On August 17, the China Electric Power Research Institute successfully completed the acceptance of the "All-Fiber Current Transformer State Evaluation Technology Research" project, a key scientific and technological initiative under the State Grid Corporation. The project was organized and evaluated by the State Grid Ministry of Science and Technology, marking a significant step forward in smart grid technology.
As a critical component in high-voltage power grid monitoring, current transformers play a vital role in both energy measurement and relay protection. With the rapid development of smart grids and ultra-high voltage (UHV) transmission systems, traditional electromagnetic current transformers have shown limitations, prompting the rise of all-fiber current transformers. These advanced devices offer superior performance, including high measurement accuracy, a wide dynamic range, fast frequency response, strong resistance to electromagnetic interference, compact size, lightweight design, and the ability to measure both AC and DC signals.
However, the core photovoltaic modules used in all-fiber current transformers account for over 70% of the total cost. The specialized optical fiber materials required for these modules are currently dominated by foreign manufacturers, resulting in most high-performance all-fiber current transformers being imported. This dependency has long been a challenge for domestic technology development.
In 2014, Beijing Yiguang Research Institute and Beijing Shiweitong Technology Development Co., Ltd. joined forces to develop high-precision photoelectric modules for current measurement. After two years of dedicated research, the team made significant breakthroughs, creating a low-birefringence fiber with independent intellectual property rights. This achievement broke the foreign monopoly and significantly improved the temperature error accuracy of fiber optic current transformers.
Today, as smart substations continue to evolve, all-fiber current transformers face new challenges. Researchers at the Chinese Academy of Electric Power have developed an optical path and circuit system based on the temperature and driving current of the light source in all-fiber current transformers. This innovation addresses the urgent need for enhanced reliability, stability, and accuracy in next-generation intelligent substations.
Through in-depth research on the impact of key parameters on overall performance, they proposed a self-diagnostic technology model and a comprehensive set of methods that incorporate factors such as light source die temperature and driving current. As a result, an all-fiber current transformer with self-diagnosis capabilities for GIS applications has been successfully developed.
The outcomes of this project are expected to greatly enhance the technical level of the fiber optic current transformer industry in China, supporting the country’s transition toward smarter, more efficient power systems.
(Sources: China Electric Power Research Institute, China Machinery Network, Beijing Municipal Science and Technology Commission)
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