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Adoption of variable speed drives yields increased plant efficiency, reliability and availability PacificLight Power

Adoption of variable speed drives yields increased plant efficiency, reliability and availability PacificLight Power

Singapore-based power generation and electricity retailer, PacificLight, utilizes variable speed drive technology from Siemens to achieve significant energy savings and improve overall plant efficiency.

PacificLight Power (PLP) is a Singapore-based power generator whose power plant stands as one of the most efficient operating units in the Singapore power market today. With an installed electrical generating capacity of 800 megawatts (MW), the state-of-the-art Combined Cycle Gas Turbine (CCGT) power plant is the first in Singapore to be completely fuelled by Liquefied Natural Gas (LNG), and is capable of producing enough electricity to meet the demands of all households in Singapore. In 2015, the plant generated over 9% of Singapore's total electricity consumption. PacificLight Energy, a subsidiary of PLP supplies electricity to contestable retail customers.

The Need for Greater Efficiency

With Singapore's growing energy needs, which are currently around 46,403 GWh per year, coupled with the increasingly competitive business environment, PLP recognized the need to improve the efficiency of its operations without compromising on reliability, availability and flexibility.

As part of an initiative to reduce onsite electrical consumption, the company elected to modify its two cooling feed water pumps. Prior to the modification, the cooling feed water pumps represented over 35% of the total unit onsite auxillary load and were the highest consumer of internal energy within the CCGT plant

The plant was installed with a mechanical throttling valve control for the feed flow, which consumed a considerable amount of energy as the pump motors were running at constant speed. In addition to vary pressure, the upstream high pressure feed water control valve was throttled to control the flow, which led to severe valve erosion.

Seeking a Partner with Automation Expertise

Automation is at the heart of today's CCGT performance and PLP wanted an automation partner that was dependable and experienced enough to help the company evolve and embrace system changes in a timely manner. PacificLight needed a partner that had:

  • Relevant experience.
  • Proven concept – with successfully commissioned products with reliable operating history.
  • Readily available engineering support expertise in terms of quality in on-site field service personnel, turnaround time, logistical sourcing of critical/contingency spares, remote engineering specialist consultation, and prompt technical update to alert the customer.
  • Competitive pricing.

Taken the above into account as well as the detailed understanding that Siemens has of PLP’s plant given its role as EPC contractor in the construction of its 2 x 400MW F-class Combined Cycle Gas Turbines that were completed in 2014, Siemens were selected for the project.

Siemens Variable Speed Drives: SINAMICS PERFECT HARMONY GH180 Converter System

The SINAMICS PERFECT HARMONY GH180 Converter System is a series of cells linked together to create the medium voltage power output of the drive system. The design features an integrated transformer and the ability to scale the drive for a wide range of voltage and output power. The drive offers increased availability due to its modular design and ability to bypass any one cell during operation.

Siemens installed the first unit of variable speed drives at PLP’s power plant in October 2015, and the second unit in January 2016. Because of the unique multi-cell topology design, the Perfect Harmony converter does not cause any significant stress on the motor insulation or bearings and does not affect the mechanical and electrical integrity of PLP’s feed water pump as it does not require repositioning of the pump and motor. Once installed, the variable speed drives were able to control the speed of the feed water pumps and modulated the discharge pressure optimally according to the load profile, delivering the required flow at much lower motor power.

Apart from supplying the technology, Siemens also contributed valuable insights and advice leading to increased reliability of the installed variable speed drives. Furthermore Siemens assisted to train PLP’s duty operators and maintenance personnel to ensure maintenance and operations can be conducted smoothly post installation by the PacificLight team.

Seeing the Results

Since the installation of the variable speed drives, PLP has achieved:

  • A significant reduction in onsite power usage of up to 50% for the feed water pumps, thereby improving the generation output and efficiency of each unit.
  • An 18% increase in energy savings due to the flexibility of the steam water cycle which has reduced the differential pressure across the feedwater control valve to a value which was initially not thought possible. The energy savings from this project will allow the company to realise a return on investment in less than 3 years.
  • Significant improvement in the noise enclosure of the feed water motor and pump at ambient conditions. The noise level of the feed water pump motor dropped from 89 dBA to 81 dBA, meaning that the plant operator does not have to wear ear plugs to carry out patrol inspections.
  • Close to 4% decline in temperature, therefore less chiller capacity required.

The technology has also enabled operators to control the speed of the pump and modulate the discharge pressure of the flow according to the load profile – delivering the required flow at a much lower motor power.

“Throughout the years of working with Siemens, the company has consistently proven itself in providing robust technological solutions that are delivered on time, within budget and that often operate even better than expected. Trust, reliability, professionalism and honesty are just some of the values that Siemens has demonstrated, and we appreciate their ability to not only handle the project smoothly from start to finish, but also provide us excellent support at every step in the plant operation. We look forward to many more years of partnership ahead,” Mr. K.K Shivakumara, Chief Operating Officer, PacificLight Power.