As “Non-Interconnected Islands” (NIIs) are considered those Greek islands whose Electricity Distribution Network is not connected to the Transmission System or the Distribution Network of the mainland. The operation of the Electrical Systems of the Non-Interconnected Islands, which includes the operation of the production, the functioning of the market and of the systems of these islands, is the responsibility of HEDNO S.A. (the Greek DSO), and is conducted in accordance with the “Operation Code of Electricity Systems of Non-Interconnected Islands”, issued pursuant to article 130 of Law 4001/2011.
After the completion of Phase A of the Cyclades Interconnection (Syros, Mykonos, Paros and Naxos) to the Mainland System in March 2018, the electrification of Non-Interconnected Islands (NIIs) substantially altered compared to the situation in the beginning of the previous decade.
With the completion of Phases B and C of Cyclades interconnection, their systems’ reliability and stability are now further secured. However, a significant number of NIIs continue still to be electrified by the local production units of PPC S.A., which are fueled with oil, either heavy (fuel oil) and/or light (diesel). The contribution of RES is also important, especially the wind and photovoltaic stations, which operate on these islands.
The Non-Interconnected Islands (NIIs) market consists of twenty-nine (29) autonomous systems. Some of them consist of several islands (island clusters).
The size of the twenty-nine (29) autonomous island electrical systems of the country varies:
- Nineteen (19) “small” autonomous systems with a peak demand up to 10 MW.
- Eight (8) “medium-size” autonomous systems with a peak demand from 10 to 100 MW.
- Two (2) “large” autonomous systems with a peak demand of more than 100 MW (Crete and Rhodes).
The annual demand for electricity in the NIIs varies in size, from a few hundred MWh on the smaller islands (eg Antikythira, Agathonisi, etc.), to some TWh in the larger ΝΙΙ (Crete).