  We present an efficient numerical technique for calculating the series
impedance matrix of systems with round conductors. The method is based on a
surface admittance operator in combination with the method of moments and it
accurately predicts both skin and proximity effects. Application to a
three-phase armored cable with wire screens demonstrates a speed-up by a factor
of about 100 compared to a finite elements computation. The inclusion of
proximity effect in combination with the high efficiency makes the new method
very attractive for cable modeling within EMTP-type simulation tools.
Currently, these tools can only take skin effect into account.
