220021enC Combined Cycle Power Plant Overview

Combined Cycle Power Plants

Combined Cycle Power Plant Overview Overview (Single- and Multi-Shaft) Training Module

)*+ )* +,

Combined Cycle Power Plants

CCPP Overview (Single- and Multi-Shaft)

)*+,

Combined Cycle Power Plants

CCPP Overview (Single- and Multi-Shaft)

Table of Contents

List of Technical Aids ............................................................................................................................................. 4 Module Objectives .................................................................................................................................................. 5 Overview..................................................................................................................... .............................................. 6 Gas Turbine Power Plant Overview ...................................................................................................................... 6 Gas Turbine Main Components and Functional Principle .................................................................................. 7 Generator Components and Functional Principle ............................................................................................... 8 Steam Turbine Power Plant Overview ................................................................................................................ 10 Basic Components of a Steam Turbine Power Plant........................................................................................ 10 Combined Cycle Power Plant Overview........................................................................... .................................. 11 Multi-Shaft Arrangement .................................................................................................................................... 11 Single-Shaft Arrangement ................................................................................................................................. 12 Overview of a Combined Cycle Plant for CHE Supply..................................................................................... 13 Multi-Shaft Arrangement .................................................................................................................................... 13 Overview of a Combined Cycle Plant for CHE Supply..................................................................................... 14 Single-Shaft Arrangement ................................................................................................................................. 14 Control and Protection System Overview............................................................ .............................................. 15

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

List of Technical Aids

Definitions

Enclosure Attachment

Integral Standard Document Attached Site-Specific Illustration or Document

Identification

Description

Attachment 1

Plant Operation and Control Concept

Combined Cycle Power Plants

)*+,

CCPP Overview (Single- and Multi-Shaft)

Module Objectives

Upon completion of this section, the trainee is able to: n

State why combined cycle power plants are used in preference for supplying electric energy.

n

Explain why a gas turbine set includes: n A turbine n A combustion chamber  n A compressor 

n

Give the reasons why the main electrical energy supply chain contains: n A generator  n An exciter  n Generator bushings n A generator breaker  n A main step-up transformer  n A grid breaker 

n

Justify the use of a boiler and a steam turbine within a steam turbine power plant.

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Overview

CCPP as energy supplier

A relative newcomer to the field of energy supply is the combined cycle power plant (CCPP). n

CCPPs take the advantages of gas turbosets and steam turbosets and combine them in a system that provides electric power at a much higher efficiency than is possible with either system operating alone.

This section will briefly describe the process of typical ALSTOM gas and steam turbine  power plants before summarizing how those processes are combined in a typical CCPP. n

The material does not describe all equipment, but rather focuses on major components, which are essential to an understanding of the overall process.

Gas Turbine Power Plant Overview

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Gas Turbine Main Components and Functional Principle Figure 1

Gas Turbine

The gas turbine is composed of three processing elements: n n n

an air compressor  a combustion chamber and the turbine itself 

The turbine itself: n

n n

Converts the thermal energy contained in the combustion gas into mechanical energy at the coupling and Is the prime mover that drives the generator and the compressor. Is driven by hot, compressed combustion gas that strikes blading mounted on the rotor, and causes it to turn. n After the combustion gas passes through the turbine it is discharged to atmosphere and is called exhaust gas

The combustion gas that drives the turbine is supplied by the combustion chamber. The latter  one: n

Converts the chemical energy of the fuel into heat and

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Generator Components and Functional Principle Figure 1

Generator

The generator: n n n

Is the driven machine and Converts the mechanical energy of the turbine into electrical energy. Is composed of  n A non-movable part called the stator and n A movable part called the rotor. n The latter is coupled to the turbine rotor, either; n directly or  n through a rotational speed reduction gear 

The rotor: n n

Is basically a magnet and Creates a rotating magnetic field inside the machine by means of the excitation or field winding, often referred to simply as the rotor winding.

The strength of the magnetic field must be adjusted to correspond to the electrical power  output of the generator. The consequences of this measurement are:

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Generator Components and Functional Principle (continued) Figure 1

Exciter

The exciter provides the direct current (DC) for the windings of the generator’s rotating magnetic field. Two types of exciters are used: n  brushless and n static Both perform the same function. n

Generator Bushings

The generator’s bushings: n

n n

Provide the connection that enables the electric energy of the generator to be delivered to the outside world. Are mounted on the generator stator housing and Receive the high voltage (HV) output of the stator windings.

The Generator Breaker

The generator breaker provides the electrical connection between the generator’s bushings and the step-up transformer.

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Steam Turbine Power Plant Overview Basic Components of a Steam Turbine Power Plant Figure 2

The supply of electricity from a steam power plant requires: a water steam cycle with: n a boiler  n a steam turbine n a generator  n an exciter  n generator bushings n circuit breaker and n step-up transformer. The role of each will be briefly described. n

Boiler

The boiler: n

n

Is a place where an energy conversion takes place, namely from chemical energy of the fuel into heat energy. n The latter one is carried by the combustion gas. Uses heat of combustion to convert water into steam, a physical conversion process.

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Combined Cycle Power Plant Overview Multi-Shaft Arrangement Figure 3.1

The objective of a combined cycle power plant with multi-shaft arrangement is to deliver  only electricity. To fulfil the above objective, the major components of a multiple shaft combined cycle  power plant are: n n n n n

n

One or more gas turbosets. One or more heat recovery steam boilers (HRSB). One or more steam turbosets. The rest of the water-steam cycle. The balance of plant equipment: n mechanically and n electrically. Control equipment.

The process begins when the gas turboset is placed in operation. n

The gas turbine operates on a mixture of air and fuel, which is ignited in the combustion chamber. n The hot gas is expanded through the turbine, causing the shaft to rotate.

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Multi-Shaft Arrangement (continued) Exhausted steam is directed to a condenser, where it is converted to water called condensate. The condensate is then directed to the feed water storage tank-deaerator. Here it is: Deaerated n Preheated and n Stored The feed water is then used by the HRSB in the throughput demanded by gas turbineset electric power output. n

Single-Shaft Arrangement Figure 3.2

The objective of a combined cycle power plant with single-shaft arrangement is to deliver  only electricity. To fulfil the above objective, he major components of a single shaft combined cycle power   plant are: n n n

A gas turbine. An alternator. A self shifting and synchronizing (SSS) clutch.

Combined Cycle Power Plants

)*+,

CCPP Overview (Single- and Multi-Shaft)

Overview of a Combined Cycle Plant for CHE Supply Multi-Shaft Arrangement Figure 3.3

The objective of a combined cycle plant for CHE supply with multi-shaft arrangement is to deliver simultaneously heat and n electricity. This process is known as combined heat and electricity (CHE) supply. n

To fulfil the above objective, the major components of a multiple shaft combined cycle plant for CHE supply are: n n n n n n

One or more gas turbosets. One or more heat recovery steam boilers (HRSB). One or more steam turbosets. One or more heating condensers. The rest of the water-steam cycle. The balance of plant equipment: n mechanically and n electrically.

All the previous descriptions apply to this type of combined cycle plant plus the following

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Overview of a Combined Cycle Plant for CHE Supply Single-Shaft Arrangement Figure 3.4

The objective of a combined cycle plant for CHE supply with single-shaft arrangement is to deliver simultaneously heat and n electricty. This process is known as combined heat and electricity (CHE) supply. n

To fulfill the above objective, the major components of a single shaft combined cycle plant for CHE supply are: n n n n

A gas turbine. An alternator. A self shifting and synchronizing (SSS) clutch. A water steam cycle, mainly composed of: n A heat recovery steam boiler. n A steam turbine alternator set. n A condenser. n A heating condenser. n Condensate extraction pumps. n A deaerator feedwater storage tank. n Boiler feedwater pumps.

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Control and Protection System Overview

Importance of automated control systems

Today's complex power plants operate at very high efficiency because of the sophisticated design of the equipment used. n

Figures 1 and 4

To reach these high levels of efficiency and reliability, automation systems have become standard in the industry. n ALSTOM's major control and protection systems are briefly outlined below. n Details are provided in the respective gas and steam turbine modules.

EGATROL

EGATROL: n n

n

n

Is the abbreviation for electronic gas turbine controller. Includes a sequencing program that automatically starts, “loads” and shuts down the gas turboset and its auxiliaries while observing ALSTOM protective limitations. Regulates during operation, the gas turboset by positioning the fuel control valves based on electric power output requirements. Includes a man machine interface (MMI): n For receiving data from the process.

Combined Cycle Power Plants

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CCPP Overview (Single- and Multi-Shaft)

Control and Protection System Overview (continued) Figures 2 and 4

TURBOMAT

The TURBOMAT: n n n

Figures 1 and 2

Is the steam turboset sequencer. Is optional equipment. When supplied is used to automatically start-up, “load”, and shut-down the steam turboset and its auxiliaries while observing ALSTOM limitations.

UNITROL

The UNITROL: n n

n

Is the excitation system for the alternators. Includes a centerpiece that is the automatic voltage regulator (AVR). The latter one: n Maintains the outlet voltage of the generator at a constant value. n Influences the exciter and thereby the electric current through the windings of the magnetic field. Has a back-up manual field current regulator (FCR). The latter one: n Fulfills the same task but requires manual input from the operator. n Adjusts the reactive electric power output of the generator, expressed in units of voltampere reactive (V·Ar ).

Combined Cycle Power Plants

)*+,

CCPP Overview (Single- and Multi-Shaft)

Control and Protection System Overview (continued) Figures 1 and 2

GSX or REG:

The generator protection system: n

n

Figure 4

Protects the generator and its associated equipment from abnormal operating conditions. When the protection equipment detects a fault: n The generator breaker is opened and n The gas or steam control valves are tripped to their closed positions. Has the designation GSX or REG, depending the selected model.

BOILERMAT

Each HRSG has several function groups and drives. The BOILERMAT: n n

n

Is the boiler controller. Coordinates different control functions of the HRSB like: n start-up n shut-down and n open-loop controls n This coordination is made in respect with the open-loop controls of the gas and steam turbosets. Regulates during operation, the HRSB's drum level closed-loop controls.

Combined Cycle Power Plants

)*+,

CCPP Overview (Single- and Multi-Shaft)

Control and Protection System Overview (continued) Figure 4

BLOCKMASTER  

The BLOCKMASTER: n n

n n

Is the overimposed power plant controller. Ensures that each major component in the CCPP process is brought into service or  removed from service in the proper sequence. Is also called UNITMASTER. Includes several MMIs: n For receiving data from the process. n To influence the process.

Summary

This section: n

Described the components used to deliver electricity from modern gas and steam turbine  power plants

 C   S  X  A  2  2   0   0  2  1   e n  C 

— — — — — — — — — — — — — — — —

P   o w  e r  P  l    a n  t   T  r   a i   n i   n  g  C   e n  t    e r  — — — — — — — — — — — — P  —  a —  g —  e 1   9  —

Chemical

Heat

Mechanical

TEG

Gas turbine electronic controller  - Sequencing - Control/ regulation - Protection ( EGATROL) *

Electrical

: Main electric energy supply

nTurbine

: Feedback signal

Synchronizer  (SYNCHROTACT)*

UG / f G

: Actuation signal : Information exchange signal Pel : Electric power  UN / f N

MV f 

Generator protection ( GSX/ REG)

MV

n

: Rotational speed

T

: Exhaust gas temperature

f

: Frequency

DI

:

Differential current

UG : Generator voltage

UG

UN : Net voltage Pel

UG

DI

Pel

fG : Generator frequency

Voltage regulator  (UNITROL) *

fN : Net frequency MV : Medium voltage

n

 Air 

Turbine fuel valves trip and control

Inputs: air  fuel

Fuel

Output: electric energy      g      n       i       l      p      u      o       C

Output: exhaust gas (heat) Rotor 

Turbine

Combustion chamber 

High voltage bushings

Neutral point

DC

Stator  Rotor field

Output: mechanical energy

Generator 

Exciter: brushless or static

Grid breaker  Generator step-up transformer  * Trade names for ABB equipment

Compressor 

Gas turbine block

Electrical energy to consumers

Generator  breaker 

Generator block

CSXA400183.cdr 

F  i    g  u r   e 1  :  i    S   t    s i   m M  p  a l   i    j   f    o  e i   r   d   C   o  O mv  p  e  o r  v i   n  e  e w n  t    s  o f    a  a n  G  d   S  a  y  s  s T   t    e  u r  m b   s i   n  e P   o w  e r  P  l    a n  t    ,

)  *  + ,

 C  P  o  o m w b   e i   n r   e P  d  l   C   a n  y   t    s  c  l    e

 (    S  i   n  g l    e  a  C  n  C   d  P  M P   u  O l   v  t   i   -  e  S  r  h  v i    a  e f   w  t  

 C   S  X  A  2  2   0   0  2  1   e n  C 

— — — — — — — — — — — — — — — —

P   o w  e r  P  l    a n  t   T  r   a i   n i   n  g  C   e n  t    e r  — — — — — — — — — — — — P  —  a —  g —  e 2   0  —

Chemical

Heat

Mechanical

Electrical

: Main electrical energy supply

Turbine- generator set sequencer  ( TURBOMAT) *

: Feedback signal : Actuation Signal : Information exchange signal Pel : Electrical power 

Steam turbine electronic controller  - Control - Regulation - Protection

f G

nG : Rotational speed of generator  fG : Frequency of generator  Synchronyzer 

UG

DI

UG : Voltage of generator  fN : Frequency of net or grid

( SYNCHROTACT) *

( TURBOTROL) *

UN : Voltage of net or grid

Generator  protection

f N

DI

( GSX/ REG) *

Pel

:

Differential current

PS : Steam pessure UN

PS

Voltage regulator 

Pel

f G TS

UG

TS : Steam temperature OUTPUT: Electrical energy to consumers

( UNITROL) *

nG Turbine steam valves trip and control

Exhaust gas

Steam turbine

Neutral point

Main steam

Generator  breaker 

High voltage bushings

Grid breaker 

Generator stator  Rotor  Inputs :

Coupling

Steam

Water 

Generator field

Exciter: brushless or static

Generator  step- up transformer 

Water 

Fuel

Boiler 

 Air 

Make- up water 

Steam and water  Cooling medium in vapor 

Condenser 

Boiler feedwater  pump

Deaerator and feed water  storage tank

Condensate extraction pump

Condensate ( Water)

Cooling medium out

* Trade names for ABB equipment

CSXA400184.CDR

F  i    g  u r   e 2  :  i    S   t    s i   m M  p  a l   i    j   f    o  e i   r   d   C   o  O mv  p  e  o r  v i   n  e  e w n  t    s  o f    a  S  n  t    d  e  S  a  y m  s T   t    e  u m r   s  b  i   n  e P   o w  e r  P  l    a n  t    ,

)  *  + ,

 C  P  o  o m w b   e i   n r   e P  d  l   C   a n  y   t    s  c  l    e

 (    S  i   n  g l    e  a  C  n  C   d  P  M P   u  O l   v  t   i   -  e  S  r  h  v i    a  e f   w  t  

 C   S  X  A  2  2   0   0  2  1   e n  C 

— — — — — — — — — — — — — — — —

P   o w  e r  P  l    a n  t   T  r   a i   n i   n  g  C   e n  t    e r  — — — — — — — — — — — — P  —  a —  g —  e 2  — 1 

Deaerator  feedwater  storage tank

Heat recovery steam boiler  Low / intermediate pressure feedwater pump

HRSB

Low pressure economizer 

High pressure feedwater pump

Steam pressure reducing valve

Low pressure deaeration steam control valve

Feedwater  control valve

Low pressure evaporator 

LP

steam drum Low pressure water  circulation pump

Intermediate pressure economizer  Intermediate pressure evaporator 

IP

steam drum Intermediate pressure water  circulation pump

High pressure economizer  Intermediate pressure superheater 

HP steam drum

High pressure evaporator 

High pressure water  circulation pump

High pressure superheater and intermediate pressure reheater 

Compressor 

Gas turbine

LP steam turbine

Generator 

G

G HP steam turbine Combustion chamber 

Natural gas Fuel gas preheater 

IP steam turbine

Generator  Cooling Medium

Main condenser 

Condensate extraction pump CSXA400185.cdr 

F  i    g  u r   e  3  .1  :   C   o m  b  i   n  e  d   C   y  c l    e P   o w  e r  P  l    a n  t   P  r   o  c  e  s  s  O v  e r  v i    e w  (   M  u l    t   i    S  h   a f    t    )  

)  *  + ,

 C  P  o  o m w b   e i   n r   e P  d  l   C   a n  y   t    s  c  l    e

 (    S  i   n  g l    e  a  C  n  C   d  P  M P   u  O l   v  t   i   -  e  S  r  h  v i    a  e f   w  t  

 C   S  X  A  2  2   0   0  2  1   e n  C 

— — — — — — — — — — — — — — — —

P   o w  e r  P  l    a n  t   T  r   a i   n i   n  g  C   e n  t    e r  — — — — — — — — — — — — P  —  a —  g —  e 2  — 2 

Deaerator  feedwater  storage tank

Heat recovery steam boiler  Low / intermediate pressure feedwater pump

HRSB

Low pressure economizer 

High pressure feedwater pump

Steam pressure reducing valve

Low pressure deaeration steam control valve

Feedwater  control valve

Low pressure evaporator 

LP

steam drum Low pressure water  circulation pump

Intermediate pressure economizer 

IP

Intermediate pressure evaporator 

steam drum Intermediate pressure water  circulation pump

High pressure economizer  Intermediate pressure superheater 

HP steam drum

High pressure evaporator 

High pressure water  circulation pump

High pressure superheater and intermediate pressure reheater 

LP steam turbine

Compressor  Generator 

Gas turbine

G Self shifting and synchronicing clutch

Combustion chamber 

Natural gas Fuel gas preheater 

HP steam turbine

IP steam turbine

Cooling Medium

Main condenser 

Condensate extraction pump CSXA400186.CDR

F  i    g  u r   e  3  .2  :   C   o m  b  i   n  e  d   C   y  c l    e P   o w  e r  P  l    a n  t   P  r   o  c  e  s  s  O v  e r  v i    e w  (    S  i   n  g l    e  S  h   a f    t    )  

)  *  + ,

 C  P  o  o m w b   e i   n r   e P  d  l   C   a n  y   t    s  c  l    e

 (    S  i   n  g l    e  a  C  n  C   d  P  M P   u  O l   v  t   i   -  e  S  r  h  v i    a  e f   w  t  

Combined Cycle Power Plants

)*+,

CCPP Overview (Single- and Multi-Shaft)

Figure 3.3: Combined Cycle Plant for CHE Supply and Multi-Shaft Arrangement

 Air  inlet

Natural gas (fuel oil)

Flue gases

100°C

Heatrecovery steam boiler  (HRSB)

Electricity

500°C

Generator 

Gas turbine

 C   S  X  A  2  2   0   0  2  1   e n  C 

— — — — — — — — — — — — — — — —

P   o w  e r  P  l    a n  t   T  r   a i   n i   n  g  C   e n  t    e r  — — — — — — — — — — — — P  —  a —  g —  e 2  — 4 

Flue gases

 Air  inlet

Deaerator  feedwater  storage tank

Natural gas (fuel oil)

Heat recovery steam boiler  (HRSB) Electricity Steam Steam turbine Boiler  feedwater pump

SSS clutch

Heating condenser 

Circulating pump

Generator 

Main condenser 

Condensate extraction pumps

Gas turbine

SSS: self synchronyzing and shifting

CW circulating pump

F  i    g  u r   e  3  .4  :   S  C  i   n  o  g m l    b   e - i   n  S  h  e  a  d  f   C   t   A  y  c r  l   r   a  e n P  l    g  a  e n m t   f    e  o n r   t   C  H E   S   u  p  p l    y  a n  d 

)  *  + ,

 C  P  o  o m w b   e i   n r   e P  d  l   C   a n  y   t    s  c  l    e

Condensate District heating system

Cooling water (CW)

CSXA400188.cdr 

 (    S  i   n  g l    e  a  C  n  C   d  P  M P   u  O l   v  t   i   -  e  S  r  h  v i    a  e f   w  t  

 C   S  X  A  2  2   0   0  2  1   e n  C 

— — — — — — — — — — — — — — — —

P   o w  e r  P  l    a n  t   T  r   a i   n i   n  g  C   e n  t    e r  — — — — — — — — — — — — P  —  a —  g —  e 2   5  —

Flue gases

 Air  inlet

Deaerator  feedwater  storage tank

Natural gas (fuel oil)

Heat recovery steam boiler  (HRSB) Electricity

Boiler  feedwater pump

Heat consumer  Generator 

F  i    g  u r   e  3  .  5  :   C  H E   S   u  p  p l    y P  l    a n  t  

)  *  + ,

 C  P  o  o m w b   e i   n r   e P  d  l   C   a n  y   t    s  c  l    e

Gas turbine

SSS: self synchronyzing and shifting Circulating pump

Condensate extraction pumps

CHE: combined heat and electricity CW circulating pump

Condensate District heating system

Cooling water (CW)

CSXA400189.CDR

 (    S  i   n  g l    e  a  C  n  C   d  P  M P   u  O l   v  t   i   -  e  S  r  h  v i    a  e f   w  t  

 C   S  X  A  2  2   0   0  2  1   e n  C 

— — — — — — — — — — — — — — — —

P   o w  e r  P  l    a n  t   T  r   a i   n i   n  g  C   e n  t    e r  — — — — — — — — — — — — P  —  a —  g —  e 2   6  —

BLOCKMASTER UNITMASTER

BOP CONTROLLER

EGATROL (open-and closedloop control)

MMI

MMI

BOILERMAT (open-and closedloop control)

TURBOMAT

MISCELANEOUS

(open-loop control)

(water steam cycle)

TURBOTROL (closed-loop control)

1 : Air compressor  2 : Combustion chamber  3 : Gas turbine 4 : Generator  5 : Exhaust gas flap or by- pass 6 : Heat recovery steam boiler  7 : Steam turbine 8 : Condenser  9 : Condensate extraction pump 10: Deaerator and feedwater storage tank 11: Boiler feedwater pump 12: Supplementary firing MMI: Man machine interface : Information exchange signal : Actuation signal : Feedback signal BOP: Balance of plant Remark: For simplicity reasons only one line is represented for: sented for: - Information exchange - Commands - Feedback informations

6

4

7 BOP equipment like: -Main cooling water  -Main condenser tube cleaning system -Cooling tower  -Closed cooling water system -Rain water system -Desalination plant -Water treatment plant -Waste water system -Fael gas supply system -Fuel oil supply system

5

12

10

8

2 4

1

11 3 9

CSXA400190.cdr 

F  i    g  u r   e 4  :  B  a  s i    c  S   c h   e m  e  o f    t   h   e  C   o n  t   r   o l    o f    a  C   o m  b  i   n  e  d   C   y  c l    e P   o w  e r  P  l    a n  t  

)  *  + ,

 C  P  o  o m w b   e i   n r   e P  d  l   C   a n  y   t    s  c  l    e

 (    S  i   n  g l    e  a  C  n  C   d  P  M P   u  O l   v  t   i   -  e  S  r  h  v i    a  e f   w  t  

 C   S  X  A  2  2   0   0  2  1   e n  C 

— — — — — — — — — — — — — — — —

P   o w  e r  P  l    a n  t   T  r   a i   n i   n  g  C   e n  t    e r  — — — — — — — — — — — — P  —  a —  g —  e 2  — 7 

KA24-1 ICS / DPR / SSPT ICS:

Innovative cycle solution

DPR:

Dual pressure reheat

SSPT: Single shaft power train

CSXA400269.CDR

F  i    g  u r   e  5  :   S  i   m  p l   i   f   i    e  d  W  a  t    e r   S   t    e  a m  C   y  c l    e

)  *  + ,

 C  P  o  o m w b   e i   n r   e P  d  l   C   a n  y   t    s  c  l    e

 (    S  i   n  g l    e  a  C  n  C   d  P  M P   u  O l   v  t   i   -  e  S  r  h  v i    a  e f   w  t