How can ring main units (RMUs) optimize the distribution network structure of urban power grids?

Release time:

2026-01-20

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Abstract

How can ring main units (RMUs) optimize the distribution network structure of urban power grids?

As the “capillaries” of urban energy supply, the reliability and intelligence level of urban power grids directly affect residents’ quality of life and the vitality of economic development. With the acceleration of urbanization and the large-scale integration of new energy sources, traditional radial distribution networks have exposed shortcomings such as insufficient power supply reliability and weak capacity to accommodate new energy. Ring Main Units (RMUs), with their modular design, intelligent features, and flexible topological structures, have emerged as key equipment for optimizing the distribution network architecture of urban power grids. This article will analyze how RMUs are reshaping the urban power distribution system from three perspectives: technical characteristics, application scenarios, and real-world case studies.

 

I. Technical Features of Ring Main Units: A Dual Breakthrough in Modularity and Intelligence

A ring main unit is a medium-voltage switchgear whose core functions include load distribution, short-circuit protection, and intelligent monitoring. Based on differences in insulation media and structural design, ring main units can be categorized into three major types: SF6 gas-insulated, solid-insulated, and air-insulated. Among these, the SF6 gas-insulated type has become the mainstream choice for urban distribution networks due to its compact size and low maintenance costs; meanwhile, the solid-insulated type, with its environmentally friendly characteristics, is gradually gaining wider adoption in scenarios involving the integration of new energy sources.

From a technical architecture perspective, the ring main unit adopts a combined design featuring a “three-position switch plus vacuum circuit breaker,” supporting both manual and electric operation modes. Its key advantages are:

1. Modular scalability: By combining standardized units, a “hand-in-hand” ring network structure can be rapidly established to meet the needs of areas with varying load densities. For example, an industrial park in Inner Mongolia deployed three ring main units to create a “three-ring road” power supply network, reducing the power supply radius by 40% and lowering line losses by 25%.

2. Intelligent Monitoring Function: By integrating FTU (Feeder Terminal Unit) and DTU (Distribution Terminal Unit), the system can collect real-time data on voltage, current, load, and other parameters, and transmit this data via 5G communication to the distribution automation master station. In Shanghai’s central urban area, the coverage rate of ring network switchgear has reached 95%, reducing fault location time from 30 minutes to just 5 minutes. As a result, the average annual outage duration for users has been reduced to below 10 minutes.

3. Self-healing capability: When a fault occurs on the power line, the ring main unit can automatically isolate the faulty section and transfer the load to a backup power source via a tie-switch. The three ring main unit circuits put into operation by the Wulateqianqi Power Supply Company in Inner Mongolia have boosted regional power supply reliability to 99.99% and increased fault-handling efficiency by 80%.

 

II. Application Scenarios for Ring Main Units: Full Coverage from Urban Core Areas to New Energy Bases

The optimization benefits of ring main units are evident in three key scenarios:

1. High-load-density urban areas: In scenarios such as high-rise buildings and commercial centers, ring main units (RMUs) adopt a “ring network + grid” topology to build multi-source power supply networks. For example, the Beijing CBD area employs a “dual-ring network + smart switches” design, which triples the load-sharing capability and ensures that users experience “zero disruption” during equipment maintenance.

2. New Energy Integration Scenarios: To address the intermittency of distributed photovoltaic and wind power, ring main units can be equipped with energy storage systems and intelligent voltage regulation devices. In a certain industrial park in Jiangsu Province, a 200 kWh energy storage system was deployed at the ring main unit connection point, increasing the self-consumption rate of photovoltaic power from 30% to 80% and keeping the distribution network voltage fluctuations within ±2%.

3. Electric Vehicle Charging Infrastructure: Ring main units provide fast and safe power distribution for charging stations. At a large-scale charging station in Guangzhou, ring main units enable a “dual-power supply + automatic switchover” configuration, allowing the station to meet the daily charging needs of 500 electric vehicles and boosting charging efficiency by 15%.

 

III. Practical Case: Verification through Practices in Inner Mongolia and Shanghai

1. Ultra-high voltage ring main units supporting the new energy base in Inner Mongolia

At the Kubuqi Desert New Energy Base, a ring network switchgear cluster has been constructed to support the ±800kV ultra-high-voltage DC transmission channel, enabling integrated operation from “base development and power transmission to load consumption.” Thanks to flexible DC technology (VSC-HVDC), the ring network switchgear reduces the impact of wind power fluctuations on the grid by 60%, with annual new energy power transmission reaching 120 billion kilowatt-hours.

2. Intelligent Upgrade of Shanghai’s Urban Distribution Network

The Pudong New Area in Shanghai has deployed intelligent ring main units that integrate AI algorithms and big data analytics, achieving a fault prediction accuracy rate of over 90%. For example, one particular ring main unit detected an abnormal temperature rise at a cable joint and issued an early warning about equipment defects three days in advance, thereby preventing a major power outage.

3. Ring-network renovation of the distribution network in Suxian County seat

Sishan County in Anhui Province has deployed load switch-type ring main units to build a network featuring “two primary power sources plus four interconnections,” thereby clarifying the division of power supply areas and expanding the coverage of the main trunk lines by 50%. After the upgrade, equipment operation and maintenance efficiency has improved by 40%, laying a solid foundation for distribution network automation.

 

IV. Future Outlook: Deep Integration of Ring Main Units with New Power Systems

As the “dual-carbon” goals are advanced, ring main units will evolve toward higher voltage levels (such as 24kV) and greater intelligence (such as digital twin technology). For example, Shenzhen plans to achieve 100% intelligent coverage of ring main units by 2030, leveraging IoT technology to enable full-lifecycle management of equipment. Meanwhile, the environmentally friendly characteristics of solid-insulated ring main units will help the power grid achieve a “zero-carbon” transformation.

Ring main units are not only “intelligent nodes” in urban power grids but also the “basic building blocks” for the construction of a new-type power system. Through modular design, intelligent monitoring, and flexible topologies, they effectively address the challenges faced by traditional distribution networks in terms of reliability, cost-effectiveness, and integration of new energy sources. In the future, as technology continues to evolve and application scenarios expand, ring main units will keep driving the transformation of urban power grids toward greater safety, efficiency, and sustainability, providing a solid power supply guarantee for high-quality economic and social development.

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