Modeling and evaluation of overvoltage

A case study will be presented demonstrating modeling of overvoltage in a moderately sized system involving medium voltage vacuum breakers, cables and transformers. The focus is on simulating high frequency overvoltage generated by circuit breaker prestrikes and re-ignitions and evaluating the impacts on transformer insulation. -Results obtained from a customized breaker TRV model which is capable of controlling the capability of switching high frequency current will be presented. -The methodology of analyzing severity of overvoltage in the frequency domain was applied in this project. Results and discussions regarding frequency domain analysis will be shared. -Simulation results regarding typical system configurations with variation of key parameters such as cable lengths, load power factors will be briefly presented. -Application of EMTP study results in assisting equipment specification, as well as overvoltage mitigation methods including optimizing switching sequences, necessity of snubber circuits will be discussed. -Case specific strategies to improve simulation speed and work flow with EMTP will be introduced and discussed.