IED Time Alignment Without External Reference
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Solution Overview
Problem
Existing electric power delivery systems face complexity and inefficiency in monitoring and protection due to the need for common time signals across merging units, which increases communication complexity and latency, especially when using different communication media and distances.
Innovation Solution
An intelligent electronic device (IED) estimates the time of sample measurement by calculating communication latency between merging units and itself, allowing for time alignment of power system samples without external time references, thereby eliminating the need for time stamps in sample communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If common time signals are used across merging units, then time alignment of samples is achieved, but communication complexity and latency increase
Solution Approach 1:
The patent extracts the time reference function from external common time signals and implements it locally within each IED using a local clock. Each IED independently timestamps samples using its own local time reference, eliminating the need for complex external time synchronization infrastructure while maintaining time alignment capability through local time domain association.
Solution Approach 2:
The patent introduces communication latency as an intermediary parameter that mediates between the local sampling times at different merging units and the arrival times at the IED. By measuring and compensating for this latency, the system achieves time alignment without requiring direct common time signal distribution, thus reducing communication complexity.
2Measurement precision
If common time signals are distributed across merging units, then sample time alignment is enabled, but communication latency increases
Solution Approach 1:
The patent performs preliminary measurement of communication latency between each merging unit and the IED before actual sample collection. This pre-measured latency information is stored and used to compensate for transmission delays when associating samples with their corresponding local time domain, thereby eliminating the need for real-time time signal distribution and reducing communication latency.
3Measurement precision
If time stamps are communicated with each sample, then time alignment is achieved, but communication data volume increases
Solution Approach 1:
The patent extracts the time reference functionality from the sample communication stream and implements it locally at each IED. Instead of transmitting time stamps with each sample, each IED independently uses its local clock to associate received samples with the appropriate local time domain based on pre-measured latency values, thereby eliminating time stamp data transmission while maintaining time alignment accuracy.
Data Source
AI summary
Disclosed herein is a system for time aligning electric power system measurements at an intelligent electronic device (IED) from signals from merging units where the merging unit does not require a common or external time source. Communications from merging units may arrive at different times due to differences in communication latency or other factor. The IED may associate digital samples from merging units with a local time domain of the IED based on the data acquisition, data processing, and data communication latency in communicating with the merging units.