The multi-point grounding of the core of oil-immersed transformers is one of the more common faults of transformers. What harm can these failures bring? Take a look with the editor.

Because the magnetic circuit part of the transformer is an iron core, the iron core is directly grounded through the small insulating sleeve after the oil-immersed transformer is installed.

During the normal operation of the transformer, the alternating magnetic field exists around the windings. The three groups of low-voltage windings and iron cores, high-voltage windings and low-voltage windings, iron cores and housings all have parasitic capacitance due to the effect of electromagnetic induction. To produce a floating point to ground, it is necessary for the live winding to generate a coupling effect through parasitic capacitance. Because the distance between the iron core and the winding is different from the distance between other metal components and the winding, there is a potential difference between the components. Only when the potential difference between the two points can break the insulation between them Spark discharge will occur, but this discharge cannot be continuous, so if it continues for a long time, it will have a certain impact on the solid insulation and transformer oil, but the shell and the iron core are connected so that the iron core and the shell have the same potential. The potential difference can eliminate this phenomenon.

However, when the iron core or other metal components are grounded at two or more points, the grounding point will form a closed loop, causing circulating current, which will cause local overheating, resulting in oil decomposition, and the insulation performance will be reduced. The core silicon steel sheet burned out, and the local overheating expanded, forming a vicious cycle, causing a major accident of transformer burning.