Fiber-optic Current Sensor with Exchangeable Sub-modules
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Solution Overview
Problem
Fiber-optic current sensors face challenges in maintaining accuracy when components need replacement, as conventional calibration processes require recalibration, which is impractical in high-voltage environments, especially when the sensor head is integrated in equipment that cannot be shut down.
Innovation Solution
The method involves calculating the current using a product of scaling functions for the measuring unit and sensor head, allowing for independent calibration and replacement of these components without losing accuracy, by storing these functions in memory and using them to calculate the current from the measured signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the sensor head or measuring unit is replaced in conventional fiber-optic current sensors, then component replacement is possible, but recalibration is required which causes downtime and operational disruption in high-voltage environments
Solution Approach 1:
The patent applies preliminary action by pre-calibrating the sensor head and measuring unit separately before assembly. Each component is calibrated independently in advance, and the calibration results are stored in respective memories. This allows components to be replaced without recalibration, as the pre-stored calibration data remains valid, eliminating downtime in high-voltage environments.
Solution Approach 2:
The patent segments the current sensor into two independently calibratable components: the sensor head and the measuring unit. Each component has its own calibration data stored in separate memories. This segmentation allows independent replacement of either component without affecting the calibration status of the other, resolving the contradiction between ease of repair and time loss.
2Reliability
If the sensor head is integrated in high-voltage equipment, then the sensor can be used in high-voltage environments, but the equipment cannot be shut down for maintenance or recalibration
Solution Approach 1:
The patent enables preliminary calibration of the sensor head and measuring unit before they are integrated into high-voltage equipment. Once calibrated and assembled, the sensor can operate continuously in high-voltage environments without requiring shutdown for maintenance. The pre-stored calibration data ensures continued accuracy without needing access to recalibration facilities.
3Measurement precision
If conventional calibration processes are used, then measurement accuracy is maintained, but recalibration is required after component replacement which increases maintenance costs
Solution Approach 1:
The patent performs calibration in advance for each component (sensor head and measuring unit) separately before assembly. The calibration results are stored in memories within each component. This preliminary calibration eliminates the need for recalibration after replacement, maintaining measurement precision while significantly reducing maintenance complexity and costs.
Solution Approach 2:
The patent creates a digital copy of the calibration data and stores it in memory within each component. This copied calibration information allows the component to be replaced and immediately used without physical recalibration, maintaining measurement accuracy while simplifying maintenance procedures.
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 enables the exchange of sensor components in the field without recalibration, reducing downtime and maintenance costs in high-voltage environments, while maintaining sensor accuracy.
Implementation Method 1
The magnetic field of the current I introduces a phase shift between the left and right circularly polarized light waves propagating in the sensing fiber
Implementation Method 2
The optical retarder causes a differential phase shift of approximately 90°, thereby converting between the linearly polarized light in the connecting fiber and the circularly polarized light in the sensing fiber
Implementation Method 3
a polarization maintaining fiber connecting the sensor head to the measuring unit
Data Source
AI summary
A fiber-optic current sensor includes a measuring unit having a light source and a light detector, and a sensing head having a sensing fiber wound around a conductor and a retarder connected to the sensing fiber. The scale factor as a function of current of the fiber-optic current sensor is described by the product of two scaling functions fe′ and fs′ for the measuring unit and the sensing head, respectively. The data describing the scaling functions fe′, fs′ is stored in a memory of the measuring unit, while the data describing the scaling function fs′ is also stored in a memory of the sensing head. Providing two such memory devices allows to store the scaling functions fe′ and fs′ separately, thereby turning the control unit as well as the sensor head into easily replaceable modules.