High voltage cables play a vital role in the transmission of electricity. With the increasing demand for electricity, the safety and reliability of power facilities are particularly important. Under this background, partial discharge detection technology has gradually become one of the important means of high voltage cable maintenance. Partial discharge refers to the phenomenon of electrical discharge in the internal or local area of the surface of the insulating material. This phenomenon is usually caused by factors such as aging, defects or contamination of the insulation material. The existence of partial discharge will not only lead to the deterioration of insulation materials, but also may lead to the failure of power system. Therefore, timely detection and evaluation of partial discharge is very important to maintain the stable operation of power system.
Formation mechanism of partial discharge
The formation mechanism of partial discharge is usually closely related to the physical and chemical properties of insulating materials. When the voltage exceeds the breakdown strength of the insulating material, the electric field will form a partial discharge channel inside or on the surface of the insulating material. These channels may be caused by defects such as bubbles, impurities, cracks, etc. The process of partial discharge can be divided into several stages: First, the electric field strength gradually increases, causing electrons inside the insulating material to be excited. Second, the excited electrons collide with molecules in the insulating material, producing free electrons and ions. Finally, with the enhancement of the electric field, a partial discharge channel is formed, resulting in an instantaneous release of current.
Detection technology and method
Partial discharge detection technology mainly includes current method, acoustic method, optical method and electromagnetic method. Each method has its own advantages and disadvantages and is suitable for different detection occasions.
1. Current method: This method identifies partial discharge phenomena by measuring current fluctuations on the surface of the cable insulator. The advantage of the current method is that it is easy to use and can quickly obtain real-time data of partial discharge. However, this method is sensitive to external interference, which may affect the accuracy of the detection results.
2. Acoustic method: The acoustic method determines the state of the insulation material by detecting the sound waves generated by partial discharge. Partial discharges create weak acoustic signals in the insulator that can be picked up by sensors. The acoustic method has high sensitivity and can effectively identify small partial discharge phenomena, but its detection range is limited by the propagation characteristics of sound waves.
3. Optical method: Optical method uses the light signal generated by partial discharge for detection. A partial discharge emits a certain wavelength of light when it occurs, and these signals can be captured using optical sensors. The advantage of this method is that it can realize remote monitoring, but the equipment cost is high.
4. Electromagnetic method: Electromagnetic method is detected by analyzing electromagnetic waves generated by partial discharge. This method has high sensitivity and can detect partial discharge signal at a long distance. However, electromagnetic method interferes greatly with environmental noise, which may lead to misjudgment.
Application of partial discharge detection
Partial discharge detection technology is widely used in the maintenance and management of high voltage cables. First, during the installation phase of the cable, partial discharge detection can be used to assess the quality of the insulation material to ensure that the cable can operate normally after installation. Secondly, during the operation of the cable, regular partial discharge detection can help operation and maintenance personnel find potential insulation defects in time, thereby reducing the risk of failure. In addition, partial discharge detection technology can also be combined with other monitoring means to form a comprehensive monitoring scheme to improve the safety and reliability of the power system.