Detection and localization of LV winding radial deformation in transformers using electromagnetic waves - a feasibility study

•Online monitoring of the radial deformation of low voltage windings using electromagnetic waves.•The online monitoring can be realized using small antenna with minimal changes in the transformer structure.•The detection and location of radial deformation is estimated by using regression tree based on three features.•Simulated by Computer Simulation Technology (CST) software, and their verification are conducted by a setup in laboratory. Recently, online methods based on electromagnetic waves have been proposed to detect the mechanical defects of high voltage (HV) windings in power transformers. In this article, for the first time, the possibility of online detecting and locating the radial deformation (RD) of low voltage (LV) windings using electromagnetic waves is presented. In the proposed method, a high frequency and wideband signal is sent to a simplified model of transformer winding via small antennas. The antennas are connected to the inner side of the oil tank cover through Radio Frequency (RF) cables, so that online monitoring can be realized with minimal changes in the transformer structure. The data of the reflected signals in different states is recorded in a database and sorted as primary data bank. By comparing the results of the sound state with measured signals, the possible faults can be detected. In this paper, the detection and location of radial deformation is estimated by using regression tree based on three features. Several cases are simulated by Computer Simulation Technology (CST) software, and their verification are conducted by a setup in laboratory. Based on comparison results, it can be claimed that the proposed method has LV windings radial deformation online detecting and locating ability with an acceptable accuracy.