Evolution Of Microcracks Inside Insulators Under High-load Operating Conditions
When the power transmission system is under high load for a long time, the electrothermal-mechanical coupling effect borne by dead end suspension insulators will cause stress concentration. In such an operating environment, the existing microcracks inside polymer deadend insulator will gradually expand, eventually threatening the safety of the equipment.
During the manufacturing process of porcelain dead end insulators, the coefficients of thermal expansion differ between different materials. When equipment operates under high load and experiences cyclical temperature changes, internal stress cannot be fully released, leading to microscopic defects at material interfaces. These defects, under the combined effects of voltage and mechanical stress, become the initiation points for crack propagation. Local electric field distortion under high-voltage conditions exacerbates stress concentration, particularly at the connection point between component suspension insulator and hardware, where stress is several times higher than at other locations.
During long-term operation, microcracks are not static. When component suspension composite insulator experiences external impacts such as strong winds, icing, or earthquakes, coupled with temperature stress, the cracks will gradually propagate along the direction of maximum stress. This process is highly concealed and difficult to detect visually in its early stages. After several months to years of operation, these small cracks may propagate to a dangerous level, causing complete breakage of the ceramic component or insulation breakdown.
Electrolytic corrosion caused by leakage current in DC transmission lines accelerates surface damage, while internal acid rain erosion further weakens the material's strength. Sudden increases in mechanical load multiply the stress at existing defects, accelerating their propagation. This multi-factor coupled deterioration process significantly shortens the failure time of the composite suspension insulator.
