Daochun Huang

Wildfires near overhead transmission line corridors can cause localized conductor heating, thermal elongation, increased sag, and reduced ground clearance. However, traditional sag-calculation formulas and simplified equivalent-temperature methods have difficulty accurately representing wildfire-induced nonuniform temperature rise. To address this limitation, a fluid–thermal–stress multiphysics model was developed for an LGJ 300/40 ACSR conductor. A prescribed flame-temperature field and surrounding airflow were calculated using a CFD model to obtain the conductor’s nonuniform temperature distribution, which was then transferred to a structural finite-element model to determine thermal expansion and sag deformation. The effects of fire-source location were also investigated. The results show that nonuniform temperature rise leads to sag responses significantly different from those predicted using the three-section equivalent-temperature method. When the average conductor temperature reached approximately 130 °C, the maximum sag increased to about three times the cold-state value. Changing the fire-source location resulted in maximum differences of 73.3 °C in average conductor temperature and 37.1% in maximum sag. These quantitative relationships provide a practical reference for assessing conductor-to-ground clearance and evaluating wildfire-induced sag risk of overhead transmission lines.

In wildfire environments, high temperatures generated by wildfires may cause thermal aging, deformation, and even burning damage to the silicone rubber sheds of composite insulators, thereby deteriorating their surface hydrophobicity and insulation characteristics. Meanwhile, ash and carbonaceous particles produced by vegetation combustion tend to accumulate on insulator surfaces, forming conductive contamination layers that reduce surface resistance, intensify leakage current activity, and increase the risk of flashover. To investigate these effects, FXBW₄-35/70 composite insulators were selected as the research object. A simulated burning test platform was established to evaluate variations in the mechanical properties of insulator sheds under wildfire conditions. In addition, the feasibility of using simulated ash was assessed. AC flashover tests were conducted on contaminated insulators to quantify the influence of ash deposition on flashover performance. Beyond confirming the thermal aging behavior of silicone rubber under wildfire exposure, this study establishes a quantitative relationship between wildfire ash deposition, equivalent contamination severity, and flashover performance. A correction model for post-fire pollution withstand voltage is further proposed, providing a practical basis for condition assessment and maintenance of transmission line insulators after wildfire events.

Wildfires can threaten the safety of transmission towers by degrading galvanized coatings and reducing the load-bearing capacity of steel members exposed to elevated temperatures. This study investigates the thermal damage evolution and structural response of transmission tower legs under localized wood-crib fire exposure through a combined experimental and numerical approach. A 1:4 scale tower-leg model was subjected to a single wood-crib fire exposure for approximately 20 min, during which temperature histories, surface damage patterns, and deformation of the fire-exposed members were recorded. The results show that the maximum measured temperature reached 803 °C and decreased approximately linearly with height, leading to distinct damage zones along the tower leg. The galvanized coating exhibited progressive degradation, including oxidation, melting, cracking, and local peeling, while the surface appearance changed from bright silver to black and finally to gray-white with reddish-brown areas in severely heated regions. A temperature-informed elastic–plastic finite element model was then used to interpret the global structural response. The analysis indicates that elevated temperature reduced the stiffness and load-bearing capacity of the fire-exposed side, causing deformation concentration and torsional distortion in diagonal members. The proposed framework provides a practical basis for post-fire damage identification and rapid structural assessment of transmission towers in wildfire-prone regions.

Vegetation fires may lead overhead transmission lines to trip and shut down, thereby endangering the power grid’s safe and stable operation. In order to study the changes of vegetation fire spread patterns under the influence of environmental wind, a square fir crib with a size of 1 m×1 m×0.6 m was taken as the research object. A 5 m×5 m×5 m outdoor site with ventilation around was established through FDS software, and simulation studies were conducted on 10 examples, covering wind speeds varying from 1 to 10 m/s. The variation of flame morphology with the magnitude of wind speed was analyzed; The calculation formula for the flame inclination angle applicable within this wind speed range has been fitted; Based on the flame inclination angle variation, the horizontal offset distance was calculated. The flame height, width, and flame area under different environmental wind speeds were simulated and calculated, and the simulation research results were verified through field tests. The results show that when the wind speed is greater, the changes in the flame inclination angle and the horizontal offset distance of the flame are smaller. The research results can serve as a reference for the analysis of the flame morphology of wildfire spreading near the transmission line corridors and the prevention and control of tripping accidents.

To address the issues of small-target missed detection, false alarms from cloud/fog interference, and low computational efficiency in traditional wildfire detection for transmission line corridors, this paper proposes a YOLOv11_MDS detection model by integrating Multi-Scale Convolutional Attention (MSCA) and Distribution-Shifted Convolution (DSConv). The MSCA module is embedded in the backbone and neck to enhance multi-scale dynamic feature extraction of flame and smoke through collaborative depth strip convolution and channel attention. The DSConv with a quantized dynamic shift mechanism is introduced to significantly reduce computational complexity while maintaining detection accuracy. The improved model, as shown in experiments, achieves an mAP@0.5 of 88.21%, which is 2.93 percentage points higher than the original YOLOv11. It also demonstrates a 3.33% increase in recall and a frame rate of 242 FPS, with notable improvements in detecting small targets (pixel occupancy < 1%). Generalization tests demonstrate mAP improvements of 0.4% and 0.7% on benchmark datasets, effectively resolving false/missed detection in complex backgrounds. This study provides an engineering solution for real-time wildfire monitoring in transmission lines with balanced accuracy and efficiency.

Wildfires frequently occur, posing a significant threat to the operational stability of transmission lines across mountainous forest areas. Therefore, this paper reviews numerous studies conducted by domestic and international scholars on the gap breakdown tests and discharge mechanisms of transmission lines under simulated wildfire conditions. It analyses and summarizes the physical parameter measurement methods commonly used in current experiments. Combining the results of existing experiments, this study analyzes the discharge mechanisms, including the research progress made in numerical simulations. The conclusion is that existing tests are limited in their measurement methods of the physical quantities related to breakdown characteristics, and it is not easy to strictly control experimental variables when considering complex factors. Numerical simulations mainly focus on multi-physical field simulations, which consider the characteristics of vegetation fires in short gaps. The synergistic mechanism of environmental factors on gap breakdown characteristics remains unclear. This paper points out the breakdown characteristics and discharge mechanisms derived from existing experiments and numerical simulations under various influencing factors, highlighting their applicability and limitations, which differ from complex actual transmission lines in the environment. Then, we look forward to the future development of simulation test platforms that could better reflect the actual transmission line corridor environment, incorporating multi-parameter measurement and in-depth numerical simulation works that consider climate and terrain factors.