Transformer partial discharge generation and prevention - Database & Sql Blog Articles

Test - lowercase jpg

Kaixin micro test

Test probe P100-M3

Partial discharge is mainly the discharge of internal insulation of 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.
The internal insulation of the 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, and the partial discharge is easy to occur in the weak place of the insulation. The cause of the partial discharge is: electric field Too concentrated on a certain point, or the electric field strength is too large at a certain point, such as bubbles in a solid medium, impurities are not removed; oil contains water, gas, and suspended particles; in different media combinations, there is severe electric field distortion at the interface. . 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.
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. In the running transformer, the aging and damage of the internal insulation, mostly from the partial discharge.
The detection methods of partial discharge of transformers generally include:
(1) Electrical measurement method. Use an oscilloscope or radio jammer to find the characteristic waveform or radio interference level of the discharge.
(2) Ultrasonic measurement. The sound wave appearing in the discharge is detected, and the sound wave is converted into an electrical signal, recorded on a magnetic tape for analysis, and the distance between the detection point and the discharge point can be obtained by using the difference in the transmission time between the electrical signal and the acoustic signal.
(3) Chemical measurement method. Detect the content and increase and decrease of various dissolved gases in oil. This test reveals changes in composition, ratio, and quantity in the oil to determine the presence or absence of partial discharge (or localized overheating).
In addition, in recent years, a partial discharge on-line detector has been developed to automatically detect partial discharge during transformer operation.
In order to prevent the occurrence of partial discharge, the manufacturing unit should carry out reasonable structural design of the transformer; carefully construct, improve the purity of the material, and strictly handle the quality of each link. The operating unit should strengthen the maintenance and monitoring of the transformer to effectively prevent the partial discharge of the transformer.