Electrophysical Processes in Composite Semiconductor Screens and Their Influence on the Dielectric Parameters of High Voltage Power Cables

Abstract

The methodology for modelling the percolation process in semiconductor shields of power high-voltage cables is proposed. The semiconductor screen is represented by a two-dimensional lattice model with a polymer matrix filled with conductive carbon black particles. Model matrix's of the composite, depending on the probability of filling and the concentration of the conductive filler, agree with micrographs of the distribution of soot in the polyethylene matrix of the semiconducting screen of the power cable. Taking into account the stochastic of the percolation process, the concentration range of the conductive filler, which determines the flow threshold in the presented model, was determined. Disturbances are observed on the experimental time dependence of the absorption current of the power cable, which is indirect evidence of the accumulation of surface charges at the interface between the semiconductor screen and high-voltage polymer insulation. The time dependences of the electric capacity and the tangent of the dielectric loss angle at a frequency of 120 Hz confirm the stochastic nature of the process of accumulation of surface charges. This process causes a time-delayed interphase polarization in power high-voltage cables. References 36, figure 5.