When the electrical fault, such as short-circuit or overload current, happens in the middle voltage network, a current transformer detects it and the vacuum circuit breakers (VCBs) quickly open and interrupt the fault current (tripping). Recently, electromagnetic actuators are widely used as operating mechanism for the VCB. In this paper the possibility of the direct tripping of the electromagnetic actuator by the current output of the current transformer is investigated numerically. In simulation, the secondary current waveform was calculated by response surface approach. It can take into account of the saturation effect of the magnetic core due to high primary current and heavy loads of the secondary circuit. The mechanical behavior of VCB in time was also simulated coupling with the actuator motion and the operating electrical circuit. Finally tripping tests by the current transformer output with high primary current was performed.
University of Lorestan