FIRST-EVER CONVERSIONof GE Frame 7EA Gas Turbines to a 50Hz Grid

In Response to Severe Power Outages, Kuwait Couldn’t Wait

SITUATIONIn response to serious power shortages in 2007, the government of Kuwait initiated an Emergency Power procurement effort to install several hundred megawatts of gas turbine fired generation. Due to the time-sensitive nature of the project, only immediately available equipment could be used.

While two projects were quickly awarded using available aeroderivative gas turbine-generator sets, equipment originally identified for a third contract at the Kuwait Ministry of Electricity and Water’s (MEW) Subiya Power Plant became unavailable, causing the client to urgently seek alternatives.

CHALLENGEElecting to purchase four GE Frame 7EA gas turbine 60Hz units, each rated at 84MWe, the client’s purchase was made with the assumption that these units could easily be converted for use at 50Hz. This was not the case.

SOLUTIONTurbine Technology Services (TTS) was awarded the contract to project manage, engineer the reapplication of and convert

the 60Hz unit frames at the MEW Subiya Power Plant to Kuwaiti grid’s 50Hz frequency. This groundbreaking project became the first-ever application of transferring Frame 7EA gas turbine-generators to a 50 Hz environment.

EXECUTIONThe frequency conversion required extensive modifications to the gas turbines, including the addition of load gearboxes and generator changes. Because insufficient natural gas fuel was available at site, the units were modified from gas-only combustion to dual-fuel standard combustors. Water injection was also added to meet contract emission requirements.

In the first months of the project, TTS mobilized an engineering team to the site to review the condition of all parts and generate an action plan. All necessary design engineering was performed on site. Since the plant was needed for emergency power generation, delivery time was a top consideration when awarding subcontracts.

Frequency ConversionThe gas turbines were already at the MEW Subiya Power Plant in Kuwait when TTS first assumed responsibility for project engineering in October 2007. To change the

electrical frequency conversion of the output power, TTS used a reduction gearbox to change generator speed from 3,600rpm to 3,000rpm.

Because of the gearbox addition, all on-base auxiliaries (fans, pumps, etc.) had to be modified for operation at 50Hz. These events slowed the generator rotor and reversed its direction. To compensate for this action, generator modifications were made to accommodate the rotor. This included installing new bearing sets, changing out the rotor cooling fans and re-installing the generators and the rotors.

Fuel System ConversionThe contract required TTS to design the turbine so that it could run on gas and liquid fuel. After a full engineering analysis, it was decided to convert the combustion system to a standard diffusion combustion system.

This modification required rework of all on-base combustion equipment, including fuel system components, atomizing air system, water injection system, piping, instrumentation and controls. To accommodate all combustion changes, the entire site of combustion hardware was redesigned and replaced.

Balance of Plant (BOP) EngineeringThe next challenge facing TTS was how to integrate multiple control systems of varying vintage, complexity and accessibility over a large physical area while seamlessly

providing operational information to the plant O&M team. These systems included gas compression, liquid fuel handling and storage, HV interconnects at 275KV and 132KV and water treatment.

All necessary power system engineering was completed on site. This engineering included a complete system protection study, load flow analysis, switchgear design, new equipment protection design and the modification and integration into existing site protection schemes.

Plant-Wide Control SystemsBecause of the new gearbox and auxiliary systems, significant reprogramming and an updated hardware installation was required for their liquid fuel and I/O requirements.

TTS selected Allen Bradley’s ControLogix Programmable Automation Controller (PAC) as the basis of the BOP control system. The TTS design included redundant I/O communications over a fiber network, multiple communications links using Ethernet TCP/IP, Modbus TCP and Allen Bradley’s Producer/Consumer model over Ethernet. An integrated GPS was used to ensure a common plant time stamp for all systems.

This complex network was then able to provide information through the OPC server to the custom-built Central Control Room.

In a groundbreaking 334MWe project, TTS converted four GE Frame 7EAs to a 50Hz grid installation. This was the first time a 60Hz GE frame has been converted to a 50Hz frequency.

No advance engineering of any kind was performed prior to purchase, leaving TTS to fully engineer, design and procure all required systems for a major conversion and installation project. All design work was performed in the field.

This extremely complex project was completed successfully and is fully operational. The units have run successfully since commissioning, validating all design work performed on this innovative project. The plant has been used extensively during the Kuwaiti summer where temperatures routinely exceed 50 degrees Celsius.

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RESOLUTION