Field test and theoretical analysis of electromagnetic pulse propagation velocity on crossbonded cable systems

In this paper, the electromagnetic pulse propagation velocity on a three-phase cable system, consisting of three single core (SC) cables in flat formation with an earth continuity conductor is under study. The propagation velocity is an important parameter for most travelling wave off- and online fault location methods and needs to be exactly known for optimal performance of these algorithm types. Field measurements are carried out on a 6.9 km and a 31.4 km 245 kV crossbonded cable system, and the results are analysed using the modal decomposition theory. Several ways for determining the propagation velocities for the coaxial and intersheath modes velocities are presented using both single- and synchronized double ended measuring methods. The accuracy of the different methods is evaluated and the results are compared to simulations and theoretical calculated values. Good agreement is found between the different proposed methods and theoretical values. The deviations are explained and a sensitivity analysis is carried out on the most important parameters.