Transient Overvoltages in Cable Systems Part 1 – Theoretical analysis of large cable systems

Abstract

This thesis provides an analysis of transient overvoltages and their propagation in cable systems. This investigation is performed through the use of two systems: an industrial steel mill and a wind farm. Cables and vacuum circuit breakers, two essential components in any medium voltage cable system, are discussed in detail and modelled in PSCAD. The two systems are then simulated and, where available, the results are compared to measured data for validity. The purpose of the wind farm section is to identify and analyze cases of interest, including energization, opening, and earth faulting of one of the feeders. The impact on the system is analyzed as well as ways to mitigate the negative effects of these transients. The impact of different wind farm topologies is also analyzed, and a discussion on protection against of the negative effects of transients is ensued for both systems. One interesting finding was that common farm topologies used today (i.e. ring topology) may not necessarily be the best in terms of providing harmless transients.