Oil-filled power transformer

An ETRA Range Adapted to Every Application

ETRA OFFSHORE WIND

The ETRA OFFSHORE WIND oil-immersed power transformer is designed for marine and coastal environments exposed to severe corrosion, vibration and access constraints.

Its design integrates:

• Reinforced anti-corrosion protection
• Architectures adapted to offshore wind farms and platforms
• Mechanical robustness compatible with marine transport and offshore installation

It ensures reliable evacuation of generated power to the transmission grid, with optimized loss performance and maximum availability.

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ETRA HYDRO

The ETRA HYDRO oil-immersed power transformer is specifically developed for hydroelectric power plants, from small installations to large dams.

It is dimensioned to withstand:

• Rapid load variations related to turbine operation
• Mechanical and thermal stresses specific to hydraulic facilities
• Strict noise and fire safety requirements

Its design optimizes losses, dielectric withstand and insulation lifetime, while facilitating integration within powerhouse buildings or constrained environments.

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ETRA SUBSTATION

The ETRA SUBSTATION oil-immersed power transformer is designed for transmission and distribution substations (primary substations, MV/HV substations, grid interconnections).

It meets the requirements of public and industrial grid operators:

• Voltage stability via On-Load Tap Changer (OLTC)
• Insulation schemes adapted to substation architecture
• Compatibility with protection and control systems

These transformers are used for both new installations and capacity reinforcement or replacement projects.

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Covered Application Fields

Power Generation and Renewable Energy

ETRA transformers are installed close to generation units: onshore and offshore wind, hydropower, solar and photovoltaic plants.

Each transformer is dimensioned according to the actual load curve of the installation to minimize losses, control temperature rise and contribute to grid stability.

Transmission, Distribution and Railway Traction

For transmission and distribution networks, the SANERGRID Group supplies transformers for:

• ENEDIS substations (primary and distribution substations)
• RTE transmission networks and interconnections
• Railway traction substations, including TER and TGV applications

Designs take into account harmonic distortion, thermal stresses and voltage regulation constraints specific to railway infrastructures and heavily loaded networks.

Critical Infrastructure and Data Centers

ETRA transformers are also adapted to highly demanding availability environments such as data centers and critical digital infrastructure.

They are designed to withstand continuous high load regimes, controlled thermal cycles and enhanced requirements in terms of reliability, redundancy and monitoring, contributing to uninterrupted power supply for sensitive IT installations.

Design, Performance and Key Equipment

Insulation, Tank and Mechanical Safety

The performance of an oil-immersed power transformer depends on insulation quality and tank design.

ETRA designs combine:

• Optimized paper/oil insulation systems
• Solid insulation materials selected for thermal endurance
• Bushings and equipment compliant with required overvoltage withstand levels

Depending on the environment, porcelain or composite insulators are integrated.

The tank is equipped with safety devices (pressure relief valves, pressure relays, oil level and temperature indicators) ensuring continuous monitoring and effective protection in case of internal fault.

Protection, Control and Monitoring

Transformers can integrate a complete protection and control chain including:

• Temperature, gas and pressure sensors
• Protection relays adapted to operational policies
• Interfaces compatible with existing SCADA and control systems

This protection chain notably includes the Buchholz relay, the reference device for internal fault detection in oil-immersed transformers.

Monitoring can be local or remote, enabling condition-based maintenance and improved operational anticipation.

From Engineering to Operation: SANERGRID Group Support

Engineering and Industrial Risk Management

The SANERGRID engineering division performs site studies integrating fire, pollution, noise and vibration risks.

This expertise results in concrete solutions such as:

• Dielectric oil containment systems
• Rainwater filtration systems
• Fire-protection and environmental impact mitigation devices

It notably relies on the EXTICOV® range, passive fire-protection covers designed to limit the spread of hydrocarbon pool fires and promote natural extinction of dielectric oils.

All these solutions are designed to integrate seamlessly into electrical substations while meeting local regulatory requirements, operator expectations and insurer prescriptions.

SONEC-KESF: Commissioning, Maintenance and After-Sales Service

Field teams handle installation, commissioning and protection parameterization in coordination with operators.

Support extends to maintenance services, diagnostics, compliance upgrades and long-term technical assistance throughout the transformer lifecycle.

Since early 2026, SONEC has become the official on-site service entity in France for the KOLEKTOR ETRA Group under the name KOLEKTOR ETRA Service France, ensuring local French-language support from within France.

KOLEKTOR ETRA Industrial Capabilities and Expertise

The KOLEKTOR ETRA range covers 10 to 500 MVA up to 420 kV, with an extensive design library enabling adaptation of each transformer to project constraints:

• Cooling modes ONAN / ONAF
• Accessories
• Industrial coatings
• Connection schemes
• Regulation options

Transformers undergo routine and type testing at the factory, with FAT in the presence of the client and SAT on site when required.

Logistics, special transport and handling are coordinated to secure delivery schedules and energization timelines.

Accessories and Spare Parts via TECHNIKELEC

To facilitate operation and maintenance, the TECHNIKELEC platform offers a selection of accessories and spare parts:

• Insulators
• Oil level indicators
• Pressure sensors
• Gaskets
• PTFE plates (to ensure tank-to-ground insulation)
• Locking devices
• MV/HV compatible protection solutions

Technical support is available to validate reference compatibility and propose alternatives when necessary.

Why Work with the SANERGRID Group?

A Comprehensive and Coherent Approach

Beyond transformer supply, the SANERGRID Group masters related challenges:

• Dielectric oil management
• Fire prevention
• Water decontamination
• Anti-corrosion solutions
• Substation protection systems

This cross-disciplinary approach simplifies multi-lot projects and strengthens overall substation compliance.

Responsiveness, Proximity and Support

With teams based in France and a European industrial network, the SANERGRID Group prioritizes direct technical exchanges, rapid decision-making and strong field proximity.

This organization secures timelines, limits interface risks and guarantees optimal installation availability.

Your Oil-Immersed Power Transformer Project

Are you preparing a power generation, transmission or distribution project?

Send us your key parameters (power rating, voltage levels, cooling mode, site constraints). We will propose an oil-immersed power transformer architecture adapted to your project, integrating energy performance, safety and maintenance requirements.

Contact the SANERGRID Group for an initial technical discussion, budgetary estimate or site visit.