Research On The On-line Monitoring Method Of Power Transformer Short-circuit Reactance

Power transformer is the one of the important electrical equipments in power system. As a long running in power system, under the impact of various short-circuit fault, windings are the most fault components of transformer and its damage rate is about 60%～70% of all the transformer accidents. Among the method of checking winding deformation, low voltage impulse method, frequency response analysis method and short-circuit reactance method, which can be used to measure and diagnose the deformation of power transformer winding are available to some extent, but they are all off-line monitoring. Accident can't be fund in time and can't fit on-line measurement. The method calculate the short-circuit reactance, by using the amplitude and phase angle of voltage and current on both sides of the transformer, and compared to experimental value of the transformer short-circuit reactance to determine the status of winding deformation.In this paper, the short-circuit reactance formulas of the transformer are derived, achieving the clear direct relationship of the interior space structure and short-circuit reactance. The changes relationship of winding deformation and short-circuit reactance value is achieved by using the ANSYS simulation technology. Through analyzing the simulation result, the relationship of the short-circuit reactance transformer winding is closed related to the size of the winding structure, so the changes of short-circuit reactance can reflect the changes in transformer windings and the operation of the transformer.The on-line monitoring short-circuit reactance of the mathematical model is established according to the both sides of the transformer voltage balance equation and the voltage and current transfer matrix theory. The establishment of the transformer short-circuit reactance calculation of mathematical model is based on the Yd11 transformer. Both sides of the excitation current of transformer is considered in the model that influent short-circuit impedance of the calculation results achieving to the purposes of lowering the error and differentiate both sides of the leakage resistance. And the feasibility of the mode is verified by the power system analysis software package PSASP.Finally, the error influence of the voltage transformer and current transformer need to be considered, the values of the on-line monitoring short-circuit reactance are calculated, then compared to the reactance values of short-circuit impedance test, achieving the smaller errors. The result method provides powerful gist for the correctness of the on-line monitoring short-circuit reactance model of the transformers.