From the motorway to the urban side street

The electricity network is split into four voltage levels:

• Extra-high voltage network (≥220,000 V)
• High voltage network (>36,000 V to 220,000 V)
• Medium voltage network (>1,000 V to 36,000 V)
• Low voltage network (up to 1,000 V)

These levels have different transport capacities. Lines of identical voltage capacity are connected together in substations. The connection of substations of different voltage levels is performed using transformers which transport the electricity from one voltage level to another.

The electricity network operates similar to the road network.

• The extra-high voltage network corresponds to the motorways. Electricity is also exchanged with other countries at this level.
• The high voltage network corresponds to the regional A roads. Large industrial operations and municipal utilities are connected directly to it.
• The medium voltage network corresponds to main roads in towns. Some industrial operations and municipal utilities are supplied directly by it.
• The low voltage network corresponds to urban side streets. Smaller industrial operations and households are connected to it. The supply voltage is typically 230 volts (single-phase) or 400 volts (three-phase).

The substations and transformers in the electricity network perform the same function as motorway access roads and exits, as well as intersections. Just as motorways do not run right past your front door, so too houses cannot be connected directly to the extra-high voltage network. The power stations correspond to the motorway access roads. They are connected to a network in accordance with their voltage rating.

The extra-high and high voltage networks are generally ring-operated. This means that if a line fails, customers are still supplied "from the other side". It is technically too difficult to operate medium and low-voltage networks as rings. Therefore, these networks are generally operated in radial configurations. Consequently, if a line fails, this may also result in a supply failure.

The higher the voltage during electricity transmission, the higher the transport capacity of a line is and the lower the losses are en route. Therefore, if the electricity has to be transported over long distances, it is transformed to as high a voltage as possible. The voltage is then lowered again in stages en route to the consumer.

A high voltage would be impractical at the consumer's house because the equipment required would be unnecessarily expensive, and the cost of insulation would be unnecessarily high. The losses which occur during transmission and distribution total around seven per cent of the volume of electricity produced in Switzerland. There are only losses of around one per cent on high and extra-high voltage networks.