Energy stress of non-gapped line arresters due to lightning strikes to a 150 kV line: concentrated tower grounding system modeling effects

This study investigates the impact of the frequency-and current-dependent behavior of concentrated tower grounding systems on the computed fast-front overvoltages across overhead transmission line (OHTL) insulation, the current flowing through line surge arresters (LSAs), and the energy absorbed by LSAs. This investigation is performed via ATP-EMTP simulations of a 150 kV double-circuit OHTL equipped with non-gapped line arresters (NGLAs). Two NGLA installation configurations are studied: 3 and 6 NGLAs at each tower. Four models are used for the concentrated tower grounding systems: (1) a resistor with a fixed resistance (ground resistance of towers), (2) frequency-dependent (FD) response with fixed and (3) FD soil electrical properties, and (4) the CIGRE model for soil ionization. A hybrid code was used to produce the FD grounding system responses. The tower ground resistance was a parameter and low-frequency soil resistivity was varied accordingly. The energy stressing NGLAs decreases notably when soil ionization is included in simulations. The adoption of the tower ground resistance (fixed value) in simulations yields conservative results in terms of NGLA energy stress.