Numerical modelling of transformers interturn faults and characterising the faulty transformer behaviour under various faults and operating conditions

Interturn short circuit faults are the leading cause of power transformer failures. If not quickly detected, these faults usually develop into more serious faults that would result in irreversible damage to the transformer, unexpected outages and the consequential costs. This contribution is aimed at obtaining a better understanding of physical behaviour of power transformers in the presence of interturn faults as well as extracting several features that would be useful to specify the faults. To this end, a circuit-coupled time-stepping finite-element model (FEM) of power transformer has been developed to characterise the transient behaviour of a real power transformer when the transformer is working under winding short circuit fault conditions. An experimental set-up consisting of the same transformer used with the FEM transformer simulation was used to validate the FEM of the faulty transformer. The results of the experiments demonstrate the remarkable ability of the model to reproduce the real behaviour of the transformer with interturn winding faults. The study characterises the faulty transformer behaviour under varying conditions of load, supplying voltage, location of the fault, and fault severity and size. Useful characteristic signatures associated with interturn faults extracted from the transformer behaviour under varying fault and transformer operating conditions are expected to yield insights into developing reliable and sensitive fault detection and localisation methods in power transformers.