Cross-Country faults in resonant-grounded networks: Mathematical modelling, simulations and field recordings

Abstract

Cross-Country Faults (CCFs) are defined by the occurrence of two Single Phase-to-Ground faults taking place simultaneously in different phases and at different locations of the galvanically connected network. Few studies about these faults in MV systems have been done so far, particularly with real fault data and simulations. In this work, first a mathematical model is derived to understand basic properties of CCFs. Then, simulations in RSCAD/RTDS® using real data obtained from an utility in Scandinavia are discussed and validated with two real faults measured in the field for resonant-grounded networks in Sweden and Norway. The mathematical calculations proved to have a good accuracy and showed important properties of CCFs such as the dependency of both faults of each others fault resistance and location. Furthermore, it was observed that such faults can be very different from more common types of faults in the power system. Interesting behaviors can appear particularly when feeders are connected in ring, where an extra current with smaller magnitude and 180∘ appears on the measurement point, as well as in lines with double infeed where a very large difference is detected depending on the fault location which influences directly both ends of the line.