NRC Electrical Cabinet Experiments

Electrical switchgear enclosures housing equipment such as circuit breakers and motor controls are a common source of fire in industrial settings, and the heat release rate (HRR) and damage caused by these fires are important considerations in facility risk assessments. This experimental test series includes measurements of the HRR of circuit breakers within electrical enclosures as well as the internal temperature of electrical cables and other equipment outside of the enclosure exposed to the heat of fires within. Previous experiments have been conducted to determine HRR probability distributions for electrical enclosure fires. Analysis was then conducted to refine these results to consider specific electrical enclosure characteristics (e.g., classifying electrical enclosures in terms of function, size, contents/fuel loading, and ventilation). To date, there are few measurements1 of the HRR of circuit breaker fires in electrical enclosures, which have been observed to grow and continue burning for tens of minutes after high energy arc fault (HEAF) events. Thus, the experiments described here seek to quantify the peak HRR, time to peak HRR, and duration of circuit breaker fires in steel electrical enclosures. The second focus of these experiments is designed to quantify the thermal exposure of electrical cables that typically are installed in trays above an enclosure.