Strategy and implementation of controlled reclosing: harmless reclosing

This paper describes a new technique named controlled reclosing in which the peak value and duration time of reclosing current can be controlled to reduce the enormous pressure to power system when reclosing in permanent fault. Based on the analysis to the reclosing current in different voltage phase angles and a fast estimation algorithm for current parameters, a new reclosing strategy named controlled reclosing was proposed in which fault phases were reclosed in turn in optimum voltage phase angle, and the periodic component amplitude of reclosing current was calculated in a very short time and compared with a setting value to find earth fault; and the pair combinations in fault phases were reclosed synchronously in turn in optimum line-to-line voltage phase angle to find the phase-to-phase fault. A new implementation for controlled reclosing using triggered vacuum switch or power electronics switch was proposed. The simulation results showed that the proposed strategy can reduce the peak value and duration time of reclosing current and determined the fault type.