In the operation and maintenance of power systems, the status of tension insulator is directly related to the safety of transmission lines. Leakage current is a key indicator reflecting the condition of the dead end insulators surface. When this value rises abnormally, it often indicates that dead end suspension insulators is undergoing a series of complex performance degradation processes.

Surface Characteristics and Flashover Risk

Fouling Layer and Wetting Effect

Industrial contaminants or coastal salt spray can accumulate on the polymer deadend insulator surface, forming a fouling layer. When dry, this contamination layer has high impedance and limited impact on operation. However, under high humidity conditions such as fog, dew, or drizzle, the soluble electrolytes in the contamination layer dissolve, and the surface conductivity increases sharply. This change in surface characteristics directly manifests as a significant increase in leakage current, creating the physical conditions for subsequent discharge phenomena.

Local Arc Development

As leakage current increases, the current density distribution on the insulator surface becomes extremely uneven. In areas where the skirt dries quickly and the current density is high, a so-called "dry band" forms. The formation of a dry strip leads to electric field distortion. When the local field strength exceeds the tolerance of air, tiny discharge sparks can occur across the dry strip. If these discharges persist, they further erode the insulator's skirt material, especially in organic composite insulators, potentially causing irreversible aging damage such as material embrittlement and corrosion, ultimately significantly shortening the insulator's service life.

Double Impact on Mechanical and Electrical Performance

Increased leakage current not only affects insulation performance but also directly relates to the insulator's electrical strength and mechanical integrity.

• Reduced Flashover Voltage: Research data shows that as the leakage current increases in the contamination layer, the flashover voltage of the insulator decreases significantly. This means that under system overvoltage or operational shocks, insulators with sufficient design margins are highly susceptible to surface flashover, causing line tripping accidents.

• Corrosion of Metal Accessories: In DC transmission systems or in the presence of AC harmonic components, continuous leakage current triggers electrochemical reactions. The synergistic effect of the DC component in the leakage current and localized high current density accelerates the electrochemical corrosion of metal accessories such as insulator legs and caps. Corrosion not only reduces mechanical strength, but in severe cases can even lead to serious accidents such as string failure.