

RE: Delta-Wye Transformer Bank Voltages

I agree with rockman.  Assume you lose phase a.  You wind up supplying phases b-c with rated voltage.  Because of the delta winding, phase a-c and b-c have to add up to rated voltage.  So you get rated on one secondary leg and half rated on the other two.

RE: Delta-Wye Transformer Bank Voltages

The voltages on the affected phases will be near the inverse ratio of the loads on the affected phases. Rather than exactly one half voltage you may get 40%:60% 30%:70% or some other values that will add up to the normal voltage of one phase.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Delta-Wye Transformer Bank Voltages

Yes, I guess you're right on that, Bill.  The 100% winding will be unaffected by load but the other two will add up to 100% and the loads will determine that.

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