Current Sensor Capacitive Electrode Parasitic Voltage Filtering
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Solution Overview
Problem
Current sensors in three-phase electrical networks face challenges in reliably detecting fuse blowing due to parasitic voltage induction and false alarms, leading to non-detection or incorrect identification of fuse issues.
Innovation Solution
A current sensor with a circular capacitive electrode and a comparison circuit that includes an analog comparator and analog-digital converter, capable of distinguishing between voltages induced by the target conductor and parasitic currents from adjacent conductors, using a threshold determined by the average of individual and adjacent conductor characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current sensor with voltage detection means is installed on each conductor to detect fuse blowing, then the ability to detect fuse conditions is improved, but false alarms are triggered due to parasitic voltage induction from neighboring conductors
Solution Approach 1:
The patent introduces an intermediary comparison circuit that mediates between the voltage detection means and the fuse status determination. This circuit compares the detected voltage with reference voltages and only triggers a fuse blown indication when the voltage exceeds both reference values, thereby filtering out parasitic inductions from neighboring conductors while maintaining reliable fuse detection capability
Solution Approach 2:
The patent changes the parameter threshold for fuse detection by using dual reference voltages instead of a single threshold. The comparison circuit evaluates both the absolute voltage level and the differential voltage level, transforming the detection criterion from a simple threshold comparison to a multi-parameter evaluation that distinguishes genuine fuse blowing from parasitic interference
2Measurement precision
If voltage detection means are added to the current sensor to detect downstream voltage, then the ability to identify blown fuses is improved, but non-detection occurs due to parasitic current induction masking the voltage signal
Solution Approach 1:
The comparison circuit serves as an intermediary that processes the detected voltage signal and distinguishes it from parasitic current effects. By comparing the signal voltage and differential voltage against reference values, the circuit acts as a filter that eliminates false negative readings caused by parasitic inductions
Solution Approach 2:
The patent implements a feedback mechanism where the comparison circuit continuously monitors the detected voltage and provides feedback signals indicating fuse status. The dual-reference voltage comparison creates a feedback loop that adjusts the detection sensitivity dynamically, ensuring accurate detection even in the presence of varying parasitic current conditions
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
Substantially reduces the risk of non-detection and false alarms by accurately identifying fuse blowing events, enabling timely and precise monitoring of electrical network conditions.
Implementation Method 1
a Rogowski coil, on each conductor in the branch circuit to measure the current flowing through that conductor
Implementation Method 2
it is known to equip a current sensor with means for detecting voltage across the terminals of the Rogowski coil
Implementation Method 3
each sensor is subject, across the coil, to a parasitic voltage induced by neighboring conductors
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
This current sensor (2) comprises a measuring toroid (22), arranged in a housing (20) positioned around an electrical conductor (12) capable of transmitting an electric current, and means (24) for detecting a voltage in the electrical conductor. The detection means (24) are configured to surround the electrical conductor (12) when the current sensor (2) is installed.