Current Differential Relay Device with Parallel Transmission Paths
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Solution Overview
Problem
Conventional current differential relay devices for power transmission line protection systems experience function stoppages and reduced operating ratios due to transmission defects in duplexed transmission paths, leading to prolonged protection function interruptions and intermittent malfunctions.
Innovation Solution
The implementation of two independent series of transmission means, timing difference measurement means, and current differential operation means for each transmission path, allowing for independent sampling pulse signal timing difference measurements and current differential operations, and generating trip signals from these results to maintain sampling synchronization and continue power transmission line protection even with a defective transmission path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single transmission path is used for current differential relay devices, then the device complexity is reduced, but the reliability of power transmission line protection is degraded due to transmission defects causing function stoppages
Solution Approach 1:
The transmission path is segmented into two independent parallel paths. Each path has its own transmission means and timing difference measurement means, allowing independent operation. When one path experiences a defect, the other path continues to provide protection functionality, thereby improving reliability while maintaining manageable device complexity through modular segmentation.
Solution Approach 2:
The system prepares backup transmission path resources in advance before defects occur. The standby transmission path and its associated timing difference measurement means are readied beforehand, so when a defect occurs in the active path, the system can immediately switch to the prepared backup path without interruption to protection functionality, cushioning against the harmful effect of transmission defects.
2Reliability
If transmission path reception changeover is performed to switch from a defective path to a standby path, then the continuity of data transmission is improved, but the protection function stops during the changeover period causing reduced operating ratio
Solution Approach 1:
Timing difference measurement and sampling synchronization are performed in advance on both the active and standby transmission paths. The standby path's timing difference is measured and synchronized beforehand, so when a defect occurs and switching is needed, the standby path is already prepared and synchronized, eliminating the need to stop protection functionality during changeover.
Solution Approach 2:
The system maintains continuous sampling synchronization on both transmission paths simultaneously. By performing timing difference measurement and synchronization in parallel on both paths, the useful action of maintaining synchronized sampling continues uninterrupted during path switching, eliminating protection function stoppages and improving operating ratio.
3Measurement precision
If sampling pulse signal timing difference measurement is performed for each transmission path, then the sampling synchronization accuracy is improved, but the device complexity increases due to multiple measurement means
Solution Approach 1:
The timing difference measurement function is segmented into separate measurement means for each transmission path. Each transmission path has its own dedicated timing difference measurement means, which improves measurement precision for each path while allowing the overall system to manage complexity through functional segmentation and parallel independent operation.
Data Source
AI summary
A current differential relay device is described. The device has two transmission parts provided in parallel and communicating with an other end of a power transmission line through two transmission paths and transmitting and receiving a quantity data of electricity of each of the terminals to and from an other end in the form of the digital data obtained through analog/digital conversion. Two current differential operation parts are connected to each of the two transmission parts and perform a current differential operation independently for each of the transmission paths by using the digital data of the quantity data of electricity of the one end of the power transmission line and of the other end of the power transmission line. A signal generation part generates a trip signal from the current differential operation result of the two current differential operation parts.