Power at a pace

Indonesia’s power demand growth rate of up to eight per cent per year led to an international consortium constructing a turnkey 860 MW power plant to an ultra tight deadline.

Jàƒ¼rgen Heufer, Ingo Pàƒ¼schmann, Siemens Power Generation, Germany

As fears grew over the power shortage Indonesia was forecast to have in the summer of 2004 the state owned utility, PLN, decided to add to the country’s generation capacity of 21 GW by commissioning a new gas turbine power plant. PLN awarded the contract to build the turnkey power station in May 2003 to a consortium led by Siemens Indonesia. Other members of the consortium were Siemens AG (Germany), Samsung Corporation (Korea) and Balfour Beatty Sakti Indonesia.

The Muara Tawar gas turbine power plant is located at the northern part of the Bekasi district, West Java, some 35 km north east of Jakarta city. The total capacity of the peak load plant is 860 MW and although it was initially designed to operate on fuel oil only, preparations have been made for a future conversion to gas firing, and measures have also been implemented in the plant design to facilitate a future conversion to a combined cycle.

Besides the new gas turbine generating plant, equipped with an SGT5-2000E gas turbine (formerly known as V94.2), the scope of supply for the consortium included the extension of the 500 kV switchyard, a new treatment plant for fuel oil and associated water treatment plant, a fuel oil forwarding system and an emergency diesel generator. The existing plant’s facilities and equipment are being used for fuel storage and for fire fighting. Access to the plant is available from the Tanjung Priok seaport and for heavy goods transportation, via an existing jetty at the already installed power plant.

Implementation schedule

Due to the urgent requirement for the extra generation capacity the plant would provide, the main focus in the planning phase of the project had to be placed on an implementation schedule. All phases of the project (design, procurement and transport as well as the site implementation work, civil construction, erection and commissioning) had to be optimized to achieve the owner’s targets.

The first unit was scheduled to be completed within twelve months from the contract signature with bi-weekly intervals for the completion of the further units. Overall completion of the plant was achieved in less than 15 months. A proven and broadly standardized plant design was selected in order to safeguard the project targets. The gas turbine building layout was produced in 3-D intergraph modelling, which allows convenient design co-ordination between the partners and assists in shortening the site execution time of the power plant.

Figure 1. Indonesia’s urgent requirement for generation capacity meant that a standard plant was selected to safeguard against delays
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Pre engineered solutions were implemented inside the main turbine building and the switchyard area. Auxiliaries to the gas turbine generator sets are designed as skid solutions. Electrical plant as well as the instrumentation and control equipment related to the turbine generator sets is located in power control centres.

The SGT5-2000E gas turbine is the most proven gas turbine of the Siemens fleet with a total operating experience of almost seven million equivalent operating hours (EOH) and with the fleet leading machine having already accumulated a total of almost 200 000 EOH. Around 150 units are installed worldwide.

A 16 stage compressor section with variable inlet guide vanes features in the gas turbine, which also includes two silo type combustion chambers, each equipped with eight dual fuel burners, suitable for fuel oil and fuel gas combustion and four turbine stages.

The TLRI 115/36 air-cooled generators, manufactured in the Siemens Westinghouse facilities in Charlotte, USA, have a design capacity of 157 MVA. A closed cooling water circuit with fin-fan type heat exchangers discharges the heat removed from the generator to atmosphere.

System siting

Power output from the generators to the Java-Bali 500 kV grid is via insulated phase busbar and a step up transformer. The generator transformers for the first two units as well as for the units four and five are three winding transformers, whereas the other units are conventionally connected to the grid. The 500 kV switchyard was delivered by ABB in addition to the existing switchyard from Muara Tawar I power plant.

Each gas turbine generator set is equipped with its own control and instrumentation system. Operation and monitoring can be either performed via the Teleperm XP system from a central control room or from local operator terminals in the power control centres of each unit.

Figure 2. Each of the six gas turbines has two silo type combustion chambers
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To support the site implementation activities, shipment of each gas turbine and generator set was consolidated and the complete turbine generator set was docked at the existing Muara Tawar jetty. The transport arrangement of the turbine generators involved the sea shipment of the generator from the US, transhipment and marrying with the gas turbine at a European harbour and a transhipment on a sea barge in Singapore.

Due to the prevailing ground conditions, piling needed to be performed. More than 2800 piles were driven into the ground to give the plant and its equipment a solid foundation.

All buildings, except for the central control building, the administration building and the diesel generator building, are designed with structural steel work and metal cladding.

Gas turbines and generators were lifted in position by means of a ‘megalift’ gantry.

Construction and operation

During start-up of the plant, a start-up frequency converter (SFC) runs up the turbine generator set to ignition speed. An ignition gas flame is established by ignition gas, which is then used to ignite the fuel oil and thus to establish a stable main flame providing sufficient energy to run up to rated speed. After synchronization, full load is achieved in no more than 15 minutes.

The main target of the new plant in Muara Tawar was to quickly support the increasing power demand of the Java-Bali grid in Indonesia. The first unit was completed in less than 12 months and handed over for commercial operation to PLN. All six units were completed in less than 15 months from contract signature and the performance values exceed the commercial guarantees of the plant.

PLN, the Indonesian state owned power generation company, awarded Siemens a ten year full scope operation and maintenance (O&M) contract that was signed in April 2004, shortly before the scheduled PAC (Provisionsal Acceptance Certificate) of the first unit out of six turbines.

As the O&M contract was awarded so late, it resulted in an extremely tight mobilization schedule of only eight weeks whereby only the most important mobilization tasks could be addressed prior to PAC of the first unit. The remainder of the mobilization tasks were still ongoing several months after the last PAC.

With support of the already employed O&M staff, the last gas turbine unit was successfully commissioned and handed over to PLN in September 2004 for commercial operation. PLN simultaneously handed over the first five combustion turbines along with the final combustion turbine to the Siemens O&M team so it could provide the services as agreed under the O&M contract.

The plant is operated and maintained by a total of 52 Siemens O&M personnel which are mostly local staff. To establish and improve the required skill level of the employees, several training activities were performed on site during the commissioning phase. Trainers were invited from other power stations where Siemens performs O&M. This included training on BFS++ system and general familiarization on the gas turbine system guided by personnel from Pulau Seraya and Santa Rita, respectively as well as support for the commercial set up. Moreover, in parallel with commercial operation, several more specific training schemes for operation and maintenance personnel took place on site in form of formal classroom training. This training was provided by Siemens Power Generation training specialists from Siemens Westinghouse Power Corporation in Orlando. To further enhance their knowledge of the plant, staff support is occasionally rendered from other stations to overcome some remaining weaknesses that are a result of the short mobilization period.

The owner of the plant (PLN) and the grid operator (P3B) have both noted the impressive performance of the new facility, which now operates at a steadily increasing capacity, although due to high fuel prices it has originally been scheduled for low capacity. This is reflecting the raising demand of the grid as well as the performance of the plant which is among the highest available units in Indonesia. During the period August 2004 – April 2005 the start reliability was 93 per cent while the Equivalent Availability Factor amounted to 98 per cent. The plant supplied a power output to the grid of 151 GWh.

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