Simulation analysis of wide-band disturbance and multi-physical field coupling based on two typical cable joint insulation defects

Abstract This article investigates the magnetic flux density distribution characteristics of two typical cable joint insulation defects under wide-band disturbance operating conditions. By establishing a multi-physics coupling simulation model for cable joints, the magnetic flux density distribution characteristics of three broadband disturbance forms, namely, sub synchronous oscillation, super synchronous oscillation, and high-frequency resonance, were classified and discussed for cable joints under two types of insulation defects: main insulation scratches and semiconductor layer air gaps. Research has found that under sub synchronous oscillation, the magnetic field distortion rate of the main insulation scratch defect is the highest, reaching 625%, with a magnetic flux density of 0.025 T, significantly increasing the main insulation loss and local overheating risk; Under ultra-synchronous oscillation, the magnetic field distortion rates of main insulation scratches and semiconductor layer air gap defects are 130.9% and 140%, respectively, which may lead to local overheating and insulation aging; Under high-frequency resonance, the magnetic field distortion rates of the main insulation scratch and the air gap defect in the semiconducting layer are 350% and 357%, respectively, with a magnetic flux density of 0.0015 T, and the impact is relatively small. Comparative analysis shows that the main insulation scratch defect is most significantly damaged under sub-synchronous oscillation, while the air gap defect in the semiconducting layer has the highest distortion rate under high-frequency resonance, but the overall damage is smaller than the scratch defect. Therefore, in the operation and maintenance monitoring of the intermediate joints of high-voltage cables, special attention should be paid to the high damage characteristics of the main insulation scratch defects under sub-synchronous oscillation, and the influence of high-frequency resonance on the air gap defects of the semiconducting layer to ensure the safe and stable operation of the cable joints.