Research And Implementation Of Power Transmission Line Parameters Detecting By Sweeping Frequency Measurement Method

The characteristic parameters of50Hz power transmission lines are fundamental for the calculation of power flow and power system protection as well as the decision of system operation modes. Their accuracy has directly impacts on the security and stability of power grid. The measurements/estimation of those parameters is very significant for the operation of power grid. There are a lot of uncertainties for their theoretical calculation, which lead to the clear requirements in electric grid operation codes that the characteristic parameters of the newly-and re-established power transmission lines should be measured through necessary experiments before they are operated.This paper focus on a new method in acquiring the physical electrical parameters of long power transmission lines under the strong electric magnetic interference. To attenuate the impacts of the electric magnetic environment, a three-phase PWM voltage source with frequency range from200-2000Hz is designed as the measurement exciting source. A series of power signal filters both analog and digital are integrated as the detecting method to achieve the purpose of higher accuracy and reliable measurement of the parameters. The main contents of this thesis are as follows:(1) The literature of domestic and international studies in the field of transmission line electrical parameter measurement is reviewed and the main technical problems and research progress are summed up.(2) A method to measure the electrical parameters of power transmission line based on a voltage source with frequency sweeping in a range is proposed and the applicability is verified. In this method, resonance point of the long-distance transmission lines is employed to extract the distributed characteristic parameters of transmission lines, which avoid solving the complex super equations in the theoretical calculation.(3) The two key technologies for the application of the above method is investigated, which are the generation of high-power three-phase voltage sources with frequency sweeping in a range, and the corresponding adaptive measurement of AC signals with frequency sweeping in a range. (4) An intelligent device to apply the above method is studied and developed.(5) The developed device is tested both in a laboratory environment and in an on-site environment. The results show the applicability and reliability of the proposed method and the developed device.The study of this paper provides a new theory and a new method in electrical parameter measurement of power transmission lines, which improves the accuracy and reliability of the related calculation and analysis of power system.