High Voltage Phasing Voltmeter Common Mode Rejection
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Solution Overview
Problem
Existing high voltage phasing voltmeters face inaccuracies due to electromagnetic interference, stray capacitance, and design uncertainties, leading to unsafe and unreliable measurements for electrical line maintenance workers.
Innovation Solution
A high voltage phasing voltmeter design featuring insulated handheld shields with conductive coatings connected to a meter ground circuit, a high impedance circuit with series resistor and capacitor, and a common mode rejection differential input amplifier, along with a battery-powered circuit and range selection capabilities, to enhance measurement accuracy and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional high voltage probes with simple resistance connections are used, then the device complexity is low and ease of manufacture is high, but measurement precision deteriorates due to electromagnetic interference, stray capacitance, and common mode errors
Solution Approach 1:
The patent introduces a common mode rejection amplifier as an intermediary device between the high voltage probes and the measurement system. This amplifier actively counteracts common mode errors, electromagnetic interference, and stray capacitance effects, thereby improving measurement accuracy without requiring fundamental changes to the probe structure
Solution Approach 2:
The patent changes the electrical parameters of the measurement circuit by incorporating high impedance connections and balanced differential signaling. This transforms the circuit's response to high voltage fields, reducing susceptibility to electromagnetic interference and stray capacitance while maintaining reasonable device complexity
2Reliability
If high voltage probes are designed with adequate insulation and safety features, then safety is improved, but device complexity increases due to additional insulation layers and safety circuits
Solution Approach 1:
The patent applies equipotential shielding by surrounding the high voltage probe elements with conductive shields maintained at ground potential. This creates equipotential regions that prevent electrical breakdown and arcing, improving safety without requiring complex multi-layer insulation structures
Solution Approach 2:
The common mode rejection amplifier serves as an intermediary safety mechanism by detecting and rejecting common mode voltages that could indicate insulation failures or arcing conditions. This provides an additional layer of safety through electrical rather than purely physical means
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 solution provides accurate and safe phase-to-phase voltage measurements by reducing common mode errors and ensuring stable ground connections, thus preventing misguidance and injury during electrical line maintenance.
Implementation Method 1
The amplifier comprises a common mode rejection differential input amplifier
Implementation Method 2
an inner surface of each tube includes a conductive coating
Implementation Method 3
The electrode is connected in series with a resistor and a capacitor or a resistor potted in the tube
Data Source
AI summary
A high voltage phasing voltmeter comprises first and second probes. Each probe comprises an insulated handheld shield supporting an electrode for contacting a high voltage electrical conductor. The electrode is connected in series with a resistor and a capacitor. A meter comprises a housing enclosing an electrical circuit for measuring phasing voltage. The electrical circuit comprises an input circuit for connection to the first and second probes and an amplifier connected between the input circuit and a display. The amplifier measures voltage across the electrodes to provide an indication on the display.