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Here are several common methods for handling multi-point grounding faults in transformer cores: (1) For cores with external grounding leads, a resistor can be connected in series within the core grounding circuit to limit the grounding current. This method should only be used as an emergency measure. (2) For grounding faults caused by metallic foreign objects, the problem can usually be identified by performing a tank removal inspection (uncovering the core). (3) For grounding faults caused by burrs on the core or the accumulation of metal powder, the following methods have proven to be quite effective: Read More

The core should be flat with intact insulation varnish film and tightly stacked laminations. The silicon steel sheets on the edges should not be curled up or wavy. The surface of all core parts should be free of oil sludge and impurities. There should be no short circuits or (lapping) between laminations, and the joint gaps must meet the required specifications. Read More