AC Voltage Measurement via Displacement Current Integration

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Solution Overview

Problem

Existing AC voltage measurement devices using capacitive dividers are prone to interference and distortion due to high internal resistance and lead capacitances, which complicates accurate voltage measurement and requires post-measurement correction.

Innovation Solution

A measuring device with low input resistance is used to directly connect to a capacitor, measuring displacement currents proportional to AC voltage changes, and integrating them using an electronic component or microprocessor to provide a signal proportional to the voltage, eliminating the need for an undervoltage capacitor and reducing interference sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a capacitive voltage divider with high internal resistance is used for AC voltage measurement, then the measurement can be performed without additional components, but the lead capacitances and input resistance distort the amplitude and phase of the measured voltage and the device is highly sensitive to interference

Engineering Contradiction:

Improvesimplicity of measurement setupVSAvoidaccuracy of voltage measurement

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

Instead of measuring voltage directly through a high-impedance capacitive divider, the invention inverts the approach by measuring the displacement current flowing through the capacitor. This current measurement is then integrated to obtain the voltage, thereby avoiding the problems of high internal resistance and interference sensitivity associated with traditional voltage measurement methods.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention replaces the traditional electrical voltage measurement system with a current measurement and integration system. By using an integration device (analog or digital) to convert the measured displacement current into voltage information, the system avoids the harmful effects of high impedance and lead capacitance that pl conventional voltage measurement circuits.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If a capacitive voltage divider is used for voltage measurement, then voltage can be measured, but the method is highly sensitive to interference and requires post-measurement correction

Engineering Contradiction:

Improvevoltage measurement capabilityVSAvoidsensitivity to interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The invention performs the measurement action in advance by measuring the displacement current before it is affected by interference and lead capacitance effects. The current measurement is performed directly at the capacitor terminals, and the integration process subsequently reconstructs the voltage information in a form that is immune to interference and does not require post-measurement correction.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If an undervoltage capacitor is connected in series to create a capacitive voltage divider, then voltage measurement is enabled, but the device complexity increases and the measurement becomes sensitive to interference

Engineering Contradiction:

Improvevoltage measurement capabilityVSAvoidnumber of components

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The invention extracts and eliminates the undervoltage capacitor component from the measurement system. By measuring the displacement current directly through the existing capacitor and integrating it, the system achieves voltage measurement capability without requiring the additional undervoltage capacitor that would increase device complexity and introduce more potential sources of interference.

Inventive Principle:

Principle #2Taking out (Extraction)

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 precise, interference-immune AC voltage measurement without distorting the amplitude or phase, enabling accurate voltage determination with high precision and protection from electromagnetic interference.

Implementation Method 1

a capacitor to which the AC voltage to be measured is applied at its first connection

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

In order to determine the AC voltage to be measured from this displacement current, it must be integrated over time. This is done using the integration device

Methodology Applied

Scientific EffectIntegration:

Data Source

PatentEP2872903B1Measuring device, use of the measuring device, and method for measuring an alternating voltage

Publication Date: 2023.07.26 SIEMENS AG

AI summary

The invention relates to a measuring device for measuring a voltage by means of a capacitor that has the voltage to be measured applied to the first terminal thereof, in which external connection points of the measuring device are provided for direct connection to the second terminal of the capacitor and earth potential, wherein the voltage measuring device has an electronic measuring device that is connected to the external connection points and has low input resistance, and an integration device is arranged downstream of said electronic measuring device. The invention further relates to a use of the measuring device, and a method for measuring a voltage.