Research on Partial Discharge Detection of a 500kV Step-Up Transformer

In response to the abnormal chromatographic analysis of insulating oil in a 500kV step-up transformer at a power plant, this paper conducts a study on partial discharge (PD) detection. First, the winding and core structure of the step-up transformer were analyzed. Combined with chromatographic monitoring data, it was found that the total hydrocarbon content continued to increase during long-term operation, and the acetylene content was abnormal, indicating potential risks of medium- and low-temperature overheating and partial discharge. Using high-frequency current transformer (HFCT) technology, high-frequency current detection was performed on the core, clamps, and grounding points of phases A, B, and C of the main transformer. Typical Phase-Resolved Partial Discharge (PRPD) patterns were obtained, clarifying the characteristics and magnitude of the discharge signals. The study results indicate the presence of multi-point discharge phenomena inside the step-up transformer, with differences in discharge intensity across phases. Finally, based on the detection results, this paper proposes improvement measures, including enhancing online monitoring, optimizing the operating environment, and conducting in-depth fault analysis, providing a solid foundation for improving the safety and reliability of the step-up transformer.