Electro-Optical Waveguiding Fiber for High Voltage Sensing
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Solution Overview
Problem
Existing high-voltage voltage measurement techniques face challenges in accuracy and cost due to high electric field strengths and dielectric breakdown issues, particularly in air-insulated substations, where expensive insulation is required to prevent dielectric breakdown.
Innovation Solution
A method using a waveguiding fiber with a crystalline core and cladding, exhibiting a Pockels-type electro-optical effect, which integrates the electric field along a continuous path, reducing field strength and allowing for accurate voltage measurement without enhancing field strengths, and can be packaged in inexpensive insulators or integrated into high-voltage components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bulk single crystal is used for voltage measurement, then measurement capability is achieved, but very high electric field strengths occur near the crystal requiring expensive dielectric insulation
Solution Approach 1:
The patent segments the measurement function from the insulation function by using an optical fiber that transmits light through the high voltage field without requiring the measurement element to be directly exposed to high field strengths. The fiber acts as a remote sensing element that can be positioned in low-field regions while still measuring voltages at distant high-voltage points.
Solution Approach 2:
The patent introduces light as an intermediary carrier that transfers voltage measurement information from the high voltage point through the optical fiber to a detection system in a low voltage region. This intermediary approach allows indirect measurement without direct electrical contact in the high field strength zone.
2Measurement precision
If multiple small electro-optical crystals are mounted in a high-voltage insulator, then local electric fields can be measured, but the technique requires extra measures like permittivity-shielding to stabilize electric field distribution
Solution Approach 1:
The patent replaces the mechanical/electrical approach of using multiple crystals with permittivity-shielding structures with an optical approach. A single optical fiber measures the line integral of the electric field directly through the Pockels effect, eliminating the need for complex field stabilization structures.
Solution Approach 2:
The patent merges multiple local field measurements into a single integrated measurement by using one optical fiber to measure the line integral of the electric field along its entire path. This combines the functionality of multiple crystals into a single element that directly provides the total voltage without requiring separate stabilization for each measurement point.
3Reliability
If expensive dielectric insulation is used to prevent dielectric breakdown, then high voltage measurement is possible, but the cost increases significantly
Solution Approach 1:
The patent replaces the expensive mechanical dielectric insulation system with an optical measurement system. Since the optical fiber itself is insensitive to electric fields and does not require insulation, the expensive SF6 gas-filled insulator tubes are replaced with simple, inexpensive protective coatings on the fiber.
Solution Approach 2:
The patent uses inexpensive protective coatings on the optical fiber instead of expensive, complex dielectric insulation structures. The fiber can be protected with simple, cheap materials that do not need to provide long-term insulation but suffice for the measurement application.
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 method provides accurate voltage measurement across high voltage ranges without errors from field distribution variations, such as rain or pollution, and is cost-effective by using a thin, inexpensive insulator tube, suitable for voltages exceeding 50 kV.
Implementation Method 1
The technique described in EP 0 682 261 relies on the electro-optical effect, in which an electrical field changes the refractive index or birefringence of a light-transmitting element, namely a bulk single crystal. The crystal is a Pockels-type electro-optical material that changes its refractive index or birefringence linearly with the applied electric field.
Implementation Method 2
A known technique for measuring high voltages is described in EP 0 682 261. The technique described in EP 0 682 261 relies on the electro-optical effect, in which an electrical field changes the refractive index or birefringence of a light-transmitting element
Implementation Method 3
two orthogonally polarized light beams are passed through the crystal twice, and the returned light beams are brought to interference, e.g. in a polarizer or an interferometer, for measuring their mutual phase shift
Data Source
AI summary
An electro-optical high-voltage sensor includes a waveguiding sensing fiber of an electro-optical material. The electrical field of the voltage to be measured is substantially parallel to the longitudinal axis of the sensing fiber. The sensing fiber carries two orthogonally polarized light waves, with the applied field affecting the birefringence between the waves. Using an electro-optical waveguiding fiber in this configuration allows the voltage between two widely spaced points to be accurately measured.