HM Power ASNA Technology
ASNA – Atmospheric Pressure Sealed Natural Air Insulation Technology – is a unique, globally pioneering SF₆-free power distribution technology developed by HM Power. Boasting fully independent intellectual property rights and more than one hundred core patents, it serves as the core technical foundation for a new generation of eco-friendly, highly reliable medium-voltage distribution solutions. It fully complies with EU F-Gas Regulation (EU) 2024/573.
HM Power ASNA Technology
ASNA – Atmospheric Pressure Sealed Natural Air Insulation Technology – is a unique, globally pioneering SF₆-free power distribution technology developed by HM Power. Boasting fully independent intellectual property rights and more than one hundred core patents, it serves as the core technical foundation for a new generation of eco-friendly, maintenance-free medium-voltage distribution solutions. It fully complies with EU F-Gas Regulation (EU) 2024/573.
What is ASNA technology?
ASNA stands for Atmospheric Pressure Sealed Natural-Air Insulation Technology. Different from other gas-filled insulation solutions, ASNA technology uses natural air as the primary insulation medium. Vacuum interrupters, disconnectors/earthing switches, connecting busbars, insulating supports and other components are housed inside a sealed air chamber maintained at ambient atmospheric pressure.
It features no greenhouse gas emissions, zero operating pressure, zero leakage, full insulation and maintenance-free operation. This foundational technology supports global carbon neutrality and the energy transition toward renewable power.
Core working principle
The atmospheric pressure sealed cabinet features an integrated structure with pressure balancing and air filtration functions. A dedicated pressure balancing device with air filtration capability keeps the cabinet’s internal pressure equal to ambient atmospheric pressure at all times, while effectively blocking dust, solid particles, salt spray and other contaminants from entering the sealed cabinet.
The air filtration medium uses inert inorganic fiber material, offering excellent air permeability, mold resistance, anti-caking and anti-aging properties. It requires no maintenance throughout its entire service life.
six core advantages
core advantages of ASNA technology
The gas pressure inside and outside the switch cabinet is balanced. There is no requirement for pressure monitoring, no risk of gas leakage, and no need for gas refilling or maintenance.
The sealed cabinet is fitted with a pressure balancing unit with air filtration capability. It protects the air within the cabinet from external contaminants, providing protection against dust, salt spray and condensation, and ensuring all switch components operate within a favorable working environment.
It adopts natural air as the insulation medium instead of industrially manufactured gases. There are no greenhouse gas emissions and no need for gas recovery and treatment. It delivers genuine green and low-carbon performance and fully meets the requirements of EU F-Gas Regulation (EU) 2024/573.
The main insulation structure adopts a single-phase insulation system. Based on air insulation, phase-to-phase insulating barriers are installed between phases. No insulating components interconnect the phases, and there is no risk of phase-to-phase surface creepage, which eliminates the hazard of phase-to-phase discharge breakdown at the insulation structure level.
The full-circuit-breaker solution comes with comprehensive relay protection devices and enables real-time monitoring of line conditions. In the event of a short circuit or severe overload fault on the line, it can precisely interrupt the short-circuit fault current and achieve local fault isolation. It meets the development requirements of smart distribution networks and improves the operational reliability of the power grid.
ASNA switchgear boasts 16 years of field operation experience. It has been fully validated under harsh climatic conditions and complex grid environments, demonstrating outstanding stability and reliability. To date, more than 60,000 units of ASNA switchgear have been put into service, holding over 35% market share in Sweden and earning trust among power users.
ASNA RMU/switchgear
Certificates and Test Reports for ASNA Switchgear
ASNA switchgear has passed third-party tests and inspections from KEMA Power Laboratory, CNAS and other institutions. It has undergone full type tests covering electrical performance, extreme operating conditions, safety and reliability, and obtained CE marking. Its technical compliance, safety and stability meet internationally leading standards.
Why ASNA RMU / switchgear Represents the Future Trend
The EU SF₆ Ban Takes Effect (Full Ban Starting from 2026)
Sulphur hexafluoride (SF₆) is recognized as the most potent greenhouse gas, with a GWP of 23,500. Under the EU F-Gas Regulation (EU) 2024/573, it will be fully prohibited for use in medium-voltage equipment from 2026 onwards. This regulatory shift creates an urgent demand for viable alternative technologies. Featuring the unique concept of atmospheric pressure sealed natural-air insulation, ASNA technology adopts natural air as its insulation medium. It has a GWP of zero, carries no leakage risk, delivers high reliability and low whole-life operational costs, and represents the future direction of technological development.
Technical Characteristics Comparison of Medium‑Voltage Switchgear with Different Insulation Types
| ASNA | SF6 Insulation | Eco-friendly gas insulation | Traditional air insulation | |
| Insulation medium | Natural air | SF6 gas | Pressurized dry air, N₂, etc. | Natural Air |
| Sealed‑tank Pressure | Atmospheric pressure (equal to ambient pressure) | ≥130kpa | ≥190kpa | No sealed‑tank |
| Leakage Risk | None | Yes; insulation capacity degrades after gas leakage | Hi; insulation capacity degrades after gas leakage | None |
| GWP | GWP=0 | GWP=25000 | GWP=0~1 | GWP=0 |
| Gas Recovery | No gas recovery required | Recovery requires specialized equipment and personnel | No gas recovery required | No gas recovery required |
| Personnel Safety | Vacuum arc‑extinguishing, no toxic substances generated | SF₆ arc‑extinguishing, toxic gases will be generated | Vacuum arc‑extinguishing, no toxic substances generated | Vacuum arc‑extinguishing, no toxic substances generated |
| Environmental Compliance | Fully compliant. Natural Air, environmentally‑friendly | Non‑compliant with new EU environmental regulations. Contains potent greenhouse gas | Compliant. Uses industrially‑produced eco‑friendly gases with no greenhouse‑gas emissions, yet carbon emissions occur during gas production | Compliant |
| Environmental Adaptability | Sealed‑tank; immune to external environmental contamination | Sealed‑tank; immune to external environmental contamination | Sealed‑tank; immune to external environmental contamination | Non‑sealed structure; the insulation system is susceptible to environmental contamination and requires regular cleaning and maintenance. |
| Maintenance‑free Performance | 1. Sealed‑tank; no cleaning or maintenance required. 2. No gas leakage; no gas monitoring or refilling required |
1. Continuous gas pressure monitoring required 2. Gas refilling maintenance with power outage required after gas leakage |
1. Continuous gas pressure monitoring required 2. Gas refilling maintenance with power outage required after gas leakage |
Periodic inspection, cleaning and maintenance are required. |
HM Power's
HM Power's platform strategy regarding ASNA technology
One core technology • Multiple scenario configurations
All HM Power products share the same ASNA technology platform to ensure consistent performance and reliability across the entire range of products. This unified approach brings significant advantages
Mature insulation principles are applied to all voltage levels and specifications
Unified design rules reduce engineering complexity and shorten production cycles
Unified maintenance procedures and training apply to all product models
Different solutions can be flexibly combined to adapt to various application scenarios
Compared with load switches and fuse switches, it provides comprehensive protection capabilities and meets the development requirements of smart distribution networks.
Our product strategy emphasizes the combination of platform standardization and application-specific optimization - achieving standardized production while maintaining the flexibility to meet specific customer needs.
faq
Questions and answered
A: The atmospheric pressure design achieves complete pressure balance between the cabinet interior and the external environment. It removes the pressure difference that causes leakage in conventional high-voltage equipment, fundamentally eliminating gas leakage risks.
A: Based on air insulation, phase-to-phase insulating barriers are installed between phases, No insulating components interconnect the phases. There is no risk of phase-to-phase surface creepage, which eliminates the hazard of phase-to-phase discharge breakdown at the insulation structure level.
A: ASNA technology R&D started in 2009, and ASNA RMUs entered the market in 2010, with 16 years of field operation experience. More than 60,000 ASNA RMUs have been operating stably worldwide.
A: Circuit breaker can be combined with various relay protection devices to achieve precise protection of the line, without affecting the normal power supply of the upper-level power grid and other sound lines. The load switchgear itself does not have the ability to cut off short-circuit current. In the "fuse switch scheme, short-circuit protection relies entirely on high-voltage fuse. Fuse is disposable passive components. Once a single-phase short circuit occurs, they often result in "non-full-phase operation" (i.e., only one phase is blown), which can easily cause the transformer at the back end to burn out due to phase loss.
A: Circuit breakers can be paired with various relay protection devices to deliver precise line protection without disrupting normal power supply to the upstream grid and other healthy circuits. Load switches themselves cannot interrupt short-circuit current. Under the fuse switch scheme, short-circuit protection relies entirely on high-voltage fuses. Fuses are disposable passive components. If a single-phase short circuit occurs, this may lead to non-full-phase operation (i.e. only the fuse on one phase blows), which can easily burn out downstream transformers due to phase loss.
A: Yes. The pressure balancing device in ASNA switchgear can effectively block salt spray and dust particles from the ambient environment from entering the cabinet. It keeps the air inside the sealed cabinet consistently clean and maintains insulation performance, making the equipment suitable for coastal regions with heavy salt spray.
A: Standard ASNA RMUs are suitable for altitudes up to 1,500 meters. For sites above 1,500 meters, please contact us for special adaptation.
A: We offer full OEM / ODM services, supporting in-depth customization of cabinet appearance, functional configurations and intelligent modules to meet specific customer requirements.
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