The path of electricity

The structure of the electricity supply system

The electricity generated in power plants has to be transmitted to the customers. This requires a transmission grid which provides customers with the required energy at all times: From the power plant, the electricity flows across lines at a voltage of up to 380,000 V to the centers of consumption. Here, it is transferred to the distribution grids at voltages of 110,000 - 10,000 V to be finally delivered to the consumers at 400/230 V.

Depending on the level of operating voltage, the following transmission lines are usually distinguished:

The voltage levels of electricity supply

• Extra high-voltage lines at operating voltages in excess of 150,000 V
• High-voltage lines at operating voltages between 60,000 V to 150,000 V
• Medium-voltage lines at operating voltages between 1,000 V and 60,000 V
• Low-voltage lines at operating voltages up to 1,000 V

Energy transmission

In the Federal Republic of Germany, the high-voltage lines are operated at voltages of 380,000 V or 220,000 V. They transmit the electrical energy from the large power plants to substations near the centers of consumption. Extra high-voltage lines bridge large distances and fulfill supra-regional transmission functions.

Energy distribution

In the substations, the extra high-voltage is usually stepped down to 110,000V. From here, 110,000 V high-voltage lines distribute the electrical energy to the centers of consumption with a demand between 10 and 100 MW, e.g. large-scale industry and the substations in the cities or rural areas.

In the substations supplied at 110,000 V, the voltage is stepped down to medium voltage, i.e. usually to 10,000 V or 20,000 V. The medium-voltage lines are operated at these voltage levels. They distribute the electrical energy within the individual rural or urban areas.

The medium-voltage lines in urban areas are usually operated at 10,000 V. Operating voltages of 20,000 V are found predominantly in rural areas because larger distances have to be bridged here than in urban areas. In some regions, different voltages may also be found at the medium-voltage level. Small industrial establishments with a power demand between several hundred kW and several MW are supplied directly from this voltage level.

In distribution substations, the medium-voltage is stepped down to low voltage of 400/230 V for a power demand of up to 1,000 kW. At this voltage, the low-voltage lines supply surrounding houses or small businesses with electrical energyAmrp