BPA's Pacific AC intertie series capacitors: experience, equipment and protection

Over BPA's 40 years of series capacitor experience, equipment evolution has dramatically reduced the complexity of capacitor protection systems. BPA and other utilities in the Pacific Northwest installed 13 new metal oxide varistor (MOV) protected series capacitors. Nearly all the banks use a simplified design which eliminates the typical triggered gap bypass protection for the MOV. The decision to use a gapless design, the MOV energy sizing, and the protective bypass thresholds require extensive EMTP fault simulations. A large number of staged system fault tests were performed to evaluate the integrity of the banks.