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Delta - Delta transformer output voltages

Delta - Delta transformer output voltages

Delta - Delta transformer output voltages

(OP)
Hi, we own and operate a 1000kVA, 13.8kV -> 600V, Delta-Delta distribution transformer. An electrician noticed during a PM that the voltages on the output were odd. Two of the line to ground voltages were approximately 300V, and the third line to ground voltage was 345V. The phase to phase voltages were similarly odd.

We immediately checked the ratios (all good), and winding resistance (good).

We think that this may be natural for an ungrounded delta transformer because there isn't a real ground point but are interested in really understanding why this is.

Does anyone have any input or a possible explanation?

Thanks...

RE: Delta - Delta transformer output voltages

rormac,

If system is ungrounded, voltages to ground are irrelevant and will vary widely when measured.

What were the "similarly odd" phase-to-phase voltages that you measured?

Good on ya,

Goober Dave

RE: Delta - Delta transformer output voltages

When the phase to phase voltages are unequal on a delta it may indicate a phase angle error on the primary supply.
Single phase voltage regulators and unbalanced loads on a distribution system may cause phase angle errors.
Phase angle errors will cause unbalanced currents and excess heating in motors.

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

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