HVDC Italy–Greece

The HVDC Italy - Greece, GRITA abbreviated, is a 313 km long high voltage direct current transmission line ( HVDC) between Italy and Greece and between the two countries is the only way to exchange information directly electrical energy. The line was put into operation in 2001, is designed to transfer a maximum power of 500 MW and can be selectively and according to need energy either from Italy to Greece or transport vice versa.

Course

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The wiring starts at the converter station near the Italian town gala Tina, runs 43 km underground cables to the coast, passing through 160 km long submarine cable, the Ionian Sea to Greece and runs on the Greek side than 110 km long transmission line to the Greek place Arachthos on which to the second converter station is located. The submarine is at the lowest point in 1000 meters of water, which represents the deepest GRITA HVDC undersea cable worldwide.

Both on the Italian side as well as on the Greek side, the converter stations are connected to the respective 400 - kV high- voltage network and part of Europe's European interconnected system. The planning and construction costs were funded by the European Union with 40 % of the total cost.

Technology

The constructed as monopolar HVDC link is operated with a DC voltage of 400 kV, at full load the conductor current is 1250 A. As a monopolar line in the section of the submarine cable is only one conductor cable available, as a return conductor grounding is used. The required anode as a ground electrode on the Greek side consists of 39 individual electrodes from corrosion-resistant steel with a titanium niobium (II ) oxide coating. The coating is needed to minimize chemical degradation of the anode, according to the current flow. The ground electrodes are located in the sea water in a closed-off for this purpose lagoon. The cathode on the Italian side near the village of Otranto, however, is not subject to corrosion by the current flow and consists of bare copper rings in 30 m deep coastal waters.

The current flow is independent of the direction of power flow is always in the same direction, while the polarity of the conductor with respect to ground, depending on the power flow direction, the two values ​​ 400 kV and -400 kV can take. The switching of the line polarity is limited to 1000 switches per year, and may be carried out within two hours once. The reason is in the deionization of the insulation material of the high voltage cable. The Deionisationsprozess is over 10 minutes, while the line can not be used.

The converter transformers are carried out at two stations as three single-phase transformers with a single power of 200 MVA and the Thyristortürme in the Umrichterhallen are designed as twelve-pulse circuit. The losses at 40 ° C ambient temperature and the maximum transmission power of 500 MW be 7 MW of the converters, primarily in the Thyristortürmen and converter transformers, and 14 MW of power losses. The conduction losses in this case correspond to a relative loss of about 0.9 % to 100 km line length.