Interface defect breakdown property and electric field simulation of distribution cable accessories

Distribution cable accessories are the key equipment of distribution network system, XLPE/SIR dielectric interface is the weak link of cable accessory insulation. In the work, the interface defect model of XLPE/SIR double-layer structure has been designed, and breakdown properties of double-layer structure with different defects have been studied. Further, the interface defect simulation model of double-layer structure and the cable joint defect are established. The experimental results show the breakdown strength of the specimens with double-layer structure decreases obviously after the defects are introduced, among which the breakdown strength of metal defects and semi-conductive defects are 41.37kV /mm and 43.66kV /mm respectively, which are decreased by 14.2 % and 9.5 % than the samples without defects. The simulation results show the electric field distortion caused by metal defects and semi-conductive defects in the double-layer structure are 44.6 kV /mm and 44.3 kV /mm respectively. The distortion caused by insulation defects is relatively small about 28.3kV/mm, which is consistent with the experimental law. The simulation of cable accessory interface defect shows that the maximum distorted electric field caused by metal defects and semiconducting defects appear at 3.5mm away from the three junction points of “XLPE-SIR-stress cone”, which is about 3.56 kV /mm; In contrast, the maximum electric field distortion caused by insulation defects occurred at the three junction points, which was about 7.23 kV/mm.