Effect of Voltage Stabilizer on Electrical Treeing and Partial Discharge Characteristics of Crosslinked Polyethylene at High Temperature

Rapid advancement of urbanization has put stringent demand on the use of power cable as it saves land resources and beautify the environment. At present, crosslinked polyethylene (XLPE) is the main insulation material for the cables due to its excellent electrical and physicochemical properties. However, the high electrical field accelerates the electrical treeing, a dielectric ageing phenomenon which forms continuous charge channels in insulating materials, and hence threatens the long-term operation of insulating materials. In this work, the voltage stabilizer is added into the XLPE to extend the service life of the cable. The effect of the voltage stabilizer on inhibiting the electrical tree inception, growth and partial discharge in XLPE under high temperature is investigated. The m-aminobenzoic acid is selected as the voltage stabilizer, and the blend powder is prepared by adding 1% of voltage stabilizer into pure XLPE through a solution-blending method, and then the needle-plate electrode sample is prepared by a hot-press method. The inception and growth characteristics of the tree with partial discharge characteristics for different samples at 30℃, 50℃ and 70℃ are analyzed by using the real-time observation and synchronous partial discharge measurement system. The results show that the electrical charge channels have typical dendritic structures in the samples at high temperature. Also, for both pure XPLE and the blend samples, the growth rate of electrical branches, partial discharges, and discharge repetition rate have significantly increased with the increase of the temperature. However, compared to the pure XLPE sample, the inception voltage of the blend samples decreased by 6.3%, 5.2% and 9.3% at 30℃, 50℃ and 70℃, respectively, and the number of electrical branches also decreased. Meanwhile, the addition of voltage stabilizer can obviously suppress the electrical tree inception, growth, and partial discharge. Based on the trap theory, the calculation results show that the voltage stabilizer reduces the trap energy level but increases the trap density. Thus, the high energy electron can be easily buffered but not trapped, which can reduce the collisions and hence prevents the molecular chain fracture. Also, the voltage stabilizer has both electron donor and electron acceptor functional groups. With its unique quantum chemical properties, it enhances the high energy electron buffer capacity and reduces the space charge accumulation, which improves the electric resistance of the XLPE material. The voltage stabilizer shows a good ability on inhibiting the electrical tree and partial discharge of the XLPE insulation material. The results provide references for the application of voltage stabilizer in XLPE cable insulation material, which may help to prolong the service life of the XLPE. © 2023 Chinese Machine Press. All rights reserved.