Analysis of 750kV Main Transformer High Voltage Side Bushing Faults Based on Multi-Detection Technology

Shahu 750 kV substation is the hub substation of the northern Ningxia power grid, the station's 750 kV system is directly connected to the 750 kV system of the ±800 kV Shanghaimiao EHV converter station, the reliable operation of the 750 kV main transformer at Shahu Station has a huge impact on the ±800 kV Shanghaimiao EHV DC outgoing transmission. The high voltage side bushing is one of the most important components of the 750 kV main transformer, and in recent years there have been a number of power grid outages caused by the high voltage side bushing of the main transformer, even resulting in a forced shutdown of the DC outgoing transmission. This paper takes the C-phase high-voltage side bushing of the No. 3 main transformer of the Shahu 750 kV substation as an example. Through site investigation and protection recording analysis, the fault site is identified, then the electrical test, physical and chemical test, and simulation analysis are used to clarify the fault mechanism and causes, and finally, the same type of bushing is investigated.