Sustainable Development - Alternatives to Sulfur Hexafluoride
 Hochspannungslabor der ETH-Zürich

written by Marcel Knobloch on Friday, August 27, 2021

SF6 is used as a protective gas in switchgear, at voltage levels of up to 1,200 kV. Bucher Hydraulics supports ETH Zurich's research project to find alternatives to the harmful greenhouse gas SF6.

ETH Zurich's research project into alternatives to SF6 (sulfur hexafluoride)

Sulfur hexafluoride (SF6) is the most powerful greenhouse gas known to date and is mainly used in electrical engineering: typically as a protective gas in switchgear, at voltage levels of up to 1,200 kV. The global-warming potential of SF6 is 23,500 times greater than that of CO2.

The Swiss Federal Institute of Technology in Zurich, ETH for short, from the German name Eidgenössische Technische Hochschule, is currently engaged in the research project "Comparative tests for non-SF6 switching gases", which is searching for possible alternatives to SF6.

The researchers led by Prof. Dr. Christian Franck have developed numerical and experimental methods to screen a large number of possible molecules and identify the best candidates. The most promising molecules are characterized with respect to their application for high-voltage insulation. This is initially an electrical problem, but as soon as a gas mixture is looked at more closely, issues such as material compatibility and the evolution of the contact resistance must of course also be considered.

Prof. Dr. Christian Franck explains: “Other efforts include an international testing initiative comparing the dielectric strength of various alternative gas mixtures, as well as conducting experiments on vendor-independent switchgear to compare their interrupting performance. One of the experimental tools used for this purpose is a flexible current-pulse source that can be used to generate sophisticated current waveforms and facilitates advanced test programs, for example the determination of the black-box parameters of the switching arc for use in development tests.”


You can find more information here: Clean air instead of SF6

ETH's project partner for "Switching in alternative, non-SF6 gases"

The ETH High Voltage Laboratory asked Bucher Hydraulics if, as part of a project partnership, they could provide the hydraulic drive for the experimental high-voltage switch. For this function, the ETH project team requires a very powerful hydraulic drive, so that the stroke speed can be kept very precisely constant for the different gas mixtures. A simple way of setting the desired speed is also advantageous. A test switching chamber was set up to test different alternative gases.

Gas-Insulated Switchgear (GIS)

Jakit17/ Exterior view of Gas-Insulated Switchgear (GIS)

Crastan V. (2015) Switchgear

At bottom center is the high-voltage circuit breaker. The drive uses extremely high acceleration to separate the contacts inside the switching chamber very quickly and with precise timing. Contact must be interrupted exactly at the zero crossing point of the sinusoidal alternating current to ensure that any arc is quickly extinguished.

Puffer CB test device – status and the next steps, High Voltage Laboratory ETH Zurich.

Note: Some parts are only drawn provisionally

The figure above shows a sectional view of the circuit breaker test bench. It is constructed from GIS containers. The switch contact located in the center can be replaced. On the left is the hydraulic drive, which drives the movable components of the switch contact.

Sustainable development conserves finite resources

In order to conserve the finite project resources, Bucher Hydraulics contributed the drive to the ETH project at low cost: a modified standard unit, using a smaller cylinder with additional orifices. This offers the possibility of varying the opening and closing speed. By using different orifice sizes, the hydraulic drive also offers the possibility of changing the force (pressure in the oil) and the speed (oil flow cross-section). In this way, tests with the desired stroke-speed curves can be carried out on the test stand. The objective is to deliver an unbiased comparison of different gas mixtures in order to provide the high-voltage industry with a basis for future investment decisions.

Current status and duration of the study

The commissioning process in the ETH high-voltage laboratory went quickly and smoothly. The project team was impressed by the easy handling and the flexibility of the hydraulic drive from Bucher Hydraulics. The ETH project has been involved in extensive tests, measurements and simulations since the beginning of the year and is expected to run for 4 years.

We will report again on the further progress of the study at appropriate intervals.

Prominent students at ETH in Zurich

What do Albert Einstein, Wilhelm Röntgen, Max Frisch and 20 renowned Nobel Prize winners have in common? They were all students at ETH Zurich. Later, Einstein was even active there as a professor. ETH is a technical and scientific university in Zurich. Founded in 1855 as the Swiss Federal Polytechnic, it has been a national educational institution with international appeal from the outset, attracting talent from all over the world. In 1911, the Eidgenössische Technische Hochschule / Swiss Federal Institute of Technology was given its present name. It enters into stable cooperations with the state and industry and increasingly invests in applied- as well as basic-research, which are gaining in importance over teaching. The university is growing steadily, and in 1961 it began the first construction phase of its second location, Hönggerberg, on the outskirts of Zurich. ETH Zurich has also had a site in Singapore since 2010.

Source: interim report: ETH, Zurich

ETH is one of the most renowned universities in the world

In the recent past, worldwide developments such as computer-aided information processing, or the far-reaching consequences of globalization have placed ever greater demands on universities and colleges. ETH Zurich is responding to these new challenges with flexible organizational structures: new research units and study courses are emerging, and research is becoming increasingly networked and interdisciplinary. Long-standing tradition, combined with the ability to constantly adapt to new requirements, contributes to the success of ETH Zurich. There are currently 23,400 students at ETH, including 4,320 doctoral students. They come from over 121 countries and are taught and guided by 640 professors.

ETH is one of the most renowned universities in the world and regularly occupies top positions in university rankings. ETH currently occupies 6th place in the "QS World University Rankings".

If wind energy from the North and Baltic Seas and solar energy from Southern Europe are to be used in Central Europe, new, environmentally compatible transmission grids must be developed. To do that, we need the best minds.

– Christian Frank, Professor of High Voltage Engineering



Follow us