The entire Swiss electricity grid measures over 250,000 kilometres. If they were placed end-to-end, its lines would reach around the Earth six times.
Extra-high-voltage electricity (380,000 volts = 380 kV and 220,000 volts = 220 kV) reaches the transmission grid from power plants as well as imports from abroad. The voltage must be as high as possible so that as much energy as possible can be transported over great distances with minimal losses.
By the time the electricity finally reaches the power sockets in homes, the voltage has to be reduced 1,000-fold (from 380,000 volts or 220,000 volts to 400 or 230 volts). This takes place across multiple stages and different grid levels.
The 380 kV or 220 kV electricity flows into the transmission grid from the power plants and from abroad. This stage is referred to as the extra-high-voltage level.
The voltage range between 36 kV and 150 kV is referred to as the high-voltage level.
The voltage range between 1 kV and 36 kV is referred to as the medium-voltage level.
Any voltage below 1 kV is referred to as the low-voltage level. This is the voltage at which the electricity reaches the power sockets of households.
Stages 2, 4 and 6 are referred to as transformer levels. They transform the electricity to the next level down (or up, if necessary).