Partial discharge (PD) is a discharge that does not completely bridge the gap between two electrodes. Partial discharge always occurs in power systems, but usually occurs in components that can withstand it (such as switchgear). You may be aware of PD activity near you (the hum you hear from medium-voltage or high-voltage substation equipment or overhead power lines). Modern cables and cable accessories cannot withstand partial discharge. Under these conditions, PD will slowly corrode the insulating material until it fails.
Partial discharge phenomenon mainly refers to high-voltage electrical equipment:
Electrical equipment insulation is a discharge that occurs in a local area under the action of a sufficiently strong electric field. This discharge is limited to only causing partial short (bridge) connections between conductors without forming conductive channels. Every partial discharge will have some influence on the insulating medium. A slight partial discharge has less influence on the insulation of power equipment, and the insulation strength decreases slowly; while a strong partial discharge will cause the insulation strength to drop quickly. This is an important factor that damages the insulation of high-voltage power equipment. Therefore, when designing the insulation of high-voltage power equipment, it is necessary to consider that under the action of long-term working voltage, strong partial discharges are not allowed in the insulation structure. It is necessary to strengthen the monitoring of the equipment in operation. When the partial discharge exceeds a certain level, the equipment should be taken out of operation for maintenance or replacement.
In a solid dielectric with gas or liquid, when the local field strength of the gas or liquid with the breakdown field strength reaches its breakdown field strength, this part of the gas or liquid begins to discharge. Partial discharge is generally caused by the special concentration of local electric fields inside or on the insulating surface. Usually this kind of discharge appears as a pulse with a duration of less than 1 μs.
When the insulation occurs partial discharge, it will affect the insulation life. Each discharge, the impact of high-energy electrons or accelerated electrons, especially long-term partial discharges, will cause various forms of physical effects and chemical reactions. For example, when charged particles hit the outer wall of the bubble, they may break the insulating chemical bond and crack. Destroy the molecular structure of insulation, cause insulation deterioration, and accelerate the process of insulation damage.
Partial discharge characteristics:
Partial discharge is a sign of local overheating and aging of electrical and mechanical components;
Partial discharge trend is the rising index of partial discharge over time. This is a tortuous process. It may decrease at a certain stage but increase at a certain stage;
When a partial discharge occurs in an insulating structure, it will be accompanied by electric pulses, ultrasonic waves, electromagnetic radiation, light, chemical reactions, and local heating and other phenomena;
Due to the above characteristics of partial discharge, how to avoid partial discharge and how to remove partial discharge in electrical equipment so as to ensure the normal and safe operation of the equipment has become the most important thing for maintenance personnel of electrical equipment. In order to remove this latent failure phenomenon, many methods for on-line detection of partial discharge phenomena have been derived for some electrical pulses, ultrasonic waves, electromagnetic radiation and other signals that accompany partial discharges.
Finally, the editor recommends a UV detector that can be used in partial discharge detection, that is, the UV photodetector introduced from Germany-TOCON_ABC1, a silicon carbide-based broadband UV photodetector with an integrated amplifier. TOCON is a 5V power supply UV photodetector, with an integrated amplifier that converts UV radiation into 0~5V voltage output. The output voltage pin of TOCON can be directly connected to the controller, voltmeter or other data analysis device with voltage input. Highly modern electronic components and a sealed metal housing with UV glass windows can eliminate noise or electromagnetic interference caused by parasitic resistance paths in the package. For various industrial UV sensing applications, TOCON is the perfect solution, from flame detection at the pW/cm2 level to UV curing lamp control at the W/cm2 level. Ten different TOCONs cover these 13 orders of magnitude, and their sensitivity is different. TOCONs are produced as UV broadband sensors or with filters for selective measurement.
