SF 6 Generator Circuit Breaker Modeling

Generator circuit breakers are located between generators and step-up transformers in power networks and their ratings usually range from 100MVA to 1300MVA. Owing to the potentially high asymmetrical fault levels at relatively low voltage near the terminals of generators, the current interruption requirements of GenCBs are significantly higher than the distribution networks at similar voltages. Because of these high current rating properties, testing of GenCBs is costly and time consuming. Consequently, it is very useful to have valid computer simulations available. In order to estimate the interrupting behavior of GenCB, a breaker model was developed in ATP/EMTP. The model incorporates arc voltages, escalation voltages and the reignition behavior of generator circuit breakers. The model was developed in EMTP by using MODELS and incorporates the four main stages of the breakers’ operating processes: the closed contacts stage, the arc burning stage, the arc extinguishing stage and the opened contacts stage. The model was incorporated into a network simulation and the results were compared with IEEE Generator Circuit Breaker standards. More than sixty simulations have been done and Monte Carlo statistical studies were also carried out and the results are presented in this paper.