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A Damage Prevention of Circuit Breaker During Energizing of Low-loaded Line with Shunt Reactors

Energizing current of low-loaded highlycompensated power lines with shunt reactors mainly consists of an aperiodic component, and for a long time has not zerocrossing points. The modern SF6 circuit breaker fails to trip such power line immediately after energizing if unexpected fault or protection relay malfunction occurs because of commutation inability of aperiodic current. This leads to a long arc burning, and eventually to the breaker damage. The paper studies the transients during the commutation of the lowloaded power line and conditions when the amplitude of aperiodic component exceeds a safe level. The study shows that effective prevention of circuit breaker failure may be achieved using controlled switching technology assuming precision control a line energizing moment. The optimal reclosing moment is located near a beat minimum of the circuit breaker voltage and corresponds to the phase of supply voltage, at which the initial amplitude of the energizing current aperiodic component does not exceed the amplitude of the fundamental component. Reclosing of power line at the proposed optimal moment guarantees the safety of commutation for the circuit breaker and ensures mitigation of switching overvoltages.