Analysis and treatment of the abnormal grounding current of 330kV transformer core
This transformer is 360,000 kVA autotransformer manufactured by shenyang transformer group co., LTD., a special transformer company, in August 2007.
The core of the transformer is a disassembled core, as shown in FIG. 1. Four cores form a three-phase five-column core, which is convenient for transportation and installation.
The insulation between iron core 1, 2.3 and 4 is 6run cardboard, and the insulation material between clamps and iron core is 2rum insulation board plus 10mmn insulation pad.
The earthing current of the transformer core 2 3 has been increasing since the first half of the month. By the middle of July, the grounding current of core 23 reached about 19A, and that of clamps reached about 33A.
Oil sample was taken for oil chromatography test, and the total hydrocarbon value was 296.3 chevrons L/L, which exceeded the attention value (150 chevrons L/L). The main growth part was methane and ethylene. Based on all aspects of the situation, the preliminary analysis and judgment for multi-point grounding fault.
Because the grounding current of the clamping part is obviously affected by the load of the transformer, its overheat point is limited to the fault point and the welding point of the clamping part. Because when the summer peak season at the same time, the electricity is not suitable for processing and the decision in the core grounding lead string into the current limiting resistor, iron core at the same time, clamp grounding current measurement instead of once every 2 hours, reduce the risk of accident caused by transformer.