By hvhipot 
[Keywords] Power transformer, winding deformation, transformer winding deformation tester
When a low voltage side outlet short circuit or near-field short circuit accident occurs during the operation of a power transformer, the impact current is very large (possibly exceeding 10 times the rated current), which has strong destructive power on the transformer, especially for domestic transformers with weak ability to withstand such impact, often causing serious deformation of the internal structure, especially the winding. After a 220kV, 150MVA main transformer in a certain power supply bureau had a short circuit at the low-voltage side outlet, various insulation tests and chromatographic analysis of the transformer oil were conducted, all of which were good. However, when using the transformer winding deformation tester produced by HV Hipot Electric Co., Ltd. to conduct winding deformation tests, the internal winding group showed severe deformation. After inspection with a hanging cover and opening the screen, it was found that the low-voltage side winding was in a mess, and timely measures were taken to avoid a major accident of transformer damage. Due to the lack of provisions for winding deformation testing in the pre-test procedures, general units do not attach enough importance to this test. We also found that some units have poor reliability of their power distribution equipment (including lines), and some substations have experienced more than 100 incidents of rapid overcurrent protection tripping accidents in a year. Some accidents occurred at the transformer outlet, but did not receive sufficient attention. It is generally believed that as long as the power transmission is successful after an accident, everything will be safe and sound. Based on the above experience, not conducting winding deformation tests after transformer outlet or near area short circuit accidents is likely to leave very serious hidden dangers. Suggestions for this:
(1) After a short circuit accident occurs at the outlet or near area of the main transformer, in addition to conducting various insulation tests and chromatographic analysis, winding deformation tests should also be conducted in a timely manner;
(2) Suggest that relevant departments such as the Electric Power Research Institute of the State Power Corporation supplement the items and requirements for transformer winding deformation testing in the pre testing regulations;
(3) It is understood that most power generation and supply enterprises currently do not have instruments for testing winding deformation, and can only seek assistance from external units, and the cost of each test is relatively high. If the power supply bureau has a large number of transformers (such as 50 or more), it is recommended to purchase a testing instrument to test all the faulty transformers and keep them as historical archives for future comparison. This will have a positive effect on strengthening equipment management and preventing major equipment accidents from occurring.