HVDC Italy-Greece
The HVDC Italy-Greece , abbreviated GRITA , is a 313-kilometer high-voltage direct current transmission line (HVDC) between Italy and Greece and represents the only way to directly exchange electrical energy between the two countries . The line went into operation in 2001, is designed for the transmission of a maximum output of 500 MW and can either transport energy from Italy to Greece or vice versa as required.
course
The wiring starts at the converter station near the Italian town of Galatina ( ⊙ ), runs 43 kilometers as ground cable to the coast, crosses 160-kilometer submarine cable , the Ionian Sea to Greece ( ⊙ ) and runs on the Greek side than 110-kilometer transmission line to the Greek Location Arachthos , where the second converter station is located ( ⊙ ). The deepest point of the submarine cable is 1000 meters under water, making GRITA the deepest HVDC submarine cable connection in the world.
Both on the Italian side and on the Greek side, the converter stations are connected to the respective 400 kV high-voltage network and are part of the European network . The planning and construction costs were funded by the European Union with 40% of the total costs.
technology
The connection, which is designed as a monopolar HVDC connection, is operated with a direct voltage of 400 kV ; the conductor current is 1250 A at full load . As a monopolar line in the section of the submarine cable, there is only one conductor cable, the earth is used as the return conductor . The anode required for this as a grounding electrode on the Greek side consists of 39 corrosion-resistant individual electrodes made of titanium steel with a niobium (II) oxide coating ( ⊙ ). The coating is necessary to minimize chemical decomposition of the anode as a result of the current flow. The grounding electrodes are located in seawater in a lagoon that is closed off for this purpose . The cathode on the Italian side near the town of Otranto , on the other hand, is not subject to corrosion by the current flow and consists of bare copper rings in the 30 meters deep coastal water.
The current flow is always in the same direction regardless of the direction of the power flow (anode and cathode were installed in a defined manner), which is why the polarity of the conductor cable to earth must be able to assume the two values +400 kV and −400 kV depending on the direction of the load flow. The switching of the line polarity is limited to 1000 switchings per year and may only take place once within two hours. The reason lies in the deionization of the insulation material of the high-voltage cable . The deionization process takes more than 10 minutes. The line cannot be used within this period.
The converter transformers in both stations are designed as three single-phase transformers each with an individual power of 200 MVA, and the thyristor towers in the converter halls are designed as twelve-pulse circuits . The losses at 40 ° C ambient temperature and the maximum transmission power of 500 MW are 7 MW at the converters, primarily in the thyristor towers and converter transformers, and 14 MW line losses. In this case, the line losses correspond to a relative loss of approx. 0.9% over 100 km of line length.
Individual evidence
- ↑ a b c The Italy-Greece HVDC Link , Cigré , 2002, engl.
Map with all coordinates: