Experimental investigating on on-line monitoring of winding deformation of power transformers

The transformer is one of the most important equipment of the power system and the winding deformation is a main aspect leading to transformer failures. The paper adopts a simple but effective method to on-line monitor of the winding deformation. One of the 600kHz~1.2MHz sinusoidal signals is applied between one end of the winding and one ground terminal via the bushing along with power frequency signal. Then the line-end, neutral-end high frequency currents are continuously measured by the high frequency current sensor and the related analog and digital filtering technology is used to derive the injected sinusoidal signal of mixed signals. With the obtained line-end and neutral-end currents, the current offsets and current deviation coefficients are calculated to detect the extent, type and location of the winding deformation. The especially designed high frequency current sensor has advantages of a wide band, good linearity and high sensitivity. The experimental results show that the method can achieve the task of detecting the winding deformation and is able to distinguish the extent and type and the current deviation coefficients have a direct relationship with the location of the winding deformation. The method has a high sensitivity, good repeatability and strong anti-interference. ©, 2014, Chinese Machine Press. All right reserved.