Lightning And Switching Impulse Discharge Performance And Voltage Correction Of Rod-Plane Air Gaps At Lower Air Pressure In 110kV System

The western of China is a very important power base of our country. In companion with the great exploitation of the west areas and the power transmission from the west to the east, more and more overhead transmission lines will be constructed in the western areas of high altitudes. Aimed at the external insulation selection task, this thesis pvovides the technology references and testing rules. This academic dissertation is based on the research results that carried by our country and other countries, the tests of atmospheric pressure simulation are carried in the large scale artificial climate chamber(the diameter F=7.8m,the height H=11.8m) of The Key Laboratory of High Voltage Engineering and Electrical New Technology of The Education Ministry in Chongqing University. The main research contents of this article are as followed: (1) The influence of atmosphere on the 500, 1000, 1500 mm and 2000 mm four kinds of length rod-plane air gaps lightning impulse discharge characteristics are analyzed, the 50% discharge voltage correction methods are calculated and presented. Further more, the rules of discharge voltage changing with the rod-plane air gap length are analyzed yet. (2) The influence of atmosphere on the 250, 500, 750, 1000, 1500mm and 2000mm six kinds of length rod-plane gaps switching impulse discharge characteristics are analyzed, the 50% discharge voltage correction methods are calculated and presented. (3) In according to the discharging oscillograms and the air discharge rules, the switching impulse discharge physcal courses of rod-plane air gaps are analyzed yet. Through the lightning and switching impulse discharging tests and the dates analyze, the main conclusion of the analyze results are as followed: (1) Both of the 50% discharge voltages of rod-plane air gaps lightning and switching impulse decrease with the air pressure descends, but the decreasing grades are different. (2) The relationship of lightning impulse 50% discharge voltages of rod-plane air gaps with the gap distances are in accordance with linear function relationships. Whereas the relationships of negative switching impulse 50% discharge voltages of rod-plane air gaps with the gap distances are in accord with logarithmic function relationships. (3) The air pressure influence characteristic index n of the 50% impulse discharge voltage correlates with the discharge voltage polarity. For the lightning impulse discharge voltages, the positive air pressure influence characteristic index are higher than the negative, the air pressure influence characteristic index n of short distances are smaller than the long distances, the influence of air gap distances and voltage polarity to the air pressure influence characteristic index and discharging times are complicated. (4) The polarity effect of impulse 50% discharge voltages are influenced by air pressures, gap lengths and voltage types, the polarity effects of switching impulse 50% discharge voltages is bigger than lightning and impulse. (5) The saturation degree of the switching impulse voltage enhances with the gap length increases, the negtive polarity saturation degree are higher than the possitive polarity. The mean breakdown times of switching impulse are correlated with the air pressure, gap length and voltage polarity, when the gap lengths are short than 500mm, the air gaps breaks down most likely in the times of the wave peaks nearby or later than the wave peaks.