A high-frequency method for determining winding faults in transformers and electrical machines

Abstract

Improvement of diagnostic methods of both power transformers and electrical machines is crucial considering the function they play in electrical networks and industry as well as the cost of those devices. High-frequency measurements are used more and more frequently as a diagnostic tool for the investigation of transformer and machine windings. They are also used for identifying winding faults. As a base are measurement results of frequency dependencies of the winding admittance or the transfer function. Therefore, relations between different kinds of winding faults and changes of frequency dependencies of winding admittances or transfer functions should be determined. Much research work is done in that field, which aims to determine the sensitivity of this method and to develop the recognition criteria with regard to the type and range of faults. This article presents the comparison of measurement results of the admittance performed on the medium-voltage transformer winding. The quantitative results of detecting deformations and dislocations of windings by means of frequency response analysis are described. Of particular importance is the early detection of winding failures in electrical machines, both during the manufacturing process and in operation. The results of investigations of winding faults in electrical machines of different construction are presented. The influence of turn-to-turn faults between adjacent winding wires on the admittance wave form has been also investigated.