Mechanical vibration of HV conductors induced by corona: roles of the space charge and ionic wind

The corona-induced force per hanging water drop from a HV conductor and the roles of the corona-induced vibration were investigated. To determine the amplitude of the corona-induced force F_t, a water drop was simulated by a conical metal point. F_t was determined using two experimental setups: in the first, conical points were fixed along the underside of a smooth conductor, subjected to a DC high voltage; the corona induced force was then determined from the vertical displacement of the conductor. The second setup is a pinwheel consisting of a rotating arm at the ends of which two conical points were fixed on opposing sides. The forces exerted on the conical points were determined from the acceleration of the arm when subjected to a HV. The velocity of the ionic wind in the vicinity of a HV water drop was measured by a laser anemometer system and the order of the amplitude of the reactive force due to the ionic wind was estimated. It was observed that even in the absence of the ionic wind, a HV sphere suspended above a grounded plane vibrates when an intermittent space charge was injected in the intervening space. It was concluded that the reactive force due to the ionic wind was small compared to the electrostatic force between the corona space charge and the water drop. Thus, the intermittent presence of the corona space charge, produced by the drops hanging from the HV conductor, would appear to be the main cause of the vibration