A criterion for thermally-induced failure of electrical cable. (February 2015)

• Record Type: Journal Article
• Authors: Fisher, Ryan P.; Stoliarov, Stanislav I.; Keller, Michael R.
• Is Part Of: Fire safety journal. Volume 72(2015:Feb.)
• Page Start: 33
• Page End: 39
• Publication Date: 2015-02
• Subjects: Electrical fire -- Nonmetallic-sheathed cable -- Short circuit fault -- Thermal degradation -- PVC insulation -- Pyrolysis modeling; Fire prevention -- Periodicals; Incendies -- Prévention -- Recherche -- Périodiques; Fire prevention -- Research; Periodicals; 628.92205
• DOI: 10.1016/j.firesaf.2015.02.002
• Languages: English
• ISSNs: 0379-7112

Abstract

Abstract: Electrical failure of 14 American Wire Gauge nonmetallic-sheathed cable, which is used widely in residential electric circuits in the United States, was examined in a range of high temperature environments. Slow heating rates were maintained in these environments to ensure that the heat transfer inside the cable was not a significant factor in the failure process. The experiments were performed in non-energized configuration (insulation electrical resistance was measured), energized with a nominal voltage of 120 V of alternating current and no load, and energized and loaded configurations. In the case of energized experiments, the main parameter that was determined was the time to cable failure. This time was found to be highly reproducible and strongly dependent on the cable temperature. Individual cable insulation components were also examined in a range of experiments including thermogravimetric analysis to gain insight into the mechanism of the failure process. It was determined that the time to cable failure can be quantitatively linked to a particular insulation component reaching a critical degree of thermal decomposition. The use of this criterion within the framework of a thermal degradation model, which was parameterized based on anaerobic thermogravimetric analysis, produced reasonably accurate predictions of the times to failure for a range of energized cable tests. Highlights: A failure of electrical cable subjected to elevated temperatures was investigated. Time to failure was measured for non-energized, energized and energized and loaded cable. A criterion for the failure based on a critical degree of decomposition of insulation was proposed. This criterion was shown to produce reasonably accurate predictions of the failure times.