Voltage upgrading - An insulation coordination challenge

When voltage upgrading, lightning-, switching- ice-and pollution performance of the insulators and airgaps in the overhead line play a very important role. The dimensioning procedure is different and technically more challenging from the one used for new lines. Amongst others, the margins available in voltage upgrading are much smaller and therefore the engineering needs to be done more precise. To be able to perform the required engineering for voltage upgrading Statnett has performed and is busy performing a number of R&D projects. Different types of insulators have been studied, as well as pollution and lightning performance of the most used glass insulator. The precise gapfactors have been determined theoretically and practically in full scale. Besides that, tools for the determination of the exact air clearances have been taken into use. A tool for determination of the total line performance with correct gapfactors and insulator performance has been and is being developed.