Cumulative Effect of Reignition Overvoltage Caused by Vacuum Circuit Breaker on Shunt Reactor Insulation in Offshore Wind Farm

When vacuum circuit breaker (VCB) frequently interrupts shunt reactor (SR) in offshore wind farm (OWF), there is a large cumulative effect of reignition overvoltage. Firstly, an OWF model, which includes the SR model with distributed parameters and the VCB model considering arc reignition, is implemented in the environment of electromagnetic transient program (EMTP). Based on the theory of waveguide, the voltage distribution along the SR winding is analyzed. The influence of reignition number on the oscillation of voltage distribution is discussed. Then, the method for evaluating the strength of overvoltage cumulative effect is proposed based on the U-N curve of insulation breakdown. The results indicate that the weakness of insulation breakdown usually occurs in the middle of the winding. The performances of three overvoltage suppression measures in reducing cumulative effect are compared. A suggestion is provided to assist in selecting suitable device and prevent the hazards of overvoltage and its cumulative effect.