Optical Voltage Sensor Assembly for DC Measurement
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Solution Overview
Problem
Existing optical voltage sensors integrated into gas-insulated switchgear face challenges in measuring direct current (DC) voltages due to space charge accumulation, which affects dielectric strength and signal stability, and are prone to stray field influences, leading to signal drifts over time.
Innovation Solution
An optical voltage sensor assembly featuring a gas-tight compartment with an electro-optic crystal and electrodes, where the crystal is attached via transparent base elements with elastic fixation, ensuring minimal space charge buildup and insensitivity to time-dependent residual space charges, and the electrodes are designed to maintain optimal electric field distribution without a surrounding insulating tube, allowing for accurate DC voltage measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an insulating tube surrounds the electro-optic crystal, then mechanical support and insulation are provided, but space charge accumulation occurs affecting dielectric strength and signal stability
Solution Approach 1:
The patent removes the insulating tube that surrounded the electro-optic crystal in prior art. Instead, the crystal is mounted directly on the high-voltage electrode surface using adhesive, eliminating the source of space charge accumulation while maintaining mechanical support and electrical insulation through the electrode structure itself.
Solution Approach 2:
The patent integrates the mechanical support and electrical insulation functions directly into the high-voltage electrode structure. The electrode serves both as the electrical component and as the mechanical mounting substrate, eliminating the need for a separate insulating tube that would cause space charge problems.
2Stability of the object's composition
If rigid fixation is used for the electro-optic crystal, then mechanical stability is achieved, but mechanical vibrations and shock affect measurement accuracy
Solution Approach 1:
The patent applies adhesive material between the electro-optic crystal and the high-voltage electrode to provide cushioning against mechanical vibrations and shock. This adhesive layer absorbs mechanical disturbances before they reach the crystal, preventing measurement errors while maintaining stable electrical contact.
3Device complexity
If the crystal is in direct contact with insulation gas, then compact design is achieved, but reactive decomposition products affect the crystal
Solution Approach 1:
The patent applies a protective coating on the surface of the electro-optic crystal that is selectively permeable or reactive. This coating allows the crystal to remain in direct contact with the insulation gas for compact design, while the coating layer specifically protects against reactive decomposition products, maintaining crystal integrity.
4Reliability
If transparent conductive coating is applied on crystal facets, then electrical contact is improved, but optical properties may be affected
Solution Approach 1:
The patent optimizes the parameters of the transparent conductive coating, including thickness, material composition, and optical wavelength range, to achieve a balance between electrical conductivity and optical transparency. By carefully controlling these parameters, the coating provides reliable electrical contact while minimizing degradation of optical transmission properties.
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 stable and accurate voltage measurements for DC voltages by minimizing space charge accumulation and stray field influences, ensuring reliable operation and maintaining dielectric strength, while being adaptable for both DC and AC voltage measurements.
Implementation Method 1
Both embodiments employ an electro-optic crystal that exhibits linear birefringence in the presence of electrical fields transverse to the direction of light propagation.
Implementation Method 2
the voltage measurement is reduced to a measurement of local electrical field
Implementation Method 3
The periodic piezo-electric deformation of the crystal as a result of an applied alternating current (AC) voltage produces a differential optical phase shift of light waves propagating in the fiber which serves as a measure for the voltage.
Data Source
Figure 1a~1b
Figure 2~3
AI summary
The invention relates to an assembly of a gas-tight compartment (1a) and an optical voltage sensor that further comprises a module (1c). The module (1c) comprises an electro-optic crystal (9) and electrodes (7, 8), wherein the electro-optic crystal (9) is the only element of the module (1c) to mechanically connect the two electrodes (7, 8) and to bridge the potentials of the two electrodes (7, 8). The assembly is particularly suited to measure direct current voltages.