John Goss, Ceejay International, Hong Kong, PR China

In March of this year, South Korea’s 565 MW Bugok II CCGT power plant began commercial operation. What is unique about the new plant is that it shares a number of common systems used in the generation of electricity with its adjacent older sister Bugok I, which not only improve performance but also reduce the environmental impact of both plants.

As many of Asia’s economies experience exceptional growth and development, the spectre of improved lifestyles and greater energy demands from industry create special problems for the governments as they attempt to match their country’s power capacity to demand. However, the power supply problems do not stop there as today’s power solutions must consider the local environment as well. So, in today’s Asia a power plant needs to provide high electrical efficiency and above average environmental performance.

After a construction period of only 26 months the combined-cycle power plant Bugok II in South Korea was put on line one month ahead of schedule in March 2008
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In recent years, South Korea has become a significant market for power plant developers and suppliers. It is estimated that the demand for power is increasing at an annual rate of between 5-6 per cent. With limited domestic energy resources, however, South Korea is almost entirely dependent on imports to meet its power and energy consumption needs. The country is the fifth-largest net importer of oil in the world and a significant importer of liquefied natural gas (LNG). Oil makes up the greatest share of South Korea’s total energy consumption, though its share has been declining gradually in recent years.

Oil supplied 50 per cent of South Korea’s total energy consumption in 2004, compared with 65 per cent in 1994. This decline in oil’s share in energy consumption reflects the faster growth in natural gas and to a lesser extent coal over the period. Coal is in fact South Korea’s second-largest energy resource, supplying 24 per cent of primary energy consumption needs in 2004. This is followed by modest contributions from nuclear power (14 per cent) and natural gas (12 per cent). Currently, hydropower and other renewable energy sources only make up a small fraction of the country’s total power generation capacity.

In 2006, South Korea joined the Asia-Pacific Partnership on Clean Development and Climate, also known as AP6. This environmental focused partnership is an international non-treaty agreement between Australia, India, Japan, China, South Korea and the USA. The partnership was first announced on 28 July 2005 at a Regional Forum meeting of the Associations of South East Asian Nations (ASEAN), and was formally launched in January 2006 at the ministerial meeting of AP6 in Sydney, Australia.

At the AP6 launch meeting, foreign, environment and energy ministers from all of the six partner countries held a series of meetings during which they agreed to cooperate on the development and transfer of technologies which enable reduction of greenhouse gas emissions. The powerful group of ministers agreed on a Charter Communiqué and Work Plan that outlined a ‘private–public’ taskforce that would address climate change, energy security and air-pollution throughout the ASEAN region.

Eco-friendly power for South Korea

South Korea’s economy has been developing steadily for some time and as a consequence its demands for power supplies are increasing dramatically year-on-year. In recent years a series of combined-cycle gas turbine (CCGT) power plants from Siemens Energy have provided significant amounts of reliable power to South Korea with their high availability, high electrical efficiencies, low environmental impacts and excellent safety records.

The latest in this series of plants is the 565 MW Bugok II CCGT power plant which is sited close to the 550 MW Bugok I power plant. The Bugok I & II power plants are located in South Korea’s Danjin Province which is 100 km south of the capital city of Seoul. An added environmental feature of the two plants is that they both share a number of common systems used in the generation of electricity.

After only 26 months of construction, Siemens Energy officially handed over the new Bugok II CCGT power plant to their customer, GS Electric Power and Services Company Limited (GS EPS) Seoul. The Bugok II power plant was commissioned and put on-line approximately one month ahead of schedule in March 2008. An added value feature of the power contract is that the customer, GS EPS, has signed a 20-year maintenance agreement with Siemens for the Bugok I and Bugok II plants.

As a mark of its efficiency and environmental friendliness Bugok II has already been given the number one ranking for combined-cycle power plants in South Korea by the Korean Ministry of Commerce, Industry and Energy. The plant has an efficiency of 58.6 per cent, and since the plant started generating electricity Bugok II has been operating primarily as a baseload unit instead of a part load/middle range unit. The power plant is also serving under ‘Frequency Control Mode’. In fact, Bugok II is currently achieving all guaranteed performance figures and in some cases even exceeds them.

Bugok II – the plant

Environmentally, the two SGT6-4000F gas turbines are an improvement on those in Bugok I. In principle they are the same heavy duty type gas turbines that feature in earlier plant. However, the difference is in their improved burner and combustion system. The improved system allows operation with high fuel gas preheating, combined with higher mass flow from the improved compressor. Consequently the turbines deliver a much more stable combustion with higher output and higher efficiency, enabling them to operate at much lower nitrigen oxides (NOX) emissions – between 30 and 20 ppm.

The handing over of the operation of the Bugok II CCGT plant in March 2008: Vice President Mr. S. I. Kim, GS EPS, Siemens Project Director A. Kessler and Mr. G.H. Cho, GPM, GS E&C
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The steam turbine is a Siemens SST6-5000 turbine, manufactured in Muelheim, Germany. This is a typical solution for combined-cycle power plant where the HP/IP turbine is in one common cylinder and the LP turbine is designed for low bay arrangement with two halves of the condenser on both sides of the LP turbine – this gives the advantage of a much smaller steam turbine building – with the related cost advantages without the high pedestals for the steam turbine foundation.

The instrumentation and control (I&C) and DCS system in Bugok II is the new Siemens SPPA-T3000 power plant control system – operating in conjunction with Bugok I’s Siemens TELEPERM XP DCS system. Both DCS systems can control common systems for both plants, including:

  • Closed cooling water system
  • Seawater cooling water system
  • Travelling screen wash pumps
  • Auxiliary steam supply system
  • Air supply system
  • Hypochlorination system

Common operation via both units is managed via integration of an additional redundant HMI (human machine interface) server and a fault-tolerant HMI bus into the existing DCS structure of Bugok I. The new operator stations (thin clients) using proven web technology for the operating of Bugok I are identical with the thin clients used as the standard HMI within SPPA-T3000. This enabled an easy interface between the added HMI bus of Bugok I (TELEPERM XP) and the SPPA-T3000 application bus of Bugok II via a redundant router connecting both operation busses. As an advantage no re-engineering of the existing HMI software from Bugok I (TELEPERM XP) was necessary.

This is the first time ever that both systems have been arranged in a manner that the common systems for both power plants can be controlled by both DCS systems. This parallel linking of the control systems provides vastly improved control capabilities for the operators, which advance the efficiencies of the two plants.

In another ‘common’ working system between the two plants that improves performance and reduces environmental impacts, Siemens, GS EPS and its consortium partner GS E&C chose an arrangement whereby both steam turbine generating units are housed within one common building.

This was achieved by extending the original Bugok I steam turbine building during the construction period of Bugok II, using the original travelling crane in the construction process. Now in operational mode, both power plants use the same circulating cooling water intake system with only some additional lifting and main cooling water pumps being installed for Bugok II.

South Korea and Siemens

In addition to the Bugok I and Bugok II power plants, since 2002 Siemens Energy has also supplied the Incheon I and the Yulchon CCGT power plants. The Incheon II power plant is currently under construction and is scheduled to go on-line during the course of the summer of 2009. All five plants, each rated at approximately 550 MW, make a major contribution towards providing South Korea with an efficient, eco-friendly supply of electrical energy.

With a total installed capacity of 10 996 MW Siemens Energy has been a significant power partner in South Korea for over 20 years. Siemens Energy has also recently posted an order for the supply of four gas turbines, two steam turbines and six generators for the POSCO Power combined-cycle plant in Incheon, where two units with a combined capacity of 1000 MW will be added to the existing units one to four.

Main piping to high-pressure (HP) and intermediate pressure (IP) steam turbine, and IP / LP bypass ducts to condenser
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The real success story of Siemens Energy in South Korea began when the government liberalized the power market to allow independent power producers. The then LG Energy Company Limited (today’s GS EPS) planned the first independent power plant to be located in the country back in 1995.

On the basis of the power plant technology offered, Siemens was awarded the contract to supply all key components and systems for their first plant. Following just-in-time plant completion and subsequent trial operation, the plant catapulted to the top of the South Korean list for power plant rankings.

Building on this successful reference project, Siemens was able to book two further orders for South Korea in 2003. The Yulchon combined-cycle power plant is equipped with two SGT6-5000F gas turbines, a steam turbine and three generators. Start-up of the 600 MW plant took place in the summer of 2005. In early 2003, Siemens received a further order, this time from the South Korean utility KOPEC/KOMIPO.

The control room for a multi-shaft combined-cycle power plant of type SCC6-4000F in Bugok. The Siemens SPPA-T2000 instrumentation and control system – previous designation Teleperm XP – is implemented here
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Siemens supplied the power island for the Incheon combined-cycle power plant. Just like Bugok II, this plant is equipped with two SGT6-4000F gas turbines, two steam turbines and three generators. Commercial operation of Incheon started in the summer of 2005. The plant has an overall capacity of 550 MW. With more than 58 per cent this plant has the highest efficiency in the country and plays a major part in meeting the increasing power demand of the suburbs that surround the South Korean capital, Seoul.

GS EPS, as a power plant operator, says that the reliabilty of its power plant equipment is of utmost importance. According to the power generator, the reliability of its Bugok I unit, which has two Siemens V84.3A gas turbines and one Siemens KN steam turbine installed, has been high. GS EPS said that it is proud of the fact that it is able to respond to any power dispatch requests from the KPX (Korea Power Exchange) at any given time. This high reliabiity has proved to be one of the main deciding factors in GS EPS selecting Siemens Energy’s gas and steam turbines for its Bugok II unit.