Discharge Performance And Voltage Correction Of Short Air Gaps And Insulator Strings At Altitude Of 4000 M And Above

The relative air density decreases with the increasing of altitude. Therefore, the discharge performance of air-gap and insulator string at high altitude regions is different from that of the referring standard conditions. This difference is one of the key question in the design of the external insulation. It is put forward that the correction of external insulation discharge voltage for the region 2000 m and below in GB/T16927 and IEC60.1. In spite that there is no unanimous voltage correction method in the region between 2000 m and 4000m, a number of investigators both at home and abroad have put forward some voltage correction method of external insulation, which should be applied in corresponding conditions. Up to new, it is no report that the correction of effect of atmospheric condition on discharge voltage of external insulation is studied in the region 4000 m and above. So, based on the important project, the discharge performance of short rod-plane air gaps and short insulator strings has been researched in this dissertation, which there is not only very important value of engineering application but also very important value of learning.Based on the result of study both at home and abroad, aimed at 27.5 kV and 35 kV power supply system of on-going Qinghai-Tibet railway, this learns the AC,lightening impulse and switching impulse discharge performance of short rod-plane air gaps below 500 mm and short insulator strings in the air condition of altitude over 4000m simulated in the cylindrical artificial climate chamber. And based on the result of test, the dissertation analyzes the discharge performance of short rod-plane air gaps and short insulator strings in the air condition of altitude 4000m and over, and put forward the correction formula of short rod-plane air gaps and short insulator strings in the air condition of altitude over 4000m. The study works and conclusion of the dissertation is followed as:The discharge voltage of short rod-plane air gaps and short insulator strings will also decrease with the altitude increasing or atmospheric pressure decreasing, but the decreasing trend is relative to the scale of altitude, the decreasing speed of discharge voltage is slower in the high altitude region. The change of atmospheric pressure reflect the change of the altitude and the change of the temperature,humidity and relative air density in the different altitude region, So the atmospheric pressure is able to be use for the characteristic parameter of token the effect of the altitude on externalinsulation voltage; the discharge voltage of short air gaps and short insulator strings is the power function of atmospheric pressure ratio, as equation U=U0(P/P0)n, the factor index n is relative to the voltage type and gap forms or insulator structures. The dissertation also analyzes the discharge basic principle of short air gaps and short insulator strings in the high altitude regions. The study result of the dissertation provide the test data and theory reference for power supply systems of on-going Qinghai-Tibet railway and the design of other external insulation in the region 4000 m and above,...