Analysis of Ferroresonance Phenomenon in 22 kV Distribution System with a Photovoltaic Source by PSCAD/EMTDC

Abstract

Overvoltage and overcurrent in the middle voltage (MV) 22 kV and low voltage (LV) 0.4 kV distribution network with photovoltaic (PV) rooftop system of the Provincial Electricity Authority of Thailand (PEA) have been investigated in order to show that these unwanted situations are caused by the ferroresonance phenomenon. This information would be useful to improve a better solution for the system protection when PV rooftops are integrated into the PEA distribution system. The software tool, PSCAD/EMTDC is used to study the overvoltage at the high side of open-delta and open-wye distribution transformer- and overcurrent at the low side of distribution transformer linked to the grid system via three single-phase fuse cutouts. The ferroresonance phenomenon can be observed when the PV rooftop system is linked to the low voltage side of the distribution transformer via three single-phase fuse cutouts. The results show a good similarity with the results from the simulation of the MV side and LV side of distribution transformers. Finally, the physical phenomena described to the overvoltage, overcurrent, and the destruction of the distribution transformer and other apparatus in load customers will occur when the system consists of the PV rooftop source, capacitance in long transmission line, nonlinear distribution transformer with saturation characteristic and the usage of single-phase switching cutouts in the system.