Statistical Characteristics Of Radio Interference Caused By UHV AC Transmission Line And Its Predition And Assessment Methods

Building a global interconnected intelligent energy internet based on the ultra high-voltage(UHV)power grid as the backbone and clean energy as the dominant consumption,is the fundamental means to solve the current problems faced by global energy consumption.China attaches great importance to the development of ultra high pressure technology,and the high speed development of several AC、DC UHV transmission projects in China,provides a strong support for the national economic and social development.However,the UHV power grid itself also has some environmental impact,which is mainly the electromagnetic environment problem produced by the corona of the line,and the radio interference(RI)is one of the main electromagnetic environment parameters wich is the important considered factor of the line design.Due to the randomness and complexity of corona discharge,weather conditions will greatly affect the level of RI produced by UHV AC transmission lines.At present,however,there is lack of long-term statistical data concerning radio interference of the UHV line in actual operation under different weather conditions both at home and abroad.Therefore,in this dissertation,three long-term measurement stations are established near the UHV AC single-circuit transmission line and double-circuit transmission line in actual operation in China for continuous measurement of radio interference for nearly a year respectively,based on which statistical characteristics of radio interference under different weather conditions are analyzed.With the corona cage of the UHV AC test,the method for predicting and evaluating the radio interference of actual UHV AC single and double-circuit lines is given,providing strong support in the subsequent construction of UHV projects.Firstly,three radio interference long-term measurement stations and the Internet-based remote control and measurement system as well as data storage and inquiry system are established.Through full consideration of the scale of measurement spot,spacing from other low voltage lines,the consistency of adjacent spans and other conditions,Henan Jiaozuo and Hubei Zhongxiang long-term measurement stations for UHV AC single-circuit transmission line and Anhui Chaohu measurement station for UHV double-circuit transmission line are established by using the method of selection via roadmap and satellite map followed by site investigation,which provides the basic test conditions for subsequent long-term measurement.The Internet-based and remotely controlled measurement system of weather parameters and radio interference data is also established.The weather phenomenon measuring device that is based on meteorological optical range and can define clearly 14 kinds of weather phenomena at most is used to solve the problems of previous domestic and foreign researches as unclear boundary between weather phenomena and weather parameters.The mass weather and radio interference data storage and inquiry system is built on the basis of the three-layer structure namely the client side,intermediate layer and server side to simplify data reading and statistics.Secondly,the testing method is proposed to remove the outliers from the measurement data of radio interference under fair weather.The Grubbs test method and Robust Z test method under the condition of normality assumption as well as Walsh test method and bounded β(g,h)distribution method under the condition of non-normality assumption are compared for their ability to detect outliers by using a same group of samples with outliers.It is found that Grubbs test method is not satisfactory;Robust Z test method is very robust but too harsh;Walsh test method and bounded β(g,h)distribution method are moderate as measurement scale,which make only a few assumptions about original samples and are robust and reliable.Walsh method is recommended to be used for detecting the outliers from fair weather data,judging from the level of difficulty of procedures.Thirdly,statistical analysis of the characteristics of radio interference under fair weather is performed.Through continuous monitoring by three long-term measurement stations for nearly a year respectively,the all-year fair weather mean,standard deviation,percentile,skewness,kurtosis and other statistical characteristics of the UHV AC single-circuit lines and double-circuit lines are obtained with the method of descriptive statistic.The seasonal fluctuation characteristics of single and double-circuit lines in fair weather mean are revealed and the gap between the month with the maximum fair-weather mean and the month with the minimum fair-weather mean in a year and the distribution characteristics of fair-weather data in a year are summarized.The correlation between radio interference and relative humidity,temperature,and wind speed under fair weather is analyzed by using the simple correlation analysis method and partial correlation analysis method.Fourthly,the statistical analysis of the characteristics of radio interference under bad weather is conducted.The mean,standard deviation,percentile,skewness,kurtosis and other statistical characteristics of the UHV AC single-circuit lines and same-tower double-circuit lines under the heavy rain,moderate rain and light rain in a year are obtained with the method of descriptive statistic.The gap between these two kinds of transmission lines in different kinds of rain is summarized.The basic distribution form of radio interference data under rainy weather is analyzed through the cumulative frequency curve.The processing curve of radio interference under different weathers is analyzed to uncover the changes of radio interference before and after the rain.The similarities and differences of all-year overall distribution of radio interference between foggy and hazy weather and fair weather are compared,it also indicates that the distribution under light snow is similar to that under light rain.The specific expression for conversion of radio interference under different rainfall conditions is proposed by means of the optimization algorithm.Finally,some suggestions are given on the prediction and evaluation of radio interference of the UHV AC lines in actual operation.The excitation function for the heavy rainfall of 10mm/h in the corona cage is obtained through measurement of radio interference current and regression of excitation function of 16 conductor combinations including 6~12 bundled LGJ630 &LGJ720 under heavy rain,and compared with measured data to prove its feasibility.With the statistical characteristics and excitation functions,the minimum sample size necessary for the evaluation of radio interference mean under fair weather,foggy weather and hazy weather is indicated to provide basis for simplifying the evaluation in the future.Besides,the gap with statistical significance between the rainy weather,fair weather,foggy weather,hazy weather and snowy weather is given,which constitutes the basis for the prediction of radio interference of UHV AC transmission lines under different weather conditions.To sum up,this thesis makes up for the lack of long-term statistical data of radio interference of UHV AC transmission lines in actual operation in domestic and foreign researches,defines clearly different weather conditions and describes statistical characteristics of radio interference under corresponding weather conditions and gives suggestions on the prediction and evaluation of radio interference of actual UHV AC transmission lines,therefore it has both academic and engineering application significance.