HVDC Cable Short-Circuit Detection via Optical Polarization
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Solution Overview
Problem
High voltage direct current (HVDC) networks face challenges in detecting and isolating short-circuits quickly, as fault currents propagate rapidly and exceed the breaking capacity of circuit breakers, potentially leading to network-wide power outages.
Innovation Solution
A detection device with optical fibers wound around HVDC cables, utilizing the Faraday effect to detect short-circuits by measuring variations in the polarization angle of optical signals, allowing for rapid identification and isolation of faulty sections before propagation, using dual detectors at each end of the cable and processing units to determine fault location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional current-based detection methods are used, then the detection system is simple, but the detection speed is too slow and fault current exceeds breaker capacity before detection
Solution Approach 1:
The patent replaces conventional electrical current-based detection with optical field-based detection using the Faraday effect. Optical fibers wound around the cable detect changes in polarization caused by magnetic fields from fault currents, enabling detection before the fault current reaches dangerous levels. This substitution of detection domain (from electrical to optical) achieves ultra-fast detection speed while maintaining system feasibility.
Solution Approach 2:
The optical detection system is installed in advance around the cable, continuously monitoring for fault conditions. The system detects the magnetic field signature of developing faults before they propagate and exceed breaker capacity, allowing preventive isolation. The optical fibers are pre-positioned to capture the electromagnetic signature of incipient faults.
2Measurement precision
If optical fiber detection using Faraday effect is implemented, then detection speed and accuracy improve, but device complexity and cost increase
Solution Approach 1:
The optical fiber serves multiple functions: it acts as both the transmission medium for optical signals and the sensor for detecting magnetic fields via the Faraday effect. The same fiber that could be used for communication purposes also provides fault detection, eliminating the need for separate sensing elements and reducing overall system complexity despite the advanced detection capability.
Solution Approach 2:
The patent uses the magnetic field as an intermediary between the fault current and the optical detection system. The fault current generates a magnetic field that modulates the polarization of light passing through the optical fiber. This intermediary approach allows indirect detection of electrical faults using optical methods, achieving high precision while maintaining a clear separation between the electrical power system and the optical detection system.
3Reliability
If dual detectors are placed at both ends of the cable, then fault detection reliability improves, but system complexity increases
Solution Approach 1:
The detection system is segmented into two independent detection units, one at each end of the cable. Each unit can independently detect faults and trigger isolation. This segmentation provides redundancy and reliability, as the system can function even if one end's detector fails. The segmented approach also allows for localized fault isolation without requiring coordination between ends.
Solution Approach 2:
The system implements feedback through bidirectional optical signal transmission. Each detector monitors the polarization state of light passing through the fiber and provides feedback about fault conditions. The feedback mechanism enables real-time monitoring and immediate response to fault detection, enhancing reliability through continuous verification from both ends of the cable.
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 quick detection and isolation of short-circuits, preventing network-wide failures by accurately locating faults and interrupting power supply before current propagation exceeds breaker limits, thus ensuring network protection.
Implementation Method 1
utilizing the Faraday effect to detect short-circuits by measuring variations in the polarization angle of optical signals
Data Source
Figure 1A~3A
Figure 3B~3C
Figure 4~5
AI summary
The present invention concerns a detection device (19) for detecting a short circuit current in an electrical power transmission cable (1), comprising: - an electrical power transmission cable (1) for a high-voltage DC network, comprising: • a central core (3), • an insulating sheath (5), • a metal screen (7) arranged around the insulating sheath (5), • at least one optical fibre (13), arranged between the electrically conductive central core (3) and the metal screen (7) by forming windings around the central core (3) in a detection region, - two optical transmitters (15A, 15B) arranged at the ends (1A, 1B) of the electrical power transmission cable (1), - two optical detectors (17A) arranged at the ends (1A, 1B) of the electrical power transmission cable (1), - two interruption devices (21A, 21B) arranged at the ends (1A, 1B) of the electrical power transmission cable (1), coupled to the optical detectors (17A, 17B) and configured to interrupt the connection of the electrical power transmission cable (1) when a change in the angle of polarisation with respect to a reference angle greater than a predetermined value is detected by the first optical detector (17A).