Equipotential bonding between HV Utility Sub grid and plant underground “loop”

[Isaiah]

We have a utility HV substation that is probably 50 feet from an industrial plant which employs an equipotential plane (buried ground “loop” of bare 4/0 cable)
The HV substation has its own buried grid installed per IEEE 80. There are HV feeders extending underground from the substation to transformers in the plant. The cables are shielded. The upstream delta-wye HV transformers in the substation have neutral grounding resistors that limit the amps on ground fault until the breaker trips via protective relaying (shielding should carry the fault)
Is it necessary to tie the two underground bonding systems together?


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[petersonra]

It seems to me that the NEC does not cover this kind of thing. Therefore, it would not appear to come under the purview of an inspection agency but rather the utility.

 

[Dale001289]

We have a utility HV substation that is probably 50 feet from an industrial plant which employs an equipotential plane (buried ground “loop” of bare 4/0 cable)
The HV substation has its own buried grid installed per IEEE 80. There are HV feeders extending underground from the substation to transformers in the plant. The cables are shielded. The upstream delta-wye HV transformers in the substation have neutral grounding resistors that limit the amps on ground fault until the breaker trips via protective relaying (shielding should carry the fault)
Is it necessary to tie the two underground bonding systems together?


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In my opinion this sort of equipotential bonding between the two is not required. The SS has its own electrode system and so does the downstream facility. Whats important is the fault path via the cable shielding back to the source at the SS. Check number of cycles before protective relaying trips via the cable shielding to ensure the cable itself is not damaged.