Modeling and Detection of Inter-turn Faults in Distribution Transformer

Abstract

In a Distribution system, transformer is one of the major equipment, which are vulnerable to various kinds of faults. Amongst all, internal winding faults are most severe. Generally, transformer protection is done by differential protection scheme. Upon an internal fault, the rise in current is comparatively less for incipient faults or shorted turns less than 10% of total turns, and may not be enough to operate a differential over current relay. As these internal winding faults are severe, it leads to complete damage of transformer and consequently shutdown of the distribution system. Practical experimental analysis is not possible for the distribution transformer internal winding faults, as, due to the experiment, the transformer may get completely damaged. Therefore, these kinds of analysis are generally done using software simulations. So far, most of the analysis on transformer internal winding faults are done by using EMTP simulations. In this work, the equivalent circuit of transformer is considered and transformer is modelled using equations. In this proposed model primary voltages are given as inputs, secondary currents are outputs and primary as well as secondary side flux equations are internal variables. The inter turn faults of distribution transformer are modelled and simulated using MATLAB/SIMULINK tool. The modelling of transformers inter turn fault is done with the help of equations and the results obtained validate the model presented.