Rogowski Coil Phase Compensation for Arc Fault Detection
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Solution Overview
Problem
Conventional protection systems for low-voltage AC circuits are inadequate in detecting and extinguishing arc faults within the required time frame, leading to potential equipment destruction and personal injury, as they often fail to provide phase-accurate current measurements using Rogowski coils.
Innovation Solution
An arrangement that includes Rogowski coils connected to an analog integrator and an analog-digital converter, with a microprocessor to compensate for phase shifts, enabling phase-accurate current determination for arc fault detection in low-voltage circuit breakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Rogowski coils are used for current measurement, then electrical isolation and high current capability are improved, but phase accuracy deteriorates due to stray field inductance
Solution Approach 1:
The patent introduces an analog integrator circuit as an intermediary component between the Rogowski coil and the evaluation system. This integrator compensates for the phase shift caused by stray field inductance, transforming the differentiated voltage signal back into a phase-accurate current representation while preserving the electrical isolation benefits of the Rogowski coil
Solution Approach 2:
The patent applies parameter changes by modifying the signal processing approach - using analog integration to change the temporal characteristics of the Rogowski coil output signal. This transforms the phase-shifted differentiated signal into a phase-accurate current signal, resolving the measurement precision issue while maintaining the reliability advantages
2Measurement precision
If shunt resistors are used for current determination, then phase-accurate current values are achieved, but power losses increase proportionally to current level
Solution Approach 1:
The patent replaces the shunt resistor (electrical resistance-based measurement) with a Rogowski coil (magnetic field-based measurement). This substitution eliminates the direct power loss associated with shunt resistors while maintaining measurement capability through magnetic coupling and subsequent analog integration
Solution Approach 2:
The patent changes the measurement parameter approach from direct voltage measurement across a resistance (shunt) to measuring the magnetic field around the conductor (Rogowski coil). This parameter change eliminates the I²R power losses inherent in shunt resistors while achieving the desired measurement precision through analog integration
3Device complexity
If conventional protection systems are used, then device complexity is reduced, but arc fault detection reliability deteriorates due to inability to provide protection within required time frame
Solution Approach 1:
The patent implements continuous monitoring of current phase accuracy through the analog integrator, ensuring that arc faults are detected without interruption or delay. This continuous phase-correct signal availability enables immediate arc fault detection while maintaining relatively simple device architecture
Solution Approach 2:
The analog integrator serves as a mediating component that enables reliable arc fault detection without significantly increasing device complexity. It provides the necessary phase correction to make Rogowski coil signals suitable for protection applications, bridging the gap between simple measurement and reliable detection
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 reliable arc fault detection and prevention of unnecessary interruptions, enhancing the protection of low-voltage AC circuits by providing phase-accurate current measurements, thus improving the safety and reliability of the energy supply.
Implementation Method 1
at least one Rogowski coil for determining the magnitude of the electric current of a conductor... which outputs an analog voltage (P1) which is equivalent to the magnitude of the electric current
Implementation Method 2
the Rogowski coil (101) is connected to an analog integrator (102), which is followed by an analog-to-digital converter (103), which converts the integrated analog voltage
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to a Rogowski coil for determining the magnitude of the electric current in a conductor of a low-voltage AC circuit, which outputs an analog voltage equivalent to the magnitude of the conductor's electric current. The Rogowski coil is connected to an analog integrator, followed by an analog-to-digital converter that converts the integrated analog voltage into a digital signal. This digital signal is further processed by a microprocessor in such a way that the phase shift generated by the Rogowski coil and the components downstream of the Rogowski coil is compensated, thus providing phase-correct current values for fault detection to protect the low-voltage AC circuit, in particular for a low-voltage circuit breaker or an arc fault detection unit.