Investigation on Power Frequency Following Current for Vacuum Circuit Breaker Interrupting Shunt Reactor in Offshore Wind Farms

Multiple reignitions would cause the overvoltage while vacuum circuit breaker (VCB) switching off shunt reactor (SR) in offshore wind farm (OWF). However, the voltage escalation may be terminated in advance due to power frequency following current (PFFC). Firstly, the formation mechanism of PFFC and the chopping characteristic of the high frequency (HF) current caused by reignition are theoretically analyzed. Then, an OWF model is implemented in the electromagnetic transient program (EMTP) to simulate reignition overvoltage. A field experiment is conducted to investigate PFFC and validate model. In addition, the influence of HF arc quenching capability on PFFC. The critical condition for triggering PFFC are studied. Finally, a method for selecting the parameters of LR snubber is proposed to effectively accelerate the attenuation of HF current. The results show that LR snubber based on the proposed method has great performance in triggering PFFC. The reignition duration is shortened and the overvoltage is lowered commendably.