Energy Meter Relay State Detection via Voltage Measurement
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Solution Overview
Problem
Existing electrical energy meters struggle to reliably detect the state of cut-off relays and circuit breakers, especially when the downstream load is high, due to parasitic noise and mechanical stress, which can lead to inaccurate measurements and potential safety hazards.
Innovation Solution
An electrical energy meter with a measurement stage comprising a phase current sensor, series measurement impedances, and a voltage source, which generates a voltage that differs based on the state of the cut-off relay, allowing for accurate detection of the relay's state and circuit breaker operation through signal processing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensor is used to detect the state of the cut-off relay, then the relay state can be determined from measured current, but when the downstream load is very high, the current through the sensor is almost zero even if the relay is closed, making detection unreliable
Solution Approach 1:
The patent introduces an intermediary measurement circuit consisting of a voltage source and measurement impedances that generates a measurable voltage signal across the cut-off relay. This intermediary mechanism allows detection of the relay state without relying on current flow through the relay, thereby solving the problem of undetectable current under high load conditions.
Solution Approach 2:
The patent replaces the current-based detection mechanism with a voltage-based measurement system. By using a voltage source and measurement impedances to generate a voltage signal that reflects the relay state, the system substitutes the mechanical current flow detection with an electrical voltage measurement approach that remains effective regardless of load conditions.
2Reliability
If the cut-off relay is open to prevent short-circuiting, then safety is improved, but parasitic noise from installation equipment can be propagated by antenna effect, disturbing measurements aimed at detecting circuit breaker state
Solution Approach 1:
The patent extracts the measurement function from the current path and places it in a separate voltage measurement circuit. By taking out the measurement mechanism from the high-current path and implementing it through a dedicated voltage measurement stage with measurement impedances, the system eliminates the antenna effect that occurs when measurement conductors are part of the high-current path with the cut-off relay open.
3Extent of automation
If bistable relays are used for cut-off functionality, then remote control capability is achieved, but the relays can open or close unexpectedly due to mechanical stress or electromagnetic stress
Solution Approach 1:
The patent implements a feedback mechanism by continuously measuring the voltage across the cut-off relay and comparing it with expected values corresponding to open and closed states. This feedback allows the system to verify the actual relay state and detect unexpected changes, providing monitoring and alerting capabilities that enhance the reliability of the automated control system.
Data Source
Figure 1~2
AI summary
The invention relates to an electrical energy meter (1) comprising a measurement stage (2) having a phase current sensor (9) connected in series to a cutoff relay (13), two serial measurement impedance components (Z, R) connected in parallel to the sensor (9) and to the relay (13), a measurement means (14) for measuring the electrical potential between the measurement impedance components (Z, R), and an additional power source (Vadd) connected in series to the measurement impedance components (Z, R). The invention further relates to a method for detecting a state of a circuit breaker of an apparatus connected to such a meter.