In 2016, a suspension insulator string on Tower No. 167 of the 500 kV Kavkasioni transmission line (located in the territory of the Russian Federation) failed, causing the conductor to fall to the ground. The failure was attributed to the fracture of the insulator pin at the socket due to severe corrosion. Inspection of the failed insulator revealed significant corrosion of the pin, as well as evidence of electrical arc flashover on the cap.
Subsequent inspections identified similar defects in the suspension insulator strings on other intermediate towers of the Kavkasioni transmission line.
As a result, the operation and maintenance personnel of JSC Sakrusenergo were instructed to inspect all transmission lines owned by the company in order to identify insulators with similar defects. In addition to the 500 kV Kavkasioni transmission line, corroded insulators were also found in the suspension strings of 169 intermediate towers on the 500 kV Imereti transmission line.
Accordingly, a defect assessment report was prepared, and the number of insulators requiring replacement was determined. It was decided to replace all corroded insulators in the defective suspension strings identified during the inspections.
The implementation of these works was of particular importance for preventing outages on the 500 kV Imereti transmission line. At that time, the Imereti transmission line was the only 500 kV transmission corridor available for transmitting the electricity generated by, and collected at, the Enguri Hydropower Plant to eastern Georgia.
The replacement of corroded insulators on the 500 kV Imereti transmission line was completed in 2018. In total, 5521 insulators were replaced.