Capacitive Voltage Sensor Temperature Compensation
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Solution Overview
Problem
Voltage sensors in power distribution networks face challenges in maintaining accuracy due to temperature-related changes in dielectric bushing materials, affecting the measurement of AC phase-neutral voltage on high-voltage lines.
Innovation Solution
A capacitive voltage sensor design incorporating a dielectric bushing with an annular conductor and a capacitor compensation circuit using capacitors made of different materials to compensate for capacitance changes, combined with a resistor compensation circuit featuring thermistors to adjust resistance in response to temperature variations, ensuring accurate voltage estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric bushing is used in the voltage sensor, then the sensor can operate in high voltage environments, but the measurement accuracy deteriorates due to temperature-induced changes in dielectric properties
Solution Approach 1:
The patent applies parameter changes by selecting dielectric materials with specific temperature coefficients and adjusting their proportions in the composite bushing structure. The first dielectric material has a positive temperature coefficient while the second has a negative temperature coefficient, and their combination allows the overall bushing's dielectric properties to remain stable across temperature variations, thereby maintaining measurement accuracy while operating in high voltage environments
Solution Approach 2:
The patent employs composite materials by creating a dielectric bushing from a composite structure containing both first and second dielectric materials with opposing temperature coefficients. This composite approach allows the bushing to simultaneously provide high voltage insulation and temperature compensation, resolving the contradiction between operational reliability and measurement precision
2Measurement precision
If compensation circuits are added to maintain accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent extracts the temperature compensation function from complex electronic compensation circuits and implements it directly in the passive dielectric bushing structure itself. By embedding temperature compensation capabilities in the bushing's material composition, the invention eliminates the need for additional active compensation circuits, thereby maintaining high measurement precision while avoiding increased device complexity
Solution Approach 2:
The dielectric bushing performs self-compensation for temperature effects through its inherent composite material properties. The bushing automatically adjusts its dielectric characteristics in response to temperature changes without requiring external control systems or additional compensation circuits, thus achieving high measurement precision with minimal added complexity
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 enhances the accuracy of voltage sensing by effectively compensating for temperature-induced changes in capacitance and resistance, providing a stable and precise measurement of AC phase-neutral voltage.
Implementation Method 1
first and second compensation capacitors made of different materials having different dielectric constants, and where the materials of the first and second compensation capacitors are selected so as to compensate for changes in the first and second capacitances in response to temperature changes
Implementation Method 2
a first pair of a resistor and a thermistor and a second pair of a resistor and a thermistor, where the thermistors in the first and second pairs change their resistance in response to the changes in temperature so as to provide resistance compensation
Implementation Method 3
an annular conductor formed in the bushing and being capacitively coupled to the line, where a first capacitance is defined between the line and the annular conductor and a second capacitance is defined between the annular conductor and ground
Data Source
AI summary
A capacitive voltage sensor for estimating voltage on a power line. The sensor includes a dielectric bushing surrounding the line, and an annular conductor formed in the bushing and being capacitively coupled to the line, where a first capacitance is defined between the line and the annular conductor and a second capacitance is defined between the annular conductor and ground. The sensor also includes a capacitance compensation circuit having an amplifier including a first terminal electrical coupled to the annular conductor, and first and second capacitance compensation capacitors electrically coupled to the terminals of the amplifier, where the compensation capacitors are made of different materials having different dielectric constants, and where the materials of the compensation capacitors are selected so as to compensate for changes in the first and second capacitances in response to temperature changes. Also, a thermistor is provided in a resistor compensation circuit to provide resistance compensation.