Simulation of switching overvoltages of 400 kV shunt reactor

Bam 400/132 kV substation in Kerman region, Iran, has a 50 MVAR shunt reactor on 400 kV busbar which is grounded through a 128 kVAR neutral reactor. The neutral earthing reactor assists in interrupting line to ground arcing current when switching for clearing a line to ground arcing fault, but the switching of shunt reactor which is grounded through a neutral reactor can impose a more severe duty on the circuit breakers than switching a solidly grounded shunt reactor. While opening shunt reactor, transient phenomena, such as chopping overvoltages and reignition overvoltage/overcurrents can occur. These overvoltages/currents can put circuit breakers, reactors and other equipment in danger. In this paper, the Bam substation’s equipment such as electrical circuits and associated equipment will be modelled in transient mode using EMTDC/PSCAD software. The arc behaviour and excessive voltage caused by the switching will be analysed. Finally, three methods including controlled switching, using surge arrester and a disconnecting switch across the neutral earthing reactor for mitigating these overvoltages will be compared