The Study On The Control Device For Measuring The Transmission Line Parameters By Variable-frequency Electrical Measurement

Transmission line is an important part of the power system. It's Line-frequency parameters consist of positive-sequence impedance, zero-sequence impedance, mutual-impedance and so on. All that is the necessary parameters for calculating the power flow and setting the means of relay protection or setting the mode of the power system operation. But when measured the line-frequency parameters, the power interference produced by near lines can affect the accuracy of measuring result. So how to erase the power interference becomes more important than before. In this paper, a new measurement using variable-frequency electrical measurement to acquire line-frequency parameters is presented. This new measurement can suppress the power interference effectively.In this paper, the fundamentals and means of measuring the line-frequency parameters of the transmission line have been presented detailedly. And pay more attention to analyze the means for processing the composite signal consists of the frequency component generated by the variable-frequency power source, power frequency component and high frequency component. Finally, design the hardware system and software system according as that. This paper is divided into seven chapters. The main content is summed up as following:In chapter 1, firstly, give the reason why to put this project forward. Secondly, compare and analyze sorts of means to acquire line frequency parneters of the transmission line and get merits of using variable-frequency measurement. In the last part of this chapter, represents meaning of this project.In chapter 2 & 3, introduces the fundamentals and means of measuring the line-frequency parameters of the transmission line. They are the foundation and starting point of the following work.In chapter 4, the primary mission is to construct an accurate stimulating line model used in ATP-EMTP to stimulate the power interference produced by near lines according to the mode of connection of the means. And come to a conclusion that the power interference can affect the accuracy of measuring result seriously.In chapter 5, the control disposal hardware system and the characters of chips have been given. The hardware system is divided into several function parts. All of function parts are discussed. But, in this chapter, the most important work is to show how to design a kind of analogue filter for variable-frequency measurement.In chapter 6, we put more attention to design data processing and the error correction function of software system. After tells the way to complete the error correction function and study on the special characters of composite signal, we make a proper scheme to acquire data and to process the data.In the last chapter, the main job is to test the effectiveness of the analogue filter and data diagrammatic representation, the accuracy of DFT and acquiring data. All tests done show that they are work well.In general, the content of this paper basically finishes the mission of this project. But this project still needs to be further completed in the future.