Analysis of short-circuit asymmetrical currents in power distribution systems

This work focuses on the study of electromagnetic transients existing in power systems in the occurrence of phase to ground and three phase faults, aiming to evaluate the dynamic capability of circuit breakers, switch disconnectors and current transformers. The substation equipments such as circuit breakers, current transformers and switch disconnectors are usually specified according to symmetrical short circuit currents. In this sense, this paper presents an analysis of the impact of short-circuit currents during the transient period, through simulations using data from a real system in the ATPDraw software. Through the results obtained from the simulations it was possible to evaluate the dynamic stress submitted to the equipment of the substations in the occurrence of faults. The study shows the importance of the analysis of asymmetrical short-circuit currents during the specification of the equipments rating, which should support these currents, or yet evaluation of existing equipments in the case of a system expansion that can significantly influence the short-circuit level.