Diminution of Transient Disturbances for High Voltage Application Integration

Abstract

The increasing global energy demand and large-scale renewable energy resources integration have intensified concerns over power system stability, particularly at extra-high voltage (EHV) transmission level. Shunt capacitor banks are widely employed to enhance voltage stability, but their energization often introduces severe transient overvoltage and inrush currents that threaten equipment reliability and grid security. This paper investigates the application of synchronous switching using the Point-on-Wave (PoW) technique as a mitigation strategy for transient disturbances during capacitor bank energization. A two-stage methodology was adopted, combining MATLAB/Simulink-based transient modelling with field implementation at Eskom’s 400 kV Delphi Transmission Substation. The simulation results demonstrated that uncontrolled switching produced peak disturbances of 1.04 kA and 479 kV, corresponding to ±480% and 22% transient elevation above nominal levels. By contrast, PoW switching at the zero-crossing reduced peak transients to 539 A and 412 kV, representing reductions of approximately 51% in current and 15% in voltage. Field experiments using a Schneider RPH2 PoW relay integrated with a GE C70 protection relay further validated these results, confirming significant reductions in inrush stress, transient duration, and breaker wear. Beyond technical validation, the study highlights operational benefits including improved equipment lifetime, lower maintenance costs, and enhanced system reliability, critical for renewable-rich and stability-constrained power systems. The findings establish PoW-based switching as a practical and scalable solution for transient mitigation in modern EHV grids.