Alternating current (AC) is the most common form of electricity transmission and is used in almost all electricity grids worldwide. It is characterized by the fact that the direction of the electrical current flow changes periodically - typically 50 times per second (50 Hertz) in Europe, including Austria. This characteristic distinguishes alternating current from direct current (DC), where the current flows in a fixed direction.

The main reason why alternating current is preferred for the transmission of electricity is its efficiency. Alternating current can be transformed relatively easily to higher voltages, which enables transmission over long distances without incurring large losses. This is particularly important for the supply of electricity in widely dispersed countries such as Austria, where electricity from hydroelectric power plants in the Alps has to be transported to urban centers and rural areas. By converting to high voltages, the energy can be transmitted over long distances before being transformed back down to lower voltages in cities and households.

In Europe, and therefore also in Austria, the mains voltage for households and small businesses is generally 230 volts at a frequency of 50 hertz. These standards have been harmonized to ensure the efficiency and compatibility of appliances and systems. For industrial applications, a three-phase alternating current supply is often used, which enables a higher power output and is necessary for the operation of large machines and systems.

When it comes to the use of alternating current, Austria benefits greatly from its geographical and climatic conditions, which enable significant electricity generation from hydropower. Power plants in the Alpine regions generate large amounts of alternating current, which is then fed into the national grid. The use of alternating current not only facilitates the distribution of the generated energy over long distances, but also enables a stable supply via the European interconnected grid.

The European electricity grid is highly interconnected, which makes alternating current a central component of the energy infrastructure. Countries such as Austria can exchange electricity with their neighbors and thus ensure security of supply. Alternating current allows surplus electricity from renewable energy sources such as wind or solar energy in one country to be used to meet demand in another country.

In recent years, however, there has also been increasing discussion about the role of direct current in electricity transmission. While alternating current is still dominant for distribution in the national grid, high-voltage direct current (HVDC) is increasingly being used to transport energy over very long distances or under the sea. For example, the transportation of electricity from offshore wind farms in the North Sea is being made more efficient with the help of HVDC systems. In Austria, however, alternating current is still the mainstay of the electricity grid and is likely to remain so in the coming years.

In summary, alternating current forms the basis of modern electricity grids due to its versatility and efficiency. In Austria, it is essential for transmitting electricity from renewable sources such as hydropower to households and businesses. Even in an increasingly integrated European electricity grid, alternating current remains the dominant technology that enables electricity to be supplied across national borders.