Corrosion mechanism and process of hardware of disc suspension type Insulators on ±800 kV transmission lines

Abstract

Hardware corrosion on porcelain and glass insulators has occurred on ±800 kV UHVDC transmission lines in China. Iron cap corroded insulators all located at the negative polarity and pin corroded insulators concentrated in positive polarity. The corrosion mechanism is analyzed from the aspect of electrochemistry and the corrosion process is researched by means of spray water simulation tests. Mechanical and electrical characteristics tests and simulation calculation have been done. Test and calculation results indicate that iron cap corrosion can aggravate the contamination accumulation on insulator�s surface and decrease the flashover voltage. Pin corrosion can decrease the mechanical strength of insulators. XP-4C type porcelain insulator and electrolytic cell are used to research the influence factors of corrosion rate of hardware. The test results show that the contamination degree on insulators' surface and its component have considerable influence on the corrosion rate. The more serious the degree of contamination is, the faster the corrosion rate is. The sequence of cation that lead to the corrosion rate from fast to slow is K+>Na+>Ca2+>Mg2+, the sequence for anion is Cl->SO42->NO3-.