| With the power system network developing, the asymmetrical operation of the power system became more and more common, especially the ultra high voltage or high voltage with long distance transmission line has been widely applied. Considering the technique and the cost factors, the high voltage transmission line is often used in the form of untransposed, which increased the unbalance and it has many adverse effects on stable operation of power system. For the fault analysis of asymmetrical three-phase transmission lines, the parameter of transmission line do not satisfied the condition of cyclic symmetry. The symmetrical components method can not be decouple the three-phase transmission line. It means that the Fortescue transformation matrix will not be able to digitalization of the parameter matrices of the transmission line. If using the phase components method, the number of calculation is much larger and the computation efficiency is lower. Therefore, this paper uses the modal analysis for the fault analysis of asymmetric transmission line. This method is much similar to the symmetrical components method. It is much simpler and more accurate.The important step of modal anaylsis is made the parameter matrix of transmission line diagonalization. For the modal anaylsis of asymmetrical three-phase transmission lines, It can not use the Fortescue matrix, but the Fortescue matrix still play an important role in determining the exact modal transformation. To solve such problem, this article introduces a new method which can diagonalize the parameter matrix based on Fortescue transformation by using the properties of the similar matrix of parameter matrix to simplify the calculation process. The corrected transformation matrix we final get will be used in the modal analysis on fault analysis and fault location. The error results from simulations shows that the corrected transformation matrix is feasibility of fault analysis of weak geometry unbalances transmission line. |
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