Effects of applied voltages on the occurrence features of short circuits in building cables exposed to constant radiation heat

Abstract

Short circuit failures in building cables exposed to incidental heat are a significant cause of major electrical fires. However, the scientific understanding of how applied voltage influences the occurrence of such faults remains limited. This study investigates short circuits in cables exposed to a cone heater with a radiant heat flux of 20 kW m⁻², focusing primarily on the effects of applied voltages ranging from 20 to 380 V alternating current (VAC). The results indicate that at voltages below 140 VAC, a physical short circuit typically occurs, characterized by a single arc that lacks ignition capability. As the voltage increases between 140 and 260 VAC, an arcing short circuit with multiple arcs is more likely, presenting a higher risk of ignition. For voltages exceeding 280 VAC, only physical short circuits with excessively intense arcs are observed, which can immediately ignite fires and trip circuit breakers. Additionally, the time to failure decreases as applied voltage increases. Through an analysis of time-to-failure, arc energy, surface temperature of the thermally degraded cable, and arc bead characteristics, this paper also explains the formation mechanisms of both physical and arcing short circuits across different voltages. This study enhances the understanding of the complex influence of applied voltage on the occurrence and ignition potential of short circuits in heated cables.