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Impact of Flashover Fire Conditions on Exposed Energized Electrical Cords and Cables

NCJ Number
Date Published
April 2019
50 pages
The findings and methodology are presented for a set of experiments conducted to expose various types of energized electrical cords for lamps, office equipment, and appliances to a growing fire, so as to determine the conditions under which the cord would trip the circuit breaker and/or undergo an arc fault.

Six cord types and three types of circuit protection were exposed to six room-scale fires, with circuit protection being remote from the thermal exposure. The six room fires consisted of three replicate fires with two sofas as the main fuel source; two replicate fires with one sofa as the main fuel source; and one fire with two sofas and MDF paneling on three walls in the room. Each fuel package was sufficient to support flashover conditions in the room; as a result, the impact on the cords and circuit protection was not significantly different. Assessments of both the thermal exposure and physical damage to the cords did not show any correlation between the thermal exposure, cord damage, and trip type. An examination of signal data showed that the only cord types that tripped with a fault to ground were the insulated conductors in non-metallic, sheathed cables. This was expected, due to the bare grounding conductor present. These results are consistent with bench-scale, steady-state, thermal-exposure studies that indicated a heat flux of more than 20kW/m2 was needed to fault the cords; however, in the current study, the heat flux at the time of the circuit faults due to the fast-growing room fire occurred at much higher heat fluxes and total heat exposures. Recommendations for future studies are provided. 22 figures and 18 tables

Date Published: April 1, 2019