Superposition Effect of Overvoltage for Vacuum Circuit Breakers Simultaneously Switching Shunt Reactor Banks in Offshore Wind Farms

The overvoltage caused by vacuum circuit breakers (VCBs) switching shunt reactors (SRs) simultaneously in offshore wind farm (OWF) would be superimposed. The interaction mechanism between the switched SR banks is analyzed. Three modes are presented, including reignition & reignition, reignition & preignition as well as preignition & preignition. The influence of some factors on superimposed overvoltage is discussed, such as switching time difference, cable length and feeder number of wind turbine generator (WTG), VCB installation position, etc. Finally, a switching strategy of VCB is proposed to prevent the superposition effect of overvoltage. The results indicate that the superposition of reignition & reignition is the most serious mode. The superposition of preignition & preignition would not lead to overvoltage. The superposition effect of reignition overvoltage can be eliminated by the proposed switching strategy. It combined with the surge arrector can limit the overvoltage peak at a low level.