ČEPS, a joint stock company, is the sole Czech Transmission System Operator and holds an exclusive licence to that effect granted by the Energy Regulatory Office under the Energy Act. The Company is responsible for the maintenance and upgrading of 43 substations comprising 78 transformers, which allow electricity to be supplied from the transmission system to the distribution network, as well as 400kV lines with a total length of 3 735 km and 220kV lines with a total length of 1909 km. ČEPS is a member of relevant European international organisations. The Company is responsible for maintaining the balance of electricity supply and demand within the Czech power system in real time (system services) and for organising cross-border power exchanges including transits. ČEPS has traditionally been closely involved in the creation of liberalised electricity markets both in the Czech Republic and Europe.