GT Percent Impedance


Thread Starter


We have ordered 3MVA 0.380/13.8 kv ,60hz with 7% impedance. Design is held on IEC 60076. But during factory test results we found % impedance is 7.89%. Due to this % impedance, changes would affect performance of transformer while in operation or in future.

According to me ... The short circuit current is get reduced...

We can do parallel operations if we require. Any other valid points or suggestions?
NKT... typically, the allowable tolerance is +/- 10.

1) The difference will not affect its load carrying function.

2) More important are the copper and iron losses. They could have a significant impact on operational cost.

3) Yes, fault-current will decrease, but it's insignificant, about 0.2%.

4) Parallel operation won't cause operational problems.

5) More important is Percent Voltage-Regulation. It will affect the parallel case if it's significantly higher than the contractual tolerance.

6) Lastly, what is the vendor willing to provide to 'salvage' your contractual agreement?

Phil Corso