Abstract
B phase of the no 2 main transformer of 500 kV XX substation was suddenly stopped on August 20, 2021 due to acetylene and an abnormal sudden increase. Acetylene reached 10.5uL / L, far exceeding the acetylene attention value of 1.0uL / L, and there is a trend of continuous growth. An internal inspection was carried out after the power outage, and no obvious abnormality was found. Then it was sent to factory for de-oiling and drying. Inspection found the following problems: 1. The upper and lower iron yoke clamps of main transformer and their pull straps, the fourth pull strap shielding cover from the left of lower clamp on the high pressure side was found to be abnormal; 2. Check the iron core silicon steel sheet, found that there are about 15mm burrs between the iron yoke (high-voltage side) core stages under the side post position; 3. There is a black mark at the connection part of low-voltage lead and the casing oil, but no signs of discharge or overheating are seen; 4. Check that there is no obvious abnormality in other parts of the body, such as insulation, lead wires, and electrical shielding. Combined with the inspection situation, analyze specific causes of the failure and propose follow-up improvement suggestions.
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