Aging Life Evaluation of Coal Mining Flexible EPR Cables under Multi-Stresses

Abstract

As important power cables for the mining mobile equipment, such as mining shearers, ethylene propylene rubber (EPR) cables often suffer from the combining effect of various stresses on site. In order to evaluate the aging state of EPR insulation, the paper carried out the multi-stress accelerated aging test on the insulation of coal mining flexible EPR cables. The infrared spectrum, elongation at break and polarization and depolarization current of cable insulation samples were measured. The insulation state of EPR cable was evaluated by using the aging factor obtained from isothermal relaxation current. Based on the failure standard of 50% elongation at break, the life formula of EPR insulation was deduced. The experimental and analytical results show that the tiny air gap was torn to the larger air gap under the mechanical stress, which leads to the increase of oxygen infiltration and promotes the thermo-oxygen reaction. The fracture energy of EPR decreases, and mechanical aging is accelerated. Aging factor and elongation at break can indicates the deterioration degree of EPR insulation. Based on the least square method and Arrhenius equation, the service life of the insulation of coal mining flexible EPR cables is deduced.