During the maintenance and monitoring of power systems, partial discharge, as a potential fault indicator, has gradually drawn significant attention from engineers and researchers. Its concealment and destructive nature make the understanding of partial discharge an important aspect in the management of electrical equipment lifespan.
The definition and basic characteristics of partial discharge
Partial Discharge (PD) refers to the discharge phenomenon that occurs locally within the insulation medium or on its surface, and this discharge does not completely break through the insulation. In other words, partial discharge is manifested as the release of electric charges in a localized area within the electrical insulation system. It usually occurs in areas with insulation defects, bubbles, cracks, or foreign objects. Partial discharge does not cause the insulation to fail instantly, but its repeated occurrence will gradually damage the insulation material and eventually lead to equipment failure.
Partial discharge has the following several notable characteristics:
1.The discharge is localized and occurs in a relatively small area, usually confined to the vicinity of insulation defects.
2. The discharge duration is extremely short, usually ranging from nanoseconds to microseconds.
3. The discharge process is accompanied by the generation of various signals such as electromagnetic waves, sound waves, chemical reactions and light radiation.
4. The discharge intensity is relatively weak and cannot be directly observed through traditional electrical detection methods.
Analysis of the Causes of Partial Discharge
Understanding the root cause of partial discharge is beneficial for controlling the safe operation of electrical equipment at its source. The generation of partial discharge is usually closely related to the defects in the insulation system, and the main causes include:
There are air gaps or voids inside the insulating material: tiny bubbles generated during the manufacturing process or during operation can become a breeding ground for local discharge.
Insulation surface contamination or damage: Dust, oil stains, and moisture penetrate the insulation surface, forming a conductive path and triggering local discharge.
Insulation material aging: Long-term operation leads to a decline in insulation performance, a decrease in dielectric breakdown voltage, and an increased likelihood of local discharge.
Cracks caused by mechanical stress or thermal stress: Equipment vibration or temperature changes lead to cracks in the insulating material, which become discharge channels.
Uneven electric field distribution: Inadequate electrode design or uneven insulation thickness leads to localized enhancement of the electric field, resulting in local discharge.
Detection technology of partial discharge
Given the concealment of partial discharge, it is particularly important to monitor it using highly sensitive detection methods. Modern technologies offer various means to detect the existence and characteristics of partial discharge, mainly including:
1.Current pulse method: By measuring the high-frequency pulse current on the insulator, the current signal generated by local discharge is captured.
2. Ultrasonic detection method: The acoustic wave signals generated by partial discharge can be received by ultrasonic sensors, making it suitable for the location of partial discharge.
3. Electromagnetic wave detection method: By using antennas to capture the high-frequency electromagnetic waves emitted by partial discharges, this method is suitable for non-contact detection.
4. Chemical analysis method: By detecting the chemical substances (such as ozone, nitrogen oxides) generated during partial discharge, the discharge condition can be indirectly determined.
5. Optical detection method: Capturing the faint light radiation generated during discharge, which is widely used in gas-insulated equipment.
During the detection process, the resolution of the signal and its anti-interference capability are the key indicators for evaluating the quality of the technology. Combining multiple detection methods can enhance the accuracy and reliability of partial discharge diagnosis.
The impact of partial discharge on electrical equipment
Although partial discharge does not immediately cause insulation breakdown, its continuous presence will lead to a series of adverse consequences and gradually weaken the insulation performance of the equipment. Specifically, this manifests as:
Insulation material deterioration: The high temperature, ultraviolet radiation and chemical reactions generated by partial discharge will damage the insulation structure, leading to the formation of more defects.
Shortened equipment lifespan: Insulation failure accelerates equipment aging, resulting in a decline in operational reliability.
Increased safety risks: Insulation failure may cause severe accidents such as short circuits and fires.
Maintenance costs increase: Frequent troubleshooting and repairs have increased the burden on the operation and maintenance team.
Therefore, promptly detecting and addressing the phenomenon of partial discharge is an important measure to ensure the safe and stable operation of the power system.
Prevention and Control Strategies for Partial Discharge
In view of the hazards caused by partial discharge, taking effective preventive and control measures becomes particularly crucial. Common methods include:
Optimize the design and manufacturing process to reduce the occurrence of insulation defects.
Use high-quality insulating materials to enhance the electrical insulation strength.
Carry out partial discharge tests regularly to promptly identify potential risks.
Control environmental conditions, such as humidity and pollution, to reduce the influence of external factors.
Update or strengthen the maintenance of old equipment to prevent the deterioration of insulation performance.

With the development of intelligent monitoring technology, online partial discharge monitoring systems have gradually become widespread, enabling real-time monitoring and early warning of equipment conditions, and significantly enhancing the security level of the power system.

Partial discharge, as a minor and concealed discharge phenomenon in the insulation system of electrical equipment, although it may not be noticeable, harbors significant risks. A thorough understanding of its causes, characteristics, and detection methods is conducive to early detection and intervention, prolonging the lifespan of equipment and ensuring the stable operation of the power system. In the future, with the advancement of materials science and monitoring technologies, the research on partial discharge will be more in-depth, providing more solid technical support for the power industry.