Setup of an outdoor hybrid AC/DC test line for corona measurements

While the installed capacity of remote renewables is increasing around the globe, the construction of new transmission lines is often delayed due to public opposition. Therefore many operators evaluate the option of an uprating of existing corridors. A conversion of existing tower infrastructure to hybrid AC/DC lines allows a significant capacity increase without low visual impact. Possible negative effects such as corona audible noise and electromagnetic fields will be a main factor for the acceptance and hence success of this conversion. However, only few experimental studies have been presented with regard to the corona effects of hybrid lines. Therefore, ETH and FKH have constructed an outdoor test line which allows to study these effects under realistic conditions. The Daeniken test line allows to measure the corona performance of a hybrid section of 35m length for typical conductor bundles and operating surface gradients. The ground clearance, the AC-DC separation distance and the voltages can be varied in order to study different ratios of coupling between both sides. The safety system and voltage control is designed to be able to run autonomously for several days in order to capture long-time trends in changing weather and pollution conditions. Existing sensor concepts were upgraded in order to cope with harsh environmental conditions such as heavy rain, as these are often the worst case for corona effects.