Noninvasive, low cost, unbalanced current sensor for multi-core cables

The most highly used monitoring systems for cables in use today are based on Rogowski coil technology which can only be used on single phase cables and terminations. To capture current and voltage at an 11kV/400V substation, 3-phase current monitoring devices are needed on each feeder of the LV panel as these are typically the only location to be able to access the single cores of each cable. This paper describes a non-invasive multi-coil sensor system which can be used on a multi-phase cable to determine the load current in an unbalanced system. The paper develops the theory behind the unbalanced measurement and compares the results of this to results generated using finite element analysis and also to experimentally measured data. The paper concludes that there is a significant amount of research still needed to overcome the measurement uncertainty at this time, but that results show promise.