Medway Power Station

Medway Power Station is a 735 megawatts gas-fired combined cycle gas turbine (CCGT) power station on the Isle of Grain in Kent adjacent to the River Medway, about 44 miles east of London. It started to supply electricity to the national grid in 1995.

History Medway Power Limited (MPL) was incorporated in September 1990. It is a joint venture company originally comprising Arlington, Virginia-based AES Corporation (trading as AES Electric) (25%) and the RECs SEEBOARD (37.5%) and Southern Electric (37.5%) (became SSE in 1998). In April 1992 MPL awarded a design, procurement and construction contract to a consortium of Europower Development Ltd and TVB Power Ltd. The contract called for a turnkey 660 MW combined cycle electricity generating plant, deliverable by 1 August 1995.

The station was built by Marubeni (Japanese), Tarmac and Kansas City-based Black & Veatch. The station is run by Scottish & Southern Energy under the name Medway Power Ltd. It was commissioned in 1995, being . In June 2002, American Electric Power (AEP) sold its SEEBOARD company to eDF, giving eDF 37.5% of the power station. SSE bought the plant from AES and eDF Energy for £242m on 3 October 2003. It is near (west of) to the Grain Power Station and next to the Thamesport.

The Site The station is on an 11 acre (4.45 ha) site, above the 200 year flood plain. There is a requirement that the noise at the perimeter must not exceed 65 dBA. The three turbines are contained within an acoustic enclosure in a containment building. The two exhaust stacks are 65 m tall. Stack emissions are limited to 45 ppm NOx. Cooling water is abstracted from the Medway and chlorinated. Water discharges are monitored and treated prior to discharge.

Specification Medway power station is a CCGT-type power station that runs on natural gas. It has two General Electric Frame 9 (9001F) gas turbines. The exhaust gas from these reaches two Nooter Eriksen heat recovery steam generators. The steam from these powers one General Electric steam turbine.

Main plant The operating parameters of the main generating plant are as follows. +Medway power station main plant specificationsParameterValueCombustion turbine generators (CGT)ManufacturerGeneral ElectricModelMS9001FATypeAdvanced Aero EngineNumber of2Combustion chambers18Firing temperature1,288°CCGT output228 MW at 11°CCGT heat rate10,180 kJ/kWhCGT efficiency35%Steam turbine generator (STG)ManufacturerNooter/EricsenTypeNatural circulation, triple pressure, reheat type HRSGNumber of2Exhaust gasesVented to 65 m high steel stacks at 113°CSTG output247 MWSTG heat rate7,934 kJ/kWhSTG efficiency88.7% HP isentropic, 91.8% IP/LP isentropicNet output available682 MWNet heat rate6,800 kJ/kWhNet plant efficiency53%GeneratorsManufacturerGEModelGE 324SRating291 MVA / 15,000 V at 0.85 power factorTypeHydrogen cooled

During a major upgrade project in 2012 the power station benefitted from the GE DLN 2.6 install as well as an upgrade to the excitation and turbine control system. Currently the power station operates as a two-shifting plant with approximately 20MW of black start capacity.

Ancillary plant Specification of the ancillary plant is as shown in the table. +Medway power station ancillary plant specificationsParameterValueStep up transformersRating290 MVA at 15 kV/420 kVManufacturerGEC-AlsthomNumber3Ancillary supplyTwo 20 MVA transformers for auxiliary servicesCooling plantManufacturerHamonTypeOpen wet mechanical cooling towerConstruction12 cell mechanical ventilationFlowrate612,000 litres per minuteDesign condition11°C, 80% humidityHeat rejection1.614 × 109 kJ/h heat rejectionCondenserManufacturerSenlor ThermalTypeSurface condenserCondensing rate655,000 kg/h using cooling water at 21°CBack pressure main steam41 mm Hg A on steam turbine at 538°C at 97 barABack pressure reheat335°C at 28 barA for hot reheat; 260°C at 6.7 barADemineraliserManufacturerGleggTypeTwo train two bedCapacity4,670 l/min (maximum NOx control

water injection when running on fuel oil)Feed water deaeratorOperating pressure150 mm Hg AWater storage tankFuel gas heaterManufacturerGraham/CraneTypeWater-to-gas heat exchangerNumber2Temperature rise27°C to 150°CAuxiliary coolingManufacturerAllfa-LavalTypePlate heat exchangersNumber3ServiceCool auxiliary cooling loop; turbine lube oil;

Generator coolersMetallurgyTitanium for saline cooling waterLube oilReservoir30,280 l (8,000 gals)EquipmentPumps; filters; heat exchangersFuel oilEquipmentDual filters; 3 x 50 % pumps; 2 x atomising air compressorsControl systemManufacturerBaileyTypeDistributed control and information system (DCIS)FacilitiesOperator interface with turbines; control outputs to generators;

Operator control functions; Control of equipment and process parameters

Medway Power Station

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