Trial Assemble of Pockels Potential Distribution Sensor by Applying Fiber Array Technique

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Information on the potential and the field profile inside electrical apparatus in which partial discharges occur is required for designing apparatus and improvement of insulation efficiency. This research started to develop a new sensing system for two-dimensional potential distribution on an insulating plate. The system was planned to consist of Pockels crystal, optical components and arrayed optical fibres.A potential probe, which has a pair of optical fibres for light transmission, is developed in the first year. This sensor can apply the high voltage measurement without any optical adjustment. After the investigation of the space resolution of this potential probe, it is proved out to be difficult to achieve the intended space resolution with the sensing system with fibre-array method. So, the design of the sensing system is discussed and improved.In the second year, the improved system is developed. The system finally consists of a pulse laser, a beam expander, PBS, a BGO Pockels crystal and a CCD camera. The two-dimensional potential distribution on an insulating plate can be measured without causing any field disturbance. The minimum resolution of this system reaches up to 0.2 nano-second. The transient change of potential distribution with a propagating negative surface discharge in atmospheric air is measured with this system. The propagating component of the electric field E_x near the tip of the propagating streamer exceeds 30kV/cm.These two-dimensional potential distribution profiles are expected to be helpful to the electric field calculation with more adequate streamer model and clarifying the propagation process of surface discharge.