Fundamental study of evaluation methods of the deepness of immersed water in pole mounted air switch by air-coupled ultrasound method

It is reported that rain water could immerse into a pole mounted air switch (PAS) due to the corrosion of the tank. Because this situation could cause the internal short-circuit of the switch, which brings to sever troubles like black out of the distribution network. Therefore, the development of diagnostic technique and the equipment to evaluate the water immersion existence and the deepness from the bottom of the tank that depends on the danger are required. In particular, noncontact method is strongly required for the safety operation. From this point of view, we focused on the air-coupled ultrasound (ACUS) method as a non- contact one, and proposed four different sensor arrangements with the ACUS method. In this paper, we firstly showed the four different arrangements (method M1 to M4) and compared them in view of the possibility to apply the actual apparatus. Then, according to the comparison results, we selected the two effective methods (M1 and M3) and investigated and discuss the estimation results taking into the ultrasound propagation properties consideration. As a result, it was experimentally and theoretically confirmed that the water immersion existence as well as the deepness of the immersed water in the PAS could be estimated by the selected two ACUS methods.