With the in-depth advancement of rural revitalization strategies and the global pursuit of carbon neutrality goals, rural photovoltaic (PV) power generation has emerged as a key force driving the transformation of rural energy structures. It makes full use of rural idle resources such as house rooftops, wastelands, and hillsides to convert clean solar energy into electrical energy, not only bringing stable additional income to farmers but also promoting the construction of green and low-carbon rural areas. Grid connection is the crucial link to realize the effective utilization of rural PV power, and the station area, as the core hub of rural power distribution, undertakes the important tasks of collecting, converting, and transmitting distributed PV power to the public grid. Among the supporting equipment of rural PV grid connection station areas, the environmentally friendly ring main unit (RMU) has become an indispensable core component due to its outstanding environmental protection performance, compact structure, high reliability, and strong adaptability to rural environments. It effectively solves the pain points of traditional SF6 ring main units, such as environmental pollution, difficult maintenance, poor adaptability to harsh outdoor conditions, and large land occupation, providing a solid technical guarantee for the safe, stable, efficient, and green operation of rural PV grid connection station areas.
To fully understand the supporting value of environmentally friendly RMUs in rural PV grid connection station areas, it is essential to first clarify the characteristics of rural PV power generation and the special requirements for supporting equipment in station areas. Unlike urban centralized PV power plants, rural PV power generation is mainly dominated by distributed projects, including household rooftop PV systems, village-level small-scale distributed PV power plants, and PV projects integrated with agriculture and animal husbandry. These projects have distinct characteristics: small single-unit capacity (usually ranging from a few kilowatts to several megawatts), scattered distribution across villages and towns, numerous grid connection points, and significant intermittency and fluctuation in power output—greatly affected by environmental factors such as sunlight intensity, temperature, rainfall, and seasons. In addition, rural areas have unique requirements for power distribution equipment, which put forward higher demands on the design and performance of supporting RMUs.
Firstly, rural areas are ecological sensitive zones with a large amount of farmland, water sources, and vegetation, so environmental protection requirements for equipment are extremely strict. Traditional SF6 ring main units use sulfur hexafluoride (SF6) as the insulation and arc-extinguishing medium, which has an extremely high global warming potential (GWP)—25,200 times that of carbon dioxide—and a long atmospheric retention period of up to 3,200 years. Once leaked, SF6 gas will not only pollute the soil and water sources but also damage the local ecological balance, which is completely inconsistent with the concept of green rural development. Secondly, most rural PV grid connection station areas are installed outdoors, facing harsh environmental conditions such as high humidity, large temperature differences between day and night, frequent dust and sand, and insect pests, which require the equipment to have excellent protection performance and corrosion resistance. Thirdly, rural areas are short of professional operation and maintenance personnel, and the overall technical level of on-site运维 is relatively low, so the supporting equipment must be easy to operate, have a low failure rate, and require minimal maintenance. Fourthly, although rural land resources are relatively abundant, station area construction must avoid occupying cultivated land and farmland, so the equipment needs to be miniaturized and compact to save land resources.
Against this background, the environmentally friendly RMU, designed with the core concepts of "environmental protection, miniaturization, high reliability, easy maintenance, and strong environmental adaptability," perfectly meets the supporting needs of rural PV grid connection station areas and has become the preferred equipment for station area matching. Its unique advantages are closely related to its optimized material selection, advanced structural design, environmentally friendly working principle, and integrated primary-secondary technology, among which the innovation of insulation and arc-extinguishing media and the optimization of structural design are the key to its adaptation to rural scenarios.
The most prominent advantage of environmentally friendly RMUs in rural PV grid connection station areas is their environmentally friendly insulation and arc-extinguishing system, which fundamentally solves the environmental pollution problem of traditional SF6 ring main units. At present, mainstream environmentally friendly RMUs mainly adopt two types of green alternative media: dry air/nitrogen (N2) mixed gas and new low-global-warming-potential (low-GWP) gases represented by perfluoroisobutyronitrile (C4F7N, abbreviated as C4). Unlike SF6 gas, dry air and nitrogen are natural, non-toxic, and harmless gases with zero GWP, causing no damage to the ozone layer. Even if accidental leakage occurs, they will not pollute the soil, water sources, or vegetation, realizing "zero carbon emissions" and "zero environmental pollution" during the entire operation cycle.
The new low-GWP gas C4F7N has more excellent comprehensive performance: its insulation strength is 2.2 times that of SF6, and its GWP is only one-tenth of SF6. It not only retains the excellent insulation and arc-extinguishing capabilities of traditional SF6 equipment but also significantly reduces environmental impact, making it an internationally recognized ideal alternative to SF6 gas. This type of environmentally friendly RMU has been widely applied in rural PV grid connection station areas in Anhui, Jiangsu, and other regions in China, with stable operation for more than 4 years, fully verifying its reliability and adaptability in rural environments. In addition, some high-end environmentally friendly RMUs adopt renewable and degradable natural ester insulating oil instead of traditional mineral insulating oil. Natural ester insulating oil has a high ignition point (above 300℃), good thermal stability, and is biodegradable, further improving the environmental protection and safety of the equipment. The entire RMU adopts a fully sealed structure, which can effectively prevent the leakage of insulation media, ensuring that no harmful substances are released during the entire service life, and perfectly complying with the environmental protection standards of rural areas.
The miniaturized and compact structural design, combined with integrated primary-secondary technology, is another key advantage that makes environmentally friendly RMUs suitable for rural PV grid connection station areas. By optimizing the internal structure layout and adopting an integrated modular design, environmentally friendly RMUs integrate functions such as load switches, circuit breakers, isolating switches, measuring instruments, digital sensing units, and intelligent monitoring terminals into a small cabinet. Compared with traditional SF6 ring main units, their volume is reduced by 45% to 50%, and their weight is significantly reduced, which can effectively save land occupation and avoid occupying cultivated land and farmland.
In rural areas, station areas equipped with such RMUs can be installed in idle corners, beside village roads, or on the edges of wastelands, without the need for large-scale construction of power distribution rooms, greatly reducing the construction cost and construction period of the station area. At the same time, the miniaturized and lightweight design also reduces the difficulty of transportation and installation in rural areas—especially in mountainous and hilly rural areas with inconvenient transportation. The equipment can be easily transported to the installation site by ordinary vehicles, and on-site installation and commissioning are simple and fast, adapting to the actual conditions of rural infrastructure.
The high reliability and strong environmental adaptability of environmentally friendly RMUs provide a solid guarantee for the stable operation of rural PV grid connection station areas. To adapt to the harsh outdoor environment in rural areas, environmentally friendly RMUs adopt high-quality insulation materials and advanced manufacturing processes, with an overall protection level reaching IP65 (in line with the requirements of GB/T 4208). This level of protection can effectively prevent dust, moisture, sand, rainwater, and insect pests from entering the equipment, avoiding equipment failures caused by environmental factors such as humidity and dust accumulation. In addition, the equipment is equipped with a full range of safety protection devices, including overvoltage protection, undervoltage protection, short-circuit protection, and leakage protection.
When the PV power output fluctuates sharply (such as sudden changes in sunlight intensity) or faults occur in the station area (such as short circuits), these protection devices can quickly cut off the fault circuit, prevent the fault from expanding, and ensure the safety of the equipment, PV systems, and on-site personnel. The average service life of environmentally friendly RMUs can reach 20 to 25 years, which is 5 to 10 years longer than that of traditional SF6 ring main units. This long service life greatly reduces the frequency of equipment replacement, avoids the impact of equipment replacement on rural PV grid connection stability, and is highly suitable for the characteristics of limited operation and maintenance resources in rural areas.
The simple maintenance and convenient operation of environmentally friendly RMUs fully adapt to the limited operation and maintenance conditions in rural areas. With the application of integrated primary-secondary technology, environmentally friendly RMUs simplify the design of power distribution terminals, realizing plug-and-play when replacing faulty components on-site. There is no need for professional software or computers to reconfigure parameters, which greatly reduces the requirements for the professional level of rural operation and maintenance personnel. In addition, the fully sealed structure of the equipment eliminates the need for regular replacement of insulation media and complex maintenance work—daily maintenance only requires routine inspection and dust cleaning, reducing the annual maintenance cost by 40% to 60% compared with traditional SF6 ring main units.
Some environmentally friendly RMUs are also equipped with a simple and intuitive intelligent monitoring module, which can real-time monitor key operating parameters of the equipment and the station area, such as voltage, current, power factor, and operating temperature. When potential faults occur, the module can issue early warnings and realize rapid fault positioning, allowing rural operation and maintenance personnel to quickly handle faults without professional technical support, further reducing the operation and maintenance burden of rural power grids.
As the core supporting equipment of rural PV grid connection station areas, environmentally friendly RMUs have awide range of supporting applications, covering all key links of rural PV grid connection and playing an irreplaceable role in various rural PV scenarios. Firstly, they are applied in household rooftop PV grid connection station areas. Most rural households have independent rooftops, and rooftop PV systems have small capacity and scattered distribution. Environmentally friendly RMUs, as the core equipment of household PV grid connection station areas, can collect and connect the PV power generated by single or multiple households to the grid, adapt to the intermittent and fluctuating characteristics of rooftop PV power output, and ensure that the PV power generated by farmers can be safely fed into the rural power grid to obtain stable income.
Secondly, they are used in village-level small-scale distributed PV power plant station areas. These power plants are built on rural wastelands, hillsides, and other idle land, with a single-unit capacity of several hundred kilowatts to several megawatts, which is the main form of centralized rural PV power generation. Environmentally friendly RMUs can realize the centralized collection, voltage conversion, and grid connection of PV power in the station area, ensure the stable operation of the power plant and the safe grid connection of power, and their environmental protection and miniaturization characteristics are in line with the construction requirements of rural distributed PV power plants.
Thirdly, they play an important role in rural PV poverty alleviation project station areas. PV poverty alleviation is an important measure to promote rural revitalization and increase farmers' income. Environmentally friendly RMUs, as supporting equipment for poverty alleviation PV project station areas, can ensure the long-term stable operation of the project, improve the power generation efficiency of PV systems, and ensure that poverty alleviation benefits are continuously realized. In addition, environmentally friendly RMUs are also widely used in rural PV complementary project station areas (such as PV + agriculture, PV + animal husbandry), adapting to the complex operating environment of complementary projects and ensuring the efficient utilization of clean energy.
The excellent economic and social benefits of environmentally friendly RMUs further consolidate their core supporting position in rural PV grid connection station areas and provide strong support for rural revitalization and green development. From an economic perspective, although the initial investment cost of environmentally friendly RMUs is 20% to 30% higher than that of traditional SF6 ring main units, their long service life, low maintenance cost, and energy-saving effect can quickly recover the investment gap. The miniaturized design reduces the investment in station area construction and land occupation, while the low maintenance cost reduces the long-term operation burden of rural power grids and PV project operators. For farmers, the stable operation of station areas ensures that the PV power generated by their rooftop systems can be smoothly connected to the grid, bringing stable additional income and improving their quality of life.
From a social perspective, the popularization and application of environmentally friendly RMUs can effectively reduce carbon emissions and environmental pollution, helping rural areas achieve the dual carbon goals and improve the quality of the rural ecological environment. According to actual test data, a 10kV environmentally friendly RMU using dry air as the insulation medium can reduce carbon emissions by about 100kg per year compared with a traditional SF6 RMU, with remarkable environmental benefits. At the same time, the stable operation of rural PV grid connection station areas can improve the reliability and quality of rural power supply, solve the problem of insufficient power supply in some remote rural areas, and promote the modernization of rural energy and the process of rural revitalization.
Practical application cases in rural areas around the world have fully verified the core supporting value and excellent performance of environmentally friendly RMUs in station areas. For example, the innovative compact environmentally friendly gas RMU developed by State Grid Suqian Power Supply Company has been widely applied in rural PV grid connection station areas in northern Jiangsu. Its volume is reduced by more than 45%, effectively solving the problem of land occupation in rural station areas. It is equipped with a full-situation operation perception function, realizing early fault warning and rapid fault positioning, which greatly reduces the operation and maintenance burden of rural power grids. In rural areas of Anqing, Anhui Province, 12kV C4 environmentally friendly gas RMUs have been put into large-scale operation in rural PV station areas, with stable performance for more than 4 years, marking the mature application of low-GWP gas RMUs in rural PV grid connection scenarios. Eaton Pingdingshan Factory has launched RVACN-type environmentally friendly gas-insulated RMUs (dry air RMUs), which are widely used in rural PV grid connection station areas and highly recognized by rural power grid companies and PV project operators due to their environmental protection, reliability, and easy maintenance.
In contrast, traditional SF6 ring main units have gradually been eliminated in rural PV grid connection station area matching due to their high environmental pollution, large land occupation, complex maintenance, and poor environmental adaptability. Although some improved traditional RMUs have optimized certain performances, they are limited by the characteristics of SF6 gas and structural design and cannot fundamentally solve the environmental, maintenance, and space problems faced by rural PV station areas. Other types of power distribution equipment either have poor reliability, large volume, or high cost and difficult maintenance, making them difficult to be widely applied in rural PV grid connection station areas.
In conclusion, the environmentally friendly ring main unit, as the core supporting equipment for rural PV power generation grid connection station areas, has unique advantages that traditional power distribution equipment cannot match, including an environmentally friendly insulation and arc-extinguishing system, a miniaturized and compact structure, high reliability, strong environmental adaptability, simple maintenance, convenient operation, and a wide range of applications. These advantages are closely related to its scientific material selection, advanced integrated primary-secondary technology, optimized structural design, and environmentally friendly working principle, fully adapting to the characteristics of rural PV power generation and the special requirements of station area supporting equipment. It not only solves the pain points of traditional equipment in rural PV grid connection station area matching but also ensures the safe, stable, efficient, and green operation of rural PV grid connection station areas, promoting the popularization and application of rural PV power generation, increasing farmers' income, and advancing rural revitalization and green development. With the continuous advancement of global carbon neutrality goals and the in-depth development of rural PV power generation, environmentally friendly RMUs will be more widely popularized and applied in rural PV grid connection station areas, making greater contributions to building a green, low-carbon, safe, and efficient rural energy supply system.
