Wideband Arc Fault Sensor Using a Resonant Current Transformer
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Solution Overview
Problem
Existing arc fault detection devices face challenges in reducing size and manufacturing costs while maintaining sensitivity over a wide frequency range, as they often require multiple sensing elements which can be large and costly or suffer from high losses and decreased sensitivity.
Innovation Solution
A single inductor-based sensor with a resonant circuit is used to detect arc faults across a wide frequency range, utilizing a resonant circuit with a resonance frequency in the Megahertz range to achieve high sensitivity and miniaturization, and incorporating a protection circuit to manage transient voltages and currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple current transformers are used to cover different frequency ranges, then the detection coverage is improved, but the device size and manufacturing cost increase
Solution Approach 1:
The patent combines multiple sensing functions into a single current transformer by designing it to detect both powerline frequency currents (50/60 Hz) and high-frequency arc fault currents simultaneously. This eliminates the need for separate transformers for different frequency ranges, reducing device complexity while maintaining broad detection coverage
Solution Approach 2:
The current transformer is designed with universal sensing capability to detect multiple types of currents across different frequency ranges using a single sensing element. This multi-functional design allows one transformer to replace what would traditionally require multiple specialized transformers
2Volume of moving object
If smaller current transformers are used to reduce size, then the device compactness is improved, but the sensitivity and performance decrease due to higher losses
Solution Approach 1:
The patent changes the operating parameters of the current transformer by optimizing its design to operate effectively across a broad frequency spectrum from 50/60 Hz to several Megahertz. This parameter optimization allows smaller transformers to maintain sensitivity by tuning the transformer characteristics rather than relying on large physical dimensions
Solution Approach 2:
The patent utilizes the natural resonance and vibration characteristics of the current transformer at different frequencies to enhance detection sensitivity. By designing the transformer to respond effectively to both low-frequency powerline currents and high-frequency arc faults, smaller transformers can achieve adequate sensitivity through resonant enhancement rather than size
3Reliability
If dedicated sensing elements for high frequencies are used, then the arc fault detection capability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent merges the function of dedicated high-frequency sensing elements into the standard current transformer design. By incorporating high-frequency detection capability into the basic transformer structure, the need for separate expensive high-frequency sensors is eliminated, reducing manufacturing cost while maintaining arc fault detection accuracy
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 allows for a compact, cost-effective arc fault detection device with high sensitivity across frequencies from 50 Hz to 20 MHz, effectively detecting arc faults with reduced manufacturing costs and size.
Implementation Method 1
a sensor (126) for providing a sensor signal (128), in particular a voltage signal, in dependence on a current through the electric line (102)
Implementation Method 2
utilizing a resonant circuit with a resonance frequency in the Megahertz range to achieve high sensitivity and miniaturization
Data Source
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AI summary
An arc fault detection device (100) for detecting an arc fault in an electric line (102) comprises: a first terminal (112) and a second terminal (114) for connecting the arc fault detection device (100) to a conductor (104) of the electric line (102); a sensor (126) adapted for generating a sensor signal (128) from a current through the electric line (102); and a controller (130) adapted for detecting the arc fault from the sensor signal (128); wherein the sensor (126) comprises an inductor (134) connected to the first terminal (112) and the second terminal (114) and a capacitor (136) connected in parallel with the inductor (134); wherein the inductor (134) and the capacitor (136) form a resonant circuit (138) with a resonance frequency (f0), the resonance frequency (f0) determining an impedance behavior of the resonant circuit (138); wherein the inductor (134) and the capacitor (136) are chosen such that the impedance behavior of the resonant circuit (138) corresponds to a desired impedance behavior (400a, 400b, 400c, 400d; 500a) over a relevant frequency range of the current through the electric line (102).