What is a partial discharge of dry transformer
Partial discharge is mainly the discharge of internal insulation of dry-type transformers, transformers and other high-voltage electrical equipment under the action of high voltage. This kind of discharge exists only in the local position of the insulation, and does not immediately form the entire insulation through breakdown or flashover, so it is called partial discharge. The amount of partial discharge is very weak, relying on the human intuitive sense, such as the eye can not be perceived, only the highly sensitive partial discharge measuring instrument can detect it.
Causes of partial discharge
The internal insulation of the dry-type transformer is under the action of the working voltage for a long time in operation. Especially with the increase of the voltage level, the electric field strength of the insulation is very high. It is easy to generate partial discharge in the weak place of the insulation. The reason for the partial discharge is : The electric field is too concentrated at a certain point, or the electric field strength is too large at a certain point, such as bubbles in the solid medium, the impurities are not removed; the oil contains water, gas, and suspended particles; in different media combinations, there is serious at the interface. Electric field distortion. The traces of partial discharge often leave only a small spot on the solid insulation, or a dendritic burn mark. In the oil, some small bubbles that decompose appear.
Harm of partial discharge of dry type transformer
Although the partial discharge time is short and the energy is small, it is very harmful. Its long-term existence will have a great destructive effect on the insulating material. First, the insulating material adjacent to the partial discharge will be directly bombarded by the discharge mass. The damage caused by local insulation is caused by the chemical action of the active gas such as heat, ozone, and nitrogen oxide generated by the discharge, so that the local insulation is corroded and aged, and the conductance is increased, eventually leading to thermal breakdown. Dry-type transformers in operation, aging and damage of internal insulation, mostly start from partial discharge.
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