Home page

The Important Role of SF6 Ring Main Unit Switchgear in Urban Power Grids

Release time:

2025-10-13

Author:

Source:

Abstract

As global urbanization accelerates, city power grids are facing multiple challenges, including the need to enhance supply reliability, manage tight space resources, and seamlessly integrate complex new energy sources. Against this backdrop, SF6 ring main units—boasting exceptional insulation performance, a compact design, and advanced intelligent features—have emerged as the cornerstone equipment for upgrading urban distribution networks. From the financial hub of Shenzhen’s Qianhai Free Trade Zone to the Jakarta-Bandung High-Speed Railway corridor in Indonesia, and from Munich’s smart grid demonstration zone in Germany to China’s Yangtze River Delta metropolitan area, SF6 ring main units are reshaping the global power distribution landscape, driving market growth at an annual average rate of 6.8%.

I. Technical Features: Small Volume, Big Energy Carrying Capacity

The core advantage of SF6 ring main switchgear stems from its use of sulfur hexafluoride (SF6) gas. This colorless, odorless, and inert gas boasts an insulation strength 100 times greater than air, along with exceptionally powerful arc-extinguishing capabilities. By sealing critical components such as load switches and circuit breakers within metal enclosures filled with SF6 gas, the equipment achieves a fully insulated and completely enclosed design. Take Schneider Electric’s RM6 series as an example—despite being 30% smaller in volume compared to conventional products, it can handle voltages up to 12kV and currents of 630A, while delivering millisecond-level fault interruption capability. This "small footprint, big power" feature makes it the ideal choice for space-constrained environments like urban underground utility tunnels or narrow street-side installations.

Structurally, the SF6 ring main unit adopts a modular design, with a typical configuration comprising three major functional areas: the switchgear room, busbar room, and cable room. The switchgear room integrates a three-position load switch (for closing/opening and grounding), while the busbar room enables multiple units to be connected in parallel, forming a ring-shaped power supply network. Meanwhile, the cable room is equipped with预留 expansion interfaces for components such as surge arresters and current transformers. This standardized design not only facilitates rapid installation but also supports "plug-and-play" scalability—for instance, a new district project in Xi'an successfully increased its power supply capacity from 10 MVA to 25 MVA by adding two additional ring main units, cutting the project timeline by 40%.

II. Enhanced Reliability: From Reactive Repair to Proactive Defense

The city's power grid has reduced its tolerance for power outages from hours to just minutes. The SF6 ring main unit (RMU) ensures uninterrupted power supply through a dual-mechanism approach: First, it employs a load switch paired with a fuse—where the load switch handles routine switching operations, while the fuse swiftly cuts off short-circuit currents within 0.02 seconds. This "division of labor" design extends the equipment’s lifespan up to 20 years. Second, the RMU integrates intelligent sensors and an edge computing module that continuously monitor critical parameters such as temperature, gas pressure, and partial discharge in real time. Siemens’ 8DJH RMU, deployed in Munich’s power grid, demonstrates how its AI-based fault prediction system boosts outage risk detection accuracy to 95%—while simultaneously slashing operational and maintenance costs by 40%.

In the distribution network renovation project in Suxian County's urban area, the "hand-in-hand" ring network structure built with SF6 ring main units played a critical role. By configuring a primary ring network using four 2-in/2-out ring main units, combined with seven reclosers, the system achieves automatic fault isolation. When a short circuit occurred on Line 107, the system swiftly disconnected the faulty section within 0.3 seconds, while simultaneously restoring power to unaffected areas via Line 104. As a result, what would have typically required a two-hour manual repair process was reduced to just 15 minutes of automated switching. This remarkable "self-healing" capability has boosted the region's供电可靠性 (SAIDI) from 99.85% to an impressive 99.997%.

III. Intelligent Evolution: The "Digital Nerve" of Distribution Equipment

The integration of 5G and IoT technologies is driving the evolution of SF6 ring main units into intelligent sensing terminals. The eco-friendly SF6 ring main unit developed by China XD Group, deployed along the Jakarta-Bandung High-Speed Railway, not only leverages digital twin technology for comprehensive lifecycle management of equipment but also incorporates quantum sensing technology, boosting the sensitivity of partial discharge detection to an impressive 0.1 pC level. Meanwhile, in Shenzhen’s Qianhai Free Trade Zone, Schneider Electric’s SM6 series ring main units are seamlessly integrated with the energy management system, dynamically adjusting operational modes based on real-time load data. This innovative approach has slashed grid losses by 30% and reduced annual carbon emissions by up to 800,000 tons per GWh.

Intelligence is also evident in the transformation of operation and maintenance models. While traditional ring main units require monthly inspections, smart products equipped with built-in SF6 density monitors, humidity sensors, and other advanced devices enable real-time, remote visualization of equipment status. According to data from State Grid Hangzhou Power Supply Company, after adopting smart ring main units, inspection frequency has dropped from four times per month to once every quarter, resulting in a 65% reduction in labor costs. Even more noteworthy is the ring main unit recycling program launched by China XD Group, which leverages IoT technology to track the retirement process of these devices, achieving an impressive 85% utilization rate for recycled materials and creating a closed-loop system spanning "design, use, and recycling."

IV. Green Transformation: The Art of Balancing Environmental Protection and Economic Growth

Faced with the EU’s stringent F-gas regulations on SF6 emissions, the industry is accelerating technological innovation. ABB has introduced the Safe Air ring main unit, which replaces SF6 gas with dry air, reducing the global warming potential (GWP) from 22,800 to less than 1. This innovative solution has already been deployed in over 5,000 units in China’s Xiong’an New Area. Meanwhile, China XD Group has developed an eco-friendly 126kV ring main unit that has successfully passed CIGRE type tests. The new product boasts an SF6-replacement gas leakage rate of less than 0.1% per year, placing it at an internationally leading level. This groundbreaking technology ensures that the cost of eco-friendly products increases by only 8% compared to traditional models, while delivering a 15% reduction in total lifecycle costs.

At the market level, the Asia-Pacific region is emerging as a major battleground for innovation. In 2024, China's exports of SF6 ring main units to Southeast Asia surged by 200% year-on-year, with these products now accounting for 30% of the market share in countries along the Belt and Road Initiative routes.

Key words:

How can industrial power distribution equipment help reduce energy consumption and emissions?

Outdoor Meter Boxes in Smart Cities: Remote Meter Reading and Data Monitoring

Hunan Chengyuan Electrical CO.,LTD

The Important Role of SF6 Ring Main Unit Switchgear in Urban Power Grids