What’s thePurpose and Significance of Partial Discharge Testing

Partial discharge refers to the phenomenon of discharge that occurs between electrodes but does not penetrate them. It is caused by weaknesses in the insulation of electrical equipment or defects in the manufacturing process, leading to repeated breakdowns and extinguishing under high electric field intensity. This discharge manifests as breakdown of insulation gas, local breakdown of solid or liquid media within a small range, and local breakdown discharge caused by the concentration of electric field strength at the edges and corners of metal surfaces. Although the energy of this discharge is small, its short-term existence does not affect the insulation strength of electrical equipment. However, if partial discharge occurs continuously under the operating voltage of electrical equipment, these weak discharges will accumulate, gradually deteriorating the dielectric performance of insulation and enlarging local defects, ultimately leading to insulation breakdown.

Traditional insulation test methods are difficult to detect partial discharge defects, and a 1-minute AC withstand voltage test can damage insulation, affecting the subsequent operational performance of the equipment.

Under the influence of partial discharge, oil-paper insulation generates unsaturated hydrocarbons such as C2H2 (acetylene) and wax. The wax accumulates on solid insulation, and the gas generated by the discharge increases the discharge, leading to breakdown at positions with high field strength or damaged portions of insulating paper. This may manifest as creeping discharge in inter-layer gaps, the formation of branched discharge, and the formation of orderly carbonization layers on discharge channels, eventually penetrating the insulation.

Although partial discharge can lead to insulation deterioration and eventual damage, its development takes a certain amount of time. The development time depends on various factors such as the operating condition of the equipment itself, the type of partial discharge, the occurrence location, and the insulation structure of the equipment.

LuShan, est. 1975, is a Chinese professional manufacturer specializing in power transformers and reactors for 49 years. Leading products are single-phase transformer, three-phase transformers, DC inductors, AC reactors, filtering reactor, expoxy resin high-voltage transformer and intermediate, high-frequency products. Our transformers and reactors are widely used in 10 application areas: rapid transit, construction machinery, renewable energy, intelligent manufacturing, medical equipment, coal mine explosion prevention , excitation system, vacuum sintering, central air conditioning.

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