Fundamental Research for Practical Application of Cryogenic Gas Insulated Transmission and Substation Apparatus with Environmentally Friendly Nature

点击翻译按钮获取中文摘要

In recent years, insulation gases which have little effect on the natural environment are now highly expected with increasing interest of environmentally friendly nature. The application of nitrogen or air at cryogenic temperature to gas insulated electrical apparatus is examined and discussed.The breakdown voltage of gas insulated gap and its corona discharges characteristics in a large cryostat whose inner volume is 1.1 m^3 are measured changing the mixture ratio and the temperature of the specimen gases.In addition, to clarify the process of the electrical discharge, a new electric field measurement system is developed by using gaseous Kerr effect. The experimental results are summarized as follows :1. The breakdown voltages of a quasi-uniform electric field gap between sphere electrodes with a diameter of 150mm and a gap length of 10 to 100mm are measured. When 50 Hz ac and dc voltages are applied to the gap, the breakdown voltages in nitrogen and air obey Paschen's law even at cryogenic temperatures (93 K).2. The discharge characteristics are observed with a non-uniform field gap of a rod-to-plane electrode geometry up to 330mm for dc voltage applications in nitrogen and synthetic air at room and cryogenic temperatures. In synthetic air at room temperature, the corona discharge just below the breakdown voltage has a shape of a thin film covering the rod electrode, and the breakdown voltage is extremely high. The breakdown voltage increases excessively with the gap length in the range of 0-200mm and is saturated in the range over 200mm.3. A new optical measurement system is developed for measuring electric field in gas without causing any field disturbance by using Kerr effect in gas itself. dc electric field in SF6, CO2 and nitrogen is successfully measured up to 50kV/cm.