Abstract
One of the main issues that affect the development of high-voltage direct-current (HVDC) cable insulation is the accumulation of space charge. The load operation of an HVDC cable leads to the formation of a radially distributed temperature gradient (TG) across the insulation. In this study, the space charge accumulation in a cross-linked polyethylene (XLPE) cable is measured under a DC electric field and TG using the pulsed electro-acoustic (PEA) method, and the effect of the TG on the space charge behavior is investigated. In addition, the bipolar charge transport (BCT) model and the conductivity model based on an improved cylindrical geometry are used to simulate the charge behavior in the HVDC XLPE cable under TG, and the experimental and simulated results are compared. The results show that the higher temperature of the cable conductor promotes the accumulation of homocharge near the side of high temperature. Additionally, with the increase of the TG, not only does more heterocharge accumulates adjacent to the side of low temperature, but more space charge also extends into the bulk of the cable insulation. More attention should be paid to the conductor shield layer and the insulation shield layer in HVDC cables. Moreover, the BCT model can more accurately describe the experimental results than the conductivity model.
Highlights
High-voltage direct-current (HVDC) transmission technology is currently the mainstream technology used in the interconnection of regional grids and the long-distance and large-capacity transmission of power energy [1]
The cylindrical geometry used for simulation was improved, and the diffusion motion of charges was added to the bipolar charge transport (BCT) model
The investigation was performed on the effect of the temperature gradient (TG) on the charge behavior, and comparisons between the simulated and experimental results were discussed
Summary
High-voltage direct-current (HVDC) transmission technology is currently the mainstream technology used in the interconnection of regional grids and the long-distance and large-capacity transmission of power energy [1]. As the key power equipment in the construction of HVDC transmission systems, the HVDC cable has many advantages including high reliability, environmental friendliness, and visual concealment, and has become the preferred alternative to overhead transmission lines [2,3]. One of the main factors that limit the long-term advancement of polymer-insulated DC cables is the accumulation of charge, which is one of the significant reasons of insulation degradation [4,5]. Rapid advances in HVDC transmission technology have led to higher requirements for the insulation performance of HVDC cables. To restrain the charge accumulation and improve the polymer insulation performance of HVDC cables, it is inevitable to master the characteristics of charge.
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