Station design and layout

1Introduction

2Power stations used on the CEGB system

2.1Fossil-fired stations

2.2Nuclear stations

2.3Hydro-electric and pumped storage stations

2.4Gas turbine stations

3Future development options

3.1Fossil-fired plant

3.2Nuclear stations

3.3Combined cycle gas turbines

3.4Wind power

3.5Tidal power

3.6Geothermal energy

3.7Combined heat and power

4Station design concepts

4.1Basic considerations

4.2Design objectives

5Plant operation

6Station layout

6.1General

6.2Main plant orientation

6.2.1Turbine-generator plant

6.2.2Boiler plant

6.3Layout conventions

6.3.1The unit principle

6.3.2Mirror imaging

'6.3.3 Turbine island concept

6.3.4Mechanical annexe

6.3.5Boiler house enclosure

7Turbine-generator systems

7.1Feedheating plant

7.2Condenser and auxiliary plant

7.3Erection and maintenance

8Boiler systems

8.1Pulverised fuel system

8.2Draught system ‘

8.3Oil firing system

8.4Boiler fittings '•

8.5Dust extraction plant

8.6Flue gas desulphurisation plant

9Main steam pipework

10Low pressure pipework and valves

11Water storage tanks

12Cranes

13Fire protection

13.1Introduction

13.2Prevention of fires

13.3Limiting the consequences of a fire

13.4Reducing the severity of fires

^14 Electrical plant layout

14.1Introduction

14.2Auxiliary switchgear

14.2.111 kV and 3.3 kV switchgear

14.2.2415 V switchgear

14.3 Turbine-generator auxiliaries 14.3.1 Excitation equipment

14.4Main connections

14.5Transformers

14.5.1Generator transformers

14.5.2Station transformers

14.5.3Unit transformers

14.5.4Auxiliary transformers

14.6Cables

14.6.1Segregation

14.7Batteries and charging equipment

14.7.1Battery rooms

14.7.2Charging equipment and switchgear

14.8Control rooms

-14.8.1 Desks and panels

14.8.2Cable access and terminations

14.8.3Control room design

15Heating, ventilation and air conditioning

15.1Introduction

15.2Ventilation of nuclear stations

15.3Smoke and fire control

15.4General layout of HVAC plant

15.4.1Turbine hall and boiler house

15.4.2Coal bunkers

15.4.3Electrical equipment annexes

15.4.4Auxiliary buildings

16Air services

17Water treatment plant

18Cooling water plant

18.1General design considerations

18.2 Cooling water pumphouse

18.2.1Direct cooled stations

18.2.2Tower cooled stations

18.3Main cooling water pumps

18.4Screening plant

18.5Pump discharge valves

18.6Section valves

18.7Discharge pipework

18.8Auxiliary systems

18.9Gates

18.10Flow measurement

19Chlorination plant

20Coal handling plant

20.1Rail-borne reception and discharging

20.1.1Typical coal handling system

20.2Water-borne reception and discharging

20.3Road-borne reception and dischargino

20.4Coal storage

20.4.1Stockpiling

20.4.2Stockpile working

Station design and layout.

20.4.3Bucket wheel stocking out/reclaiming machine

20.5Conveyance from unloading poinr ro station bunkers or coal store

20.6Plant control

21Ash and dust handling plant

21.1Ash handling plant

21.2Dust handling plant

21.3Ash and dust disposal

22Auxiliary boilers

23Gas generation and storage

23.1Hydrogen

23.2Carbon dioxide

23.3Nitrogen

23.4Miscellaneous gases

24Pumped storage plant

24.1Hydraulic machines

Chapter 2

24.2Generator-motors

24.3Main inlet valves

24.4Draft tube valves

24.5Gates

24.6High integrity pipework

25Gas turbine plant

25.1Introduction

25.2Operational requirements

25?3 Aero-engine-derivative gas turbines

25.4Industrial gas turbines

25.5Gas turbine power station layout

25.5.1Introduction

25.5.2Station plant

j 25.5.3 Industrial gas turbine site layout

25.5.4Cowes gas turbine station layout

25.5.5Littlebrook D auxiliary gas turbine installation

26 References

1 Introduction

Power stations arc complex arrangements of individual plant items, equipment and mechanical and electrical engineering systems. The term 'station' in its widest sense can be taken to include all the plant equipment, engineering systems and buildings which are normally accommodated within the confines of the site bound­ ary, but it is often convenient to consider the design process as being sub-divided into two areas. Firstly, the main station buildings which contain the major plant items and systems such as the steam raising process and turbine-generators, and secondly, the auxiliary supporting systems and services such as the coal handling plant, ash handling plant, cooling water pumps, etc., which are often located around the site outside the main buildings. Whereas the design of the main building is, in the main, independent of siterelated factors above foundation level, the design and layout of the major auxiliary systems is often influenced to a significant extent by site-specific features.

The content of this chapter follows this philosophy where, following a review of the major factors influenc­ ing the design process and the types of power stations operated by the CEGB, details of the layout consider­ ations, which influence the design of the main plant areas, are given. The following sections of this chapter describe the features which have a major influence on auxiliary equipment and systems.

2 Power stations used on the CEGB system

The CEGB operates a number of different power station types to ensure a secure and cost effective - supply of electricity, as is required by its statutory duties. Presently these may be classified under the following headings:

•Coal-fired.

•Oil-fired.

•Dual-fired (combination of coal and oil or natural gas).

•Nuclear.

•Hydro and pumped storage.

•Gas turbines.

The first four categories mentioned comprise the majority of stations operated on the CEGB system and utilise a similar concept, which is ;> steam raising source supplying steam to a turbine-generator to produce electrical power.

2.1 Fossil-fired stations

Coal, oil and dual-fired (either coal or oil) stations have many similar design features, with the main difference being the type of fuel used to generate steam in the boiler. Coal-fired stations require extensive fuel storage and handling facilities, ash collection and dis­ posal facilities, and larger boilers than oil-fired ones due to the generally lower calorific value of the fuel. They are therefore inherently more expensive from a capital cost viewpoint than oil-fired stations. By impli­ cation, dual-fired stations are even more expensive due to the need for duplicate fuel storage and handling facilities.

Fossil-fired stations can be constructed employing large individual unit sizes; currently up to 660 MW is operational in the UK utilising both subiritical and supercritical steam cycles. Fossil-fired stations provide the bulk of generation on the CEGB system, currently accounting for more than 80% of the total system capacity. Figures 2.1, 2.2 and 2.3 illustrate typical stations on the CEGB system, showing coal-fired, oil-fired and dual-fired stations respectively.

62

Fig. 2.2 1 .i:denio<»k D ? - '■(>'/ MW J .station

layout and design Station

2 Chaplet