Grounding of Power Station 4,160-Volt Auxiliary Systems

As the size of power station units has increased, it has become economical to raise the voltage on auxiliary systems to 4,160 volts. Almost universally, 2,400-volt systems have been operated ungrounded. With the higher voltage, the question again arises whether the system should be grounded and if so, whether there should be neutral impedance. It is apropos then to enumerate the advantages and disadvantages of each mode of operation and then select the one that appears most justified for power station auxiliary supply. An exact answer cannot be expected; the probabilities can be weighed and the best possible decision made. To simplify the study, the question is divided into two parts: a comparison between grounded and ungrounded systems, and a discussion as to what mode of grounding is best suited to the problem. For the sake of completeness, a discussion of resistor rating and the type and performance of ground relays is included.