Capacitive Voltage Sensor with Compensated Insulating Layers
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Solution Overview
Problem
Existing voltage sensors using capacitive dividers with insulating layers made of materials like elastomeric silicone are not accurate due to temperature-dependent dielectric constants, leading to significant variations in capacitance and voltage estimation errors.
Innovation Solution
The electrical accessory employs a capacitive voltage divider with at least two insulating layers having dielectric constants with opposite temperature dependency coefficients, allowing for compensation of temperature-induced variations, thereby reducing capacitance changes to less than 1% within the intended temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single insulating layer with high thickness is used to withstand high voltage, then electrical stress resistance is improved, but measurement precision deteriorates due to temperature-dependent dielectric constant variations
Solution Approach 1:
The patent applies composite materials by combining multiple insulating layers with different dielectric constant temperature dependencies. Specifically, it uses a first insulating layer with positive temperature dependency and a second insulating layer with negative temperature dependency, creating a composite structure that maintains stable capacitance across temperature ranges while withstanding high voltage stresses.
Solution Approach 2:
The patent changes the dielectric parameter (dielectric constant) temperature dependency by selecting materials with opposite temperature coefficients. By adjusting the thickness ratio and material composition of the two insulating layers, the overall capacitance temperature dependency is compensated, achieving stable voltage measurements despite temperature variations.
2Strength
If insulating layer thickness is increased to handle high voltage, then electrical stress resistance is improved, but capacitance stability deteriorates due to dimensional changes with temperature
Solution Approach 1:
The patent uses composite insulating layers with different thermal expansion characteristics. The first insulating layer (e.g., epoxy resin) and second insulating layer (e.g., silicone rubber) have different linear expansion coefficients, and their combination compensates for dimensional changes, maintaining stable capacitance values across temperature ranges.
Solution Approach 2:
The patent exploits thermal expansion differences between materials. By carefully selecting materials with opposite or complementary expansion characteristics and optimizing their thickness ratios, the overall dimensional stability of the capacitor is improved, reducing capacitance variations due to temperature-induced dimensional changes.
3Ease of operation
If a capacitive voltage divider is used for indirect voltage measurement, then ease of operation is improved, but measurement precision deteriorates due to temperature-dependent capacitance variations
Solution Approach 1:
The patent applies composite insulating materials in the capacitive voltage divider capacitors to eliminate temperature dependency. The first and second insulating layers with opposite dielectric constant temperature dependencies work together to maintain constant capacitance ratios, ensuring accurate voltage division and measurement across the full operating temperature range.
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 significantly improves the accuracy of voltage measurement on high-voltage conductors by minimizing temperature-dependent capacitance variations, ensuring precise voltage estimation across a wide temperature range.
Implementation Method 1
a voltage sensing element forming a capacitive voltage divider to determine a voltage on the current-carrying conductor, comprising: a first capacitor formed by the at least one insulating layer; a second capacitor electrically connected to a ground potential and to the first capacitor
Implementation Method 2
at least two insulating layers having a dielectric constant whose temperature dependency coefficient has opposite signs with respect to each other
Data Source
Figure 1~2a
Figure 2b
Figure 3~4
AI summary
The invention concerns an electrical accessory comprising: - a tubular conductor (43) through which a current-carrying conductor (32) can pass ; - at least one insulating layer (34, 36) disposed around the tubular conductor (43); - a voltage sensing element (38) forming a capacitive voltage divider to determine a voltage on the current-carrying conductor (32), comprising: • a first capacitor (40) formed by the at least one insulating layer (34, 36) ; • a second capacitor (42) electrically connected to a ground potential and to the first capacitor (40); characterized in that the first capacitor (40) comprises at least two insulating layers (34, 36) having a dielectric constant whose temperature dependency coefficient has opposite signs with respect to each other.