Advanced Wideband Line/Cable Modeling for Transient Studies

The grouping of propagation modes in line/cable systems involving a large number of conductors has been central in recent research regarding the stability of simulations for electromagnetic transient (EMT) studies. This article presents three improvements to the existing wideband line/cable modeling techniques for EMT analysis. The first improvement consists of calculating optimum time delays such that the oscillations in the phase angle of the propagation function are reduced. The second is a novel strategy for grouping propagation modes. As a third improvement, the maximum fitting frequency of a rapidly decaying mode is limited when its magnitude is below a threshold value. It is demonstrated that these modifications improve the stability characteristics of time-domain simulation, compared to the existing implementation of line/cable models in an EMT-type software. The proposed modifications are applied to several cable systems, including a very challenging real system involving 96 cables and one double-circuit overhead line, all with a length of 250 m.