Partial discharge detection by RF coil in 161 kV power transformer

Abstract

The partial discharge (PD) sensor based on the copper coil will be used to on-line detect the radio frequency (RF) signal emitted from PD in 161 kV power transformer. The coil sensor is attached onto the surface of the power transformers to increase the sensitivity of PD signal detection. In the oil-filled power transformer, according to the electromagnetic (EM) wave propagation theory, the PD-induced EM wave could propagate to the metal tank, and most of the electric field attenuates within the short range (i.e. skin depth) of the inner surface of metal tank. However, the magnetic field of the EM wave could pass through the metal tank. Thus, the PD signal can be detected with RF coil sensor placed the outside surface of metal tank. Three RF sensor arrays with line configuration are designed to achieve PD detection and localization. From the amplitude variation among the sensors, we can predict where PD occurs. In the open-tank examination, the results show that the PD source location in power transformer is consistent with the experimental results of proposed RF detection method. Therefore, in this paper, the proposed RF detection method provides a simple and reliable early-stage on-line examination for the power apparatuses.