On-line monitoring of winding parameters for single-phase transformers

Abstract

The condition of transformer windings can be gauged by monitoring their equivalent circuit parameters. These parameters are not affected by external faults and change only in the presence of an internal aberration. Changes in the insulation temperature are reflected in winding temperature and can be monitored by observing the winding resistance values. Similarly changes in the short circuit reactance can give information on the condition and structure of windings. Rapid and reliable protection can be implemented by monitoring these parameters since inrush current and over-excitation does not affect these parameters. Presently, there is no accurate measurement method for the transformer winding parameters and generally require the transformer to be disconnected from the power system. A new simple algorithm for extracting transformer winding parameters which can be implemented online is presented in this paper. This method takes only the input currents and voltages as inputs and thereby eliminates the need for the disconnection of the transformer from the power system. In this method, winding parameters are obtained by solving the equivalent circuit equations in real time continuously which allows for interpretation and detection of faults in real-time. The proposed method has been tested and validated by simulations.