Wave Propagation Characteristics of 3-Phase Distribution Cables

Energisation transients in distribution systems are of great concern to the users of equipment supplied by these systems. Such equipment is usually connected to the system by a length of cable. Consequently, the characteristics of the cable are required when any calculations are to be made on the magnitude and nature of such transients. In particular, and as far as high-speed transients are concerned, it is the wave-propagation characteristics of the cable that are of prime importance. Wave-propagation characteristics of the 3-core cables used in distribution systems are, however, difficult to obtain by analytical methods due to the complex geometry of the cable. It will be the purpose of the present work to derive the wave propagation characteristics of a typical 3-core, 3-phase distribution cable for use in transient studies and, in particular, high-speed transient studies. Numerical techniques are described for obtaining the series impedance and shunt admittance matrices from which the propagation characteristics are derived. Studies are made on representative cables and the effect that the various cable parameters have on the propagation characteristics are investigated and illustrated. The effect that the energisation source impedance characteristics have on the wave launched down the cable, and received, are also studied.