Environmentally friendly, robust and highly efficient products for OEMs of wind turbine generators

Siemens Energy has delivered more than 4000 units of sustainable transformers and gasinsulated switchgear for the installation in the nacelles and towers of offshore wind parks. This is an important contribution to the expansion of renewable energy sources, which is in line with the outcome of the latest world energy forum report. Besides, it supports the implementation of the United Nations Sustainable Development Goals. 

November 2020

Enabling higher voltage levels within offshore wind turbines

In parallel to the worldwide increasing power demand, utilities and OEMs in the power sector strive for environmentally friendly and resource efficient power generation. Wind power applications make a major contribution to meeting these goals. While wind turbines were producing 0.5 MW of power at a height of 40 meters in 1990, today’s wind turbines produce 10 MW and beyond requiring higher voltage levels and innovative technologies. A transmission voltage of 66 kV has now become standard for offshore wind projects. One core aspect: The high voltage within the wind turbine network has a positive impact on cable losses and efficiency. This is where reliable, compact and environmentally friendly high-voltage products from Siemens Energy can make an excellent contribution. We are delivering sustainable high-voltage equipment to the global wind turbine market since decades.

Transformers, installed up high, serving stable power flow on point

Step-up transformers convert generated electricity to the requisite voltage level for power transmission on high-voltage lines and cables. A step-up transformer in a nacelle of a wind turbine converts the generated wind electricity to the kV-level needed, to serve the switchgear at the bottom of the wind tower.


Siemens Energy offers two kinds of step-up transformers for wind application: Fire resistant GEAFOL cast-resin transformers for up to 40.5 kV and FITformer REN transformers up to 66 kV, with ester, a flame-retardant, biodegradable insulating



For on- and offshore windparks we delivered about 30.000 units of GEAFOL transformers and 1.000 units out of it where delivered for offshore wind projects. More than 2.500 units of the ester fluid immersed FITformer REN where installed in wind offshore applications worldwide.


The latest development is the FITformer REN model that enables power transmission at the 66 kV level for even more efficiency and highest proven reliability. The extremely compact transformers fit directly into the nacelle. To enable the transformers to withstand the strong vibrations in the nacelle, Siemens Energy developed a mechanically reinforced version specifically for wind turbines. The first practical application for the FITformer REN was the

28 MW offshore wind farm Nissum Bredning Vind located in the waters of North-western Denmark.

Gas-insulated switchgear (GIS) in the bottom of the wind turbine

The switchgear protects wind turbine individually against

overloads and short-circuits and makes it possible to supply

electricity reliably and without interruption. The Siemens

Energy 8VM1 Blue GIS is specially designed for offshore

wind turbine installations, based on proven component

technology. The innovative vacuum interrupting technology

enables the implementation of clean air as insulating

medium for the 66 kV GIS. Both technologies realize the

F-gas-free insulation and support the demand for fully

environmentally compatible wind power.


Up till now we produced over 800 units of 8VM1 Blue GIS

for offshore wind turbine generators.


In 2017 the project Nissum Bredning paved the way with

the first installation of our innovative Blue GIS with a special

component design providing highest operational safety and

maintenance freedom.


1,600 t CO2e* can be saved by the application of one

8VM1 bay, compared to a standard SF6-filled gas-insulated

switchgear bay.


*Calculated with a global warming potential of 22,800

(GWP) acc. to EU-F-Gas-Regulation no. 517/2014

Siemens Energy products benefitting the environmentally friendly aspect of renewable energy

Environmentally friendly, robust and highly efficient products from Siemens Energy have many benefits to offer. Despite the power level, our low maintenance products are designed especially for the tough conditions of offshore use, are lightweight and have a particularly compact structure. Siemens Energy high-voltage transmission products score high in terms of environmental compatibility, efficiency, maximized availability and robustness. They do not apply any fluorinated greenhouse gas, nor do they apply mineral oil. As a result, they save time and money, while assuring outstanding grid and application stability. All products are successfully IEC, seismic, and IEEE tested regarding common industry standards.

Saving tones of CO2e by installing Siemens Energy high-voltage products

By supporting one of the most promising future energy sources, renewable wind power generation, we are in line with the outcome of the world energy forum report, published in 2014. In comparison to coal and gas power generation, wind power generation has significantly lower lifecycle emissions per GWh.

Source: World Energy Forum report on climate change published in 2014

The transition to a low carbon energy system can only be realized by increasing the share of renewable energy sources in the energy mix. With our innovative and sustainable products, we support the expansion of wind energy and provide our customer best in class efficiency, sustainability and availability.
Eduardo Terzi, Siemens Energy’s Senior Vice-President for Non-Switching Products

For decades, high-voltage products from Siemens Energy have proven the highest level of safety in operation as well as excellent electrical, mechanical, and thermal properties. Installation of our innovative step-up transformers and GIS in wind turbine generators avoids the application of climate-damaging oil and SF6 gas and enables the highly

efficient connection of the wind turbines for bringing wind home, making power generation from renewable energy sources even more eco-friendly and economical.


The new standard voltage level of 66 kV for connection of increasingly powerful offshore wind turbines reduces the amount of cable needed for connection of a wind farm and the process losses – making wind power even more cost-efficient.

UN sustainability goals

As a leader in innovative and sustainable products, Siemens Energy Transmission is supporting the implementation of the United Nations Sustainable Development Goals. With biodegradable ester insulating fluids for step-up transformers, dry-type transformers and clean air insulation for gas-insulated switchgear we support the implementation of goals number 3 “good health and well-being”, 7 “Affordable and clean energy”, 8 “Decent work and economic growth”, 9 “Industry, innovation and infrastructure", 11 “Sustainable cities and communities”, 12 “Responsible Consumption and Production”, 14 “Life below water” and 15 "Living on land".