Optical Waveguide Hotspot Detection in Superconductors

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Solution Overview

Problem

Current hotspot detection techniques for superconductors, particularly in high-voltage direct current (HVDC) grids and Superconducting Fault Current Limiters (SFCLs), are inefficient and costly, often leading to unnecessary shutdowns and inability to quickly detect singular hotspots, which can cause material degradation and damage.

Innovation Solution

A Mach-Zehnder Interferometer-based optical waveguide/fiber sensing system that rapidly detects hotspots by producing an optical interference signal with a signature phase shift, allowing for quick identification of hotspots within 10 ms, enabling rapid alarm raising and preventing thermal runaways.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If optical waveguide/fiber sensing is used for hotspot detection, then detection speed and precision are improved, but device complexity increases

Engineering Contradiction:
Improvehotspot detection precisionVSAvoidmonitoring system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the optical waveguide sensing function directly with the superconductor structure, integrating the monitoring capability into the existing device rather than adding separate external sensing systems. This merging approach improves detection precision while minimizing the increase in overall device complexity.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The optical waveguide acts as an intermediary element that converts thermal changes in the superconductor into optical signal variations. This mediator enables precise hotspot detection through optical interference patterns without requiring direct thermal contact or complex electrical sensing arrangements.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If rapid hotspot detection is implemented, then thermal runaway prevention is improved, but response time requirements increase system demands

Engineering Contradiction:
Improvethermal runaway preventionVSAvoiddetection response time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The optical waveguide is pre-positioned along the superconductor length before operation, establishing the sensing network in advance. This preliminary arrangement enables immediate detection response when hotspots occur, as the sensing infrastructure is already in place and does not require activation or setup during critical events.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent replaces traditional electrical or thermal sensing methods with optical sensing. The optical interference-based detection system responds to thermal changes through optical path length variations, providing faster response times and eliminating the delays associated with electrical signal processing or thermal conduction-based detection.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If optical interference signaling is used for hotspot detection, then detection sensitivity is improved, but system cost increases

Engineering Contradiction:
Improvehotspot detection sensitivityVSAvoidsystem manufacturing cost
Core Design Contradiction:
Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent uses optical copying of the thermal field distribution along the superconductor through the waveguide. The optical interference pattern creates a spatial map of temperature variations, enabling sensitive detection of hotspots without requiring expensive point-by-point thermal sensors or complex imaging systems.

Inventive Principle:
Principle #26Copying

Solution Approach 2:

The system detects hotspots by monitoring changes in optical parameters (phase, intensity) of the waveguide rather than directly measuring temperature. This parameter transformation converts thermal information into optical signals that can be detected with high sensitivity using standard optical components, reducing overall system cost.

Inventive Principle:
Principle #35Parameter changes

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 solution provides a cost-effective and efficient method for monitoring superconductor health, enabling swift decision-making and preventing damage by detecting even singular hotspots, thus enhancing the reliability and safety of HVDC grids and SFCLs.

Implementation Method 1

The phase shift is dependent upon the length and temperature of the hotspot or hotspots in the superconductor

Methodology Applied
Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The phase shift is dependent upon the length and temperature of the hotspot or hotspots in the superconductor

Methodology Applied
Scientific EffectThermo-optic effect:

Implementation Method 3

interference means configured to overlay or superimpose the first optical signal and the reference optical signal to produce an optical interference signal

Methodology Applied
Scientific EffectOptical interference: Interference

Data Source

PatentEP4022689B1Hotspot monitoring system for superconducting device
Publication Date: 2024.01.24 ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (EPFL)
  • EP4022689B1 patent drawingFigure 1~2
  • EP4022689B1 patent drawingFigure 3~4
  • EP4022689B1 patent drawingFigure 5~6B

AI summary

Hotspot monitoring system for superconducting devices including: - a superconductor; - a first optical waveguide attached to the superconductor for providing a first optical signal; - a second optical waveguide for providing a reference signal; and - interference means configured to overlay or superimpose the first optical signal and the reference optical signal to produce an optical interference signal.