Ignition Model for Insulating Material under Coupled Multi-Path Heat Transfer from a Low-Voltage DC Arc and Heated Copper Electrodes

Ignition of nearby insulating materials is a critical thermal consequence of fault arcs in low-voltage DC systems. Most studies on arc-induced ignition rely on one-dimensional heat transfer analysis, while arc power transfer coefficients and coupled multi-path heat transfer remain insufficiently understood. An ignition model based on two-dimensional heat transfer analysis is developed to account for direct arc radiation and heat transfer from heated copper electrodes. Results show that the arc-to-copper power transfer coefficient decreases with increasing mean arc power, whereas the arc-to-insulating-material power transfer coefficient increases. Approximately 45%–75% of the total arc power is transferred to the copper electrodes, while only 0.3%–1% is transferred directly to the insulating material. Nevertheless, direct arc radiation accounts for 8.70% of the cumulative heat input into the insulating material up to ignition, whereas heat transfer from the heated copper electrodes accounts for 91.30%. In equal-area local regions, the direct path contributes 67.54% of the cumulative heat. A higher mean arc power leads to a shorter ignition time, with measured ignition times ranging from 2 to 16 s. With a fixed ignition criterion of 330 °C, most deviations between the simulated and experimental ignition times fall within ±30%. When the measured ignition temperature variation of 310–350 °C is considered, 73.3% of the experimental ignition times fall within the corresponding simulated ranges, indicating that ignition temperature variability explains a substantial part of the discrepancy. The results provide a mechanistic basis for predicting the ignition of nearby insulating materials under coupled direct arc radiation and heat transfer from heated copper electrodes.