Determination of transient overvoltages during shunt reactor deenergization

This paper presents an analytical solution and computer simulations of switching transient overvoltages during the disconnection of shunt reactors. The interruption of reactor current provokes excessive overvoltages particularly across the reactor and the circuit breaker grading capacitor. The magnitude of these overvoltages may exceed 2 p.u. which, consequently, may jeopardise the insulation of the reactor and accelerate the ageing of circuit breaker grading capacitors. In this work, the transient overvoltages were computed using ATP/EMTP simulations and analytical solution of the equivalent circuit during switching. For different switching times the distribution of overvoltages and the influence of switching angle is presented.