Research On Parameter Measurement Of Transmission Line And Harmonics Analysis System (The Part Of Parameter Measurement Of Transmission Line)

With the development of power systems, the number of transmission lines with mutual inductance is constantly increasing for the limitation of line corridors. The reliable operation of power systems depends on the correct setting values of relaying protection. The computation of protective relay setting values needs parameters including zero-sequence parameters of transmission lines. Especially, relevant standards and regulation in China and some other countries require practical measurement of zero-sequence parameters of transmission lines. After analyzing the traditional computing theories of zero-sequence parameters of transmission lines and the traditional measuring methods which require the complete power-off, we pointed out the shortcomings of old methods for zero-sequence parameters and proposed some new methods in the paper.We establish the mathematic model of the zero-sequence parameters of thetransmission line in the paper, and put forward the solution to construct adequate independent operating modes. In order to improve the accuracy of measurement, Global Positioning System (GPS) and system identification are proposed and used in the measurement, which are used as synchronous signal and signal process respectively.We also apply the parameter identification theory to the signal processing of our measuring system,including fourier algorithrrK least square method and Kalman filtering aigorithm.And We use the least square method to solve the equations we deduced.We also introduce two new measuring method-the differential method and the integral methd in the paper. After lucubrating on them.we elaborate the practical application of the differential method and put forward the sinusoidal differential theorem.We can get the real differential value of a sampling point by amending the difference of the point. It means we can achieve the same precision as using high sampling rate by this means.In addition.we here give the integral method to improve the differential method.And we put forward the sinusoidal integral theorem and the sinusoidal integral amending coefficient.We also give the amending-coefficient characteristics and tables to sampling rates.The two measuring methods have advantages over the conventional metods for easy operation and computation and only once measurment on most occasions.Apparently they have the braight prospect of applying in the power system.As for the zero-sequence impedance. zero-sequence capacitance. positive-sequence impedance , positive -sequence capacitance.we give the measuring methods and the computing algorithms.We improve the traditonal measuring methods greatly to meet the demands of our users.The new measuring modules have friendly man-machine interfaces and can be operated easily.The precision of the measuring results is also very high.Moreover,we introduce the hardware and software structures in detail in the paper.The software part includes the DSP data sampling program > GPS signal receiving program, interface program, measuring and computing programs, An experiment that simulate the operation of transmission lines was carried out, theresults showed that the designs of hardware and software are correct.The experimental wiring diagrams and results are all showed in the paper. At last.we analyze and compare the direct computing method ., traditional measuring method. on-line measuring method.The theoretical analysis and measurement results proved that the new methods described in the paper are correct effective and will play an important role in improving the level of reliable operation of power systems.