Sustained Overvoltage due to Zero Sequence Resonance for Shunt Compensated Transmission Lines

Shunt compensation reactors, deployed in long AC transmission lines, serve to mitigate overvoltages induced by capacitive charging under light load conditions. However, these reactors can introduce operational challenges, notably sustained overvoltages due to zero sequence resonance. Such resonance occurs in unbalanced conditions, often stemming from circuit breaker malfunctions that result in one- or two-phase disconnections. The zero-sequence resonance is triggered between shunt reactors and phase capacitance in disconnected phases. The overvoltage caused by this resonance can lead to equipment damage. The overvoltage caused by this resonance can lead to equipment damage. The presentation will cover: • Zero Sequence Resonance: Background on the phenomenon and resulting sustained overvoltages.