Capacitive Cable Voltage Sensing Without Contact or Centering

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Solution Overview

Problem

Existing non-contact voltage measurement devices are limited to insulated cables, lack adaptability to various voltage ranges, require cumbersome centering, and are bulky due to multiple voltage sensors, making them less user-friendly and versatile.

Innovation Solution

A single-component system using a capacitor and voltage sensor with high impedance and low capacitance, coupled capacitively to the cable, allowing non-contact voltage measurement on any type of cable and any voltage range, without physical contact, and utilizing a capacitive voltage divider for high-voltage reduction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple voltage sensors are used for non-contact voltage measurement, then measurement coverage and reliability are improved, but device size and complexity increase

Engineering Contradiction:
Improvemeasurement reliabilityVSAvoiddevice size
Core Design Contradiction:
ReliabilityVSVolume of moving object

Solution Approach 1:

The patent combines multiple voltage sensing functions into a single voltage sensor by using a capacitive divider network. The capacitive divider splits the voltage signal in a controlled manner, allowing one sensor to effectively measure multiple voltage levels or ranges, thereby reducing the number of sensors needed while maintaining measurement reliability

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The voltage sensor is designed with multi-functionality through the capacitive divider configuration, enabling it to measure different voltage ranges and types (insulated and uninsulated cables) using the same sensor component, thus eliminating the need for multiple specialized sensors

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Measurement precision

If existing non-contact voltage measurement devices are used, then insulated cable voltage measurement is achieved, but adaptability to different cable types and voltage ranges is limited

Engineering Contradiction:
Improvevoltage measurement capabilityVSAvoidcable type adaptability
Core Design Contradiction:
Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The device achieves universality by using a capacitive coupling mechanism that works with both insulated and uninsulated cables. The capacitive divider network can be configured to measure different voltage ranges, making the same device adaptable to various cable types and voltage levels without requiring specialized sensors for each application

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention allows parameter changes in the capacitive divider configuration to adapt the measurement range and characteristics. By adjusting the capacitor values in the divider network, the device can be tuned to measure different voltage ranges and cable types, providing versatility without changing the fundamental measurement mechanism

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If existing non-contact voltage measurement devices are used, then voltage measurement is achieved, but cable centering requirements make operation cumbersome

Engineering Contradiction:
Improvevoltage measurement accuracyVSAvoidcable positioning ease
Core Design Contradiction:
Measurement precisionVSEase of operation

Solution Approach 1:

The capacitive coupling mechanism provides self-aligning properties that automatically compensate for cable position variations. The electric field distribution in the capacitive divider naturally adapts to the cable's position, eliminating the need for precise manual centering while maintaining measurement accuracy, thus making the device easier to operate

Inventive Principle:
Principle #25Self-service

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 system provides versatile, compact, and user-friendly non-contact voltage measurement capable of handling any cable type and voltage range, ensuring safety and accuracy by eliminating the need for physical contact and reducing device size.

Implementation Method 1

The main electrode can be capacitively coupled to said cable and the device can be free of galvanic contact with said cable

Methodology Applied
Scientific EffectCapacitive coupling: Capacitance

Implementation Method 2

the voltage sensor can have high impedance and low capacitance

Methodology Applied
Scientific EffectElectrical Impedance: Electrical Resistance

Implementation Method 3

the capacitor in the measuring instrument can be arranged to reduce the voltage on the main electrode relative to the catenary voltage

Methodology Applied
Scientific EffectCapacitive voltage divider: Capacitance

Implementation Method 4

behaves like a capacitive voltage divider

Methodology Applied
Scientific EffectVoltage division: Ohm's Law

Implementation Method 5

the voltage sensor can have high impedance and low capacitance

Methodology Applied
Scientific EffectHigh impedance measurement: Electrical Resistance

Data Source

PatentEP4242668B1Device for contactless voltage measurement
Publication Date: 2026.01.21 SNCF RESEAU
  • EP4242668B1 patent drawingFigure 1~2
  • EP4242668B1 patent drawingFigure 3~4A
  • EP4242668B1 patent drawingFigure 4B~5

AI summary

The invention relates to a device (100) for the non-contact measurement of a voltage of a cable (102) defined with respect to a reference potential (114), said device (100) comprising an enclosure (104), connected to the reference potential (114), comprising: - an opening (106) oriented towards said cable (102), - an internal volume (108) comprising: ▪ an electrode (110), called the main electrode (110), positioned at the opening (106) and with respect to said cable (102), ▪ a measuring means (112) arranged to measure a voltage between the main electrode (110) and said enclosure (104).