Clock Synchronization via Time Interval Filtering for Differential Protection
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Solution Overview
Problem
Synchronizing clocks of network elements in packet-switching networks for differential protection devices is challenging due to varying transmission and reception times influenced by network nodes, traffic, and priority, requiring precise time protocols and symmetrical networks, which are not always feasible.
Innovation Solution
Determining and using only synchronization messages with transmission and reception time differences below a predetermined threshold to synchronize clocks, allowing for adaptive synchronization even in networks without PTP protocol requirements, by selecting messages with minimal time interval differences for accurate clock alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PTP protocol with delay request is used for clock synchronization, then clock synchronization precision is improved, but network complexity and equipment requirements increase
Solution Approach 1:
The patent extracts only the essential synchronization information (transmission and reception times of synchronization messages) from the complex PTP protocol, discarding the delay request/response mechanism and other elaborate synchronization procedures. This allows achieving sufficient clock synchronization for differential protection without requiring full PTP protocol implementation or specialized network equipment.
Solution Approach 2:
Instead of using the conventional approach where the receiving端 sends delay requests to the transmitting端 to measure round-trip time, the patent inverts the approach by having both ends independently record the transmission and reception times of synchronization messages and calculate the time difference directly, eliminating the need for interactive delay measurement.
2Measurement precision
If PTP protocol is used for clock synchronization, then time synchronization accuracy is improved, but network symmetry requirements increase
Solution Approach 1:
The patent extracts only the one-way transmission time measurement from the PTP protocol, discarding the requirement for symmetrical network paths and complex delay measurement mechanisms. By using only the transmission and reception times of synchronization messages, the solution achieves sufficient accuracy without imposing network symmetry constraints.
3Productivity
If all synchronization messages are used for clock synchronization, then synchronization frequency is improved, but synchronization accuracy deteriorates due to varying transmission times
Solution Approach 1:
Instead of using all received synchronization messages for clock synchronization, the patent selectively uses only those messages whose transmission and reception time differences fall within an acceptable range. This partial selection approach filters out messages with abnormal transmission delays, ensuring synchronization accuracy while maintaining adequate synchronization frequency through continuous monitoring and selection.
Data Source
Figure 1~2
AI summary
A method for the synchronized acquisition of measurement data required for the control of differential protection devices of electrical power lines (1) is described, which are summarized in packets and transmitted via packet-switched networks (7) between two network elements (2, 3), whose clocks are synchronized on the basis of measured transmit and receive times (Ts1, Ts2, Te1, Te2) of synchronization messages transmitted between the network elements (2, 3) via the packet-switched network (7).To ensure favorable synchronization conditions, it is proposed that the time intervals ΔTs, ΔTe) between the transmission times (Ts1, Ts2, Te1, Te2) of successive synchronization messages be determined from the transmission and reception times (Ts1, Ts2) on the one hand and between the reception times (Te1, Te2) on the other hand, and that the difference (ΔT) between the transmission and reception time intervals ΔTs, ΔTe) be determined from these transmission and reception time intervals, and that only those synchronization messages in which the absolute value of the difference (ΔT) between the transmission and reception time intervals ΔTs, ΔTe) is below a predetermined threshold (S) be used for synchronizing the clocks.