Acoustic noise emitted from overhead line conductors with superhydrophobic coating

Overhead lines can generate significant levels of audible noise containing low frequency hum and/or high frequency crackling. The frequency of hum is twice the supply frequency while the crackling noise is in the frequency range of 1 kHz to 20 kHz. While conductor choice and the use of bundles can reduce electric fields and minimize noise, some surface defects including damage, insects, raindrops and pollution will always enhance electric fields and lead to noise generation. This results in the need to use specific conductor types/geometries to avoid the creation of a significant nuisance. This paper presents work that has examined whether the noise level generated by an overhead line can be reduced by coating overhead line conductors with superhydrophobic coating. To test audible noise, an enclosed chamber with a low noise level is utilized. The conductor is either bare or coated with a superhydrophobic coating of which contact angle is 168°. With water manually placed on the conductor, the noise levels at 100 Hz are higher than background noise at different voltages, showing that the noise at 100 Hz is generated by water droplets on the conductor. Furthermore, compared with a bare conductor, testing of the conductor with a superhydrophobic coating shows lower noise levels at 100 Hz under different voltages. The superhydrophobic coating can be used to reduce noise levels at low frequency because water droplets, the reason for the hum, cannot stay on the conductor.