Modeling of transient overvoltages in wind power plants

Compared with conventional power plants, wind power plants (WPP) have their own characteristic, which are more vulnerable to transient overvoltages. Transient overvoltages may contribute to insulation failures of step-up transformers. In WPPs, the transient overvoltage is mainly caused by switching operations of vacuum circuit breakers. In this paper, suitable models for the simulation of transient overvoltages are developed. A detailed model of vacuum circuit breaker, which is required to simulate both the capability of high-frequency current interruption and the withstand capability of transient recovery voltage, is developed. Input parameters for cable models are calculated on the basis of the parameters of actual cables. A wide band transformer model is also proposed for studying the transient behaviors in WPPs. Simulations of transient overvoltages during circuit breaker switching operations in WPP have been carried out in PSCAD/EMTDC. In case studies, it considers some influence factors of transient overvoltages, such as the length of cable feeders and the collector system topology adopted in WPPs. The results obtained from this research can be used as a reference for the insulation level designation of electrical components in WPPs.