Influence of hydrophilic conductor surface treatments on OHL audible noise

Both the ever increasing demand for energy as well as the current change in power generation strategies necessitate a constant augmentation of overall overhead line transmission capacity. However, neither the construction of new overhead lines nor the refurbishment of existing ones is ever met with a lot of acceptance. One of the most annoying side effects associated with power lines is audible noise, which often occurs along overhead lines during foul weather. These noise emissions are caused by corona effects which in return are abetted by water droplets deposited on the conductor ropes. As research has shown, new conductor ropes are much more prone to this effect than well aged ones. This is a fundamental problem frequently encountered during the commissioning of new lines and the refurbishment of existing ones. Adequate ways of mitigation must be found to ensure a minimum of opposition towards planned reinforcements of the overhead transmission line system. To be able to assess the different concepts for corona noise reduction comprehensively, this paper discusses the underlying mechanisms. Furthermore, various corrective measures with the focus on hydrophilic conductor surface treatments, which strive to reduce the development of corona-inducing water droplets, are introduced. To investigate their effectiveness extensive laboratory tests with variously treated conductor ropes were carried out in a high voltage laboratory. During all measurements increased efforts to ensure a constant and realistic artificial rain rate were made. For this a specifically developed rainfall simulator was used.