ElectricPersonality
Member
- Location
- Philadelphia, PA
A utility is requiring we install a grounding transformer for a new rooftop solar install that will intertie with the existing building electrical distribution system. The existing building system is 480/277 volt, 3 phase 4 wire, with the neutral grounded, which is typical. The question is, if we install a zig zag grounding transformer at the building service, is it correct, then to say that the neutral reference for the building will now be at the zig zag transformer AND NOT at the utility transformer outside the building? Does this cause any voltage to ground reference issues for the existing line to neutral loads in the building? Although the NEC does not define what "high impedance" grounding means, I think that a zig zag without a resistor would not be high impedance grounded and therefore this connection "should" be acceptable.
second question, it seems to follow that since we are deriving a new neutral conductor, then the neutral wire from the utility transformer would have to be disconnected at the service switchboard or is it okay to keep it connected? The Code has some verbiage about zig zags not being installed on the load side of system ground connections, so perhaps its okay to leave the service neutral connected, AS LONG as the connection to earth at the service is through the zig zag transformer?
second question, it seems to follow that since we are deriving a new neutral conductor, then the neutral wire from the utility transformer would have to be disconnected at the service switchboard or is it okay to keep it connected? The Code has some verbiage about zig zags not being installed on the load side of system ground connections, so perhaps its okay to leave the service neutral connected, AS LONG as the connection to earth at the service is through the zig zag transformer?