Differential Optical Protection for Mixed Power Line Faults
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Solution Overview
Problem
In mixed electrical power transmission lines with both overhead and cable sections, existing fault detection systems struggle to accurately identify the location of faults, leading to unnecessary shutdowns and increased maintenance costs, as they often incorrectly diagnose temporary faults in overhead sections as permanent, affecting system availability.
Innovation Solution
A differential optical protection system using passive optical current sensors and fault discrimination devices connected via single-mode optical fibers, eliminating the need for electrical power supplies at measurement points and reducing the number of optical fibers required, allowing for remote fault identification and discrimination in mixed lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current transformers and circuit breakers are used for fault detection in mixed lines, then fault detection capability is provided, but the system cannot accurately distinguish between overhead and cable section faults, leading to unnecessary shutdowns
Solution Approach 1:
The patent divides the transmission line into distinct segments (overhead sections and cable sections) and applies different protection strategies to each segment. By segmenting the line and using optical current sensors at specific locations, the system can identify which segment contains a fault, thereby improving measurement precision without requiring a completely complex system redesign.
Solution Approach 2:
The patent introduces optical current sensors as intermediary devices that convert electrical current measurements into optical signals. These sensors act as mediators between the electrical power system and the detection system, enabling accurate fault identification while maintaining system simplicity through standard optical communication infrastructure.
2Measurement precision
If optical current sensors are deployed at multiple locations along the line, then fault detection precision is improved, but the number of optical fibers and infrastructure requirements increase
Solution Approach 1:
The patent merges multiple measurement functions into a unified optical sensing system. By combining the measurements from multiple optical current sensors and processing them centrally, the system achieves high fault detection accuracy while minimizing the quantity of optical fibers needed, as sensors can share communication infrastructure.
Solution Approach 2:
The optical current sensors are designed to serve multiple functions: they detect faults, provide measurement data for system monitoring, and can operate with existing optical fiber infrastructure. This multi-functionality reduces the need for dedicated infrastructure for each sensor, thereby reducing the total quantity of optical fibers required.
3Productivity
If re-engagement is automatically performed after fault detection, then system availability is improved, but temporary faults in overhead sections may be incorrectly identified as permanent cable faults, causing unnecessary shutdowns
Solution Approach 1:
The patent implements preliminary fault classification using optical current sensors before triggering re-engagement or shutdown decisions. By performing preliminary measurements and analysis at the fault detection stage, the system can accurately distinguish between temporary overhead faults (which can undergo re-engagement) and permanent cable faults (which require shutdown), thereby improving both system availability and reliability.
Solution Approach 2:
The system incorporates feedback mechanisms where optical current sensors continuously monitor line conditions and provide real-time data to the protection system. This feedback enables dynamic decision-making regarding re-engagement, allowing the system to automatically resume operation after temporary faults while maintaining high reliability by preventing re-engagement when permanent faults are detected.
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 enables accurate fault detection in mixed lines without power supply at sensors, reduces infrastructure needs, and minimizes maintenance costs by using passive optical sensors and multiplexing techniques, ensuring system availability and reliability.
Implementation Method 1
a sensor fiber (551) surrounding an electrical power transmission cable (24) whose current intensity is to be monitored
Implementation Method 2
The sensor fiber (551) is connected at one end to a passive optical circuit (68a, 68b, 68c)
Implementation Method 3
connected to the passive optical circuit (68a, 68b, 68c) by means of a splice to the free end of an insensitive optical fiber (561), and the free end of the insensitive optical fiber (561) is connected by means of a connector to a single-mode optical fiber (89) configured for sending an optical signal
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A differential optical system for remote identification of faults on a mixed electrical power transmission line, comprising: at least one first optical current sensor (40) situated at one end of the cabled section, which comprises: a sensor fiber (41, 51) which may be disposed surrounding an electrical power transmission cable whose current intensity is to be monitored, and one passive optical circuit (48, 58), at least one second current measurement device independent of the former one, configured to take measurements of the current intensity that circulates through an electrical power transmission cable; and one fault discrimination device (70, 80) to process the current measurements and detect faults in the mixed line. The device (70, 80) is connected to the optical current sensor (40) by means of single-mode optical fiber (89). The sensor fiber (41) is made up of a section of sensitive optical fiber (451, 551) and a section of insensitive optical fiber (552). The free end of the sensitive optical fiber (451, 551) is connected by means of a splice (E) to the free end of said insensitive optical fiber (552).