recently , a new tap-changer transformer has been placed in our plant (132kv/33 kv) parallel with two old transformer. but it has been observed that the voltage developed by it different than others. My Q
what is the impact if it connected parallel to others presisitng problem?

 

SCE... voltage differences are the result of differences between the new and old Tap-changer step-intervals.

For example, the new units may have tap-positions having a step-intervals of +/- 2.0%, while for the old units the corresponding tap-position step intervals of +/- 2.5%.

The solution is to determine what combination of taps will produce minimum circulating-currents!

I suggest you search the Control.Com Archives for "Paralleling Transformers", "Circulating Amps", or the like!

Regards, Phil Corso (cepsicon [at] aol [dot] com)