Digital Protection Control System Terminal Expansion
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Solution Overview
Problem
Conventional multiple-terminal transmission line protection systems face limitations in expanding terminals and communication paths, leading to restrictions in high-speed operation and increased complexity with the number of terminals, particularly in current differential relay devices.
Innovation Solution
A digital protection control system with a hybrid configuration that uses a terminal station as a master clock, synchronizing multiple terminal stations in a tree-like topology, allowing for easy expansion of terminals without increasing communication capacity, by calculating and transmitting only necessary data for relay calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of terminals is increased to accommodate dispersed power supply and difficult site acquisition, then the adaptability and coverage of the power system is improved, but the communication path complexity and data transfer burden increase significantly
Solution Approach 1:
The patent divides the multiple-terminal system into hierarchical segments with one master terminal and multiple subordinate terminals. Each terminal independently performs current differential protection calculations using locally available current information and synchronization signals, eliminating the need for complex centralized data collection and processing across all terminals.
Solution Approach 2:
The patent extracts the critical function of sampling synchronization from the communication data stream by using a dedicated synchronization signal transmitted separately. This allows terminals to synchronize their sampling clocks independently without burdening the communication path with large volumes of current data from all terminals.
2Measurement precision
If current information from all terminals is collected through communication paths to enable current differential principle, then the protection accuracy is improved, but the transmission capacity requirements and communication burden increase
Solution Approach 1:
The patent extracts only the essential synchronization timing information from the communication path and transmits it as a separate synchronization signal. Each terminal uses this synchronization signal to align its sampling clock locally, eliminating the need to transmit actual current data from all terminals through the communication path while maintaining accurate differential protection calculations.
Solution Approach 2:
Each terminal independently performs the current differential protection calculation using its own current measurements and the synchronization signal. The terminals self-service their own protection functions without requiring centralized data collection and processing, significantly reducing communication data volume while maintaining protection accuracy.
3Measurement precision
If sampling synchronization is achieved by considering transmission path delay in loop system configuration, then the sampling accuracy is improved, but the number of data transfer relays and processing times increase
Solution Approach 1:
The patent segments the synchronization function from the data transfer function. A dedicated synchronization signal is transmitted separately to establish timing references at each terminal, while current data remains local to each terminal. This eliminates the need to relay and retransmit large volumes of current data through multiple intermediate terminals, significantly reducing data transfer time while maintaining sampling synchronization accuracy.
4Device complexity
If a representative terminal judgment type is used with radial communication connections, then the communication path structure is simplified, but the number of communication ports and relay calculation processes increase with terminal expansion
Solution Approach 1:
The patent creates a universal terminal architecture where each terminal can function as either a master or subordinate terminal depending on system configuration. The standardized interface and synchronization protocol allow terminals to be added or removed flexibly without requiring special representative terminals or increasing communication ports, as each terminal independently performs protection calculations using the same algorithm.
Data Source
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AI summary
Disclosed are a digital protection control system and a digital protection control apparatus, wherein the digital protection control apparatus can easily be made to have more terminals, even when the number of terminals of a power transmission line increases. The digital protection control system has, as terminal stations thereof, a reference station that is to become the reference point for the sampling time at which power grid current information is to be taken in, tail-end stations that take in power grid current information from the power grid system, and intermediate stations that are connected between the reference station and the tail-end stations via transmission paths. The intermediate station is provided with an uplink transmission unit that is connected to a transmission path at the reference station side thereof, and a plurality of downlink transmission units that are connected to transmission paths at the tail-end station side thereof. The intermediate station also has the time thereof to be subordinate to the time of the terminal station connected to the uplink transmission unit thereof, and the time of the terminal stations connected to the downlink transmission units thereof are made to be subordinate to the intermediate station, with the time thereof used as reference time.