Research On Electric Unbalanced Degree Of Multi-circuit Transmission Line On The Same Tower And The Optimization Of The Phase Sequence Arrangements

With China's sustained economic development, there has been more and more multi-circuit transmission line on the same tower and most of the same tower transmission lines are not transposed, at the same time, the power system also appears more and more power electronics and so on Unbalanced equipments, which makes the imbalance becoming increasingly acute on the normal operation of power system.In this paper, multi-circuit transmission line with the same tower is researched , on the basis of previous research, using multi-port Thevenin equivalent method to analyze the problem of imbalance, and considering the impact of the phase sequence arrangements, the main work is as follows: First, the theoretical transmission line parameters is calculated by EMTP and the order parameter by MATLAB , and the characteristics of them are gained. Meanwhile, the impact of the phase sequence arrangements on them is derivated, and characteristics of the order parameter of the multi-circuit transmission lines are analyzed. Second, Symmetrical component and the phase component methods on the power system is analyzed,and parameters used for the power system simulation software are processed, which Obtains a conclusion ,on the imbalance analysis, the external network uses sequence components,and transmission lines itself uses phase component will be more convenient.Third, the multi-port Thevenin equivalent of the principle is introduced and analyzed , and equivalents about two-port impedance matrix and power equivalent matrix of Merry, Lee Gang studied in this thesis are calculated by PSS / E .Fourth, based on the analysis in the front, model on Electric Unbalanced Degree of Multi-circuit Transmission Line on the Same Tower and Imbalance indicator systems are established based on the multi-port Thevenin equivalent ,and programs are composed by MATLAB. Fifth, the phase sequence arrangements has been optimized using unbalanced degree of lines itself and the system,and the optimized results are checked and evaluated using maintenance and operation mode on the power system.