Determination of rail capacitance for Taipei rapid transit system using the MOM

Rapid transit systems use running and third rails as mediums for electrical power and control signal transmission. Hence, the transmission line parameters (i.e., resistance, inductance, capacitance, conductance) are important. This paper concentrates on the calculation of the capacitance parameter. Because of the rail´s irregular cross section shape, the calculation of capacitance is not as easy as that of a circular conductor. Two methods, the finite element method (FEM) and the method of moment (MOM), are proposed to solve this problem. The geometric allocation of the running and third rails in the Taipei rapid transit system is taken as an example and the results of calculation obtained using the two methods are to be compared.