Multi-terminal Power Line Relay Segmentation
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Solution Overview
Problem
Current power line protection systems face challenges in efficiently managing a large number of terminals in multi-terminal power networks, particularly with the increasing complexity of high-voltage transmission lines and distributed power sources, as they require extensive communication infrastructure and data processing capabilities, leading to limitations in scalability and accuracy in fault detection.
Innovation Solution
A multi-terminal power line protective relay system that divides transmission lines into sections with shared terminals and uses current-driven differential relays, inter-terminal, and intra-terminal communication channels to detect faults and trigger circuit breakers, incorporating distance relay elements for precise fault detection and error reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of terminals in a power transmission line is increased to meet increasing electric power needs and accommodate distributed power sources, then the capacity and coverage of the power network is improved, but the complexity of communication apparatus and channels required to link all terminals increases significantly
Solution Approach 1:
The patent divides the multi-terminal power transmission line into multiple power line sections, where each section is protected by a dedicated protective relay. This segmentation allows each relay to handle a manageable subset of terminals while collectively covering all terminals in the system, thereby maintaining network capacity without proportionally increasing communication complexity.
2Measurement precision
If current-driven differential protective relays are used to achieve accurate fault detection and discrimination, then measurement precision is improved, but the burden on data processing and hardware/software capacity increases
Solution Approach 1:
By dividing the protection scope into multiple power line sections with dedicated relays, each relay performs current-driven differential calculations on a limited set of terminals rather than all terminals. This segmentation maintains high measurement precision for fault detection while significantly reducing the data processing burden on individual relays and the overall system.
3Speed
If protective relays are provided for each terminal to enable rapid fault isolation, then speed of fault response is improved, but the quantity of protective relays and associated hardware increases
Solution Approach 1:
The system segments the protection function by assigning specific power line sections to specific protective relays. Each relay is responsible for detecting faults in its designated section and triggering appropriate circuit breakers. This segmentation enables rapid fault response within each section while reducing the total number of relays compared to providing dedicated relays for every terminal.
Solution Approach 2:
Each protective relay is designed to perform multiple functions: detecting faults in its designated power line section, determining whether faults are internal or external, and controlling circuit breakers at multiple terminals. This multi-functionality allows fewer relays to achieve comprehensive protection across all terminals.
4Adaptability or versatility
If the existing protective relay system is expanded to handle more terminals, then adaptability is improved, but retesting and modification of existing relays becomes necessary
Solution Approach 1:
The patent designs the protection system with segmented power line sections that can be independently configured. When new terminals are added to the network, new power line sections can be created and assigned to existing or new relays without requiring modifications to the protection logic of other sections. This modular segmentation greatly simplifies system expansion and eliminates the need for retesting and modifying existing relays.
Data Source
AI summary
A multi-terminal power line protective relay system is provided, which divides a power transmission line having four or more terminals into two or more power line sections composed of three adjacent terminals and portions of the power transmission line lying among the three adjacent terminals and one of the three adjacent terminals being shared by two adjacent power line sections, and includes protective relays at the respective terminals including a current-driven differential protective relay element for detecting a fault occurring in a power line section through current-differential calculation by using measured currents, inter-terminal communication channels linking two protective relays at two different terminals; and intra-terminal communication channels linking two protective relays at each shared terminal. Each protective relay that detected the fault transfers a trip instruction to the other protective relays via the inter-terminal and intra-terminal communication channels and causes the other protective relays to trip circuit breakers.