Current Measurement Apparatus for Live and Neutral Conductors
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Solution Overview
Problem
Current current measurement technologies face challenges in simultaneously measuring currents in live and neutral conductors with high accuracy and responsiveness, particularly in detecting ground faults and arc faults, which are critical for safety and efficiency in electrical systems, while also being cost-effective and compact.
Innovation Solution
The development of current measurement apparatus comprising first and second measurement devices that operate simultaneously to measure currents in live and neutral conductors, allowing for real-time determinations and control, including the detection of differences between these currents to identify fault conditions, and featuring adaptive threshold settings and self-learning capabilities for improved fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current shunt is used to measure high current values, then measurement accuracy and linearity are improved, but the device becomes invasive and provides no isolation
Solution Approach 1:
The patent uses a current transformer as an intermediary device that provides galvanic isolation between the high-current primary circuit and the low-current secondary measurement circuit. The current transformer acts as a mediator that transfers current information from the primary side to the secondary side through electromagnetic induction, enabling accurate measurement without direct electrical connection, thus resolving the contradiction between measurement accuracy and isolation requirements.
2Ease of operation
If a current transformer is used to provide isolation and reduce invasiveness, then ease of operation is improved, but the device can only measure AC and suffers from non-linearity and phase error
Solution Approach 1:
The patent combines multiple measurement devices - a current transformer for AC measurement and isolation, and a Hall effect sensor for DC and AC measurement - into a single integrated measurement system. The current transformer handles AC current measurement with isolation, while the Hall effect sensor supplements measurement capabilities for DC and AC currents. The controller integrates signals from both devices, merging their respective strengths to achieve comprehensive current measurement with both isolation and accuracy across AC and DC ranges.
3Adaptability or versatility
If a Hall current probe is used to measure both AC and DC, then versatility is improved, but non-linearity and temperature drift occur in open loop configuration
Solution Approach 1:
The patent employs a closed-loop feedback configuration for the Hall effect sensor where the sensor output is fed back through a feedback winding on the magnetic core. The controller adjusts the feedback current to cancel the measured current, creating a null-balance condition that linearizes the measurement and compensates for temperature drift. This feedback mechanism transforms the inherently non-linear Hall effect into a linear measurement system with improved temperature stability.
4Reliability
If simultaneous measurement of live and neutral conductor currents is implemented, then fault detection capability is improved, but device complexity increases
Solution Approach 1:
The patent designs the measurement system with multi-functional capability where the same current measurement devices and controller serve multiple purposes: measuring live and neutral currents for power calculation, detecting ground faults through current imbalance, identifying arc faults through waveform analysis, and providing over-current protection. The controller performs diverse functions including signal processing from multiple sensors, mathematical calculations for power parameters, fault detection algorithms, and control operations, making the system universal and reducing overall complexity despite handling multiple measurement tasks.
Data Source
AI summary
The present invention relates to current measurement apparatus. The current measurement apparatus comprises first and second measurement devices with each of the first and second measurement devices being operative to measure current in a respective one of a live conductor and a neutral conductor substantially simultaneously. The current measurement apparatus is operative to make plural different determinations in dependence on the substantially simultaneous current measurements.