In the early days of the industrial use of electricity neither distribution nor transmission systems were needed; electricity was generated solely for the producer’s own use. The first distribution networks were built in the first decade of the 20th century, together with the first public power stations.
The main impetus for the formation of a national power system in its current form was provided in 1919 by the passing of legislation on the supply of electricity to the whole of the country. The role of the emerging transmission system was aptly described in a promotional brochure published in 1924 by the Provincial Authority for Business Promotion in Brno: “The aim of systematic electrification is to develop an inclusive chain of large power plants in Czechoslovakia built near to resources of natural energy, i.e. coal mines or major rivers, so that generated electricity supplied to a common grid can be distributed economically and in the required amount throughout the whole of the country”.
The construction of a backbone transmission network was finally completed in the 1980s. It currently consists of 400kV power lines together with 220kV lines, the construction of which was completed in the early 1970s and which are currently used mainly as reserve lines. In addition, the transmission system comprises 41 substations with 71 transformers for both basic voltage levels. The older 110kV grids have been used for distribution purposes since the 1970s.
The Czech 400kV and 220kV electricity transmission network, often termed the “backbone network”, is required for the distribution of the output of large Czech power plants throughout the whole of the Czech Republic and, at the same time, forms an important part of the international European network. The transmission network supplies electricity to distribution networks from which electricity is then supplied to end consumers. The Czech transmission network is interconnected, via cross-border lines, with the transmission networks of neighbouring countries thus enabling its synchronous operation with the interconnected power systems of the rest of Continental Europe.
Voltage level is a very important aspect of any transmission system. High voltage is used for electricity transfer over long distances in order to reduce transmission losses caused by the passage of electric current. Ohm’s law states that with increasing voltage, electric current passing through a conductor decreases and, consequently, losses also decrease. The highest voltage level used in the Czech Republic is 400kV whilst some countries (e.g. Russia and China) use a voltage level of 1000kV.