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Steady and transient characteristics analysis for parallel cables

With the increasing power consumption, single-core power cables in parallel have been widely used to improve the transmission capacity. However, there is a complex electro-magnetic coupling between parallel cables in same phase, the current distribution may not be even. This phenomenon will not only lead to a decline in transmission capacity of the line, but also may cause the overheating, even breakdown in parts of the cables. In this paper, based on the model to analyse the current unbalanced degree in parallel cables, the influential factors were studied. It was found that the arrangement was the most important influential factor. The Mutual Unbalanced Degree(MUD) was the least when cables were under symmetry-reverse phase sequence. By using the monitoring data of a 220 kV cable line in parallel, the analysis model was proved to be extremely accurate. Also the transient characteristics of parallel cables were analysed by ATP-EMTP electromagnetic transient analysis software. When single-phase grounding fault happened, the short-circuit current at different fault points was calculated. It was found that single-cable grounding happening at the middle section was the most serious. Single-phase grounding happened at terminal was slighter. Single-phase grounding happened at headend was the slightest.