Set-up for AN test. up simultaneously on large portions of the wetted surface, resulting in strong adhesion. This fundamental difference might prove important for real applications where stresses due to wind and mechanical movement
of the conductor could play a major role in ice shedding.
From the outdoor test, it was confirmed that, in the case of the super-hydrophobic conductor, a thinner layer of rime type of ice was observed compared to the others. No such difference, however, was seen from laboratory tests in which glaze ice was created and a possible explanation for this may be that, in the case of the super-hydrophobic conductor, initial ice accretion has a different character.
Results of AN test. Acid treated conductor( lowest curve) is much shorter and should not be compared with others.
B. Corona & Audible Noise Corona effects and in particular audible noise( AN) are important parameters when investigating superhydrophobic conductors. Common knowledge is that traditional hydrophobic conductors( i. e. newly greased or RTV-coated) usually have higher AN levels than service-aged or intentionally sand-blasted ones. In addition, proposals for special hydrophilic paints to reduce AN have been put forward and verified. Therefore, it was seen as especially important to also demonstrate this in the case of super-hydrophobic conductors.
Photos courtesy of STRI
Change of form of voltage of water drops on super-hydrophobic surface at different voltage gradients( observed during AN test under rain).
AN measurements were performed under dry and wet( rain) conditions for different conductors, i. e. new, sandblasted, painted, acid-treated, RTV-coated & super-hydrophobic. The conductors were tensioned horizontally, one by one, 2 m above the floor inside STRI’ s climate test hall.
Noise was measured using a Norsonic Sound Analyzer equipped with a microphone placed 4 m away from the conductor and 1 m above the floor. Equipment was configured to record the spectrum from 10 Hz to 20 kHz at 1 min intervals. Rain was simulated by 10 nozzles mounted on a horizontal beam, hung parallel to the conductor and placed 2 m away horizontally and 5 m
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