Electrolytic corrosion of metal hardware of HVDC line and station insulators

Insulators on HVDC lines may be damaged by or lose their mechanical strength because of electrolytic corrosion of the metal hardware. DC exposure tests of insulators have been conducted for 20 years at the Central Research Institute of Electric Power Industry in Japan. The authors describe the results of investigations of the electrolytic corrosion of the metal hardware of DC disk insulators with zinc-sleeved pins and cylindrical insulators and of the leakage electricity quantity flowing on their surface. Methods of life estimation of the metal hardware of insulators and corrosion prevention. The mechanism of hardware cracking of station-post insulators is clarified, and measures against the cracking are proposed