Modelling of non-uniform lines using rational approximation and mode revealing transformation

The authors present a methodology to improve the rational modelling of non-uniform lines (NuLs). First, they formulate a segmented chain matrix representation of the NuL, which is converted into a nodal admittance formulation with respect to the two line ends. The admittance matrix is fitted with rational functions while utilising the so-called chain matrix in combination with a mode revealing transformation matrix, to improve the identification of poorly observable modes and poles. The procedure is demonstrated for a case of a very wide river crossing where the transmission towers are over 300 m high. The results compare favourably with the ones obtained using a numerical Laplace transform. © The Institution of Engineering and Technology 2017.