The purpose and significance of partial discharge detection for prefabricated cable accessories

Since cables are laid in cable trenches, pipes and tunnels, the laying environment and use conditions will greatly affect the life of the cables. After the cables are put into operation, they will be in contact with soil, moisture, and moisture for a long time, and the insulation is susceptible to corrosion and penetration. Local defects in cable manufacturing or installation of accessories. Under the action of electricity, heat, mechanical external forces, water, oil, organic compounds, acids, alkalis, salts and microorganisms, insulation aging often occurs, accompanied by partial discharge, tree aging and other forms, but ultimately it is attributed to electricity Tree branches cause insulation breakdown.

In order to ensure the reliable operation of power cables and conduct preventive tests, the regulations stipulate that the insulation resistance, DC withstand voltage, AC withstand voltage, dielectric loss tangent, leakage current measurement and outer sheath withstand voltage test of the power cable insulation should be carried out. But for the characteristics of multi-composite insulating medium for high-voltage accessories.

At present, the preventive test data is single, and the test data cannot fully reflect the insulation status. There is no timeliness and forward-looking for the handling of cable accidents. With the expansion of the power grid and the increase of power cable lines, the traditional preventive maintenance and test mode will It is becoming less and less adaptable to the needs of modern large-scale power grid operation and management. Operating experience and research have shown that the partial discharge of power cables is closely related to the insulation status of power cables. The change of partial discharge indicates that the cable insulation reflects potential hidden defects to a certain extent. Existence is one of the effective methods to quantitatively analyze the degree of dendritic degradation. The international power authority unanimously recommends partial discharge test as the best method for evaluating the insulation condition of XLPE power cables.

At present, partial discharge tests are being widely used in field tests. The measuring points are mainly cable accessories. The partial discharge on-line monitoring technology of cable accessories can be used to detect the operating conditions of cable accessories and take necessary measures in time according to their detection conditions. To ensure the normal operation of the power system, the research on PD detection of high-voltage cable accessories has important practical value for ensuring the safe operation of XLPE power cables.