Neutral Wire Break Detection via Virtual Star Point
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Solution Overview
Problem
Existing devices for detecting a broken neutral conductor in a three-phase network face challenges in distinguishing the interruption from other asymmetries, leading to unreliable detection and incorrect measurements, especially when line-to-line voltages cannot be correctly measured without a neutral conductor.
Innovation Solution
A device forms a virtual star point by connecting phase conductors and the neutral conductor via voltage dividers, with a mapping circuit that applies the envelope of phases to the neutral conductor measurement input, allowing for reliable detection of a DC component indicating a neutral conductor interruption, which is unambiguous and unaffected by other asymmetries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If asymmetry detection is used to detect neutral conductor break, then detection capability is provided, but false detection occurs due to other asymmetry causes
Solution Approach 1:
The patent segments the detection function into two independent parts: (1) detection of asymmetry in phase conductors, and (2) detection of neutral conductor break. This is achieved by using separate detection circuits - one for phase asymmetry and another for neutral conductor integrity - allowing each function to be performed independently without interference, thus eliminating false detections
Solution Approach 2:
The patent introduces a virtual star point as an intermediary reference potential. By comparing the neutral conductor potential against this virtual star point rather than against a fixed reference, the system can distinguish between asymmetry caused by phase issues (which affects the virtual star point equally) and asymmetry caused by neutral conductor breaks (which creates a potential difference relative to the virtual star point)
2Measurement precision
If differential measurement is used for line-to-line voltage measurement without neutral conductor, then measurement capability is provided, but measurement accuracy deteriorates
Solution Approach 1:
The virtual star point serves as an intermediary reference that enables accurate line-to-line voltage measurement even when the neutral conductor is absent. By using this dynamically generated reference potential, the system can perform measurements without requiring the neutral conductor to be physically present, maintaining measurement accuracy while simplifying operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables clear and reliable detection of a broken neutral conductor, preventing false measurements and ensuring accurate line-to-line voltage measurement even when the neutral conductor is interrupted, without additional hardware.
Implementation Method 1
if the neutral conductor (N) is interrupted, the mapping circuit maps the envelope of one, two or three phases onto the measurement input of the neutral conductor
Implementation Method 2
mapping circuit (11) with resistive and rectifying properties
Implementation Method 3
connecting the phase conductors and the neutral conductor via voltage dividers
Data Source
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AI summary
The invention relates to a device for detecting a neutral conductor break in the supply line to a device (100) operated on a three-phase network (1) with phase conductors (L1, L2, L3) and a neutral conductor (N), characterized in that a virtual star point (2) is provided in the device by connecting the phase conductors (L1, L2, L3) and the neutral conductor (N) via voltage dividers (3, 4; 5, 6; 7, 8;9,10) is formed, that the device has a measuring device (12) with a measuring input for detecting at least the measurement signal waveform of the neutral conductor (N) at the center tap of the voltage divider (9, 10) associated with the neutral conductor (N), that the device has a mapping circuit (11) having resistive and rectifying properties, which is connected in the device between the three phases (L1, L2, L3) and the neutral conductor (N), whereby, in the event of an interruption of the neutral conductor (N), the measurement signal of the neutral conductor is supplied with a DC component with reference to the virtual star point.;