Smart Meter Grid Impedance Detection via Thevenin Calculation
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Solution Overview
Problem
Existing methods cannot accurately determine the impedance of an electrical power distribution grid from measurements taken by each electrical power meter, specifically the resistance and reactance of the segment of cable from the utility company's transformer to the meter.
Innovation Solution
The method involves measuring RMS voltage and current values at two different times by a smart electric meter, using a computing device to calculate the equivalent grid impedance based on Thevenin's theorem, considering the head-end voltage remains unchanged, and applying a statistical adjustment procedure to converge on a stable impedance value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impedance measurement methods from prior art are used, then meter bypass detection or load monitoring is achieved, but accurate determination of grid impedance from customer meter measurements is not possible
Solution Approach 1:
The invention enables customer meters to autonomously measure and process voltage and current data to calculate grid impedance locally. The meter itself performs the measurement function rather than requiring external measurement equipment, allowing each customer meter to contribute to grid impedance determination using Thevenin's theorem with locally available measurements.
Solution Approach 2:
The invention transforms the approach by changing from direct impedance measurement to calculating impedance through parameter relationships. By measuring voltage and current parameters and applying Thevenin's theorem, the system derives grid impedance without requiring direct access to grid equipment, thus enabling measurement where previously it was impossible.
2Productivity
If traditional impedance measurement methods are used, then grid monitoring is limited, but comprehensive grid monitoring from distributed customer meters is achieved
Solution Approach 1:
The invention makes customer meters multi-functional by enabling them to perform not only their primary billing function but also grid impedance measurement and monitoring. This universal approach allows distributed meters to contribute to overall grid monitoring, significantly expanding coverage without adding dedicated measurement devices at every location.
Solution Approach 2:
The invention segments the grid monitoring function across multiple distributed customer meters rather than using a centralized measurement system. Each meter independently measures local voltage and current and calculates impedance, with results aggregated to provide comprehensive grid-wide monitoring coverage.
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 allows for accurate detection of grid impedance, enabling the identification of technical losses, fault detection, and inventory validation, improving grid monitoring and fault localization.
Implementation Method 1
an impedance detector is coupled to the electrical power distribution grid to detect an actual impedance of the electrical power distribution grid
Data Source
Figure 1~2
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AI summary
The method comprises measuring RMS voltage VM1, VM2; RMS current IM1, IM2; and power factor PF1, PF2 values at a first time t1 and at a second time t2 using a meter (13). The method also comprises running an algorithm which determines a value of the equivalent grid impedance ZTH from a transformer (10) to the meter (13) considering that ZTH is similar to the grid impedance calculated according to Thevenin's theorem; that the line head-end voltage according to Thevenin VTH remains unchanged at t1, t2, and provides voltages as a result of implementing ZTH * IM1 + VM1 and ZTH * IM2 + VM2; and that RMS voltages VM and RMS currents IM include complex terms due to the alternating current grid, wherein said algorithm implements ZTH = (VM1 - VM2) / (IM2-IM1), and the acquisition of VM1, VM2, IM1, IM2, PF1, PF2 and the running of the algorithm are performed by means of a computing device.