The Relationship Between the Sound Velocity and Deterioration Degree of Long-Term Operation XLPE

With the continuous progress of urbanization, cross-linked polyethylene (XLPE) cable has been widely used in the construction of urban power grids. XLPE cable will deteriorate under the action of electricity, heat, and other factors for a long time, endangering the operation safety of the power grid. The trap characteristic is a significant means to reveal the mechanism of cable deterioration. To explore the relationship between cable deterioration and trap characteristics, this paper uses the pulsed electro-acoustic (PEA) method to analyze the trap characteristics of XLPE cables with the service life of 0, 15, and 30 years, respectively. And the sound velocity of XLPE were carried out under different temperature profiles. With the increase in operating life, the internal defects of the XLPE gradually expand, and the accumulation of charge increases significantly. The sound velocity increases gradually at the same temperature and the breakdown field strength gradually decreases. Taking 293 K as an example, compared with the 0A, the breakdown field strength of the 15A and 30A decreased by about 16.0% and 16.4%, respectively. And the corresponding medium sound velocity increased by about 5.89% and 13.71%, respectively. The results take the increase degree of sound velocity of polymer insulating medium as the characteristic parameter to characterize the deterioration level of cable, which provides a theoretical basis for evaluating the deterioration level of cable.