Diverted neutral current detector, apparatus, and method

Abstract

A diverted neutral current (DNC) detector 100 comprises current sensors CTP, CTN, CTE for phase, neutral and earth currents. Different types of neutral current diversion fault are detected by measuring first and second conditions. In a first condition, the earth current on conductor E1 and the neutral current on conductor N1 are approximately equal, indicating that protective earthed neutral conductor PEN1 is broken at installation 1, creating a diverted neutral path via installation 2 (figure 5). In a second condition, the direction of the current in E1 is measured; reversal of the expected direction indicates than conductor PEN is broken between installations 1 and 2 (figure 6). A third condition may also be sensed, where the neutral and phase currents differ by more than a threshold, indicating a fault in installation 1 (figure 7). An optional fourth condition measures the voltage between phase and neutral with voltage sensor VS, which also detects a fault (figure 5).

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