Vacuum circuit breaker modelling for the assessment of transient recovery voltages: Application to various network configurations

Vacuum circuit breakers (VCBs) are widely used for medium voltage applications when low maintenance, long operating life, and large number of allowable switching cycles are required. The accurate estimation of the transient recovery voltages (TRVs) associated with their switching operation is indispensable for both VCB sizing and insulation coordination studies of the components nearby the switching device. In this respect, their accurate modelling, which is the object of the paper, becomes crucial. In particular, the paper illustrates two applications of a VCB model, which show the model capabilities of simulating TRVs due to opening/closing operation, namely the switching of large electrical motors and the switching of cables collecting offshore wind farms (OWFs). Data from digital fault recorder (DFR) in a water-pumping plant and from a measurement campaign in an OWF using a high-bandwidth GPS-synchronised measurement system, respectively, are used for model validation. It is shown that the inclusion of detailed VCB models significantly improves the agreement between the measurements related to both pre- and restrikes and the corresponding simulation results obtained by using two well-known electromagnetic transient simulation environments, namely, EMTP-RV and PSCAD/EMTDC. The procedure adopted for the identification of the VCB model parameters is described.