Physical Processes of Aging and Assessment of the Technical Condition of Power Cables with Paper-Impregnated Insulation

Generalized theoretical and experimental diagnostic studies of power cables with paper-impregnated insulation of NPP cables according to mechanical and electrical characteristics are given. Understanding the complex synergistic mechanisms of aging of power cables made it possible to estimate the degree of aging of solid paper-impregnated insulation based on the determination of its individual parameters. Laboratory studies have proven the difference in the mechanical and electrical properties of phase and tape insulation in the process of thermal aging of power cables. The use of the number of double folds as a highly sensitive parameter for assessing the technical condition of paper insulation is substantiated. Criteria for the limit state of paper insulation according to mechanical characteristics have been established. The effectiveness of determining the individual values of the electrical parameters of phase and strip insulation based on the results of the tangent of the dielectric loss angle of power cables has been proven. For nuclear power plant cables, it was established that the difference tg$\delta$ of phase and belt insulation at a frequency of 10 kHz exceeds 5 times and can be considered as a sign of reaching the critical condition of the cable during long-term operation. For power cables of electrical networks, a negative correlation was established between the tangent of the dielectric loss angle of the paper insulation for a frequency of 50 Hz and the number of double bends. The critical values of the tangent of the dielectric loss angle of the phase and tape, which correspond to the limit value of the number of double bends of the cable paper of the power cables operating at a frequency of 50 Hz, have been determined.