Polyphase VA Metering via Digital Phase Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electricity metering technologies face inaccuracies in measuring volt-ampere (VA) hours, especially in polyphase systems with harmonics, leading to inefficiencies in determining the size of power sources and delivery equipment, as current methods for calculating VA in single phase systems do not translate effectively to polyphase systems.
Innovation Solution
A polyphase electricity meter that automatically calculates source or load VA using digitally sampled voltage and current signals, employing an A/D converter and processing circuit to generate digital samples and perform arithmetic or vector VA calculations, allowing users to select between source and load VA measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-phase VA calculation methods are used in polyphase systems, then the calculation process is simple, but the measurement precision deteriorates due to harmonics and phase differences
Solution Approach 1:
The patent segments the polyphase system into individual phase measurements, where each phase's voltage and current are measured separately. The total VA is calculated by summing the VA of each phase individually (VA_total = VA_phase1 + VA Phase2 + VA Phase3), rather than measuring total voltage and current simultaneously. This segmentation approach maintains calculation simplicity while improving accuracy in polyphase systems with harmonics.
2Measurement precision
If watt-hour measurements are used, then the actual energy consumption is accurately measured, but the sizing of power delivery equipment becomes inaccurate due to reactive power components
Solution Approach 1:
The patent introduces VA (volt-ampere) measurement as an intermediary quantity that bridges the gap between actual energy consumption (watt-hours) and source sizing requirements. While watt-hours measure the actual energy consumed by the load, VA measurement captures the total apparent power that determines the sizing of transformers and power lines. This intermediary measurement allows utility companies to properly allocate costs and size infrastructure without requiring complex reactive power analysis.
3Loss of information
If VA measurement capability is added to meters, then source sizing information is obtained, but the device complexity increases
Solution Approach 1:
The patent merges the VA measurement function with existing watt-hour metering capabilities by using the same voltage and current measurement circuits. The meter already measures voltage and current for watt-hour calculation; the invention simply adds a computational path that multiplies instantaneous voltage and current to obtain VA, then integrates over time for VA-hours. This merging approach provides source sizing information without requiring separate measurement hardware, thereby minimizing the increase in device complexity.
Data Source
AI summary
An arrangement includes an A/D converter and a processing circuit. The A/D converter is configured to generate digital samples of voltage and current waveforms in a polyphase electrical system. The processing circuit is operably coupled to receive the digital samples from the A/D converter. The processing circuit is further configured to combine a value substantially equal to two times the magnitude of the phase A current sample with the phase C current sample to generate a first value, and generate a VA calculation using the first value and at least one other value. The processing circuit is further configured to provide information representative of the VA calculation to one of a group consisting of a display, a communication circuit, and a billing calculation unit.