by Hakavik Power Station. A further power station, at Kjofossen feeds single phase AC directly in the overhead wire. In Denmark and Finland, 50 Hz is used for the main lines (if electrified) and the electricity comes from general suppliers. As such, much simpler equipment than in Sweden and Norway is needed for conversion. South Africa In the Republic of South Africa there are extensive AC and DC traction schemes, including 50 kV and 25 kV AC single phase systems. Electrification in Natal was stimulated by the takeover of the South African Railways' system by the Electricity Supply Commission (now Eskom) based on the Colenso Power Station. United Kingdom In the United Kingdom, the Network Rail 750 V DC electrification system in the southeast of England is supplied with power from an extensive 33 kV power distribution network. Areas with traction power networks United Kingdom Germany (except Mecklenburg-Western Pomerania and Saxony-Anhalt), total length 7,959 km Switzerland Austria (separate traction power network for the Mariazeller Bahn) Central Sweden Southern Norway east of Oslo USA (Amtrak's former Pennsylvania Railroad lines between Philadelphia and New York City, Washington, D.C., and Harrisburg, PA running with single phase 25 Hz AC, see also Amtrak's 25 Hz traction power system) South Africa Melbourne, Australia (dedicated high voltage transmission wires between former Newport A Power Station and traction substations. However these lines are operated with three phase AC) Riyadh, Kingdom of Saudi Arabia (Riyadh Metro Networks) Characteristics Traction current lines are used to power the railway systems of countries which use alternating current of a lower frequency than the public supply. This is typically the case in the German-speaking countries of Europe. For example, 16.7 Hz AC is used in Germany, Austria and Switzerland. A specific example is the Mariazeller narrow gauge railway in Austria, operating with single phase AC with a frequency of 25 Hz, which has its own traction current lines with an operating voltage of 27 kV. These lines are mounted on the pylons of the overhead wire over the lines. The voltages used for traction current lines are 110 kV in Germany and Austria and 66 kV or 132 kV in Switzerland. Traction current lines are operated symmetrically against earth. In the case of 110 kV lines, for example, each conductor has a voltage of 55 kV against earth. The grounding is made in larger substations and in power stations for traction current,