Non-Contact Voltage Measurement Using Dual-Frequency Current Analysis
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Solution Overview
Problem
Existing non-contact voltage measurement methods, such as those described in PTL 1, suffer from inaccuracies in measuring voltage applied to a core wire through an insulator due to variations in capacitance caused by factors like temperature and humidity, posing risks of electric shock and short circuits.
Innovation Solution
A measurement apparatus that injects an injection current with a second frequency into a core wire through an insulator, measures a composite current composed of the injection and leakage currents, and calculates active and reactive powers to determine the voltage applied to the core wire with higher accuracy, distinguishing between the two currents based on their frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a clip is connected to a live wire section to measure voltage, then measurement can be performed, but there is a risk of electric shock to the operator and short circuit
Solution Approach 1:
The patent introduces an insulator as an intermediary between the measurement device and the live wire section. The insulator allows the measurement probe to approach the conductor without direct contact, enabling voltage measurement through capacitive coupling while preventing electric shock and short circuit risks to the operator
Solution Approach 2:
The patent replaces the mechanical contact-based measurement method with a non-contact capacitive coupling method. Instead of using a clip that physically contacts the live wire, the measurement is performed through the insulator utilizing electric field coupling, thereby eliminating the harmful effects of direct contact
2Ease of operation
If voltage is measured through an insulator in contact with a core wire, then non-contact measurement is enabled, but measurement accuracy deteriorates due to capacitance variations caused by temperature and humidity
Solution Approach 1:
The patent compensates for the deterioration of measurement accuracy by introducing correction parameters that account for temperature and humidity effects on capacitance. The measurement system dynamically adjusts for these environmental variations, maintaining high measurement precision while preserving the ease of non-contact operation through the insulator
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
Enables precise measurement of voltage and phase of leakage current from a cable sheath with reduced environmental influences, enhancing safety and accuracy while avoiding direct contact with live wires.
Implementation Method 1
an insulator, through which the measurement probe is to be inserted, is to be in contact with the core wire
Implementation Method 2
a coupling capacitance is obtained based on an input signal, which is divided between the insulator and the coupling capacitance between electrodes
Data Source
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AI summary
A measurement apparatus includes a controller configured to inject an injection current with a second frequency through an insulator into the core wire, to which the voltage to be measured, with a first frequency, is applied, acquire a composite current in which the injection current and a leakage current of the voltage to be measured having leaked out of the core wire through the insulator are superimposed in a circuit unit, calculate, by analyzing the composite current, measured active and reactive powers equivalent to active and reactive powers based on a contribution of the voltage to be measured, calculate the voltage to be measured, based on the measured active and reactive powers, the first and second frequencies, a voltage of the injection current, and a current effective value of the leakage current, and output the calculated voltage to be measured.