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Grounding of feeder concentric neutrals

Grounding of feeder concentric neutrals

Grounding of feeder concentric neutrals

(OP)
Hello.

I'd like to know if there are standards, sketches or photos available for grounding of the outgoing feeder concentric neutrals (or tape shields, or LC neutrals) at the point where the feeder leaves the transformer substation and terminates on the riser pole. We currently ground the concentric neutrals at the pole to the ground rod but we are considering grounding them through 3kV lightning arrestors.
Thanks in advance.

RE: Grounding of feeder concentric neutrals

If the concentric neutral/tape shield/LC neutral acts as the system neutral, i.e. there is no separate neutral conductor, then it must be grounded to provide a fault current return path.  If it is not connected metallically to the transformer neutral (through the station ground grid) and to the OH neutral, then the only path for ground fault current is through earth.  This is probably not the basis for zero-sequence impedance and ground fault current calculations.

If there is a separate neutral, then it could be left ungrounded, but there could be high induced voltages (the reason for the arrester).  

RE: Grounding of feeder concentric neutrals

(OP)
Thank you jghrist for the response.  There is a separate nertral brought out from the transformer (350MCM cable).  Here we are just grounding the concentral neutral.

Steve

RE: Grounding of feeder concentric neutrals

Suggestion: The more does not necessarily mean the better. If there happen to be created neutral loops, they may have circulating currents induced, which can cause problems, e.g. they can elevate temperatures at various places, e.g. terminals, conductors, lugs, etc.

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