A Study on Switching Control Strategy of Circuit Breaker under Capacitive Load

The circuit breaker supplies the load current in the normal state and separates the faulted section in the event of a fault. Whenever the circuit breaker is operated, the switching process is repeated, and a resulting transient phenomenon inevitably occurs. In case when capacitor load is energized, a large inrush current can be generated when the voltage across the circuit breaker is sufficiently high that can cause prestrike. The generated inrush current may not only damage internal components of the circuit breaker, such as wear on the contact surface or nozzle perforation but may also cause malfunction of the protection relay. As a result, the cost of maintenance increases and, product life and power quality deteriorated. The transient varies depending on the phase during switching, and since the switching phase of the conventional circuit breaker is randomly determined, a resistor is inserted into the circuit breaker, also known as pre-inserted resistor, to reduce the transient. However, over the past few decades and with significant improvements in intelligent electronic devices (IEDs) in reliability and cost, control switching solutions applied to high voltage circuit breakers have provided relevant electronic alternatives to more traditional methods. That is, by controlling the point of switching, the load is energized and de-energized at the optimal phase angle, the transient phenomenon can be minimized. In this paper, switching control strategy to minimize transient of circuit breaker while energizing capacitive load is studied.