Electricity Meter Circuit Breaker State Detection via Impedance
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Solution Overview
Problem
Existing electricity meters face challenges in reliably and cost-effectively detecting the state of a circuit breaker when the internal cut-off device is open, particularly due to the need for expensive transformers and the lack of suitable cut-off members with multiple entry points, which also hinder PLC signal transmission.
Innovation Solution
An electricity meter with a detector circuit that uses a coupling capacitor to apply a reference voltage and measure impedance, allowing detection of the circuit breaker state without a transformer, and incorporating a processor to evaluate impedance and determine the breaker's state, compatible with both single-phase and multi-phase meters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer is used to provide electrical isolation for detecting circuit breaker state, then detection reliability is improved, but cost and device size increase
Solution Approach 1:
The patent extracts the detection function from the main power circuit by using a separate detector circuit that operates on a different principle (impedance measurement rather than direct current measurement). This allows detection without requiring a transformer for electrical isolation, reducing device complexity while maintaining reliability
Solution Approach 2:
The patent introduces an intermediary measurement approach by using impedance measurement as a mediator to infer circuit breaker state. Instead of directly measuring current (which would require transformer isolation), the system measures impedance changes that correlate with circuit breaker state, eliminating the need for expensive isolation transformers
2Difficulty of detecting and measuring
If a cut-off member with three entry points is used for detection, then detection capability is improved, but manufacturing maturity and availability worsen
Solution Approach 1:
The patent segments the detection function into separate components: the existing two-entry cut-off member remains unchanged, while a separate detector circuit performs the detection function. This avoids the need for a complex three-entry cut-off member that isn't yet manufactured, using instead standard available components
Solution Approach 2:
The detector circuit serves multiple functions: it detects circuit breaker state, measures impedance, and operates without interfering with PLC communications. This multi-functionality compensates for not using a specialized three-entry cut-off member, achieving detection capability through a more universally applicable approach
3Measurement precision
If current measurement is used to detect circuit breaker state, then detection accuracy is improved, but PLC signal transmission is interfered with
Solution Approach 1:
The detector circuit operates periodically or on-demand rather than continuously measuring current. It activates only when needed to detect circuit breaker state, minimizing interference with continuous PLC communications while maintaining detection accuracy when required
Solution Approach 2:
The patent uses impedance measurement as an intermediary approach that indirectly indicates circuit breaker state without directly measuring current in the power path. This intermediary measurement method avoids the harmful effect of current measurement interference with PLC signals, achieving detection accuracy through a non-intrusive measurement principle
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
Enables robust, reliable, and inexpensive detection of the circuit breaker state while the internal cut-off device is open, without interfering with PLC communication, and is applicable to various types of internal cut-off devices.
Implementation Method 1
coupling components comprising a coupling capacitor and connected, downstream from the internal cut-off device, to an injection conductor selected from the phase conductor and the neutral conductor, and an injection component arranged to apply a reference voltage to the injection conductor via the coupling capacitor
Implementation Method 2
a measurement component arranged to measure a measurement voltage across the terminals of one of the connection components, the measurement voltage being representative of an impedance of the installation
Data Source
AI summary
An electricity meter includes at least one phase conductor and a neutral conductor, an internal cut-off device includes at least one phase cut-off member connected in series with the phase conductor, and at least one detector circuit for acting when the internal cut-off device is open to detect whether a circuit breaker of the installation is open or closed. The electricity meter includes coupling components connected, downstream from the internal cut-off device, to an injection conductor selected from the phase conductor and the neutral conductor, and an injection component arranged to apply a reference voltage to the injection conductor via the coupling capacitor; and connection components connected to a measurement conductor selected from the phase conductor and the neutral conductor, and a measurement component arranged to measure a measurement voltage across the terminals of one of the connection components, the measurement voltage being representative of an impedance of the installation.