Live Line Transformer Error Analysis Using GNSS Synchronization
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Solution Overview
Problem
Current and voltage transformers in electricity transmission and distribution networks experience metrology performance deterioration over time, leading to significant measurement uncertainties in power and energy measurements, which affect the accuracy of billing and energy management.
Innovation Solution
A real-time live line measurement system is developed to analyze the properties of current and voltage transformer assemblies, allowing for the determination of errors in power and energy measurements caused by these transformers and energy meters. The system uses upstream and downstream current and voltage sensors with GNSS time stamping to calculate phase displacement and ratio errors, enabling online testing without taking transformers offline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional offline testing methods are used for current and voltage transformers, then measurement accuracy can be ensured, but the transformers must be taken offline causing loss of time and reduced productivity
Solution Approach 1:
The system dynamically switches between different measurement modes (offline calibration mode and online live-line measurement mode) to maintain measurement accuracy while enabling continuous operation. The measurement system adapts its configuration based on operational requirements, allowing transformers to remain in service during measurement.
Solution Approach 2:
Additional measurement sensors and reference standards are introduced as intermediary elements to enable accurate measurements during live-line operation. These intermediaries facilitate the comparison between transformed and non-transformed signals without requiring the transformer to be removed from service.
2Measurement precision
If traditional offline testing methods are used for current and voltage transformers, then comprehensive error analysis can be performed, but the complexity of removing and reinstalling equipment increases device complexity and reduces ease of operation
Solution Approach 1:
The measurement system is designed to perform multiple functions: it can conduct both offline calibration measurements and online live-line measurements using the same hardware infrastructure. This multi-functionality eliminates the need for separate testing procedures and reduces operational complexity.
Solution Approach 2:
The system enables self-measurement capabilities where the transformer under test serves its own measurement function during live-line operation. The transformer continues to transform signals while simultaneously being measured, eliminating the need for external testing equipment to be physically connected during operation.
3Productivity
If live-line measurement is implemented, then productivity is improved by avoiding downtime, but the device complexity increases due to additional sensors and synchronization requirements
Solution Approach 1:
The measurement functions are merged with the existing operational infrastructure. The same current and voltage transformers that perform power transformation also serve as measurement subjects, while additional sensors are integrated into the existing protection and monitoring systems, reducing overall system complexity.
Solution Approach 2:
The system implements real-time feedback through GNSS synchronization and continuous measurement, allowing immediate detection and correction of measurement errors. This feedback mechanism enables the system to maintain accuracy without requiring complex manual calibration procedures.
4Measurement precision
If live-line measurement with GNSS synchronization is used, then real-time error determination is achieved, but the loss of substance increases due to data management requirements
Solution Approach 1:
Data processing and error calculation are performed in real-time as measurements are taken, rather than requiring post-processing of large datasets. The system pre-calculates error components during the measurement process itself, reducing the burden of subsequent data management.
Solution Approach 2:
The system extracts only the essential error components (ratio errors and phase displacement errors) from the full measurement data, rather than requiring complete data retention and processing. This selective extraction reduces data management requirements while maintaining measurement precision.
Data Source
AI summary
A real-time live line method analyses properties of an electricity substation. The method uses an upstream current sensor and an upstream voltage sensor to obtain a series of upstream current data points and a series of upstream voltage data points during a first time period and attributes respective GNSS time stamps provided by a first and a second GNSS signal receiver to the data points. The method uses a downstream current sensor and a downstream voltage sensor to obtain a series of downstream current data points and a series of downstream voltage data points during the first time period and attributes respective GNSS time stamps provided by a third and a fourth GNSS signal receiver to the data points. The method calculates a current transformer phase displacement error, a current transformer ratio error, a voltage transformer phase displacement error, and a voltage transformer ratio error. The method also calculates upstream active and reactive power data and calculates downstream active and reactive power data.