Asymmetry in Three-Phase Short Circuit Through Electric Arc in Electrical Installations with Voltage of 6-10 kV

Abstract

Estimation of the influence of the transition resistance of electric arc on symmetry breaking of three-phase short circuits in electrical Cabinet design with voltage of 6-10 kV. The calculations of currents of short circuit is made for electric network with one-way power, where the system equivalentamount symmetric three-phase EMF source with a symmetric resistance on all three phases. It doesn't account for resistance of mutual induction. The contact resistance of electric arc made is active. Obtained an approximate analytical expression to determine the currents and voltages. It is established that for the calculation of short circuit currents in electrical Cabinet design possible resistance performance of electric arc as a linear resistance depending on the voltage drop across the arc column and current metal short circuit. Analysis of these dependencies allows us to conclude that the change in the modules of the phase currents does not exceed 11% of the setting current three phase metal short circuit when the voltage drops in the arc column is not more than 15% nominal phase-to-phase voltage of the installation.