Evaluation of a 3-φ bolted short-circuit on distribution networks having induction generators at customer sites

This paper addresses the effect of distributed generators, specifically squirrel cage induction generators, on 3-φ bolted short-circuit fault currents to make sure that they do not interfere with the interruption capability of circuit breakers. Results of a laboratory experiment, and simulation results for 16 different induction machines, including their feeder and transformer connections to the substation, are presented for a short-circuit at the substation site. An equation was developed for the upper boundary envelope of the current peaks contributed by the induction generators, and was used for successful comparison with simulation results. It is hoped that it can serve as a useful complement to the existing IEEE and IEC standards methods for calculating short-circuit currents of induction machines.