Zero-Crossing Synchronization for Partial Discharge Monitoring
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Solution Overview
Problem
Existing methods for synchronizing data acquisition devices in electrical distribution networks face challenges due to GPS inaccuracies and cable attenuation, which affect the accuracy of locating partial discharges.
Innovation Solution
A method and system for synchronizing data acquisition devices using local timestamping and zero-crossing detection to estimate the period of the electrical signal, followed by synchronized acquisition phases triggered at specific instants based on these estimates, allowing for precise determination of synchronization differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If data acquisition devices use independent local clocks for time-stamping, then each device can operate autonomously and record events independently, but synchronization errors occur between devices located at different points in the electrical network
Solution Approach 1:
The patent introduces a synchronization signal derived from the electrical network voltage waveform as an intermediary reference. All data acquisition devices use this common reference to trigger their sampling and time-stamping operations, eliminating the need for separate clock synchronization while maintaining autonomous operation. The zero-crossing detection of the voltage signal serves as the mediating event that coordinates all devices.
Solution Approach 2:
The patent establishes a common temporal reference level by having all devices synchronize their operations to the same electrical signal phase (zero-crossing points). This creates an equipotential condition in the time domain, where all devices operate from the same temporal baseline, eliminating relative time drift between devices.
2Measurement precision
If data acquisition devices sample at high frequencies to capture transient events, then measurement precision improves, but data transmission volume and processing complexity increase
Solution Approach 1:
The patent extracts only the critical information from high-frequency sampling by triggering data acquisition specifically at zero-crossing events. Instead of continuously transmitting all sampled data, the system identifies and extracts only the relevant transient events that occur at or near zero-crossings, significantly reducing data volume while maintaining detection precision.
Solution Approach 2:
The patent uses periodic zero-crossing detection as a gating mechanism to control data acquisition. By sampling and triggering events only at these periodic intervals (synchronized with the electrical frequency), the system reduces continuous high-frequency processing to discrete periodic events, lowering computational complexity while preserving transient detection capability.
3Adaptability or versatility
If data acquisition devices are distributed at multiple locations in the electrical network, then monitoring coverage improves, but synchronization coordination between devices becomes more difficult
Solution Approach 1:
The patent applies a universal synchronization mechanism based on the electrical network's own voltage signal that works identically at all distribution points regardless of location. Each device independently detects zero-crossings of its local voltage waveform and uses this as its trigger reference, providing a location-independent synchronization solution that scales to any network configuration.
Solution Approach 2:
The system uses the electrical network's own voltage signal to provide synchronization to all devices. Each data acquisition device autonomously extracts the synchronization reference from its local voltage waveform without requiring external coordination or master-slave relationships, enabling self-organizing synchronization across the distributed network.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances synchronization accuracy by eliminating GPS-related errors and cable attenuation, enabling precise location of partial discharges without the need for surface-mounted GPS antennas.
Implementation Method 1
each data acquisition device samples the electrical signal traversing the network and deduces an estimate T'A or T'B of the period of the electrical signal by detecting the zero-crossing times of the sampled signal
Implementation Method 2
locally time-stamped by a time-stamping means associated with each data acquisition device
Implementation Method 3
We can then determine a synchronization difference Δtoa between two high-frequency events acquired, on a given cycle, by the two data acquisition devices by calculating the difference between the second trigger instant tRB and the first trigger instant tRA
Data Source
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AI summary
The invention relates to the synchronization between at least two data acquisition devices of an online monitoring system for an electrical distribution network, each located at a known point A or B of the network and configured to detect high-frequency events during data acquisition phases. According to the invention, during a first phase of estimating the period of the electrical signal traversing the network, each data acquisition device samples the electrical signal traversing the network and deduces an estimate T'A or T'B of the period of the electrical signal by detecting the zero-crossing times of the sampled signal, locally time-stamped by a time-stamping means associated with each data acquisition device.One of the devices then sends an information signal at a first locally time-stamped detection instant tZCA1,1, of a new zero crossing of the sampled signal, and triggers a data acquisition phase at a first time TRA separated from the first detection instant by a duration corresponding to the first estimate T'A of the period of the electrical signal. The time of reception of this signal at the other device is also time-stamped by a local time-stamping method. After a duration corresponding to half the second estimate T'B of the period of the electrical signal following the reception instant, this other device triggers a high-frequency event acquisition phase over a plurality of successive cycles of predefined cycle duration, at a second locally determined trigger instant tRB, corresponding to a second locally time-stamped detection instant of a new zero crossing of the sampled signal.We can then determine a synchronization difference Δtoa between two high-frequency events acquired, on a given cycle, by the two data acquisition devices by calculating the difference between the second trigger instant tRB and the first trigger instant tRA.