Micro-CPoW Line Current Sensing Without PMU Infrastructure
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Solution Overview
Problem
The high cost of phasor measurement units (PMUs) for monitoring current in power distribution systems due to the need for robust electrical isolation, on-site power, and dedicated communication infrastructure limits their widespread installation in distribution systems.
Innovation Solution
A low-cost, time-synchronized, micro-scale continuous point-on-wave (CPoW) measurement device, referred to as micro-CPoW, which is inductively powered by the current flowing through a distribution conductor and communicates wirelessly, allowing for real-time measurement of instantaneous line current without the need for external support equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PMUs are installed to obtain time-synchronized measurements, then measurement precision and system observability are improved, but device cost and installation complexity increase
Solution Approach 1:
The patent extracts and eliminates the complex support infrastructure (instrument transformers, dedicated power sources, communication cabling) from the PMU system, retaining only the essential measurement functionality that can operate directly on the distribution line
Solution Approach 2:
The measurement device performs multiple functions including voltage measurement, current measurement, frequency measurement, and time-synchronization using a single integrated unit that mounts directly on the distribution conductor, eliminating the need for separate instrument transformers and support equipment
2Measurement precision
If robust electrical isolation is implemented between medium-voltage lines and measurement hardware, then measurement precision is improved, but device cost increases
Solution Approach 1:
The patent uses the distribution conductor itself as an intermediary medium to provide both mechanical mounting and electrical measurement functions, with capacitive coupling providing the necessary electrical isolation without requiring traditional instrument transformers
Solution Approach 2:
The measurement device creates an electrical copy of the distribution line conditions through capacitive coupling, allowing accurate measurements to be obtained without direct galvanic connection to the high-voltage conductor
3Reliability
If on-site power sources are provided for measurement hardware, then reliability of operation is improved, but device cost and installation complexity increase
Solution Approach 1:
The measurement device harvests power directly from the distribution conductor it monitors using electromagnetic induction, eliminating the need for separate on-site power sources and reducing installation complexity while maintaining continuous operational reliability
4Loss of information
If dedicated communication infrastructure is installed to relay measurements, then loss of information is reduced, but device cost and installation complexity increase
Solution Approach 1:
The measurement device utilizes existing communication infrastructure (cellular, Wi-Fi, or power line communication) that is already present in most distribution environments, eliminating the need for dedicated communication cabling while maintaining reliable data transmission
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
The micro-CPoW measurement device enables cost-effective, real-time monitoring of instantaneous line current, facilitating the detection of harmonics, incipient fault conditions, and power quality issues, while eliminating the need for ground-mounted instrument transformers, low-voltage power sources, and dedicated communication cabling.
Implementation Method 1
an inductive energy harvesting circuit configured to power the micro-CPoW measurement device from a power line
Implementation Method 2
a CPoW measurement circuit configured to generate line current measurements from the power line
Data Source
AI summary
A time-synchronized micro-scale continuous point-on-wave (CPoW) measurement device, referred to as micro-CPoW, is provided. The distribution system is an integral part of the electric power system, but not much is known about how it behaves in real-time. To address this knowledge gap, a low-cost, time-synchronized, CPoW measurement system is designed, built, and characterized herein. The purpose of the micro-CPoW measurement device is to monitor the instantaneous electric current flowing through a distribution line in real time. Detection of harmonics, identification of incipient fault conditions, and general power quality monitoring are typical uses for the measured information. Because the micro-CPoW measurement device is self-powered by the line current and communicates wirelessly, it can be installed without ground-mounted instrument transformers, low-voltage power sources, or communications cabling. Thus, this particular design of CPoW module is intended to be installed directly on a power line without the need for external support equipment.