Breakdown Mechanism Of Insulators In Power Transmission System Operation

During the actual operation of a high-voltage transmission network, the electric field and environmental stress borne by the polymer deadend insulator will change with the change of the grid load. If the circuit is under high load for a long time, electric field concentration will occur to varying degrees inside and along the surface of the porcelain dead end insulators dielectric, and the probability of dielectric breakdown of the material will increase significantly under such conditions. Breakdown refers to the loss of insulation properties of the insulating medium, allowing current to break through the dielectric barrier and form a conductive path. This phenomenon can occur inside the material or along the surface region, resulting in the insulator no longer blocking current conduction.

Material microstructure defects are a factor affecting the electric field carrying capacity of suspension insulator under high load conditions. Microcracks and pores may develop in ceramic or composite materials during manufacturing or long-term operation. When the applied electric field strength reaches the local "amplification conditions" of these defects, partial discharge activity within the dielectric will generate ionization channels. This process is particularly pronounced with load fluctuations and may evolve into a complete breakdown channel over time.

Humidity and contamination in the transmission environment can also catalyze breakdown. Contaminants accumulated on the surface of suspension composite insulator can form conductive paths under high humidity conditions, making surface discharge more likely to occur than in a dry environment. If a surface discharge event continues under high voltage, the electrical stress along the surface insulation layer will increase further. Combined with the effect of a large load voltage, the initiation electric field threshold of the breakdown event may decrease significantly.