Novel Method for Predicting Limit Performance of Bus-Transfer Switching by Disconnectors

In order to accurately predict the performance of disconnectors conducting bus-transfer switching in gas insulated substations, the influencing factors of the switching process itself as well as the reignition characteristics need to be analyzed. For this, an LC-oscillating ac current source in combination with a nonstandardized full bus-transfer loop was built. Based on experiment data from a total of 347 reignitions and 570 extinctions, the reignition characteristic of the disconnector at current zero was investigated. Thereby, the derivation of a reignition criterion depending exclusively on the prediction of the instantaneous recovery voltage and the prospective arc voltage was possible. Using this criterion, time-dependent simulations of the bus-transfer process can be made to predict the performance of disconnectors for a wide variety of scenarios such as worst case bus-transfer current for varying circuit parameters and ratings. This minimizes the need for extensive testing during substation planning or disconnector development.