International Journal of Scientific & Engineering Research Volume 3, Issue 5, May-2012 1 ISSN 2229-5518 IJSER © 2012 http://www.ijser.org Simulation Modeling of Incipient Faults in Power Transformer Anil Kumar, Ajay Rathore, Ashish Patra Abstract - This paper presents a method of modeling internal winding faults of three-phase, power transformers to single-phase, distribution transformers. The model which is compatible with the alternative Transients Program, ATP, allows the simulation of turn-to- earth and turn-to-turn faults on either windings of a single-phase, two-winding, distribution transformer. Results of staged internal winding faults of a distribution transformer are compared with the simulation results to validate the model. The experimental results were found to be comparable to those of the simulation. Index Terms – Internal winding, power transformer, distribution transformer, compatible, alternative transients program (ATP), simulation, ——————————  —————————— 1. INTRODUCTION he transformer is one of the most expensive and important electrical equipment of a power distribution system and hence the loss of such an equipment through catastrophic failure can be very costly. Deregulation in the USA has caused a drastic change in the electricity market. This change has put utilities under stress since electric energy has become a bulk commodity traded and sold under free market competition resulting in a cost consciousness among utilities. The main driving forces are to reduce maintenance costs, prevent forced outages with the consequential costs, prevent forced outages with the consequentail costs, and work existing equipment harder and longer [1]. utilities are therefore looking for ways to detect developing or incipient faults before they become catastrophic and allow for a change from periodic-to condition-based maintenance. Different techniques have been used in the area of transformer fault detection and diagnosis. The most established diagnostic and monitoring method is the analysis of dissolved gases in the transformer[1]. The method is based on analyzing the types, concentration and production rates of generated gases [2, 3]. The technique is well accepted and has the capability to detect a wide range of failure types. Determination of the degree of polymerization value of cellulose (used in paper insulation) is a standard method for quantifying the degradation of cellulose [4]. Other methods have utilized the measurement of transfer functions of the transformer to detect deformations of the windings [5, 6]. Deformation or changes in geometrical distances of the windings leads to changes in internal capacitance, and thereby a change in the transfer function of the transformer. A study of the records of modern transformer breakdowns which have occurred over a period of years shows very conclusively that between 70 and 80% of the number of failures are finally traced to short-circuits between turns [7]. These short circuits are a result of degradation or wear of the transformer winding insulation (often called the minor insulation) causing adjacent turns to short (turn-to-turn fault) or turn (s) shorting to any grounded part of the transformer (turn-to-earth faults). The purpose of the work reported here is aired at developing a technique that utilizes electrical indicators for internal winding fault detection and diagnosis. Towards this, it is attempted to simulate some of the winding faults of single-phase transformers and validate the same with experiments. A model developed in [8] for three-phase power transformers is adapted to model single-phase distribution transformers to study the effect of internal winding faults at the terminals. Simulation and field test results of staged internal winding faults are presented. A comparison of the two results is made to show the validity of the model. T