EHV AC Earth Switch Induced Current Capability Using Frequency Domain Approach

This paper introduces a frequency-domain (FD) approach for evaluating induced current duties of high-speed earthing switches in EHV AC systems. Unlike conventional EMTP simulation tools, the FD method solves Maxwell’s equations for the entire conductor network, accurately capturing electromagnetic (EM) and electrostatic (ES) coupling, soil influence, and distributed earthing paths. Validation against EMTP simulation tools confirms close agreement. The study covers real-world configurations double-circuit overhead lines, underground cables, and hybrid routes and benchmarks induced currents and voltages under various conditions. Parametric analysis highlights that substation impedance, tower footing resistance, and soil resistivity have negligible effect on phase coupling (<1% for currents, <0.3% for voltages), influencing only earth-return current distribution. In contrast, conductor phasing and phase sequence significantly impact coupling, with optimal sequence reducing induced voltages. These findings emphasize that geometry and phasing dominate coupling behaviour, while earthing parameters primarily support maintenance safety. The FD approach provides a versatile, high-fidelity tool for assessing induced current switching duties across diverse transmission configurations, to ensure compliance against IEC 62271-102 limits and enabling robust, future-ready design.