Development of a Turn-to-turn Fault Detection Method in the Three-phase Transformer's Winding

Reveal the regularities of turn-to-turn faults influence on to parameters of a three-phase network transformer in the disconnected transformer mode with the supply of control voltages and currents from an external source in the transformer linear operation. To achieve the purpose, experimental studies were carried out on the power transformer (Trihal with a voltage of 20 / 0.4 kV) with an artificially created turn-to-turn fault, mathematical modeling and calculations of the three-phase transformer magnetic system parameters. The influence of the turn-to-turn fault on the magnetic system of the three-phase transformer with the application of voltages and currents of zero and direct sequences is investigated. A mathematical model of three-phase transformer magnetic system has been developed, which makes it possible to determine the change in the parameters of the transformer windings and to establish the relationship between the primary and secondary voltages and currents in conditions of the occurrence of а turn-to-turn fault. An effective method for detecting turn-to-turn faults by measurements with the supply of zero sequence currents is proposed. A simplified model of the three-phase transformer magnetic system has been developed. This model allows us to qualitatively evaluate the changes in the transformer parameters when a turn-to-turn fault occurs.