Interruption strategy of fault current fed by high-capacity generator based on phase selection and current-zero prediction

Abstract

The high asymmetrical degree (AD, >100 %) of the fault current fed by high-capacity turbine generator (HTG) results in high arc energy (E_arc), hindering reliable interruptions of generator circuit breakers (GCBs). Traditional GCBs with simultaneous three-phase separation at random moments suffer from uncontrollable arcing time and high E_arc, severely undermining the interruption reliability of GCB. To limit E_arc, GCBs with phase-separated operation mechanism should be applied, along with the first pole to clear (FPTC) selection and ideal current-zero prediction. Contributions of the paper are: first, it is revealed the phase with medium AD should be selected as the FPTC, and contacts should be controlled to separate near the current zero at the end of a small half-wave. Second, combined with FPTC selection and ideal current-zero prediction, an interruption strategy is proposed, which can limit E_arc to <50 kJ in random faults, improving the GCB interrupting reliability for highly asymmetrical currents. Simulation results verified its effectiveness.