Aging diagnostics of power transmission cable insulation by fluorescence techniques

A number of spectroscopic investigations have been conducted on Conductor Products, Inc. Distribution cable, with cross-linked polyethylene as the insulation, subjected to accelerated aging tests. The principal finding of the study is that measurement of the ratio of XLPE inherent fluorescence at 580 and 650 nm, under 514.5 nm Ar-laser excitation, provides a means of determining remaining cable life. Penetration profiles of fluorescent dyes show promise in this diagnostic effort as well. Other fluorescence studies, such as bow-tie tree examination, although potentially useful in elucidation of aging processes, were not found useful in remaining cable life diagnostics. Service-aged sample, albeit necessarily few, have been examined. The emerging trend is that low fluorescence ratio and/or high fluorescence intensity are associated with long service life. The opposite is found for cables that have failed quickly. To firm up this trend, extensive data bases will be needed. Samples of ethylene propylene rubber cables have been examined. Substantial fluorescence changes occur on aging. A study akin to that performed for XLPE is called for