Upgrading an old 500 kV DC line

Customer challenge

An old DC line already upgraded twice needed to be refubrished and upgraded again to a higher voltage, while keeping the initial structures and string length at their original dimension.

What we delivered:

Over a period of 10 years the original porcelain strings were tested and evaluated to identify possible weaknesses while at the same time various pollution studies were performed on site and in the Sediver DC pollution laboratory. The diagnostic of the existing insulators showed clearly an end of life situation and therefore could not be reused, since the electric stress would have resulted in numerous punctures all along the line. New insulators were suggested with a higher leakage distance while keeping the overall design of the line unchanged. The refurbishment and upgrade of the line were initiated following Sediver recommendations