Modal Domain-Based Modeling of Parallel Transmission Lines With Emphasis on Accurate Representation of Mutual Coupling Effects

Transient and harmonic coupling effects between parallel overhead lines are normally modeled via frequency-dependent traveling-wave-type transmission-line models. Several electromagnetic transient programs rely on a line model based on a constant transformation matrix and modes (FD-line). These line models can, however, give substantial errors in the studies of coupled disturbance from one line to a neighbor line. In this paper, we show that the accuracy of the FD-line in these applications can be greatly improved by representing the line system by independent FD-lines in combination with rational models that take the mutual coupling between the lines into account. A mode-revealing transformation is used for further enhancing the accuracy of the coupling effect. The approach is demonstrated for the simulation of transient coupling between two parallel overhead lines caused by line energization and for assessing the disturbance of a railway signaling system from a neighboring overhead line caused by a transformer inrush current and fault transients.