Simplified HV tower grounding system model for backflashover simulation

The article presents the application of a simplified model for the transient simulation of an overhead line tower grounding system. The model, based on a Pi-equivalent circuit, also accounts for non-linear soil ionization phenomena. The ATP-EMTP backflashover study of a typical European 150 kV overhead line using the proposed model is compared to one carried out by using a full circuit-based grounding system model, already validated by comparison with experimental tests and with simulation results yielded by field models available in literature. Results show an excellent agreement between Pi-circuit and full model, both in terms of lightning current values causing backflashover and time plots of insulator voltage and ground potential rise at tower foot. Moreover, the simplified model drastically reduces the computational resources (i.e. memory occupation and execution time) required when complex power systems must be studied in transient and non-linear conditions. Results show that the proposed model is suitable for massive, Monte Carlo-type statistical direct lightning simulations.