Back-flashover Investigation of HV Transmission Lines Using Transient Modeling of the Grounding Systems

The article presents the transients analysis of the substation grounding systems and transmission line tower footing resistances which can affect to the back-flashover (BF) or overvoltage across insulator chain in an HV power systems by using EMTP-RV software. The related transient modeling of the grounding systems is based on a transmission line (TL) model with considering the soil ionization. In addition, different configuration of grounding system have been simulated to calculated the BF, including number of vertical grounding rod, length of rod, point of lightning current injection into the grounding grid and using two depth design of grounding system where the surface of substation under consideration is very small orit is necessary to bury the grounding grid in the rocky media, occasionally. The simulation results have shown that how the mentioned parameters can considerably affect inception of BF, and suitable design of grounding system can reduce damages caused by lightning.