IEC standard high voltage circuit-breakers: Practical guidelines for overvoltage protection in generator applications

The IEEE C37.013, [1] standard defines the overvoltage withstand requirements for circuit breakers (CBs) intended for use in generator applications. The constraints of these requirements may lead to larger sized CBs to be used. In Oil & Gas offshore applications, IEC 62271-100, [2], certified CBs are often preferred due to their more compact size. However, detailed validation of IEC CBs for generator applications has not been as well defined compared to IEEE CBs. Hence, validation of IEC CBs for overvoltage protection in generator applications is required, usually by performing computer transient simulation and analyses. Very often a simplified model of the generator is believed to be sufficient to provide reliable results. However, as this paper will demonstrate, correct modeling of the generator has a significant impact on the overvoltage results, especially with salient pole machines. The main purpose of this paper is to discuss the aspect of Transient Recovery Voltage (TRV) analysis that have to be conducted when an IEC breaker is intended for use in generator applications. Main guidelines to understand and perform such overvoltage analysis are also provided. The influence of generator saliency on the TRV peak and slope is demonstrated.