Rogowski Transducer Dual-Screen Interference Reduction
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Solution Overview
Problem
Rogowski coils face interference from high-frequency voltages and voltage transients due to capacitive coupling with external conductors, leading to measurement errors, and existing screening solutions compromise bandwidth and signal-to-noise ratio.
Innovation Solution
A dual-screening approach is implemented, where an outer screen bypasses interference currents to ground and an inner screen acts as the coil return path, separate from the integrator input, to reduce capacitive coupling and maintain high bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single screen is fitted around the Rogowski coil to reduce interference from high-frequency voltages, then measurement accuracy is improved, but bandwidth is reduced and signal-to-noise ratio deteriorates
Solution Approach 1:
The screening function is divided into two separate screens: an outer screen for interference protection and an inner screen for signal return path. This segmentation allows each screen to perform its specific function optimally without compromising bandwidth, resolving the contradiction between measurement accuracy and bandwidth that plagues single-screen designs.
Solution Approach 2:
The outer screen acts as an intermediary element between external high-frequency voltage sources and the Rogowski coil, providing electrostatic shielding without directly interfering with the signal path. This intermediary structure protects the measurement while maintaining bandwidth integrity.
2Adaptability or versatility
If the coil cross-section diameter is reduced to enable insertion in cramped situations, then adaptability is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
The solution moves the signal return path from the traditional central axial position to a radial dimension by using the inner screen as the return path. This dimensional change allows the coil to maintain a thin cross-section for adaptability while preserving the magnetic coupling efficiency and signal-to-noise ratio through the screen-coil capacitive coupling mechanism.
3Reliability
If screening is added to prevent interference, then reliability is improved, but device complexity increases
Solution Approach 1:
The inner screen serves dual functions: it provides electrostatic shielding from external interference and simultaneously acts as the signal return path for the Rogowski coil. This multi-functionality reduces overall device complexity by combining two necessary functions into a single component, while the outer screen provides dedicated interference protection.
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 configuration effectively reduces interference while maintaining high bandwidth and signal-to-noise ratio, avoiding the limitations of single-screen designs and complex constructions.
Implementation Method 1
If the voltages have relatively high rates of change then, due to the capacitive coupling between an external conductor and the coil, displacement currents will be injected into the coil
Implementation Method 2
a screen is generally fitted around the coil as described in 'The effect of electrostatic screening of Rogowski coils for wide-bandwidth current measurement in power electronic applications'
Implementation Method 3
The coil has a plurality of turns. In order to measure the value of a current I (Amps) in an electrical conductor, the Rogowski coil is placed around the conductor in order to induce a voltage E (V) in the coil. The induced voltage in the coil is proportional to the rate of change of the measured current dI/dt
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A current measuring device is disclosed, comprising: an electrically conductive coil having a first end and a second end; a first screen surrounding the coil and arranged to provide a current path from the second end of the coil to a location proximal to the first end of the coil; and a second screen surrounding the first screen and the coil.