XHP1-70 160 255 400 16 90 50 42 120 135 120 ≈20 35 52.5 70 5.6 Main dimensions mm Type frequency voltage kV rms no less than full-wave lightning impulse voltage kV peak pressure of not less than the increase rate% flashover tensile mechanical load kN Weight kg structural height H disc diameter D nominal creepage distance L connection type labeled stem wet flashover flashover breakdown 1min wet withstand 50% flashover withstand routine tests lh electromechanical electromechanical test is not less than the destruction of the AC voltage is applied to the XHP1-70 bell insulators porcelain insulator strings, no matter how many of their number of pieces, which have high voltage distribution curve ends, middle and low saddle features. This is due to the self-capacitance of the insulator and the conductor stray capacitance, stray capacitance to ground caused. As can be seen from the distribution voltage value, close to the wire side of several pieces of high voltage insulator withstand the large electric field strength. Site observation, straight wire rod suspension insulator strings near the first and second sheet insulator saline corrosion worst contamination. This is because the air mixed with dust rise, first encountered close to the wire first piece porcelain insulator skirt, online clip on the windward side and will form a gas vortex, vortex air causes dust to accumulate easily formed in the skirt of the porcelain insulator. On the other hand, the higher the first piece by wire insulator electric field strength near the dirt, impurities are part of the electric field force is absorbed in the inner surface of the skirt porcelain insulator after ionization. Suspension porcelain insulator skirt inner surface by rain is not easy to wash. So over time, dust, impurities in the porcelain insulator skirt piled up, ESDD, the aging rate gradually increased, so that the insulator flashover voltage decreases. Insulator ESDD measure the surface of the waste results in Table 1.