Optical Sensor Assembly with Segmented Magnetic Concentrator
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Solution Overview
Problem
Existing current and voltage sensors for high voltage electricity distribution systems face challenges in achieving a wide dynamic range, sensitivity, and bandwidth while being cost-effective and capable of installation without disrupting the cable function, with limitations in dynamic range, sensitivity to adjacent fields, and temperature sensitivity.
Innovation Solution
An optical sensor assembly with a magnetic concentrator having a distributed airgap and a base unit with a pivotable concentrator housing, allowing the sensor to be clamped onto the cable without cutting it, featuring a polarized light input and output, and an integrated voltage sensor, optimized for maximum sensitivity and dynamic range using mixed magnetic materials and glass optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic concentrator with a single airgap is used, then the saturation level is limited, but increasing the airgap increases sensitivity to adjacent fields
Solution Approach 1:
The magnetic concentrator is divided into multiple segments with distributed airgaps between them. This segmentation allows the saturation level to be increased by distributing the magnetic path length across multiple segments, while each individual airgap remains small enough to minimize sensitivity to adjacent fields. The total effective airgap length is distributed rather than concentrated in a single location.
Solution Approach 2:
The airgap is distributed along the length of the magnetic concentrator rather than being concentrated at one location. This dimensional distribution transforms a single-point sensitivity issue into a distributed property, maintaining low sensitivity to adjacent fields while achieving the required saturation level through cumulative magnetic path length.
2Measurement precision
If bulk glass or fiber optic cable surrounds the current carrying cable, then dynamic range is very high, but installation requires opening the cable which is expensive
Solution Approach 1:
The sensor is designed as a clamp-on device with a magnetic concentrator that can be opened and closed around the cable. This segmentation allows installation without cutting or opening the cable, reducing installation cost while maintaining the optical sensing capability through the magnetic concentrator structure.
Solution Approach 2:
A magnetic concentrator is introduced as an intermediary component that concentrates the magnetic field from the current carrying cable onto the optical sensor. This mediator enables the sensor to achieve high dynamic range measurements without requiring direct contact with or modification of the cable insulation.
3Measurement precision
If traditional separate sensors are used for different applications, then each application has dedicated optimization, but multiple sensors increase complexity and cost
Solution Approach 1:
The optical sensor assembly is designed to perform multiple measurement functions including current measurement, voltage measurement, and power quality assessment. By integrating multiple sensing capabilities into a single device, the system eliminates the need for separate sensors for different applications, reducing overall complexity while maintaining application-specific optimization through configurable measurement parameters.
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
Enables accurate, cost-effective measurement of current and voltage with improved dynamic range and sensitivity, reduced temperature sensitivity, and the ability to be installed without disrupting the cable, suitable for multiple applications including fault detection and power quality assessment.
Implementation Method 1
Optical current sensors based on the Faraday effect are known in the art
Implementation Method 2
Optical current sensors utilizing a magnetic concentrator with bulk optics in an airgap are also known in the art
Implementation Method 3
Woods et al., U.S. 5892357, discloses an electro-optic voltage sensor for sensing voltage in an electric field, the sensor being based on Pockel's electro-optic effect
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An optical sensor assembly (10) has a base unit (20), an optical current sensor (40), and a magnetic concentrator (54). The optical current sensor (40) is mounted on the base unit (20) and includes a polarized light input (42), a reflective prism (44), and a light output (46). The magnetic concentrator (54) defines an airgap (60) and is mounted on a concentrator housing (30) such that the magnetic concentrator (54) fits around the current carrying cable (12) when the base unit (20) is hung from the current carrying cable (12) in a closed position. The reflective prism (44) is operably positioned in the airgap (60) when the concentrator housing (30) is in the closed position. The optical sensor assembly (10) enables a method of measuring a current through the current carrying cable (12).