Working on the electrical field for a few year now, I came across the use of an isolation transformer on the incoming service from the utility company. Can anybody tell me the main reasons for this configuration?
Could be several reasons:
Provide an isolated ground source so plant ground faults do not affect utility relaying and utility faults don't trip plant.
Add impedance to reduce short circuit fault levels.
Utility service was ungrounded delta and customer needed a grounded wye or a high resistance grounded wye.
Mitigate harmonics going back to utility or from utility.
Change phase angle 30 degrees to match an existing system in the plant.
Provide taps for adjusting voltage +/-5%.
MV load is a VFD, electric boiler or arc furnace that causes ground current or harmonic issues.
or???
