Modelling of transpositions and double circuit transmission lines in switching surge calculations

The paper extends the method of recursive convolutions for the calculation of electro-magnetic transients on transmission lines with ground return to discretely transposed lines and double circuit lines. A review of the recursive convolution method is first given, completed with a starting procedure for the calculation of transients from a known steady state. Effects of transpositions, such as mode reflections and mode conversion, are then discussed. For double circuit lines, it is shown that they can be represented as two equivalent single circuit lines, thus making possible the use of most simple subroutines for line response calculations.