In Bergen, a transformer station supplies electricity to Norway's largest port for cruise ships. Since in recent years the number of ships docking there had been rising sharply, two years ago the regional electricity network operator BKK Nett decided to upgrade the station from 45 kV to 132 kV. The upgraded station has a special feature: for its high-voltage switches it uses clean air as an insulating gas - instead of sulfur hexafluoride (SF6), which has been the standard for more than fifty years to prevent short circuits and arcs in substations.
Within the power grid, from power generation to the end consumer, transformer stations with gas-insulated switchgear connect extra-high-, medium- and low-voltage in the smallest possible space. In recent years, demand for such systems has risen sharply. This is due to decentralized renewable energy production, the global rise in electricity consumption and increased urbanization which increases demand for small substation and hence for compact switchgear. With this, the demand for SF6 has grown, as it is the gas mostly used in switchgear. After all it’s largely safe to handle and allows for space-saving switchgear-designs.
But more and more often, SF6 is no longer the gas of choice. For a simple reason: if the gas escapes, it contributes to climate change. It is around 23,500 times more warming than the greenhouse gas CO2 and has a life span of 3,200 years in the earth's atmosphere. According to the Intergovernmental Panel on Climate Change IPCC, abandoning SF6 completely could contribute 1.5 percent to achieving no more than 2 degrees Celsius global warming by 2100. In recent years, the potential climate impact of SF6 has led to a steady increase in demand for SF6 alternatives. Most prominent among available options are “clean air” solutions, i.e. purified air, and gas mixtures that both have a fraction of the climate impact of SF6.
Hermetically sealed systems with clean air as an insulating gas take up more space than SF6, but combined with digitalised current and voltage transformers these systems can be built as small as current SF6 systems. In addition, they are durable and can be used without any problems at the lowest temperatures - down to -50 degrees Celsius. And if the purified air escapes, there is no danger to the environment whatsoever. The use of vacuum switching also results in increased performance. And a shorter arcing time – compared to SF6 – leads to less wear and tear on the system.