A. Koronides, S. Efstathiou G. Koutzoukos, N. Boulaxis

1. Interconnection of the Cycladic islands of Syros, Tinos, Mykonos, Paros and Naxos to the Mainland System via submarine cables A. Koronides, S. Efstathiou G. Koutzoukos, N. Boulaxis

2. Background • The Interconnection of the Northern Cycladic Islands has been considered as early as the early 90‘s because of: • Rapid growth of their consumption (development due to tourism) • Building new Generating Capacity was always very difficult due to environmental constraints (all existing in proximity to the main towns) • High operating cost using diesel and heavy fuel

3. Area of Concern

4. Evolution of Demand Evolution of Energy demand (1980-2004) 2005 Evolution of Peak load (1980-2004) Year of connection of Andros-Tinos to the Mainland

5. Load Forecast Forecasted Energy demand (2005-2025) Forecasted Peaks (2005-2025)

6. 90 80 70 60 50 40 30 20 10 0 Local Generation [MW] 15 11 20 (30) 6 8 54 34 24 12.3 Andros Syros Mykonos Paros Current capacity Possible additional capacity Planned Expansion

7. Initial Interconnection Plan • Introduced in the late 80’s to be implemented in early 90’s : • weak interconnection to the Mainland by single cable • OHL on the islands and submarine cables between them (shortest distances) • development of new geothermal power plant in Milos • Foreseen implementation in two phases: • Phase A: interconnection of Andros,Tinos, Mykonos and Syros to the Mainland • Phase B: expansion of the connection to Milos (reaching the Geothermal Field) and installation of Geothermal Power Plant in Milos

8. New 150kV OHL New 150kV submarine cable New 66kV OHL New 66kV submarine cable Existing 150kV substation New 150kV substation New 66kV substation Existing PS New PS (geothermal) Initial Plan (made in1989) PHASE Α PHASE Β

9. What has been done (1/2) • By the end of the 90´ were installed • the cables (mid 90’s ) : • Main System – Andros • Andros – Tinos • Tinos – Syros • Tinos – Mykonos • the OHL over Andros (late 90’s)

10. What has been done (2/2) In the meantime : • Local Reaction against construction of OHL (150kV, 66kV) on the islands has escalated also • Local Reaction against Geothermal plant in Milos started However, a new interconnection plan was prepared

11. Existing 150kV OHL New 150kV OHL Existing 150kV submarine cable New 150kV submarine cable New 66kV OHL Existing New 66kV submarine cable Existing 150kV substation New 150kV substation New 66kV substation Existing PS New PS (Diesel) Revision of Initial Plan (2001)

12. Revision of Initial Plan (2001) • Expansion of the Interconnection to Paros and Naxos • Revised plan for installation of new “big scale” thermal station in Naxos • Expectations to overcome local reactions • Sitting of thermal station in Naxos considered possible

13. Court Decisions (2001-2004) • Local Reactions Escalated • State Council Decision was issued against construction of new High Voltage Lines on the Islands • Sitting of new thermal stations almost impossible • Nevertheless in 2003 the construction of an AIS in Andros was completed

14. New Design (2004 - 2005) Facing said facts, a more “pragmatic” design was done • No new OHL over the islands • No new thermal stations on the islands • Use of existing thermal plants only as cold reserve - No thermal Production on the islands • Possibility to exploit significant wind capacity (installation of W/F)

15. Existing 150kV OHL New 150kV OHL Existing 150kV submarine cable New 150kV submarine cable Existing 66kV cable Existing 150kV substation New 150kV substation Existing PS Final Plan (2005)

16. Pros and Cons of the Interconnection • Pros • Secure power supply of the Islands (from the mainland interconnected grid) • Long-term solution – no new local generation every 2-3 years • Substitution of power (Diesel) from existing local PS (gradual decommissioning) with power from the Interconnected System  Economic and Environmental benefits • Increase of wind power penetration on the interconnected islands • Possible future extension of the Interconnection to the Southern Cycladic Island (further exploitation of considerable wind and geothermal potential of the islands) • More economical than feeding the islands by diesel stations in the long run • Cons • Considerable initial investment cost: • submarine cables • advanced interconnection technology (DC with VSC, GIS substations,) • Long amortization period • Use of new innovative, but not sufficiently proven technologies (long XLPE* submarine cables, DC control in abnormal situations e.t.c). * XLPE cables have low MVAR/km than OIC (1,5 vs 2,5)

17. Technical Description • 4 new GIS Substations 150/20kV in Syros, Mykonos, Paros and Naxos • Submarine Interconnection of above substations (cables 1×3phase /AC / XLPE / 150kV / 200MVΑ): • Syros - Mykonos 36km • Syros - Paros 50km • Paros - Naxos 16km • Naxos - Mykonos 40km • Syros - Andros 32km Reactive compensation (reactors) of the cables is required • Submarine Interconnection of Syros to the Mainland (Lavrion EHV Substation). Two alternative technologies: • D.C. Interconnection: • Submarine D.C. interconnection Lavrion - Syros ~100km 250ΜW (2+1 cables) • An AC/DC converter station at each end of the interconnection (-50/+150ΜVA) • A.C. Interconnection: • Submarine A.C. interconnection Lavrion - Syros ~110km 250ΜW (2×3phase /AC / XLPE / 150kV / 200MVΑ).One stop at Kythnos for junction and reactive compensation with SVC in Syros ~ +/- 150 MVAR

18. Basic Economic and Technical assumptions Πηγή: ΔΕΗ/ΔΣΠ * Price in 2006 570€/lt

19. Comparative Cost Analysis(estimates with 2005 pricesin MEuros) * new OHL over the islands, submarine cables between the islands, connection with new cables and lines to the north ** New prices increase 40% new oil prices

20. D.C. Solution Lavrion EHV 400kV ΑΝDROS 150kV AC/DC Converter station -50/+150MVAr ~ 1×16MVAr DC (2+1 cables) 250MW 100km MYKONOS 150kV 150kV XLPE AC 1×3 200MVA 32km 1×18MVAr 1×16MVAr 1×16MVAr 150kV XLPE AC 1×3 200MVA 36km 1×18MVAr 1×18MVAr AC/DC Converter station -50/+150MVAr 150kV XLPE AC 1×3 200MVA 40km 1×16MVAr ~ 1×19MVAr 1×16MVAr 1×16MVAr 1×9MVAr NAXOS 150kV 150kV XLPE AC 1×3 200MVA 50km 150kV XLPE AC 1×3 200MVA 16km SYROS 150kV 1×9MVAr 1×16MVAr 1×9MVAr 1×9MVAr PAROS 150kV ~ 1×16MVAr

21. A.C. Solution Lavrion EHV 400kV Transformer 400/150kV ANDROS 150kV ~ 150kV 1×9MVAr 1×18MVAr 1×18MVAr 1×16MVAr MYKONOS 150kV 150kV XLPE AC 2×3ph/280MVA 110km 150kV XLPE AC 1×3 200MVA 32km 1×18MVAr Junction point in the island of Kythnos 1×9MVAr 2×18MVAr (junction at Kythnos) 1×16MVAr 1×16MVAr 150kV XLPE AC 1×3 200MVA 36km 1×18MVAr 1×18MVAr 150kV XLPE AC 1×3 200MVA 40km 1×18MVAr 1×16MVAr ~ 1×18MVAr 1×18MVAr 1×16MVAr 1×9MVAr 150kV XLPE AC 1×3 200MVA 50km 150kV XLPE AC 1×3 200MVA 16km SVC -50/+150MVAr 1×9MVAr SYROS 150kV 1×16MVAr 1×9MVAr 1×9MVAr PAROS 150kV ~ 1×16MVAr

22. Conclusions 1/5 • Expansion of the Network (Overhead Lines) Faces huge local Reaction • Generalized use of Cables is not realistic: • Huge Cost • Technical Problems (reactive capacitance) • Use of Cables in the mainland is restricted to very specific cases involving heavily populated areas

23. Conclusions 2/5 • The Cycladic Islands are the closest islands of the Aegean Archipelago to the mainland. • They represent a significant load with high rate of increase. • Development of local generating units is associated with high operational cost and practical difficulties to find new locations. • A submarine “cable” connection to the mainland is the only “pragmatic” solution.

24. Conclusions 3/5 • The least cost solution, would involve several overhead HV lines on islands and new ~70km in the mainland in Evia • New OHL on the Islands would “insult” dramatically the aesthetically sensitive landscape of the islands and was denied by the State Council • Licensing of new long OHL in Evia considered impossible

25. Conclusions 4/5 Solution Chosen : • Long Submarine Connection of the central island of Syros to the Lavrio production center in the mainland and, • DC converters and cables or • AC XLPE Cables and junction in island in about half distance plus SVC in Syros • Connection to other Islands by AC XLPE cables

26. Conclusions 5/5 Solution Chosen • Has high initial investment cost • But is economically feasible in the long run • Is environmentally friendly, therefore is pragmatic • Allows installation of Wind Power up to about the peak load of the islands (otherwise very limited) • Is acceptable by the local communities

27. Other interesting cases experienced by HTSO (1/4) Corfu South Evia

28. Other interesting cases experienced by HTSO (2/4) In the Island of Corfu a second 150 kV submarine cable was planned to satisfy the reliability needs for the island (N-1 criterion ) Total length ~ 17 km submarine To ease the local reaction the 3 km OHL line on the island was designed as underground cable Nevertheless the project faces big delays since reaction appeared requesting transferring of the local Substation (existing for many decades) to a new location and use of GIS technology.

29. Other interesting cases experienced by HTSO (3/4) A new Connection of Evia to the mainland was designed to support Wind Energy Initially least distance submarine cable solution was chosen (~17 km OHL and ~8 km submarine cable) It was rejected and replaced by a solution with ~ 20 km submarine cable and 2 km underground cable through a small town Recently, local reaction appeared against the underground cable through the town.

30. Other interesting cases experienced by HTSO (4/4) Lesson Learned : Use of cables, Although is expected to be acceptable by the local societies might bring new reaction and further requests.