Differential Protection Device Rectified Average Voltage Detection
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Solution Overview
Problem
Current differential protection devices for electrical installations, particularly those detecting DC fault currents, lack significant dynamics and linearity in their tripping function, leading to ineffective fault current detection and control.
Innovation Solution
A differential protection device with a detection and control module that utilizes a measurement toroid, an AC signal generator, and a measurement winding to generate a fault signal, which is then processed to provide a control signal for breaking or opening mechanisms, featuring a rectified mean value circuit and a comparator to ensure linear and dynamic response to fault currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If peak value detection method is used for DC fault current detection, then the device can detect DC fault currents, but the tripping function lacks linearity and dynamics
Solution Approach 1:
The patent changes the detection parameter from peak value to rectified average value of the fault signal. This parameter transformation enables the tripping function to exhibit proper linearity and dynamics, as the rectified average value provides a continuous and proportional representation of the DC fault current magnitude, unlike the peak value method which creates non-linear response characteristics
2Device complexity
If conventional detection circuits are used, then the device structure is simple, but the detection lacks linearity and dynamics for DC fault currents
Solution Approach 1:
The patent introduces a rectified average value circuit as an intermediary between the fault signal generation and the tripping decision. This intermediary circuit processes the raw fault signal to extract its rectified average value, which then serves as the basis for linear and dynamic tripping control, bridging the gap between simple detection and precise measurement
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
The solution enables effective detection and control of fault currents across a wide frequency range, ensuring safety by providing a direct and proportional indication of differential currents and avoiding non-linearity, thus improving the reliability of fault current detection and prevention.
Implementation Method 1
the conductors form the primary winding, and the toroid has one or more secondary windings. The toroid acts as a magnetic flux concentrator. Thus, in the event of a leakage, resulting in an imbalance between the input and output currents in the conductors of the lines to be protected, the flux created in the toroid by this imbalance in the primary winding induces a voltage in the secondary winding, constituting a fault signal.
Implementation Method 2
a circuit providing a signal corresponding to the rectified average value of the fault signal, or of a derived signal directly dependent on the latter
Data Source
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AI summary
The subject of the present invention is a differential protection device allowing fault currents in an electrical installation to be detected and comprising a detection and control module (3) with a measurement torus (4) through which the conductors (2, 2', 2'', N) of the network pass, an excitation circuit (15) and a measurement coil (5) capable of and designed for generating a fault signal (SD') that is connected to circuits (7, 8, 9) for processing and evaluating the fault signal (SD') and transmitting a control signal (SC) for a cut-off means (11), forming the components of an operational electronic chain (14). Device (1) characterized in that the circuits (7 to 9) of said operational chain (14) comprise at least a circuit (7) supplying a signal (SVMR) corresponding to the rectified mean value of the fault signal (SD') and a circuit (8) comparing said rectified mean signal (SVMR) with a predetermined or preset threshold value and selectively delivering a control signal (SC).