Industrial Plant GPR

[kmh1]

I am attempting to model an industrial plant 115/13.8 kV switchyard ground grid using ETAP software. The step down transformer secondary power feed cables (and low voltage control cables) leave the fence enclosed switchyard and connect to the medium voltage switchgear approximately 2000 feet away. A solid ground connection exists between the high voltage switchyard and the main plant ground system via insulated ground cables and various internal cable ground conductors within the cable tray bridge.

Can the plant be modeled as a remote ground electrode to the switchyard? or does the entire combined switchyard/plant area need to modeled in its entirety to calculate the switchyard GPR? Or should the safety ground connection between the plant and switchyard be severed (and maintain only an insulated ground connection to the transformer neutral grounding resistors)?

 

[advidana]

Contract etap and asked your question. Those people are very helpful

 

[jghrist]

You will probably find that a 115 kV fault gives the highest GPR for the switchyard.

 

[kmh1]

My main concern is transferred potential to the plant grounding system in the event of a 115 kV fault. The was some discussion in old design documents of separating the high voltage switchyard ground from the plant ground but the present configuration has both grounding systems tied together.