Siemens is supplying two gas-insulated high-voltage switchgear sets for the Rogun hydropower plant in Tajikistan. The power plant is part of the Rogun Dam project. At a height of 335 m, the dam taking shape there will be the highest in the world. The 8DQ1 switchgear, covering a voltage range of up to 550 kV with 21 circuit breakers, and the 8DN9, covering up to 220 kV with four circuit breakers, will protect the power generation and transmission systems in the hydropower station against short circuits and overloading. The switchgear should be fully installed and ready for operation by 2018.
The Rogun Dam stands on the river Vakhsh, about 100 km north-east of Tajikistan’s capital, Dushanbe. It will be upriver from the Nurek Dam, which is currently the world’s highest at 300 m. A hydropower station with a generating capacity of 3600 MW is planned for Rogun, with generation provided by six 600 MW turbines. This will enable 13.3 billion kWh of electricity to be generated annually from one of the largest hydropower stations in the world.

The switchgear sets are fitted with online monitoring devices to enable automatic remote diagnosis and self-monitoring. The 8D series switchgear is metal-enclosed to minimise dielectric and dynamic stresses. Aluminum is used for the metal enclosure to keep the weight of the system to a minimum and ensure optimum corrosion resistance. SF6 is used as the insulating and arc extinguishing gas.
The extremely tight enclosure prevents environmental contamination. Static filters in the head spaces provided on the inner side of the assembly openings absorb moisture and decomposition products, assisting in achieving an estimated total service life for these units of more than 50 years, says their maker Siemens, and they are almost maintenance-free once in operation. The switchgear has corrosion-free enclosures and uses self-lubricating drives, which contributes greatly to their long service life.