Electricity Meter Load Detection with Floating Reference Node
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Solution Overview
Problem
Traditional electricity meters face challenges in distinguishing between phantom loads and real loads, leading to unsafe conditions and incorrect disconnection of service, as they cannot differentiate between phantom and real load conditions based on voltage measurements alone.
Innovation Solution
The introduction of an electricity meter with a disconnect switch, line-side sense circuit, and load-side sense circuit connected to a floating reference node, which analyzes readings from both circuits to determine the presence of loads and differentiate between cogeneration, borrowed power, or phantom arrangements, preventing incorrect disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional electricity meters use voltage measurements to detect load conditions, then they can identify the presence of loads, but they cannot differentiate between phantom loads and real loads
Solution Approach 1:
The patent segments the reference voltage system into multiple independent reference voltages (first reference voltage for phase A, second reference voltage for phase C). By measuring each phase against its own reference, the system can detect phantom voltages that appear on one phase but not the other, enabling differentiation between phantom and real loads.
Solution Approach 2:
The patent changes the measurement parameter from single-phase voltage magnitude to differential voltage comparison between phases. By comparing the measured voltage of each phase against its reference and analyzing the difference, the system can identify phantom voltage conditions where the measured voltage does not match the reference voltage.
2Device complexity
If electricity meters use a fixed reference voltage for load detection, then the measurement circuit is simple, but phantom voltage readings cannot be eliminated
Solution Approach 1:
The reference voltage system is segmented into phase-specific reference voltages stored in memory. Each phase has its own reference voltage value that can be independently compared against measurements, allowing the system to identify and eliminate phantom voltage readings while maintaining a relatively simple overall architecture.
3Ease of operation
If electricity meters measure voltage against a hard reference, then the measurement circuit is straightforward, but unsafe disconnection conditions may occur due to phantom load detection
Solution Approach 1:
The patent implements feedback by comparing the measured voltage against the stored reference voltage and using this comparison to determine whether to allow disconnection. The system continuously monitors the voltage-reference difference and uses this feedback to make safe disconnection decisions, preventing unsafe disconnection under phantom load conditions.
Data Source
AI summary
An electricity meter includes a disconnect switch connected to a service transformer, a line-side sense circuit, a load-side sense circuit, and a measurement and control circuit. The disconnect switch is configured to receive a phase voltage and an anti-phase voltage from the service transformer. The line-side sense circuit includes a first sense circuit configured to detect the phase voltage delivered to the electricity meter and a second sense circuit configured to detect the anti-phase voltage delivered to the electricity meter, the first sense circuit and the second sense circuit are each connected to a floating reference node. The load-side sense circuit is configured to detect the existence of a phase load and an anti-phase load at a service entrance. The measurement and control circuit is configured to receive a phase output voltage and an anti-phase output voltage from the line-side sense circuit and further configured to receive a phase load output voltage and anti-phase load output voltage from the load-side sense circuitry.