Vacuum interrupters are characterized by small size, long service life, stable manufacturing processes, and reliable performance, making them widely used in the medium-voltage switchgear field. To extend their excellent performance and quality, solid insulated ring main units (SIRMUs) developed overseas in recent years all adopt vacuum isolating switches and vacuum earthing switches.
China's three major vacuum interrupter manufacturers have also collaborated with SIRMU R&D enterprises to develop vacuum interrupters with different structural forms, including those with one-tube three functions (breaking, isolating, and earthing), one-tube two chambers (breaking chamber, isolating/earthing chamber), and three-position (closing, isolating, earthing) types. It is generally believed that the series combination of a three-position vacuum isolating/earthing switch (TPS) and a vacuum interrupter offers optimal economy and reliability.
Users' acceptance of using vacuum breaks for isolation functions depends on two aspects. Firstly, it relies on the persuasiveness of the technical scheme. The principle and standards must be recognized, and the acceptance that the break of the isolating switch can be "invisible"—while its position indicating device must be rigidly connected, directly driven, and provide clear and reliable indication. Secondly, there must be confidence that the vacuum degree of the vacuum interrupter remains stable throughout its service life, its insulation is reliable, and the overall insulation performance of the SIRMU (outside the vacuum interrupter) is also reliable.
Due to gaps in management, manufacturing processes, and materials, the leakage rate of domestic vacuum interrupters is higher than that of foreign products. Meanwhile, domestic operational experience with vacuum isolating switches is indeed insufficient. Currently, users in China's power system cannot fully accept vacuum isolating switches.
Chinese users' understanding and acceptance of vacuum isolating switches will take time, but in this era of rapid informatization and technological development, this process will not be too long. To promote the development of SIRMUs, two key tasks need to be accomplished during this period: Firstly, vacuum interrupter manufacturers must strive to reduce leakage rates. Secondly, power system users should strengthen their confidence in the quality of domestic products and formulate corresponding on-site operating procedures to ensure they are willing to use and can effectively utilize these products.
This article is compiled and edited by DAYA Electric Group Co., Ltd. (https://www.hygraphics.com). Reproduction is permitted with proper attribution.