Prospects of life estimation of low voltage electrical cables insulated by PVC by emissivity measurement

Abstract

Life estimation of low voltage PVC insulated cables is usually evaluated by invasive or destructive tests, or by visual inspection which leads to qualitative and imprecise conclusion. This paper experimentally assesses the usability of emissivity, a noninvasive and nondestructive measurement from infrared thermography, to estimate useful life and end point of life of these cables. Low voltage PVC insulated cables, light blue and black colors, commonly used in phase and neutral conductors, were thermally degraded in an accelerated way. Throughout this process, reference tests (aging index and thermogravimetric analysis — TGA) and proposed test (emissivity measurement) were performed and compared. TGA requires the removal insulation PVC from cable, and aging index is potentially destructive. Emissivity measurement is a non-invasive and nondestructive technique, performed with the electrical installation in operation. For light blue cables, emissivity measurement can replace the traditional invasive and potentially destructive tests to estimate end point of life with similar results. However, emissivity variation did not present enough sensitivity to monitor evolution of degradation throughout the useful life, similar to tests suggested by technical standards. For black cables, emissivity did not appear as a suitable variable to monitoring useful life neither to detect end of life.