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High Resistance Grounding Units

High Resistance Grounding Units

High Resistance Grounding Units

(OP)
Just seeking advice of the higher powers on this board.  I have a client who has three ungrounded secondary unit substations.  They want to connect high resistance grounding units to these substations.  I understand the concept of these HRG units but I am not sure of how to physically wire them.  Do you need a secondary feeder breaker to feed these units or can you tap directly off the transformer neutral?

I believe the units are Eaton C-HRG.  

The Contractor is asking that we provide a secondary feeder breaker when wiring these HRG's.  From my reading I thought you only need a direct connection from transformer neutral to the HRG, hence not needing this secondary breaker.  

Any information you guys have, as always, is appreciated.

Thanks

RE: High Resistance Grounding Units

First, are the transformer windings delta or ungrounded wye?  If the winding is delta, there is no neutral to connect to.  

For a wye transformer, you just need a HRG unit with a resistor and associated fault sensing equipment and it is connected to the transformer neutral (and ground, of course).  There is no circuit breaker in the neutral.  

For a delta winding, you will need some type of grounding transformer, either a delta-wye or zig-zag unit plus the grounding resistor.  This can all be provided in one package or the grounding transformer can be a separate item.  



RE: High Resistance Grounding Units

(OP)
Sorry dpc.

I should have mentioned they were ungrounded wye transformers.  Thanks for the info

RE: High Resistance Grounding Units

The plan may be to monitor the current through the grounding resistor and shunt trip the breaker open in the event of a ground to avoid or reduce arcing damage. When this is done, the breaker or contactor will be a part of the HRG unit and the complete assembly will be approved.
If this is just a disconnect without alarms to indicate an open breaker I would strongly resist the installation of a breaker. In Canada an automatic breaker in a grounding conductor is prohibited by Rule 10-800 of the CEC.
respectfully

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