Lightning Performance of High Voltage Transmission Lines Protected by Surge Arresters: a Simulation for the Hellenic Transmission Network

Lightning strikes to overhead transmission lines are a usual reason for unscheduled supply interruptions in the modern power systems. In an effort to maintain failure rates in a low level, providing high power quality and avoiding damages and disturbances, plenty of lightning performance estimation studies have been conducted and several design methodologies have been proposed. The protection of overhead transmission lines is achieved using shield wires and surge arresters. Surge arresters should be insulators at any voltage below the protected voltage, and good conductors at any voltage above, to pass the energy of the lightning strike to ground. In this work an analysis of the lightning performance of 150kV transmission lines of the Hellenic interconnected system is presented, using Simulink and data collected by the Hellenic Public Power Corporation S.A. The lines are divided into regions each of them has different keraunik level, length and tower footing resistance. All the lines are protected with shield wires and in the current simulation surge arresters are implemented on every tower or in a given step. The installation of surge arresters improves the lightning performance of the line. The simulation results are compared with real recorded failure rates, provided by the Hellenic Public Power Corporation S.A., and show that shield wires combined with surge arresters in every tower is the best protection against lightning overvoltages. By increasing the tower footing resistance, the lightning failure rate becomes greater, especially when the line is protected only with shield wire. Additionally, smaller arresters intervals decrease the failure rate. The results of the current work could be useful for the maintenance and the design of transmission lines in the Hellenic System.