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.[1] It is a joint venture company originally comprising Arlington, Virginia-based AES Corporation (trading as AES Electric) (25%) and the RECsSEEBOARD (37.5%) and Southern Electric (37.5%) (became SSE in 1998).[2] 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.[2]
The station is on an 11 acre (4.45 ha) site, above the 200 year flood plain.[2] 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.[2]
The operating parameters of the main generating plant are as follows.[2]
Medway power station main plant specifications
Parameter
Value
Combustion turbine generators (CGT)
Manufacturer
General Electric
Model
MS9001FA
Type
Advanced Aero Engine
Number of
2
Combustion chambers
18
Firing temperature
1,288°C
CGT output
228 MW at 11°C
CGT heat rate
10,180 kJ/kWh
CGT efficiency
35%
Steam turbine generator (STG)
Manufacturer
Nooter/Ericsen
Type
Natural circulation, triple pressure, reheat type HRSG
Number of
2
Exhaust gases
Vented to 65 m high steel stacks at 113°C
STG output
247 MW
STG heat rate
7,934 kJ/kWh
STG efficiency
88.7% HP isentropic, 91.8% IP/LP isentropic
Net output available
682 MW
Net heat rate
6,800 kJ/kWh
Net plant efficiency
53%
Generators
Manufacturer
GE
Model
GE 324S
Rating
291 MVA / 15,000 V at 0.85 power factor
Type
Hydrogen 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.[2]
Medway power station ancillary plant specifications
Parameter
Value
Step up transformers
Rating
290 MVA at 15 kV/420 kV
Manufacturer
GEC-Alsthom
Number
3
Ancillary supply
Two 20 MVA transformers for auxiliary services
Cooling plant
Manufacturer
Hamon
Type
Open wet mechanical cooling tower
Construction
12 cell mechanical ventilation
Flowrate
612,000 litres per minute
Design condition
11°C, 80% humidity
Heat rejection
1.614 × 109 kJ/h heat rejection
Condenser
Manufacturer
Senlor Thermal
Type
Surface condenser
Condensing rate
655,000 kg/h using cooling water at 21°C
Back pressure main steam
41 mm Hg A on steam turbine at 538°C at 97 barA
Back pressure reheat
335°C at 28 barA for hot reheat; 260°C at 6.7 barA
Demineraliser
Manufacturer
Glegg
Type
Two train two bed
Capacity
4,670 l/min (maximum NOx control
water injection when running on fuel oil)
Feed water deaerator
Operating pressure
150 mm Hg A
Water storage tank
Fuel gas heater
Manufacturer
Graham/Crane
Type
Water-to-gas heat exchanger
Number
2
Temperature rise
27°C to 150°C
Auxiliary cooling
Manufacturer
Allfa-Laval
Type
Plate heat exchangers
Number
3
Service
Cool auxiliary cooling loop; turbine lube oil;
Generator coolers
Metallurgy
Titanium for saline cooling water
Lube oil
Reservoir
30,280 l (8,000 gals)
Equipment
Pumps; filters; heat exchangers
Fuel oil
Equipment
Dual filters; 3 x 50 % pumps; 2 x atomising air compressors
Control system
Manufacturer
Bailey
Type
Distributed control and information system (DCIS)
Facilities
Operator interface with turbines; control outputs to generators;
Operator control functions; Control of equipment and process parameters
^ abcdefLeis, Darrell M.; Boss, Michael J.; Melsert, Matthew P. (June 1994). "Medway: A High-efficiency combined cycle power plant design". American Society of Mechanical Engineers, ASME, 1994 International Gas Turbine and Aeroengine Congress and Exposition, June 13–16, 1994. The Hague, Netherlands.
