Characteristics and heat transfer mechanism of low-voltage AC series arc faults under coupled ambient temperature and wind speed

Electrical fires occur frequently in complex environments, where environmental factors such as ambient temperature and wind speed contribute to fire occurrence and spread by changing the behavior of series arc faults. This study investigates the patterns of low-voltage AC series arc faults under the combined effects of ambient temperature and wind speed, with a focus on temperature field evolution, spatial heat transfer, current and voltage responses, and arc energy.

A two-dimensional axisymmetric magnetohydrodynamic model is developed in COMSOL Multiphysics to simulate the thermal-fluid-electromagnetic coupling behavior of an AC series arc fault. This model integrates magnetic and electric fields, heat transfer, laminar flow, and an external circuit. The simulation domain consists of a copper electrode, a graphite electrode, a 3 mm arc gap, an ignition heat source, and the surrounding air. The circuit comprises a 5 Ω resistor and a 220 V/50 Hz AC source. Arc formation is initiated by setting the ignition heat source to 12,000 K. A two-dimensional orthogonal combined design is adopted, including three ambient temperatures (288.15, 298.15, and 308.15 K) and three wind speeds (0, 2, and 4 m·s⁻¹). Average temperature, temperature integral, the root mean square (RMS) of current and voltage, and arc energy are selected as evaluation indicators. Observation points, arranged from the arc center to the outer region, are used to quantify spatial variations in the thermal response.

The results show that the arc temperature field expands and contracts with the power-frequency cycle, and this behavior is closely associated with voltage variations. In the absence of wind, the temperature field exhibits a spindle-like shape, with heat accumulating around the arc. At a wind speed of 2 m·s⁻¹, the temperature field shifts in the direction of airflow, and the high-temperature region moves toward the graphite electrode. The effects of wind speed on the temperature field demonstrate clear spatial dependence. In the arc core region, temperature slightly increases with rising wind speed due to thermal contraction concentrating energy near the arc column. In the peripheral region, however, convective cooling dominates. At 4 m·s⁻¹, the average temperature in the outer region decreases by more than 12.06%, and the temperature integral at wind-cooling-dominated observation points decreases by up to 42.27%. The current RMS remains stable between 34.4 and 34.7 A. The voltage RMS is more sensitive to wind speed than ambient temperature, decreasing by approximately 2.55 V when wind speed increases to 4 m·s⁻¹. The arc energy remains stable at 2 m·s⁻¹ and decreases slightly at 4 m·s⁻¹. Ambient temperature has a limited effect on arc energy, exerting only a weak influence under strong wind conditions.

Wind speed is the primary environmental factor controlling the temperature field and electrical response of low-voltage AC series arc faults, whereas ambient temperature has a limited effect. Wind enhances heat concentration in the arc core while increasing cooling in the outer region. The current conduction channel remains stable, but voltage and arc energy respond more distinctly to airflow disturbance. These findings provide a theoretical basis for early warning and prevention systems for electrical fires in complex environments.