Fundamental study on ultimate utilization of the substance co-existing in nature to insulation of electrical apparatus

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This study has been made aiming at the proposal of optimum insulation design of power apparatus in which environmentally-friendly substance is effectively used. As the development, of noncontact measurement technique of electric field and electron density is required for evaluating the insulation condition, two measurement, methods are proposed in the report.A laser wavefront sensor based on the Shack-Hartmann method is constructed for measuring electron density of discharge in air. The wavefronts of two lasers passing through the discharge on a same optical path are measured by fast-gated ICCD cameras with micro-lens arrays. With this sensor, electron density distribution of discharge can be measured without causing any field disturbance.A noncontact measurement of electric field in gases has been developed based on the Kerr effect by the authors. With this measurement technique, ac stressed uniform and non-uniform electric fields in atmospheric air are successfully measured. It is al … More so found that ions generated due to electrical discharges may have very large Kerr effect and this fact may provide with a new method for measuring ion densities in gas.SF_6 gas has high global-warming-potential and is one of the gases for the restriction. Therefore, many researches of alternative insulating gases to SF_6 have been actively done in recent years. In this research, CF_3I gas, which is one of promising SF_6 substitutions, is examined. The insulation performance of CF_3I and SF_6 is examined through measuring sparkover voltage of various electrode geometries which have different electric-field utilization factors. The sparkover voltage for CF_3I gas is 1.2 times higher than that for SF_6 gas under a uniform electric-field condition. On the other hand, under an extremely non-uniform field condition, that for CF_3I gas is 0.7 times lower than SF_6 gas. The insulation property of CF_3I gas becomes almost equal to that of SF_6 gas when the electric-field utilization factor is in the range of 0.3 to 0.4. Less