09-03 2026
Application of FZN21-12 Series Vacuum Load Switches in the Photovoltaic Industry
The FZN21-12 series indoor and outdoor high-voltage AC vacuum load switch (including the FZRN21-12 series load switch-fuse combination unit) is a core control and protection device designed for 12kV, 50Hz three-phase AC power distribution systems. It adopts advanced vacuum arc-extinguishing technology, which is an environment-friendly alternative to SF6-based switching equipment, aligning with the global "double carbon" goals of peak carbon emission and carbon neutrality by eliminating the use of SF6, a potent greenhouse gas with a global warming potential thousands of times higher than CO2. With its compact structure, reliable operation, strong environmental adaptability, and cost-effective performance, the FZN21-12 series has become an indispensable key equipment in the photovoltaic (PV) power generation industry. As the global photovoltaic industry develops rapidly, from large-scale centralized PV power plants and industrial and commercial rooftop PV systems to distributed PV projects and integrated optical-storage-charging systems, the demand for safe, stable, and efficient medium-voltage switching equipment is increasingly prominent. The FZN21-12 series, with its unique technical advantages and flexible configuration, is widely used in PV power station step-up substations, power collection lines, inverter output circuits, and grid-connected nodes, providing safe and reliable switching and protection solutions for the entire photovoltaic power generation chain. This article systematically elaborates on its application scenarios, functional value, technical advantages, and practical application effects in the photovoltaic industry, combining the operational characteristics of different types of PV projects.
1. Application in Large-Scale Centralized Photovoltaic Power Plants
Large-scale centralized photovoltaic power plants are the core force of renewable energy power generation, usually built in deserts, grasslands, and other areas with abundant solar resources. These power plants have large installed capacity, scattered PV arrays, long power collection lines, and high requirements for the stability and reliability of the power distribution system. The FZN21-12 series vacuum load switch plays a crucial role in the medium-voltage power distribution system of centralized PV power plants, undertaking the tasks of control, isolation, and fault protection of power collection lines and step-up transformers.
In a centralized PV power plant, hundreds or even thousands of PV modules are connected in series and parallel to form PV strings, which are then connected to inverters to convert direct current into alternating current. The low-voltage alternating current output by the inverter is boosted to 12kV through a box-type step-up transformer, and then connected to the power collection line to converge to the main step-up substation. The FZN21-12 series load switch-fuse combination unit is installed on the 12kV high-voltage side of each box-type step-up transformer, serving as the core protection and control component of the transformer. Under normal operating conditions, it can reliably make and break the rated load current, transformer no-load current, and cable charging current, ensuring the stable operation of the step-up transformer and the smooth transmission of electric energy.
In the event of a short-circuit fault in the transformer or the low-voltage side inverter, the fuse in the FZN21-12 combination unit can quickly break the fault current within a few milliseconds, realizing rapid fault isolation and avoiding the spread of faults to the entire power collection network. This effectively reduces the scope of power outages and minimizes economic losses caused by faults. In addition, the FZN21-12 series has excellent environmental adaptability, with an operating temperature range of -25℃ to +40℃, which can withstand harsh weather conditions such as high temperature, strong radiation, and dust in desert and grassland areas. Its compact structure is highly compatible with the box-type step-up transformers commonly used in centralized PV power plants, effectively reducing the volume and floor area of the transformer cabin, lowering the overall construction cost, and adapting to the modular construction requirements of large PV parks.
2. Application in Industrial and Commercial Rooftop Photovoltaic Systems
Industrial and commercial rooftop photovoltaic systems, installed on the rooftops of factories, shopping malls, office buildings, and other commercial and industrial buildings, have the characteristics of small installed capacity, flexible layout, and close proximity to the user side. These systems usually adopt a distributed grid-connected mode, which requires switching equipment to have compact structure, easy installation, and reliable protection performance. The FZN21-12 series vacuum load switch is perfectly adapted to the application needs of industrial and commercial rooftop PV systems.
In industrial and commercial rooftop PV projects, the FZN21-12 is mainly installed in the rooftop PV distribution cabinet and the grid-connected point of the building’s internal power distribution system. It is responsible for controlling the on-off of the PV power generation system and protecting the inverter, distribution transformer, and grid-connected line. Due to the limited installation space on the rooftop, the compact structure of the FZN21-12 series becomes a key advantage—it occupies a small area, can be flexibly installed in small-sized distribution cabinets, and does not affect the normal use of the rooftop.
In addition, industrial and commercial buildings have high requirements for power supply safety and reliability. The FZN21-12 series adopts vacuum arc-extinguishing technology, which has no oil, no pollution, no explosion risk, and no arc pollution, effectively avoiding fire and safety hazards caused by oil-immersed switches, which is in line with the safety requirements of densely populated industrial and commercial areas. It is equipped with a reliable five-prevention interlock mechanism to prevent misoperation such as incorrect closing and opening, ensuring the safety of equipment and operators. When the PV system needs maintenance or fails, the FZN21-12 can quickly disconnect the power supply, isolate the fault point, and ensure the safety of maintenance personnel and the normal operation of the building’s internal power distribution system.
3. Application in Distributed Photovoltaic Power Generation Projects
Distributed photovoltaic power generation projects, including residential rooftop PV, rural distributed PV, and industrial park distributed PV, are important supplements to centralized PV power generation. These projects have the characteristics of decentralized layout, small single-unit capacity, and close integration with the user’s power demand, requiring switching equipment to have strong flexibility, easy installation, and low maintenance costs. The FZN21-12 series vacuum load switch has become the preferred equipment for distributed PV power distribution systems due to its excellent performance and cost-effectiveness.
In rural distributed PV projects, the FZN21-12 is installed in the outdoor distribution box near the PV array, responsible for the control and protection of the PV string inverter and the grid-connected line. Rural areas have harsh operating environments, with large temperature differences, more dust, and inconvenient maintenance. The FZN21-12 series has a protection level of IP65 or higher, which can effectively resist rain, snow, dust, and corrosion, ensuring stable operation in rural outdoor environments. Its manual and electric dual operation mode is convenient for rural power grid maintenance personnel to conduct on-site operation and remote control, reducing maintenance workload.
In residential rooftop PV projects, the FZN21-12 is mainly used in the grid-connected cabinet of the PV system, connecting the PV inverter to the residential power distribution network. It can reliably make and break the PV power output current, and provide overcurrent and short-circuit protection for the inverter and grid-connected line. The compact structure and low noise of the FZN21-12 series are suitable for residential environments, avoiding affecting residents’ daily life. In addition, the FZN21-12 has a long mechanical life and low failure rate, reducing the maintenance cost of residential PV systems and improving the user experience.
4. Application in PV Energy Storage Integrated Systems
With the rapid development of the photovoltaic industry, PV energy storage integrated systems have become an important development trend. These systems combine photovoltaic power generation with energy storage equipment, realizing peak shaving, valley filling, and emergency power supply, which can effectively solve the problem of instability of photovoltaic power generation and improve the utilization rate of solar energy. The FZN21-12 series vacuum load switch plays an important role in the medium-voltage power distribution system of PV energy storage integrated systems, undertaking the tasks of switching control and fault protection between the PV system, energy storage system, and power grid.
In a PV energy storage integrated system, the FZN21-12 is installed in the medium-voltage distribution cabinet connecting the PV step-up transformer, energy storage converter (PCS), and power grid. It can realize the switching between the PV power generation mode, energy storage charging and discharging mode, and grid-connected mode. When the PV power generation is excessive, the FZN21-12 controls the energy storage system to charge; when the PV power generation is insufficient, it controls the energy storage system to discharge to supplement the power demand; in case of grid failure, it can quickly disconnect the grid connection and switch to the off-grid mode, ensuring the stable power supply of important loads.
The FZN21-12 series has fast operating speed and stable breaking performance, which can adapt to the frequent switching needs of PV energy storage integrated systems. Its vacuum arc-extinguishing technology ensures that there is no arc pollution during the switching process, avoiding interference to the energy storage converter and other precision equipment. In addition, the FZN21-12 can be equipped with an intelligent controller and communication module, realizing remote monitoring, remote control, and remote signaling functions, which is compatible with the intelligent management needs of PV energy storage integrated systems, facilitating the unified management and operation of the system.
5. Application in PV Grid-Connected Nodes
Grid-connected nodes are the key links connecting photovoltaic power generation systems and the public power grid, requiring switching equipment to have reliable breaking performance, strong anti-interference ability, and good compatibility with the power grid. The FZN21-12 series vacuum load switch is widely used in PV grid-connected nodes, providing reliable grid connection and disconnection functions for photovoltaic power generation systems.
At the PV grid-connected node, the FZN21-12 is responsible for connecting the PV power collection network to the public power grid. It can reliably withstand the impact of inrush current when the grid is connected, and stably break the load current when the PV system is disconnected from the grid for maintenance or fault. The FZN21-12 series has a rated voltage of 12kV, a rated current of up to 630A, a 4S thermal stable current of 20kA, and a dynamic stable current of 50kA, which can fully meet the grid-connected requirements of medium and small-sized photovoltaic power generation systems. It is equipped with a complete overcurrent and short-circuit protection mechanism, which can quickly respond to grid faults, isolate the PV system from the faulty grid, and avoid the impact of grid faults on the PV system.
In addition, the FZN21-12 series has good compatibility with the power grid’s protection system, which can coordinate with the grid’s relay protection device to realize accurate fault positioning and rapid fault handling. This improves the stability and reliability of the PV grid connection, ensures the safe and smooth integration of photovoltaic power into the public power grid, and promotes the large-scale development of the photovoltaic industry.
6. Technical Advantages of FZN21-12 in Photovoltaic Applications
6.1 Environmentally Friendly and Safe Performance
Adopting vacuum arc-extinguishing technology instead of SF6 gas, the FZN21-12 series has a global warming potential (GWP) of 0, which is in line with the global "double carbon" goals and environmental protection requirements of the photovoltaic industry. It has no oil, no toxic gas, no explosion risk, and no arc pollution, avoiding environmental pollution and safety hazards, and is suitable for photovoltaic power plants in various environments, including densely populated areas and ecological sensitive areas.
6.2 Stable and Reliable Breaking Performance
The FZN21-12 series has stable and reliable vacuum arc-extinguishing performance, which can reliably make and break rated load current, loop current, capacitive current, and transformer no-load current. The fuse in the combination unit can quickly break short-circuit current, realizing rapid fault isolation, which is suitable for the load fluctuation characteristics of photovoltaic power generation systems. The core component of the switch, the vacuum interrupter, has undergone rigorous performance testing, ensuring long-term stable operation under frequent switching conditions.
6.3 Compact Structure and High Space Utilization
The FZN21-12 series has a compact structure and small volume, which can be flexibly installed in box-type substations, distribution cabinets, and outdoor distribution boxes. It is especially suitable for photovoltaic projects with limited installation space, such as rooftop PV, distributed PV, and container-type PV energy storage systems, effectively reducing the occupied area and construction cost of the project.
6.4 Strong Environmental Adaptability
The FZN21-12 series has excellent environmental adaptability, with an operating temperature range of -25℃ to +40℃, and a protection level of IP65 or higher. It can resist harsh weather conditions such as high temperature, low temperature, rain, snow, dust, and corrosion, and can operate stably in various photovoltaic application environments, including deserts, grasslands, rooftops, and rural areas.
6.5 Cost-Effective and Low Maintenance
Compared with traditional circuit breakers, the FZN21-12 series has the advantages of low cost, simple structure, and low maintenance. It has a long mechanical life (up to 10,000 times of opening and closing) and electrical life, reducing the operation and maintenance cost of photovoltaic power plants. The manual and electric dual operation mode is convenient for on-site operation and remote control, improving the efficiency of operation and maintenance.
7. Conclusion
Against the background of global energy transformation and the rapid development of the photovoltaic industry, the demand for safe, stable, environmentally friendly, and efficient medium-voltage switching equipment is increasingly urgent. The FZN21-12 series vacuum load switch, with its excellent technical characteristics, strong environmental adaptability, and cost-effective performance, has become a core equipment in the photovoltaic power generation industry, covering large-scale centralized PV power plants, industrial and commercial rooftop PV systems, distributed PV projects, PV energy storage integrated systems, and PV grid-connected nodes.
In the photovoltaic industry, the FZN21-12 series not only ensures the stable and continuous operation of the photovoltaic power generation system, improves the reliability of power supply and grid connection, but also conforms to the environmental protection and low-carbon development requirements of the industry. It reduces the construction and operation and maintenance costs of photovoltaic projects, and provides strong equipment support for the large-scale and high-quality development of the photovoltaic industry. With the continuous advancement of photovoltaic technology and the expansion of installed capacity, the FZN21-12 series will further optimize its performance, integrate with intelligent power management systems, and continue to play an important role in the photovoltaic power distribution field, contributing to the global energy transformation and the realization of "double carbon" goals.
