Critical factors to consider when paralleling power transformers
Critical factors to consider when paralleling power transformers
(OP)
I have a small project that will require installing a 2000KVA, 13800v/ 480-277y transformer on the same bus as another unit the same size. This parallel operation will be controlled by a tie breaker on the LV bus. What is the critical level of impedance difference that will determine which transfoemer to use? The load on both will be Approx. 500amps @480V.






RE: Critical factors to consider when paralleling power transformers
Mike
RE: Critical factors to consider when paralleling power transformers
That said, you must, as mpparent points out, consider the effect on the available fault current. Should not be a problem if you have fused switchgear, but could be a major headache if you have circuit breakers.
RE: Critical factors to consider when paralleling power transformers
If you go parallel, closed transition, with two 2000kVA transformers, your available fault current(keep in mind this is the maximum with no motor contribution, you'd have to do an actual analysis), is approximately 83kA(that's assuming a Z% of 5.75). This is also assuming the fault is right at the switchgear bus. Take a look at your mains and feeder breakers to make sure you don't have an issue with bracing.
Mike
RE: Critical factors to consider when paralleling power transformers
Example:
trf1 = 8.35; trf2 = 7.67
8.35- 7.67 = 0.68
0.68 / 7.67 *100 = 8.87%
<10% difference, thus can do.