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 ( )
Year of connection of Andros-Tinos to the Mainland

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

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

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. Initial Plan (made in1989) PHASE Α PHASE Β 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)
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. Revision of Initial Plan (2001)
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)

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 ( )
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. Final Plan (2005) 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

16. Pros and Cons of the Interconnection
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
Basic economic assumptions (in 2005 prices)
Inflation 3%
Rate of fuel price variation above Inflation 2%
Cost of Fuel
Diesel
410 €/t*
Heavy oil
190 €/t
Cost of Energy from Interconnected System
54 €/MWh
Cost of Energy from local PS
80 €/ΜWh
O&M cost of old local PS
96.03 €/KW&year
O&M cost of expansion of existing local PS
38.41 €/KW&year
Investment Cost (after taxes)
7%-9%
Basic technical assumptions (in 2004 prices)
CO2 emissions
8-20 €/ton CO2
Efficiency of new PS (diesel)
42%
Investment Cost (new PS)
1100 €/KW&year
Cost of Expansion of old PS
825 €/KW&year
Πηγή: ΔΕΗ/ΔΣΠ
* Price in €/lt

19. Comparative Cost Analysis (estimates with 2005 prices in MEuros)
Cost Component [MW]
Final Solution
Expansion of existing PS
No further interconnection
Least Cost Approach*
Investment Cost
170 ~230
133.03
101.26
Cost of Fuel (Diesel)**
472.74
Cost of Energy from Interconnected System
380
61.62
380.72
CO2 emissions  0
11.86
Fixed O&M Costs
10 ~ 75
49.53
48.62
Total Cost
728.77*
530.6
* 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 MYKONOS 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
AC/DC Converter station
-50/+150MVAr
150kV XLPE AC
1×3 200MVA
40km
1×18MVAr
1×16MVAr ~
1×19MVAr
1×16MVAr
1×16MVAr
1×9MVAr
150kV XLPE AC
1×3 200MVA
50km
NAXOS 150kV
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
Junction point in the island of Kythnos
1×18MVAr
1×9MVAr
2×18MVAr
(junction at Kythnos)
1×16MVAr
1×16MVAr
150kV XLPE AC
1×3 200MVA
36km
1×18MVAr
150kV XLPE AC
1×3 200MVA
40km
1×18MVAr
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.