| This thesis is supported by State Grid major and basic foresight science and technology project: Research on transmission line early warning technology based on refined meteorological information(SG20141187).Overhead transmission lines are the important part of power system, but because of their own operating characteristics, faults often occur on overhead transmission lines by the impact of meteorological environment factors. The gale has a high probability of occurrence, its effect area is wide and the harm is great, and each district power grid may be hit by wind disaster. Thus wind disaster becomes the most serious one among the natural disasters which lead failures to overhead transmission lines. However, the cost is so high to promote the wind resistance ability of overhead transmission lines completely from the primary side, thus it cannot be fully realized at present. Therefore, to establish wind disaster early warning model which integrate line information with meteorological environment information from the perspective of operation, then providing targeted analysis result and decision support for operators and dispatchers of power grid, has become an economical and efficient solution to enhance the ability of power grid against wind disaster. This paper has made comprehensive and thorough research on the early warning method for common line breakage and tower collapse fault caused by typhoon and wind swing discharge fault. The main contents are as follows:①The main reason of line breakage and tower collapse caused by typhoon is that actual wind speed exceeds the wind resistance design standard of transmission lines. Based on this, a typhoon disaster early warning method for overhead transmission lines considering the effect of micro-terrain is proposed. In the method, area is divided into grids according to precision requirement based on longitude and latitude, and associate transmission line information with the meteorological information and micro-terrain information in the same grid through geographical logic. Then combined with the typhoon forecast information, the set of line that may impacted by typhoon is obtained. Further through comparison between design wind speed of line which is corrected by actual running situation and forecast wind speed of grid which is corrected by micro-terrain around the line, the severity of impact by typhoon disaster on overhead transmission lines can be identified more accurately, and typhoon risk rank is used to do the early warning. The effectiveness of the proposed method is verified by instance analysis.② The root cause of line wind swing discharge is that the air gap distance between line and tower decreases under adverse weather conditions such as strong wind, rainfall, etc. Based on this, a wind swing discharge early warning method for overhead transmission line with correction of rainfall is proposed in this paper. According to the refined weather forecast information and related line parameters, the wind swing angle of suspension insulator string is got. And aimed at early warning common wind swing discharge of conductor towards wineglass-type tangent tower and jumper towards “JG†type strain tower, the formula to calculate minimum air gap between conductor or jumper and tower under wind loading is derived, through introducing two dimensional Descartes coordinate system into tower model. Then compared with the designed minimum air gap, the wind swing discharge warning results can be obtained according to the warning rank table. Moreover, considering that the rainfall will reduce the discharge voltage of air gap, the least square method is used to get the relational expression between rainfall intensity and rainfall influence coefficient referred to the relevant literature and data, and then the designed minimum air gap is revised by this rainfall influence coefficient to make warning results more consistent with the actual situation. The effectiveness of the proposed method is verified by instance analysis. |
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