Single shaft combined cycle power plant
The recently completed 800MW Chana combined cycle power plant Block 2 extension in the Chana district of Songkhla province in Southern Thailand was handed over this month to the Electric Generating Authority of Thailand (EGAT).
Combined with the 731MW existing plant, the Chana multi-shaft combined cycle power plant can now deliver 1,531MW to the Southern Power Grid of Thailand. The Chana-2 single-shaft combined cycle plant was built by the Siemens-Marubeni consortium who had also delivered the first block of the power station in 2008. Construction on the new block started in 2011.
Siemens and Marubeni have completed the Chana 2 combined cycle power plant in Thailand to Electric Generating Authority of Thailand.
The Chana-2 natural gas-fired power plant consists of two single-shaft combined cycle units, each comprised of a gas turbine, a generator and a steam turbine arranged in a single train. The plant boasts an efficiency of 57.3% while offering short start-up time and flexibility to accommodate fast load changes. It is considered to be one of the most efficient and environmentally friendly power plants in South East Asia.
Chana-2, like the existing plant, is supplied with fuel from the offshore Thailand-Malaysia joint development area (JDA) gas field. The highest fuel demand of the new power block is estimated to be 148 million ft³ of gas per day.
Chana-2 will use diesel as back-up fuel to ensure its operation during gas supply interruptions. A diesel storage tank for the plant is currently under construction and is scheduled for completion in 2015.
Power generated from the combined cycle power plant is fed into Thailand’s southern grid via a 230kV transmission line. A new transmission system with a total distance of 90 circuit-kilometres, connecting the new power plant with the Khlong Ngae transmission system via the Chana Junction, was built at a cost of THB1.29bn ($40m) as part of the project. The transmission project also included the expansion of the existing Songkhla and Khlong Ngae sub-stations.
Each of the two units of Chana-2 power plant feature a Siemens SGT5-4000F gas turbine, an SST5-3000 series steam turbine and a SGen5-2000H generator. Under the turnkey contract, Siemens also supplied the overall electrical system and the SPPA-T3000 instrumentation and control (I&C) system that comes with a distributed control system (DCS). The SPPA-T3000 can perform all power plant automation tasks including turbine control, boiler control and protection, as well as the balance of plant (BoP) and integration of third party systems.
Marubeni was responsible for the heat recovery steam generators, the main transformers, the outdoor switchgear system, cooling tower and the civil and installation works for the new plant.
Siemens and Marubeni were jointly awarded the engineering, procurement and construction (EPC) contract for the Chana-2 combined cycle power plant in August 2011. Marubeni’s share in the JPY43.5bn ($425m) worth contract was JPY20bn ($196m).
Black & Veatch was selected by Marubeni Corporation in September 2011 to provide the design, engineering and procurement for balance-of-plant equipment. The contractual scope also included provision of other services including technical field assistance, supply of the heat recovery steam generators and commissioning of other plant equipment.
Image: The Chana 2 combined cycle units. Photo: courtesy of Electricity Generating Authority of Thailand (EGAT).
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