Some developments on phase coordinates line modeling based on Idempotent decomposition

Four test cases were considered including two previously reported cases where unstable simulation responses were found using ULM with a simple interpolation scheme. A Numerical Laplace Transform (NLT) approach was used to compare the time-domain responses. While results indicate that the Idempotent decomposition can be used to model underground cables, there is some accuracy loss in the rational approximation of the propagation function in the case of overhead transmission lines when a large number of phases is involved.