High Resistance Grounding Units

[SparkyJunior]

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

 

[dpc]

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.

 

[SparkyJunior]

Sorry dpc.

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

 

[waross]

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