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.
When the transformer is in normal operation, the alternating magnetic field exists around the winding. The three groups of low-voltage winding and iron core, high-voltage winding and low-voltage winding, iron core and shell all have parasitic capacitance due to the effect of electromagnetic induction. To produce a floating point, 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 various components. Sparking phenomenon will occur.
However, 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. this phenomenon.