Transient analysis of voltage transformer in order to fault location in medium voltage network

This paper deals with voltage transformer (VT) transient analysis in order to investigate the influence of voltage transformer behavior during the fault operation in medium voltage network. An accurate model of VT is described, when parasite capacities of secondary windings are taken into account in equivalent circuit and mathematical model of VT. The mathematical model of VT is described and derived in accordance with its equivalent circuit. All parameters of VT equivalent circuit are investigated by FEM or by measurements, including parasite capacity of secondary windings. These parameters are as inputs into mathematical model of VT. In accordance with mathematical model a transient analysis are carried out for voltage decreasing during sudden short circuit fault when the voltage will be zero in a short time. The simulated states are compared with measured ones on a real VT in the medium voltage network and some recommendations are given for fast fault location in medium network.