Analysis of the potential distribution in a relay cell generated by a direct lightning strike in a 500 kV substation

The protection and controlling devices have been moved into the relay cell in the switchyard from the controlling building in some newly-built 500 kV substations in China. The transient grounding potential rise will be caused in a relay cell by a direct lightning strike in a 500 kV substation and be harmful to the secondary devices. Therefore, it is very important to predict the transient potential distribution in the relay cell. The authors calculated and analyzed the transient grounding potential distribution, found the appropriate mode of the inner grounding grid in the relay cell. Thus, the electromagnetic interference that the protection and controlling devices will suffer from the transient grounding potential rise in the relay cell can be reduced greatly.