Here are some common reasons for causing partial discharge in Dry Type transformers:
1. Non-uniform voltage gradients: Non-uniform voltage distribution within the insulation material is a major contributing factor. When voltage is unevenly distributed in the insulation, some areas may experience localized overvoltage, leading to discharge.
2. Contamination and pollution: The presence of contaminants, pollution, or impurities within the transformer can lead to partial discharge. These contaminants can reduce the electrical resistance of the insulating material and increase the local electric field intensity.
3. Insufficient dielectric strength: Insufficient dielectric strength or aging of insulating materials can increase the risk of partial discharge. This may be due to factors such as high temperature, chemical reactions, mechanical stress, or ultraviolet radiation.
4. Defects in insulating materials: Defects within the insulation material, such as air bubbles, cracks, or foreign objects, can serve as discharge sources during partial discharge events.
5. Electrode gaps: When the spacing between insulating materials is insufficient to withstand the electric field strength, partial discharge may occur.
6. Temperature rise effects: During transformer operation, current passing through the windings generates temperature rise. When the temperature rise reaches a certain level, it may trigger partial discharge.
7. High-frequency voltages: High-frequency voltages can trigger partial discharge as they may penetrate the insulation material and induce discharge.
8. Mechanical vibrations: Mechanical vibrations within the transformer can cause wear and tear on insulating materials, increasing the risk of partial discharge.
To prevent partial discharge, it is essential to perform regular maintenance and inspections of transformers, ensure the quality of insulating materials, remove contaminants and pollutants in a timely manner, and maintain appropriate operating conditions to minimize the likelihood of partial discharge. If partial discharge is not effectively controlled, it can lead to transformer failure and damage.
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