I'm in the process of expanding the electrical distribution system of an existing Healthcare facility. The expansion will consist of a new building that will house Medium Voltage (12.47 kV) switchgear, parallel connected generators (2 new and 1 future), and utility paralleling switchgear. The generators will be rated 12.47 kV, 2250 kW. My experience with 12.47 kV, paralleled generators is limited although the research I have done tells me that I should employ neutral grounding resistors (NGRs) or some other ground fault limiting devices on the generators. Would someone be so kind as to answer the following questions?
1. Is it best to employ one resistor for the system or individual resistors for each generator? The future generator will not be installed initially and the size of the third generator is not yet known due to unforeseen future load conditions.
2. What impact does utility paralleling have on sizing the resistors?
3. What other methods of limiting fault current (if any) might be more suitable or cost effiective?
Your assistance is much appreciated!
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