Research On Wind Swing Discharge And Lightning Stroke Trip Risk Early Warning Methods For Transmission Lines Under Severe Convective Weather

As the primary medium of electric energy transmission,transmission lines operate in natural environment for long term and are vulnerable to the invasion of external severe conditions which may cause faults.Severe convective weather frequently occurring in summer is always accompanied with violent wind and lightning storm phenomenon which puts transmission lines under the risks of wind swing discharge and lightning stroke trip.Meanwhile transmission lines mostly operate in heavy load while the power grid is meeting summer peaks.Faults occurring on transmission lines will bring serious bad influence to electric power enterprises and users.Reasonable and effective early warning for fault risks of transmission lines under severe convective weather can make operating and dispatching personnel of power grid clear about the transmission line risks in advance and provide important evidence for specific decision-making in prevention and control.This paper analyzes the risks of wind swing discharge and lightning stroke trip of transmission lines under severe convective weather and proposes the corresponding early warning methods.The main contents are as follows:(1)It is difficult for present wind forecasting service to meet the requirement of power grid early warning under severe convective weather.However,development and application of Doppler weather radar technology provide a powerful tool for severe convective weather forecasting.Wind scale forecasting under severe convective weather is summarized as the problem of classification with supervised learning in this paper and the wind scale forecasting model under severe convective weather based on weather radar data is proposed.In the basis of monitoring data for severe convective weather of weather radar and historical wind speed observed by automatic weather stations under severe convective weather,the appropriate classifier is constructed and then the wind scale forecasting can be achieved through machine learning.Validity of the model is verified through testing on the actual samples.(2)The risk of wind swing discharge of transmission line and the corresponding early warning method are further studied in the paper based on output result of the wind scale forecasting model under severe convective weather.The critical wind swing angle and the critical wind speed of wind swing discharge of transmission line are deduced based on line parameters such as geometric structure of the tower and analyzing the effect of non-horizontal wind.The probability of wind swing discharge is calculated according to the wind scale forecasting result and the critical wind speed of wind swing discharge on the basis of wind speed distribution fitting of historical severe convective weather and the early warning for wind swing discharge risk of transmission line can be then released.Validity of the proposed early warning method for wind swing discharge is verified through actual line fault example analysis.(3)Lightning activities in different regions have different characteristics and Lightning Location System(LLS)can provide sufficient data for accurately assessing the lightning stroke risk of transmission lines.The early warning method for lightning stroke trip of transmission line correlated to past adjacent lightning activity is proposed in the paper.Based on the historical monitoring data of LLS,the regional lightning current amplitude distribution is fitted and adopted instead of the fixed distribution in corresponding standards.Lightning activity of future short-term period is represented through the past adjacent happened lightning activity monitored by LLS under severe convective weather in the paper,the probability of lightning stroke trip of transmission line is then calculated according to the line parameters and the regional lightning current amplitude distribution and the early warning for lightning stroke trip risk can be released.Validity of the proposed early warning method for lightning stroke trip is verified through actual line fault example analysis.