Determination of Characteristic Impedance Matrix of Earth Return Circuit for Autotransformer-Fed Traction Power Network

It is incorrect in principle for existing method to derive characteristic impedance matrix(CIM) of earth return circuit for autotransformer-fed(AT-fed) traction network.For semi-infinite earth return circuit,the CIM seen from any designated port to the infinite should be identical.Utilizing transmission parameter matrix of earth return circuit,it is derived that the CIM should satisfy the complex form of algebraic Riccati equation and it can be solved by eigen-decomposition method.Results of calculation cases show that the results calculated by the proposed method are close to those by existing methods,and results of sensitivity analysis show that the CIM is most sensitive to the variation of rail to earth conductance and that of grounding wire to earth conductance.