Actively Calibrated Capacitive Voltage Transducer for PMU Accuracy
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Solution Overview
Problem
Current methods for high and medium voltage voltage sensing in smart grid infrastructure are costly and lack accurate line-mounted solutions, with existing technologies like electrostatic field and capacitively coupled measurements failing to meet the accuracy standards required for Phasor Measurement Units (PMUs).
Innovation Solution
The development of actively calibrated line-mounted capacitive voltage transducers (LMCVT) that inject a perturbation voltage onto a capacitive probe, using a capacitive sensor and digital signal processor to track real-time changes in capacitance and estimate line voltage, enabling accurate and cost-effective high and medium voltage sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If capacitively coupled measurements are used for voltage sensing, then cost is reduced and deployment is simplified, but measurement precision deteriorates and cannot meet PMU accuracy standards
Solution Approach 1:
The patent implements active calibration by injecting a perturbation voltage and measuring the response to determine probe capacitance in real-time. This feedback mechanism continuously corrects for capacitance variations, maintaining measurement precision while using simple capacitively coupled hardware, thus resolving the contradiction between low cost and high accuracy.
Solution Approach 2:
The system dynamically changes the operating parameters by injecting perturbation voltages at different frequencies to actively probe and track capacitance variations. This allows the system to adapt to changing environmental conditions and maintain accuracy without requiring expensive fixed-calibration hardware.
2Device complexity
If offline calibration is used for capacitive probes, then device complexity is reduced, but measurement precision deteriorates due to capacitance drift over time
Solution Approach 1:
The patent replaces static offline calibration with dynamic online calibration using feedback from perturbation voltage measurements. The system continuously monitors capacitance changes and adjusts measurements in real-time, eliminating accuracy degradation while keeping the additional hardware complexity minimal.
Solution Approach 2:
The calibration system is self-contained and automatically performs capacitance tracking without external intervention. The probe self-calibrates by measuring its own capacitance through perturbation voltage injection, eliminating the need for periodic manual recalibration while maintaining high precision.
3Measurement precision
If perturbation voltage injection is implemented for active calibration, then measurement precision is improved through real-time capacitance tracking, but device complexity increases due to additional signal processing requirements
Solution Approach 1:
The system uses periodic perturbation voltage injection at known frequencies to probe capacitance. By using frequency-domain separation, the calibration signals are easily distinguished from power frequency measurements, simplifying the signal processing required and reducing computational complexity while maintaining high precision.
4Productivity
If line-mounted capacitive transducers are deployed without substation infrastructure, then productivity and deployment speed are improved, but measurement precision deteriorates due to environmental sensitivity
Solution Approach 1:
The patent compensates for environmental sensitivity by actively tracking capacitance parameter changes in real-time. The system measures actual capacitance values under operating conditions and uses this information to correct measurements, allowing accurate readings without controlled environmental conditions or substation infrastructure.
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
This approach reduces voltage measurement errors by an order of magnitude, allowing for the widespread deployment of PMUs on medium to high voltage transmission lines, improving estimation time and accuracy without the need for parametric models or offline calibration.
Implementation Method 1
measuring, using a capacitive sensor, a retrieved perturbation voltage, where the retrieved perturbation voltage is dependent on a capacitance between the capacitive probe and a ground capacitance
Data Source
AI summary
A method of estimating a line voltage is provided that includes configuring a capacitive probe to a power line, injecting a perturbation voltage onto the capacitive probe, where the perturbation voltage has a different frequency than a frequency of the line voltage, measuring, using a capacitive sensor, a retrieved perturbation voltage, where the retrieved perturbation voltage is dependent on a capacitance between the capacitive probe and a ground capacitance, using an appropriately programmed computer to track real time changes in the capacitance of the capacitive probe, and estimating a line voltage.