Degradation mechanism and measurement methods of cable composite insulation induced by interface pressure evolution: A systematic review

Maintaining adequate interfacial pressure at the composite insulation interface is of paramount importance for the secure functioning of cable lines. In practice, however, the interface pressure is prone to deteriorate under the influence of multifaceted operating conditions and the synergistic action of electro-thermal-mechanical stresses. This pressure degradation facilitates the emergence of defects like air gaps and contaminant particles at the interface. These imperfections cause significant local distortions in the electric and thermal fields, typically initiating partial discharge as a precursor to ultimate insulation failure. The defects of impurity particles at the interface of composite insulation produce air gaps, leading to local electric field and thermal field distortion at the interface, which induces partial discharge and eventually leads to insulation breakdown. And as the voltage level of the cable system increases, the cable and its accessories operating conditions become more and more severe, the interface pressure degradation caused by the insulation failure problem is more prominent. The paper firstly starts from the three stages of cable accessory design and production, on-site installation and operation, and summarizes the influencing factors of interfacial pressure at different stages, such as interfacial structure, bending, internal defects, multi-stress aging, and hot and cold cycles, etc.; on this basis, it systematically describes the mechanism of interfacial pressure degradation and its current research status; secondly, it combs and summarizes the interfacial pressure measurement methods at present stage, and gives an overview of the advantages and disadvantages of the various methods. The advantages and disadvantages of various methods are analyzed and compared; finally, a systematic outlook is given to the research on the degradation mechanism of interfacial pressure and its measurement methods, aiming to provide theoretical guidance for the assessment of the state of the interface of composite insulation of cables and the optimization of the design of accessory insulation.