400 kV Western Corridor of the Peloponnese

With the current load levels, the Peloponnese region exports energy during the greater part of the year. Since 2005, the Peloponnese region presents with a local maximum of 1000 MW during night time hours.

In these cases, the Peloponnese is a particularly critical region for the stability of the South System voltages, in case of loss of production in the region. Moreover, the Peloponnese is connected to the rest of the System exclusively via 150 kV lines, and therefore has a reduced transmission capacity. Specifically, to date, the Peloponnese is connected:

  • with Attica via three 150 kV heavy-duty double circuit Transmission Lines and
  • with Western Greece through two 150 kV submarine cables.

The new Megalopoli V unit is in full operation (operates up to 500 MW under special status according to Law 4533/2018), and moreover significant capacity is expected to be added from new RES Stations.

In this light, potential voltage problems and in particular the issue of absorption of the power produced by the generating Stations expected to be developed in the area, are effectively addressed with the expansion of the 400 kV System towards the Peloponnese (with beneficial effects for the entire South System).


Western Corridor (Megalopoli - Patra - Western Sterea)

The construction of a new High Voltage Center in Megalopoli is critical for the Peloponnese region. The Megalopoli HVC, which was entered into full operation in 2014, was necessary for the connection of the new generating plant in Megalopoli (“Megalopoli V” Unit), for increasing the penetration of RES in the Peloponnese and supporting voltages during high load hours.

The interconnection of the Megalopoli HVC with the 400 kV circuits on the Antirrio side, is carried out via the new double circuit 400 kV Transmission Line, consisting of overhead, underground and submarine parts, as well as the respective compensator self-inductances.




  • The expansion of the 400 kV System to Megalopoli (followed by the creation of a 400 kV Patra - Megalopoli - Corinth loop) drastically increases the transmission capacity to and from the Peloponnese, offers the opportunity for the development of RES and thermal Stations, significantly improves the voltage stability margin for the South System and shields the Peloponnese against any combination of production and load conditions. Also, it powerfully connects the Megalopoli generation center with the high load areas (Attica and Patra) and contributes in achieving an evenly distributed development of the Production and Transmission Systems in the South System. Finally, it should be noted that the development of the 400 kV System to the Peloponnese, contributes towards reducing the total losses of HETS.