Analysis of Temporary Overvoltages During Open-Phase Faults in Distribution Networks With Resonant Grounding

This paper analyzes the temporary overvoltages (TOVs) that may appear in open-phase states in distribution networks with resonant grounding. The high overvoltages recorded during the open-phase states exceed the overvoltages corresponding to the existing theory. The detailed analytical study of the temporary overvoltages is performed. The closed-form expression of the neutral voltage is derived. The conditions for maximum phase-to-earth overvoltages are obtained. The case study for open-phase faults in the 33-kV resonantly grounded distribution network is described. The dependence of the TOVs on the number of distribution feeders, on the feeder loading, on detuning factor, on the additional damping factor, as well as on the saturation of the voltage transformers are analyzed. Remedies for the reduction of TOVs are considered. Detuning of the Petersen coil is compared with the permanent connection of the wattmetric resistance in parallel to the Petersen coil.