Грузино-немецко-норвежско-индийско-американский ГОЭЛ-ГР

Akhaltiskhe Substation

The 500/400/220-kV Alhaltiskhe substation, constructed by Siemens, is located 13 km (8 miles) from the city of Akhaltsikhe on a site approximately 1100 m (3609 ft) above sea level. The substation is connected to the Tbilisi-Akhaltsikhe highway by a 3.2-km (2-mile) access road constructed as a part of the project.

The 500-kV and 400-kV switchyards of the Akhaltsikhe substation are designed with the breaker-and-half-bus configuration. The substation’s 500-kV switchyard is connected to the 220-kV side by three 167-MVA single-phase autotransformers, which were installed to interconnect the substation with hydropower plants currently under construction in the region. The Akhaltsikhe substation may be operated either from the local control room — using Ethernet or a local area network — or remotely from the national dispatch center through the power line carrier system using multiplexers.

In each HVDC link, the three-phase AC of the 500-kV feeding network is linked with converter valves by three 140.4-MVA, 500/40/40-kV single-phase converter transformers, then converted into direct current (DC) and transmitted directly through the DC link to the inverter station. There, the DC is converted back into three-phase current with a simultaneous adjustment to the parameters of the network, before being connected to the three 140.4-MVA, 400/40/40-kV single-phase converter transformers. The HVDC links are designed to transmit 350 MW in both directions.

Three synchronous condensers, with capacities of 60 MVAR each, are installed for compensation of the reactive power and capable of operating under the N-1 contingency. Each synchronous condenser is connected to the 400-kV side of the substation through the individual 63-MVA, 400/11-kV transformers. During the operation of the HVDC links, these synchronous condensers maintain the reactive power at near-zero level. Each control, protection and measurement system is designed with redundancy. The changeover logic of the system selection function ensures, at any given time, only one system actively controls the process.