Pressurized Air Cable Technology

Technology for the Future

The Hivoduct technology sets new standards in power transmission: By using pressurized air as an insulating medium, it offers significant advantages over conventional cables and gas-insulated systems (GIS).

It combines the highest efficiency and maximum safety with a significantly reduced environmental impact.

Learn more about how this groundbreaking technology works and its specific benefits in the following sections.

Hivoduct Pressurized Air Cables – The Future of High-Voltage Technology

The expansion and modernization of high-voltage grids face growing challenges: environmental regulations, higher transmission capacities, increasing demands on grid stability, and the impacts on surrounding areas make traditional solutions more difficult. Underground high-voltage cables offer an alternative but come with new challenges, including thermal limitations, joints as cost drivers and weak points, magnetic field emissions, and special requirements for grounding and reactive power compensation.

Hivoduct Pressurized Air Cables – A Groundbreaking Technology
To offer grid operators a new, better option for network expansion, Hivoduct has developed the new product category "Pressurized Air Cables," setting new standards in high-voltage technology. The innovative pressurized air cables provide technical advantages over conventional overhead lines and XLPE cables. Thanks to a coaxial pipe-in-pipe arrangement and pressurized air as the insulating medium, they combine proven concepts from GIS technology with a forward-looking, environmentally friendly solution.

No SF6 and PFAS Gases – With the Same Performance
While GIS busbars and GIL (gas-insulated lines) have traditionally relied on SF6 or PFAS gas mixtures as insulating gases, there is growing global pressure to replace these climate-damaging gases. Hivoduct pressurized air cables eliminate these completely while still covering the entire medium- and high-voltage range.

Innovation with 50 Years of Experience
The decision to eliminate SF6 required a fundamental re-development. Hivoduct has therefore developed a completely new technology that combines over 50 years of experience with gas-insulated high-voltage products with new design ideas, resulting in unique, innovative features.

Our Drive: Sustainable High-Voltage Technology for a Safe and Efficient Energy Supply.

Our Vision: Pressurized Air Cables are the New Standard for Modern Electric Power Transmission.

Enhancing the Neighborhood

No Greenhouse Gas Potential of the Insulating Material

Minimization of Electromagnetic Fields

Material Savings & Sustainability

Reduced Energy Losses

The result of this development process is the Hivoduct pressurized air cable – a groundbreaking solution for powerful, environmentally friendly, and future-proof power transmission.

Insulation Design

We have leveraged the well-established and well-researched dielectric properties of air to develop optimal conductors, housings, spacers, and shields for operating pressures up to 10 bar.

The graphic shows the optimization of the housing and inner conductor for different lightning impulse voltages.

For a nominal voltage of 145 kV, according to IEC 62271 standards, a lightning impulse withstand voltage (BIL) of 650 kV is required. With a housing diameter of Da=210 mm, inner conductors with a diameter of about 80 mm are ideal for minimizing the field strength at the inner conductor. With a wall thickness of 10 mm from the inner conductor, this results in a conductor cross-section of approximately 2200 mm². An optimal diameter ratio of housing to inner conductor is achieved at e=2.7.

The highest electrical field stress occurs at the surface of the conductor and the shields. Details can be found herer LINK.

Mechanical Design

The key aspects of the mechanical design are:

Design for air internal pressures up to 10 bar.
This ensures that the insulation distances are as small as possible while still keeping the burst values for the housing manageable. Burst tests in accordance with standards such as SVTI 704, EN 12952, EN 12953, EN 13445, ASME, etc., with burst values up to 50 bar (5 * 10 = 50 bar), must be taken into account.
Reduced number of sealing surfaces and a double sealing system to ensure reliable air tightness over the entire product lifespan.
No welded flanges, as gas-tight welding of thin-walled aluminum pipes is a complex and error-prone challenge, both in the factory and on-site. It also does not allow for non-destructive disassembly.
No bolted flanges, as they require high material and assembly costs.
Example for 1 km, 3-phase installation:
--> GIS : 48.000 small parts (16 bolts per flansche, nuts, washers)
--> Pressurized Air Cables: 0 small parts
Additionally, manual inspection of each screw connection is prone to errors. Therefore, we have consciously avoided screw connections for pressurized air cable flanges.
Flexible elements for flexible installation, such as along roads or through tunnels.
This includes flexible flanges, elbows, and compensators that absorb thermal expansions during operation.
Sealing of the flanges against water and dust ingress, if needed.
Fast installation and disassembly for easy expansion, maintenance, and repairs.
Especially advantageous for test or laboratory installations, where frequent, non-destructive disassembly and reconfiguration are required.

Hivoduct Cable Components – Flexibility for Every Application

Our extensive portfolio of pressurized air cable components enables customized solutions for a wide range of requirements:

Straight Pipe – Any length up to 5 m
Flexible Flanges - For compensating slight directional changes
Fixed Elbows – 90° and others available on demand
Variable Elbows – Flexible adjustment of ±8° in all directions
Adjustable Angles -Any angle through Z-connections in the layout
Length Compensation Element – ΔL = 0–100 mm to compensate for thermal expansions
Side-Removable Element – Allows the lateral removal of a section of a cable
Outdoor Bushing – Direct connection to high-voltage lines
GIS Interface – Compatible with standardized interface IEC62271-209
GIS Direct Conncetion - Direct adapter to a GIS flange
Cable Interface – Compliant with IEC 62271-209 standard for high-voltage cables
Transformer Direct Connection - Customizable for any transformer bushing
Roller System – Supports installation, alignment, and maintenance of pressurized air cables in compact pipes, tunnels, or confined spaces
Pressure Monitoring System – Ensures constant operating conditions
Installation and Dismantling Tools – For quick, efficient, and safe installatios

Maximum Flexiblity through Modular Combination

All components of each series are freely combinable to achieve the desired technical characteristics optimally. The right selection and adjustment are part of the engineering process.

Our 3D engineering tools have all components available, allowing us to quickly create an initial layout based on customer specifications for detailed discussions.

Installation Design – Efficient, Space-Saving, and Flexible

For underground or closed applications, it is crucial to minimize the space requirements and the effort for cable ducts, installation, thermal measures, and construction work.

The key design features that enable this are:

Low Losses – The low conductor resistance reduces losses, eliminating the need for parallel systems and additional spacing between phases.
Compact Dimensions – he absence of traditional flanges and bolts reduces the outer dimensions, allowing for narrower trenches and smaller cable ducts.
Innovative Roller System – Specifically developed for installation in pipes and confined spaces. The roller system remains in the pipe, enabling thermal expansion during operation and allowing for quick repairs or replacements.
Long Continuous Cable Sections – Pressurized air cables can be pulled into pipes, cable trays, or under tunnel linings without direct access for workers or machines.
Minimal Bending Radius – 90° elbows have no bending radius, making it easy to implement complex arrangements.
Passive Arc Fault Safety – Even in the extremely rare case of an internal arc fault, there are no external effects. This allows pressurized air cables to be safely installed alongside roads, railways, communication infrastructure, cable trays, tunnels, or bridges.
Fire and Environmental Protection – Hivoduct pressurized air cables feature robust, thick-walled aluminum housings that are non-flammable. This enables safe integration into critical infrastructures.

Further details can be found in the products tab.

Apllication Examples:

Hivoduct pressurized air cables in prefabricated concrete ducts, under tunnel linings, or in underground pipes.
Microtunneling with concrete pipes allows installation without the need for extensive digging.
The roller system ensures quick installation and easy removal during maintenance or expansion.

Shielded Electromagnetic Fields – Maximum Safety

Hivoduct Pressurized Air Cables rely on encapsulated conductor arrangements with conductive, grounded housings to reduce electromagnetic fields to an absolute minimum.

Complete Shielding of the Electric Field – The closed, conductive, and grounded aluminum housing completely prevents the emission of electric fields.
Reduced Magnetic Field Emissions –
- The magnetic field depends on the actual current flow in the conductor.
- Since the housing is conductive and firmly grounded, the current flow in the conductor induces a compensating current in the housing, which largely cancels out the external magnetic field.
- As a result, the magnetic emissions of Hivoduct cables are significantly lower than those of high-voltage lines or conventional cables.

The Best Solution for Minimal Electromagnetic Fields

When minimizing electromagnetic emissions is crucial, Hivoduct pressurized air cables offer the best technical solution – regardless of current strength or transmission power.

See comparisons here.