The implementation of Phase A was completed in the early months of 2018. Up to that time, and according to the forecasts regarding the development of the Autonomous Production Stations and the evolution of demand in the Cyclades islands to be interconnected, the existing and scheduled new production at the APS Units of the Cyclades was sufficient for safely meeting the demand for power in the islands to be interconnected.
According to the revised planning, Phase A includes the connection of Syros with Lavrio, as well as the islands of Paros, Mykonos and Tinos. After its completion, the APS units were put in emergency reserve and the loads of the Islands are now supplied from HETS (the loads of Andros - Tinos are already supplied from HETS through the Transmission Line connecting South Evia with Andros).
Specifically, Phase A of the interconnection of the Cyclades, includes the following separate sub-projects;
- Initial connection of Syros to Lavrio with a submarine tripolar 150 kV AC cable of a rated 200 MVA capacity, with a length of 108 km.
- Connection of Syros with the northern end of Tinos with a submarine tripolar AC cable of a rated 200 MVA capacity, with a length of 33 km.
- Radial supply of Paros from Syros, with a submarine tripolar
AC cable of a rated 140 MVA capacity, with a length of 46 km.
- Radial supply of Mykonos from Syros, with a submarine tripolar 150 kV AC cable of a rated 140 MVA capacity, with a length of 35 km
- Construction of GIS Substations in Syros, Paros and Mykonos (including the installation of coils, capacitors and SVC in Syros, coils and capacitors in Paros), and the necessary works for connection at Lavrio (GIS with one autotransformer and bays) and at the coupling point on Tinos. In addition to connecting the Lavrio - Syros cable, the GIS 150 kV Switching Substation at Lavrio will be used for diverting to it all these 150 kV departures of the existing 150 kV outdoor Substation of Lavrio.
This diversion achieves the following:
1. Stronger connection between 400 kV and 150 kV Systems at the Lavrio complex (through the existing and the new autotransformer), which will increase the reliability of the System of the broader region, in view of the withdrawal of Units I, III (final) and II (upcoming) of the Lavrio Station.
2. Greater reliability in the interconnection of the Cyclades, following the completion of Phase A, since in case of loss of one autotransformer, the connection of Lavrio-Syros remains active through the second autotransformer.
3. The possibility is presented to service the second Lavrio - Syros connection (Phase C) without an additional autotransformer.
4. Also, the addition of new 400 kV bays at the GIS 400 kV Lavrio HVS may be postponed for the future.
- Phase A of the Cyclades interconnection ensures the transmission of power from HETS to Syros up to a minimum of 170 MW even in the case of failure of the Lavrio-Syros cable. This volume of transmitted power generally suffices to meet demand on the islands for the stipulated time frame of the project’s operation.