Calculation of the Three-Phase Internal Fault Currents in Medium-Voltage Electrical Installations

Fault arc tests showed that the three-phase fault arc currents depend on the arrangement of electrodes at the fault site and vary stochastically. Up to now, experimental investigations have mainly been carried out for the medium-voltage switchgears, and the fault arc currents are either recognized by the experimental results or derived by the probability method. A calculation method used for the determination of the three-phase fault arc currents is introduced in this paper, which can be expressed accurately by mathematics according to the characteristics of the three-phase internal faults.