October 19, 2021
8 min read

On the front line of SF6-free switchgear technology

Nina Terp

The new high-voltage substation in Burladingen, Germany, is the world’s first eco-efficient facility operated without SF6 and digitalized with new equipment connectivity and intelligence. “This is the future,” say planners and operators.

Distribution system operators are also being impacted by the major trends of our times. For one, increasingly volatile power generation is presenting a challenge to transmission as well as distribution networks. Handling growing electromobility is also a major challenge, particularly for local grids. And finally, operators now see digitalization as a major opportunity for improving their systems: Automated processes based on comprehensive data transparency are the key to bringing eco- and economic efficiency as well as supply security to a new level.

Exactly what this means and how it will function in the future can be seen in a special pilot project in Burladingen, in southern Germany. Siemens Energy is building a new state-of-the-art, eco-friendly, and digitized substation for Netze BW GmbH, a large German distribution system operator. “We’ll be using this substation to more closely and reliably connect Burladingen and the surrounding region with the supra-regional power grid. At the same time, we’re getting ready to handle the growing use of renewable energy sources and spread of electromobility,” explains Netze BW project manager Torge Andersen. The new substation node will have an installed capacity of 80 megavolt amperes (MVA) and 110 kilovolts (kV). Construction of the project began in late 2020, and commissioning is planned for 2022.

Eco-efficient and digitalized

What’s special here? “The new substation in Burladingen is the world’s first facility that combines eco-efficiency and digitization on this scale,” explains Marcel Engel, Netze BW expert for grid development. Specifically, the new high-voltage system will, for one, completely dispense with the insulating gas sulfur hexafluoride (SF6) and thus be especially eco-friendly and greenhouse gas free. “Secondly, we’re relying on vacuum circuit breakers that we’ve been using for two years as the first customer worldwide, and innovative space-saving low power instrument transformers,” continues Engel. “And thirdly, all signals and measured values from the substation will be transmitted fully digitized from a process bus to the protection and control systems via fiber optic cables, which reduces the use of resources like copper. This combination is our way to the substation of the future.”

The innovation level in this project is very high. The substation of the future is a bold step for us, that requires trust.

Marcel Engel

Netze BW expert for grid development

Strong partnership with the customer

As general contractor for the project, Siemens Energy is responsible for the planning, supply, turnkey construction, and commissioning of the substation. The company is providing all products used in the substation and fully integrating innovative technologies into the project’s concept. “Such technologically highly integrative projects can be successfully executed only through close cooperation with the customer,” says Mathias Reumann, the Siemens Energy project manager responsible for the turnkey substation. “We’ve nurtured a strong partnership with Netze BW for this purpose, and the gain in information for both sides is enormous.” In addition to supplying the substation’s complete medium-voltage system, Siemens Energy will deliver five 8VN1 switchgear bays designed for 110 kV with low power instrument transformers and merging units, two 40-megavolt ampere power transformers, 14 surge arresters, and three arc suppression coils.

The substation’s entire protection and control technology is based on Siprotec 5 and Sicam as well as the company’s process bus technology. Another highlight: By integrating Sensgear®, Sensformer® and Senscoil® systems, the smart sensors on all components are pre-assembled and tested at the factory. They record all relevant product operating data such as the oil pressure and temperature of the transformers, as well as gas pressure, temperature, and number of switching cycles. And like the substation’s overall technology, the built-in sensors have a service life of around 40 years.

Looking ahead: SF6-free switchgear

Siemens Energy is using various products from the company’s so-called Blue Portfolio in the substation. These products completely dispense with SF6. This fluorinated gas is a highly effective switching and insulating medium traditionally used throughout the industry: its excellent chemical and electrical properties enable the design of compact and economical substations. However, SF6 is a greenhouse gas that, if it escapes into the atmosphere, can have an impact to the climate change. “Our specialists handle the gas extremely carefully, of course,“ stresses Engel. At the same time, operators as well as manufacturers are looking for alternatives so they can gradually replace the fluorinated gas in new systems with more environment-friendly and equally efficient switching and insulation alternatives. Engel: “As Netze BW, we believe in the transformation into SF6-free switchgear technology and have been supporting this goal for years. With appropriate transition periods and strong partnerships between manufacturers and operators, we will succeed. I am convinced of that.” 

Instead of using SF6, the alternative products in the Blue Portfolio rely on technically processed and purified air (“clean air”) in a compressed form. The industry has been working with clean air in the high-voltage sector since 2018. For the ground-breaking Netze BW substation Nördlingen, Siemens Energy has delivered and installed its new outdoor circuit-breakers with vacuum switching technology as well as a combined voltage and current transformer insulated with clean air – for the first time worldwide in a 110-kV high-voltage grid. “We’ve already had very good experience with the combination of purified air and vacuum switching technology in Nördlingen, Germany. We’re now taking this one step further at the substation in Burladingen and are happy to be working with our experienced partner Siemens Energy again,” says Engel. 

The energy transition is progressing. More and more solar parks like this one in Riedlingen in southern Germany are feeding electricity into the grids. Marcel Engel explains: "The substation in Burladingen will become an important grid hub that will contribute to the success of the energy transition."

Compact design

Netze BW has also opted for another innovative technology from Siemens Energy: low-power instrument transformers (LPIT) are being used in Burladingen. The innovation: they use Rogowski Coils to measure the current and an electric field probe with capacitive principle to measure the voltage in the gas-insulated switchgear (GIS). Together, they are used in conventional GIS gas compartment cast resin partition. They provide a very compact solution for precisely and safely measuring both current and voltage.

Digital data transmission saves 850 kilos of copper

And that’s not all as far as innovations go. A cable transmits analog signals from the substation to the merging unit, located near the converter. This unit records, digitizes, and analyzes the measured values. With a process bus, the data is then transmitted via a fiber optic Ethernet cable over a distance of about 100 meters to the structurally separate station and control system. This process complies with the IEC 61850 standard that defines the general transmission protocol for protection and control systems in electrical switchgear. In this project, the protective relays no longer work with analog values, but rather directly use digital values from the data stream of measured values. This innovative transmission path is also cost-effective. “Using a fiber optic system to transmit internal data in the Burladingen substation eliminates the many copper cables normally needed to transmit analog signals to the protection and control system,” explains Engel. The company calculates that it will save 850 kilos of copper with this solution.

Engel concludes: “From our point of view, all this will make Burladingen one of the most innovative substations in the world. The substation of the future is a bold step for us, that requires trust. We already have many systems from today’s Siemens Energy in operation. For decades. We appreciate the partnership."

October, 2021

Nina Terp works as a freelance science and technology journalist in Germany. Her work has been published in a number of German and international specialist media. 

Combined picture and video credits: Martin Friedrich