Abstract
Space charge is one of the main causes of electrical tree initiation in high-voltage cable insulation. To investigate the influence of DC pre-stress on the space-charge distribution of cross-linked polyethylene (XLPE), a two-dimensional needle-plate electrode model is established in this study. Based on the bipolar charge-transport model, the space-charge distribution characteristics of the needle-plate electrode model under DC pre-stress are simulated and analyzed. The space-charge distribution characteristics are compared with that of the grounded DC electrical tree initiation properties. The work in this study illustrates that the pre-stress time and value affect the space-charge distribution characteristics. There is a certain relationship between space-charge distribution characteristics and electrical tree initiation characteristics. The distribution range of the DC grounded electrical tree is very similar to that of space charge. Both have a similar distribution shape and increased trend under different pre-stress times, and both have an obvious polarity effect.
Highlights
With the rapid development of high-voltage direct-current (HVDC) transmission, cross-linked polyethylene (XLPE) cable has been widely used in new energy transmission, submarine cable transmission, and other fields because of its excellent electrical insulation performance and simple construction technology [1].Relevant studies have shown that the formation and development of an electrical tree are the symptoms of cable insulation deterioration, which seriously affects the safe and stable operation of cables, and the accumulation of space charge is the main cause of electrical treeing [2]
When a DC pre-stress is applied, the homo-polar space charge is continuously injected into the tip of the needle, and the density and distribution range of the charges gradually increase over time
Based on a simulation study, the influence of DC pre-stress on space-charge characteristics is analyzed in this study
Summary
With the rapid development of high-voltage direct-current (HVDC) transmission, cross-linked polyethylene (XLPE) cable has been widely used in new energy transmission, submarine cable transmission, and other fields because of its excellent electrical insulation performance and simple construction technology [1]. H. Liu et al.: Simulation of Influence of DC Pre-Stress on Space-Charge Characteristics of XLPE in Inhomogeneous Field tip, the trapped space charge will de-trap quickly, releasing a large amount of mechanical electrical energy, and even lead to material breakdown [11]. Wang et al used the bipolar charge-transport model to simulate and analyze the space-charge distribution characteristics in samples under DC pre-stress at different temperatures [14]. There are few studies on the influence of space-charge distribution in XLPE under DC pre-stress in extremely uneven fields, and the mechanism of the influence of space-charge distribution on DC electrical tree initiation is not clear. The influence of pre-stress time of DC voltage on the space-charge distribution characteristics under an extremely inhomogeneous field was investigated, and the space-charge distribution characteristics were compared with the initiation characteristics of grounded electrical trees. In (6), S0, S1, S2, and S3 are the coefficients of recombination; Be and Bh are the trapping coefficients of electrons and holes, respectively; noet and noht are the densities of deep traps for electrons and holes, respectively, De and Dh are the de-trapping coefficients for trapped electrons and holes, respectively; and subscripts eu, et, hu and ht represent mobile electrons, trapped electrons, mobile holes, and trapped holes, respectively
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