Charge injection characteristics and charge migration mechanism of magnetic particle-modified EBA-based semi-conductive shielding layers

Abstract

The space charge accumulation problem within insulation layer of high voltage direct current (HVDC) cable in engineering applications has attracted much attention. The inner semi-conductive shielding layer is located between the conductor and the insulation layer, which is the only way for charge injection into the insulation layer. The performance of the inner semi-conductive shielding layer has an important influence on the charge accumulation of the insulation layer. In this paper, the matrix resin EBA of high voltage grade DC cable shielding material is used as the research object. The magnetic particle SrFe12O19 is used to modify the EBA-based shielding material. The semi-conductive composites of CB/SrFe12O19/EBA with different SrFe12O19 concentrations (with different Lorentz Forces) are prepared. The mechanism of the influence of Lorentz Forces on the space charge injection characteristics of insulation layers and the mechanism of the charge migration are investigated. The trajectories of space charges in shielding layers are simulated using the finite element method. The experimental results show that SrFe12O19 can significantly reduce the space charge accumulation of the insulation layer. When SrFe12O19 is 5%, the shielding layer has the most obvious inhibition effect on the charge injection of the insulation layer. The simulation results show that the critical value of magnetic induction intensity is B′= 0.6 T when space charge moves in the shielding layer. This work provides a new way to solve the problem of space charge accumulation in HVDC cables, and has important reference significance for the development of HVDC cables.