Transient earth potential rise in gas insulated substations

Switching or dielectric breakdowns within GIS enclosures lead to voltage transients propagating towards the terminations. Amplitudes can range to 2.0 pu with risetimes of under 20 ns. At terminations, one component of the transient continues along the overhead conductor while another propagates back into the station along the exterior of the enclosures. Successive grounding bonds attenuate and shorten the duration of this component. The hazard when touching the enclosure depends on energy dissipated in the body, estimated from the potential squared and integrated over time, divided by an assumed body resistance of 500 ohm. This paper describes tests and models in support of EMTP simulations to review this body energy, as requested by some utilities.