Acknowledgment

Industrial training provides students the opportunity to test their interest in a particular zone and
also provides students a moderate level of practical knowledge. It was a great privilege for the
graduating students, us, to attend the Industrial Training course introduced by the Department of
EEE, Rajshahi University of Engineering & Technology (RUET) at Sirajgonj NWPGCL
Combined Cycle Power Plant to have a clear view of the operation of thermal power plants as
well as professional life in power sector of Bangladesh. The Industrial Training course was started
on 22/04/2022 and ended on 28/04/2022 which included theoretical and practical visit classes. We,
a team of 7 members attended the training program. We gained practical knowledge about power
plants and observed the operating system of power plants. There we also got the knowledge of
power distribution and maintenance of that plant. We got a chance to visit steam power plant, gas
engine power plant, substation, water management plant and other auxiliary components of power
station. We gathered practical experience about different major components of power station such
as gas turbine, steam turbine, operation and control unit, cooling system and maintenance
procedures of the plants. We gathered practical knowledge about different types of equipment used
in the substation of the plant such as power transformers, instrument transformers, circuit breakers,
relays, lightning arresters, bus bar, and transmission and distribution system. We learnt about the
water management system. Inside the report I have described about my experiences at Sirajgonj
NWPGCL Combined Cycle Power Plant.
I am deeply grateful and humble to my respected supervisor, Dr. S M Abdur Razzak
, Professor, Department of Electrical and Electronic Engineering, Rajshahi University of
Engineering & Technology for his guidance, encouragement and kind consideration in many ways
regarding this industrial attachment.
My special and profound respect to all my teachers for their encouragement and support through
our entire life.

_______________________

Md. Jahid Hasan

Department of EEE, RUET
4th year, odd semester
Roll No.: 1701011

1
 Objectives
The prime purpose of the training was to integrate our academic knowledge with the practical
knowledge of power station. This program was taken to satisfy our academic requirement. In
this training main focus was on generating system, transmission process and maintenance of
North-West Power Generation Company Ltd (NWPGCL) to achieve a complete overview.
The objectives were:

▪ To gather practical knowledge of a real power plant.

▪ To become familiar with the various equipment and devices that are used in power

plants.

▪ To know about generation system of electricity.

▪ To become introduced with practical generation and transmission system.

▪ To compare the theoretical knowledge gained with the practical one.

▪ To get an overview of a real electrical power generating plant.

2
 Contents
Acknowledgement
2
Objectives
3
Contents
4-6

Chapter 1 Introduction
1.1 Power Station
9
1.2 About Sirajgonj NWPGCL Combined Cycle Power Plant
9
1.3 Plant overview
9-14

Chapter 2 Schematic Arrangement of Sirajgonj NWPGCL CCPP

2.1 Short Description
15
2.2 Schematic Arrangement of CCPP
15-16

Chapter 3 Gas Turbine Plant

3.1 Introduction
16
3.2 Operation of Gas Turbine 16-
17
3.3 Different Parts of Gas Turbine unit
17
3.4 Compressor
17
3.5 Combustor
17
3
 3.6 Turbine
18
3.7 Stack Damper 18-
19

Chapter 4 Water Treatment Plant

4.1 Water Treatment Plant 19

4.2 Importance of Water Treatment Plant
20
4.3 Working Principle of Water Treatment Plant 20
4.4 Makeup Water Intake 20
4.5 Coagulation 20-
21
4.6 Filtration and Ultrafiltration
21-22
4.7 Ion exchange softening
22
4.8 De-alkalization
23
4.9 Demineralization
23
4.10 Remove Osmosis and Nano-filtration
23
4.11 Demineralized water tank
23

Chapter 5 Steam Turbine Plant

5.1 Introduction to Boiler

24
5.2 Parts of Boiler
24
5.3 Furnace
24
5.4 Feed Water Pump
24-25
5.5 Steam Separator
25
5.6 Steam Drum
25-26

4
 Low Pressure Drum
26
Intermediate Pressure Drum
26
High Pressure Drum
26
5.7 Super Heater
27
5.8 De-aerator
27
5.9 Chimney
27
5.10 Heat Recovery Steam Generator (HRSG)
27-28
5.11 Steam Turbine
29

Chapter 6 Sub-Station

6.1 Introduction to Sub-Station

29

6.2 Importance of Sub-Station 30

6.3 Elements of sub-station

30-31
6.4 Power Transformer
31
6.5 Auxiliary Transformer
31-32
6.6 Current Transformer
32-33
6.7 Potential Transformer
33-34
6.8 Bus Bar
34-35

6.9 Circuit Breaker

35

5
 6.10 Isolator
35

6.11 Lightning arrester 36

6.12 Insulators
36

6.13 Capacitor Bank 37

6.14 Protective Relay 37

Chapter 7 Switchgear and Control Room

7.1 Introduction to Switchgear

37-38

7.2 Control room of Sirajgonj NWPGCL CCPP

38

7.3 Control Panel

39

7.4 UPS Panel

40

Chapter 8 Safety Rules

8.1 Introduction
41
8.2 Protection for complex requirements
41-42

Chapter 9 Conclusion
42

6
 List of Figures

Figure 1.1: Sirajganj NWPGCL Combined Cycle Power Plant (Unit-1) 10

Figure 1.2: Sirajganj NWPGCL Combined Cycle Power Plant (Unit-2) 11

Figure 1.3: Sirajganj NWPGCL Combined Cycle Power Plant (Unit-3) 12

Figure 1.4: Sembcorp North-West Power Company(unit-4) 14

Figure 1.5: Sirajgonj 7.6MW(ac) grid connected solar photovoltaic power plant 14

Figure 2.1: Schematic Arrangement of Sirajgonj NWPGCL CCPP 16

Figure 3.1: Construction of Gas Turbine 17

Figure 3.2: Combustion Chamber 18

Figure 3.3: Gas Turbine Generator 18

Figure 3.4: A photograph of Stack Damper 19

Figure 4.1: Water treatment element of Sirajgonj NWPGCL CCPP 20

Figure 4.2: A clarifier tank 21

Figure 4.3 : A Photograph of Ultra Filtration 22

Figure 4.4: catiaon exchanger 22

Figure 4.5: Anion exhanger 22

Figure 4.6: A photograph of DM Water Tank 23

Figure 5.1: Feed Water Pump 25

Figure 5.2: Pump for hp drum and lp drum 26

Figure 5.3: A photograph of HRSG 28

Figure 5.4: Steam Turbine 29

7
Figure 6.1: A photograph of sub-station of Sirajgonj NWPGCL CCPP 30

Figure 6.2: A photograph of power transformer 31

Figure 6.3: Unit Auxiliary Transformer of Sirajganj NWPGCL 32

Figure 6.4 :A photograph of Current Transformer 33

Figure 6.5: A photograph of Potential Transformer 34

Figure 6.6: A photograph of Circuit breaker 35

Figure 6.7: A photograph of Lightning arrester 36

Figure 7.1: Switchgear Room of Sirajgonj NWPGCL CCPP 38

Figure 7.2: PLC installed I/O Cards room 39

Figure 7.3: Electrical switch of Control panel room 39

Figure 7.4: A photograph of UPS Panel 40

Figure 8.1: Fire Extinguisher chart 42

8
 Chapter 1
Introduction
1.1 Power Station
A power station is an industrial facility that generates electricity from primary energy. An
alternator is used to produce electrical power where a prime mover (e.g., diesel engine, steam
turbine, water turbine, etc.) is coupled with each alternator to produce mechanical energy for
the rotation of the rotor of the alternator. While designing a power station two important factors
should be considered.
The first one is the necessary power-generating equipment should be selected and placed in
such a way that maximum return will result from minimum expenditure over the working life
of the station or plant. The second one is the plant operation will be such to provide cheap,
reliable
and continuous service.

1.2 About Sirajganj NWPGCL Combined Cycle Power Plant

Sirajganj NWPGCL Power Plant is a combined cycle dual fuel-fired power project. It is located
at Soydabad, Sirajganj, Bangladesh. The plant has four 4 units. Three of them have the ability
to produce 225MW power and the last one capacity is 414 MW. There is also a solar plant in
the station which can produce 7.6 MW(AC). So, the station can produce 1100 MW The project
is developed and owned by North West Power Generation Company Limited. There is a
Combined Cycle Gas Turbine (CCGT) power plant that is used for Baseload. The power plant
runs on dual fuel. The primary fuel being used in the power plant is natural gas. In case of a
shortage of natural gas, the plant can also run on High-Speed Diesel Oil.

Fig 1.1: Sirajganj NWPGCL Combined Cycle Power Plant (Unit-1)

9
1.3 Plant Overview
The following table shows an overview about Sirajganj NWPGCL CCPP:

Power Plant Location Soydabad, Sirajganj

Executive Agency North-West Power Generation Company Limited (An Enterprise

of Bangladesh Power Development Board)

EPC Contractor M/s. China National Machinery Import & Export Corporation

(CMC), China

Financer GOB & ADB

EPC Contract 12 October, 2010 (Simple Cycle),

Signing Date 08 August, 2012 (Combined Cycle)

Manufacturer of GT Siemens (GT),

and ST Dongfang Electric Machinery Co. Ltd. (ST)

Fuel Type Primary – Natural Gas, Alternative – HSD

Generation Capacity 214 MW

Commercial Simple Cycle: 22 November, 2012

Operation Date Combined Cycle : 14 July, 2014

ISO Certification ISO 9001: 2015, ISO 14001:2015 & ISO 45001:2018 Certified

10
Sirajganj NWPGCL Combined Cycle Power Plant (Unit-2)

Fig 1.2: Sirajganj NWPGCL Combined Cycle Power Plant (Unit-2)

Power Plant Soydabad, Sirajganj

Location

Executive Agency North-West Power Generation Company Limited (An Enterprise of

Bangladesh Power Development Board)

EPC Contractor Consortium of M/s. China National Machinery Import & Export

Corporation (CMC), China and Fujian Electric Power Survey &

Design Institute (FEDI), China

Financer Standard Chartered Bank (SCB)

(ECA)

11
 EPC Contract 20 August, 2014

Signing Date

Manufacturer of Siemens (GT),

GT and ST Dongfang Electric Machinery Co. Ltd. (ST)

Fuel Type Primary – Natural Gas, Alternative – HSD

Generation 220 MW

Capacity

Commercial 05 Feb, 2018

Operation Date

Sirajganj NWPGCL Combined Cycle Power Plant (Unit-3)

Fig 1.3: Sirajganj NWPGCL Combined Cycle Power Plant (Unit-3)

12
 Power Plant Soydabad, Sirajganj

Location

Executive Agency North-West Power Generation Company Limited (An Enterprise of

Bangladesh Power Development Board)

EPC Contractor Consortium of M/s. China National Machinery Import & Export

Corporation (CMC), China and Fujian Electric Power Survey &

Design Institute (FEDI), China

Financer Standard Chartered Bank (SCB)

(ECA)

EPC Contract 12 July, 2015

Signing Date

Manufacturer of Siemens (GT)

GT and ST Dongfang Electric Machinery Co. Ltd. (ST)

Fuel Type Primary - Natural Gas, Alternative - HSD

Generation 220 MW

Capacity

Commercial Simple Cycle: 09 Aug 2018

Operation Date Combined Cycle: 20 Jan 2019

13
Sirajgonj NWPGCL CCPP Power Plant (Unit-4)

Fig 1.4: Sembcorp North-West Power Company(unit-4)

NWPGCL has joint venture with Sembcorp Utilities of Singapore to build a 414-megawatt
power plant in Sirajganj.

Sirajganj 7.6MW(ac) grid connected solar photovoltaic power plant

Fig.1.5: Sirajgonj 7.6MW(ac) grid connected solar photovoltaic power plant

There is a 7.6MW(ac) grid connected solar photovoltaic power plant located at Soydabad,
Sirajgonj. The executive agency of the plant is NWPGCL. The operation of the plant started
on 29 march, 2021.

14
 Chapter 2

Schematic Arrangement of Sirajgonj NWPGCL CCPP

2.1 Short Description

The whole power generation process for a unit starts when natural gas enters into the Gas
Booster Compressor and meanwhile air from atmosphere is sucked into the Air Filter. At the
Gas Booster Compressor, pressure of the natural gas increases from 9-10 bar to 22 bar and at
the filter, the air is filtrated. Then the fuel enters into TCA Cooler where it its temperature
increases before entering Combustor and the air enters into Gas Turbine after getting
compressed in the Compressor. The fuel is burned and a large amount of heat is produced
which is used by the air to rotate turbine blades. As the gas turbine works as the prime mover
of the alternator, so there produces voltage in the alternator which is in amount of 15.75 kV.
Then at the switchyard, the generated voltage is stepped up at 230 kV with the help of
transformer and supplied to the PGCB substation.

The flue gases are passed through the HRSG to recover the heat energy and using the heat
energy steam is produced. This steam rotates the steam turbine and the alternator coupled with
it produces voltage of 10.5 kV. Then at the switchyard, the generated voltage is stepped up at
230 kV with the help of transformer and supplied to the PGCB Substation. The water needed
for producing steam is supplied from DM Plant or water treatment plant and cooling tower.
Water treatment plant purifies the water and cooling tower cools down the wet steam from the
turbine. The total plant is monitored and operated from Central Control Room and the electrical
equipment are protected by the switchgear.

2.2 Schematic Arrangement of CCPP

Fig.2.1: Schematic Arrangement of Sirajgonj NWPGCL CCPP

15
 Chapter 3

Gas Turbine Plant

3.1 Introduction

A gas turbine is a combustion engine at the heart of a power plant that can convert natural
gas or other liquid fuels to mechanical energy. This energy then drives a generator that
produces the electrical energy that moves along power lines to homes and businesses.

3.2 Operation of Gas Turbine

The basic operation of the gas turbine is a Brayton cycle with air as the working fluid: atmospheric
air flows through the compressor that brings it to higher pressure; energy is then added by spraying
fuel into the air and igniting it so that the combustion generates a high-temperature flow; this high-
temperature pressurized gas enters a turbine, producing a shaft work output in the process, used to
drive the compressor; the unused energy comes out in the exhaust gases that can be repurposed for
external work, such as directly producing thrust in a turbojet engine, or rotating a second,
independent turbine (known as a power turbine) that can be connected to a fan, propeller, or
electrical generator.

Fig.3.1: Construction of Gas Turbine

3.3 Different Parts of Gas Turbine unit

A gas turbine, also called a combustion turbine, is a type of continuous flow internal
combustion engine. The main parts common to all gas turbine engines form the power-
producing part (known as the gas generator or core) and are, in the direction of flow:
• A rotating gas compressor
• A combustor
• A compressor-driving turbine

3.4 Compressor
A compressor is a mechanical device that increases the pressure of a gas by reducing its
volume. An air compressor is a specific type of gas compressor. The compressor used in the plant

16
is generally of rotatory type. The air at atmospheric pressure is drawn by the compressor via the filter
which removes the dust from air. The rotatory blades of the compressor push the air between
stationary blades to raise its pressure. Thus, air at high pressure is available at the output of the
compressor.

3.5 Combustor
A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where
combustion takes place. It is also known as a burner, combustion chamber or flame holder. In
a gas turbine engine, the combustor or combustion chamber is fed high-pressure air by the
compression system. The combustor then heats this air at constant pressure as the fuel/air mix
burns. As it burns the fuel/air mix heats and rapidly expands. The burned mix is exhausted
from the combustor through the nozzle guide vanes to the turbine .

Fig.3.2: Combustion Chamber

3.6 Turbine
The products of combustion consisting of a mixture of gases at high temperature and pressure
are passed to the gas turbine. These gases in passing over the turbine blades expand and thus
do the mechanical work. The temperature of the exhaust gases from the turbine is about 900˚F.
In an ideal gas turbine, gases undergo four thermodynamic process: an isentropic compression,
an isobaric combustion, an isentropic expansion and heat rejection.

Fig.3.3: Gas Turbine Generator

17
3.7 Stack Damper
stack Dampers are designed to minimize heat loss from boiler and to prevent the ingress of
rain water. Stack damper can be either a butterfly or multi louvre design and can incorporate an
automatic pressure relieving system to prevent over pressure and damage to the HRSG and gas
turbine.

Fig.3.4: A photograph of Stack Damper

18
 Chapter 4

Water Treatment Plant

4.1 Water Treatment Plant

Water treatment is the process of removing all those substances, whether biological, chemical, or
physical, that are potentially harmful to the water supply for human and domestic use.

4.2 Importance of Water Treatment Plant

1. To protect the health
2. To ensure that water is not wasted
3. To restore the water
4. To protect the environment
5. To solve the problem of water shortage and fulfill the increasing demand of water
6. To solve the problem of water scarcity in the world

Fig.4.1: Water treatment element of Sirajgonj NWPGCL CCPP

4.3 Working Principle of Water Treatment Plant

A water treatment plant is installed away from the source of water to remove the impurities
and make it safe for human application.

The general procedure of wastewater treatment worldwide involves the following steps-

4.4 Makeup Water Intake

19
Makeup water, or water replacing evaporated or leaked water from the boiler, is first drawn
from its source, whether raw water, city water, city treated effluent, in plant wastewater recycle
(cooling tower blowdown recycle) well water, or any other surface water source. Here in
Sirajgonj NWPGCL CCPP most of the time, water is collected from ground. The condensed
water of cooling tower is recycled for further use.

4.5 Coagulation

After all the large objects are removed from the original water source, various chemicals are
added to a reaction tank to remove the bulk suspended solids and other various contaminants.
This process starts off with an assortment of mixing reactors, typically one or two reactors that
add specific chemicals to take out all the finer particles in the water by combining them into
heavier particles that settle out.

Fig.4.2: A clarifier tank

4.6 Filtration and Ultrafiltration

The next step is generally running through some type of filtration to remove any suspended
particles such as sediment, turbidity and certain types of organic matter. It is often useful to do
this early on this process, as the removal of suspended solid upstream can help protect
membranes and iron exchange resins from fouling later on the pretreatment process. Depending
on the type of filtration used, suspended particles can be removed down to under one micron.

20
 Fig.4.3 : A Photograph of Ultra Filtration

4.7 Ion exchange softening

When pretreating boiler feed water, if there’s high hardness complexed with bicarbonates,
sulfates, chlorides or nitrates, a softening resin can be used. This procedure uses a strong acid
cation exchange process, whereby resin is charged with a sodium ion and as the hardness comes
through, it has a higher affinity for calcium, magnesium and iron so it will grab that molecule
and release the sodium molecule into the water

21
 Fig.4.4: catiaon exchanger
Fig.4.5: Anion exhanger

4.8 De-alkalization

After the softness process, some boiler feed water treatment systems will utilize de-alkalization
to reduce alkalinity/pH, an impunity in boiler feed water that can cause foaming, corrosion and
embrittlement. Sodium chloride de-alkalization uses a strong anion exchange resign to replace
bicarbonate, sulfate and nitrate for chloride anions. Although it doesn’t remove alkalinity 100
percent, it does remove majority of it with what can be an easy to implement and economic
process. Weak acid de-alkalization only removes cations bound to bicarbonate, converting it
to carbon dioxide. It is a partial softening process that is also economical for adjusting the
boiler feed water pH.

4.9 Demineralization

Demineralization is the process of removing mineral salts from water by using ion exchange
process. Demineralized water is also known as deionized water with removed mineral ions.
Mineral ions such as cat-ions of sodium, calcium, iron, copper etc. and anions such as chloride,
sulfate, nitrate etc. are common ions present in water.

22
4.10 Remove Osmosis and Nano-filtration

Reverse osmosis and nano-filtration are often used down the line in the boiler feed water
treatment system process so most of the harmful impunities that can foul and clog the RO/NF
membranes have been removed.

4.11 Demineralized water tank

After all the treatments performed, demineralized water is reserved in the plant for supplying
to boiler in future.

Fig.4.6: A photograph of DM Water Tank

23
 Chapter 5
Steam Turbine Plant
5.1 Introduction to Boiler
A boiler is a closed vessel in which water or other fluid is heated to produce steam in high
temperature and pressure. The boilers make sure that the turbine is receiving the steam in
such a condition required by the turbine itself to meet its rated capacity. Boilers are engaged
in producing steam by recovering the heat from the exhaust gas. The boilers make sure that
the turbine is receiving the steam in such a condition required by the turbine itself to meet its
rated capacity. There is only one kind of boiler in Bheramara 410 MW CCPP and it is exhaust gas
boilers.

5.2 Parts of Boiler

Furnace
Feed water pump
Steam drum
Super Heater
Economizer
De-aerator
Chimney

5.3 Furnace
The purpose of furnace is to attain a higher processing temperature in comparison to open-air
systems, as well as the efficiency gains of a closed system. Here, with the presence of air the
natural gas is burned to produce heated gas or flue gas. The ratio of gas and air is 1:14.

5.4 Feed Water Pump

To control the flow of water from feed water tank to steam drums or economizer, there are
two feed water pumps. Water flows in two directions from feed water tank. One is from feed
water tank to low pressure drum and another is from feed water tank to the economizer of the
boiler.

24
 Fig.5.1: Feed Water Pump

5.5 Steam Separator

In boiler drum cyclone separators are used to separate steam particles from water. Cyclones are
mostly used for removing industrials dust from air or process gases. They are the principal type of
gas-solid separator. Most common form of particulate removal gas is spun rapidly-heavier 23

particulate matter to collect on outside of separator by centrifugal force, where it is collected and
removed.
5.6 Steam Drum
Steam drum is a reservoir of water or steam at the top end of the water tubes. The drum stores the
steam generated in the water tubes and acts as a phase-separator for the steam/water mixture.
There are three types of steam drum:
1. Low Pressure Drum
2. Intermediate Pressure Drum
3. High Pressure Drum
Low Pressure Drum
There is a low pressure drum where the water of low pressure is stored coming from feed water
tank. The pressure is around 7 bar at LP Drum. The water is then transferred to the low pressure

25
evaporator of Boiler through some valves. The steam produced in LP Evaporator is then
transferred to the LP Drum. The low pressured steam of 190 degree Celsius is transferred to
places where low pressure steam consumption is necessary.
Intermediate Pressure Drum
There is an intermediate pressure drum where the water of moderate pressure is stored
coming from the low pressure drum. The water is then transferred to moderate pressure
evaporator of boiler through some valves. The steam produced in IP evaporator is then
transferred to IP drum. The moderate pressure steam of around 250 degree Celsius is
transferred to places where moderate pressure steam consumption is necessary .
High Pressure Drum
This is a type of steam drum where steam of high pressure is stored and supplied. The steam
from economizer is stored at HP Drum firstly and then it is transferred to the high pressure
evaporator of boiler through valves. Then the steam of increased temperature is again stored
into HP Drum and then again transferred into super heater in the Boiler. The extremely
heated steam from super heater is again stored in HP drum and then transferred to the header
to be supplied to the turbine

Fig.5.2: Pump for hp drum and lp drum

5.7 Super Heater
This section increases the temperature of steam to 265 degree Celsius to remove any
remaining water and feed to the high pressure drum through the highest positioned way. A
line is available below to take back some of the steam back to super heater for perfect
heating. When steam has no water it is called saturated heated steam. The super heated

26
steam’s main purpose is to increase the temperature of saturated steam without raising its
pressure.

5.8 De-aerator
De-aerator is a device which is used to remove air and other dissolved gases from the feed
water to steam generating boilers. The metal piping and other metallic equipment is
damaging because of dissolved oxygen in boiler. It increases the efficiency and optimum
thermodynamic utilization. So de-aerator is used in Sirajgonj NWPGCL CCCPP to keep safe
of the equipment.
5.9 Chimney
A chimney is a structure which provides ventilation for hot flue gases or smoke from a boiler
to outside atmosphere. Furnace produces flue gas. This flue gas is used to create the steam for
rotating the turbine. The flue gas passes through several numbers of equipment and finally
goes into the nature through chimney. In Sirajgonj, there are two chimney. One is for gas
turbine and the another is for steam turbine.

5.10 Heat Recovery Steam Generator (HRSG)

A heat recovery steam generator (HRSG) is one of the major pieces of equipment in a gas
turbine combined cycle power plant that boasts a high thermal efficiency and produces
minimal CO2 emissions. An HRSG is a kind of heat exchanger that recovers heat from the
exhaust gases of a gas turbine to an extreme degree. The heat is recovered in the form of
steam which is served as the power source of a power-generating steam turbine.

For the heat-transfer tubes of an HRSG, finned tubes with excellent heat-transfer
performance are employed. By adopting a compact design, the installation footprint of the
equipment is reduced.

In addition, Selective Catalyst Reduction (SCR) equipment is installed inside the HRSG,
reducing the content of nitrogen oxides in the exhaust gases released into the atmosphere.

27
 Fig.5.3: A photograph of HRSG

5.11 Steam Turbine

Steam turbine power plant uses steam to move the turbine. In Sirajgonj NWPGCL CCPP, steam
is used to move turbine so it is a steam turbine power plant.

A steam turbine works by using a heat source (gas, coal, nuclear, solar) to heat water to
extremely high temperatures until it is converted into steam. As that steam flows past a turbine's
spinning blades, the steam expands and cools.

28
 Fig.5.4: Steam Turbine

Chapter 6
Sub-Station
6.1 Introduction to Sub-Station

A substation is a part of an electrical generation, transmission, and distribution system.

Substations transform voltage from high to low, or the reverse, or perform any of several other
important functions. Between the generating station and consumer, electric power may flow
through several substations at different voltage levels. A substation may include transformers
to change voltage levels between high transmission voltages and lower distribution voltages,
or at the interconnection of two different transmission voltages.

Substations may be owned and operated by an electrical utility, or may be owned by a large
industrial or commercial customer. Generally substations are unattended, relying on SCADA
for remote supervision and control.

The word substation comes from the days before the distribution system became a grid. As
central generation stations became larger, smaller generating plants were converted to
distribution stations, receiving their energy supply from a larger plant instead of using their
own generators. The first substations were connected to only one power station, where the
generators were housed, and were subsidiaries of that power station.

There are many types of sub-station such as- transmission sub-station, distributor sub-station,
collector sub-station, converter sub-station, switching sub-station etc.

6.2 Importance of Sub-Station

29
 ➢ To transform the voltage at a very high level during transmission phase & step down
the voltage during distribution phase.
➢ To protect the complete power system during fault
➢ To detect and isolate failures in the transmission system as quickly as possible.
➢ To do switching of the supply
➢ To increase the efficiency of the power plant.

Fig.6.1: A photograph of sub-station of Sirajgonj NWPGCL CCPP

6.3 Elements of sub-station of Sirajgonj NWPGCL CCPP

The sub-station consists of many elements. The list is given below:
➢ Power Transformer
➢ Current transformer
➢ Potential Transformer
➢ Insulator
➢ Isolator
➢ Busbar
➢ Circuit Breakers
➢ Lightning Arrester
➢ Capacitor Bank
➢ Relay

30
6.4 Power Transformer
The transformer is the heart of the substation. The transformer changes the relationship
between the incoming voltage and current and the outgoing voltage and current. Substation
transformers are rated by their primary and secondary voltage relationship and their power
carrying capability.
In Sirajganj NWPGCL the output of gas generator is 15.75KV,190 MVA and for steam
generator is 10.5 KV,120 MVA.There are two types of Power Transformer.One is for the Gas
generator and other is Steam Generator. For both cases these voltages(15.75kv,10.5kv) are step
up to 230 KV and pass through bus bar. Step Down Transformer step down it to 6.6KV for
Auxiliary Elements.

Fig.6.2: A photograph of power transformer

6.5 Auxiliary Transformer

Auxiliary transformers are used for lighting purposes, heating the train wagons or for producing
single-phase auxiliary for the safety systems supply or the substation's own supply.

31
UAT(Unit Auxiliary Transformer) is an Auxiliary Transformer used in the plant . UAT is a
step-down transformer in which 15.75KV from the plant is stepped down to 6.6KV to operate
the plant load when the generation is off.

Fig.6.3: Unit Auxiliary Transformer of Sirjganj NWPGCL

6.6 Current Transformer

The Current Transformer ( C.T. ), is a type of “instrument transformer” that is designed to
produce an alternating current in its secondary winding which is proportional to the current
being measured in its primary. Current transformers reduce high voltage currents to a much
lower value and provide a convenient way of safely monitoring the actual electrical current
flowing in an AC transmission line using a standard ammeter.

32
Current Transformers produce an output in proportion to the current flowing through the
primary winding as a result of a constant potential on the primary

Fig.6.4 :A photograph of Current Transformer

6.7 Potential Transformer

A potential transformer (P.T.) is an instrument transformer which is used for the protection and
measurement purposes in the power systems. A potential transformer is mainly used to measure
high alternating voltage in a power system.

Potential transformers are step-down transformers, i.e., they have many turns in the primary
winding while the secondary has few turns.

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 Fig.6.5: A photograph of Potential Transformer

6.8 Bus Bar

An electrical bus bar is defined as a conductor or a group of conductors used for collecting
electric power from the incoming feeders and distributes them to the outgoing feeders. In other
words, it is a type of electrical junction in which all the incoming and outgoing electrical current
meets. Thus, the electrical bus bar collects the electric power at one location.

The bus bar system consists the isolator and the circuit breaker. On the occurrence of a fault,
the circuit breaker is tripped off and the faulty section of the busbar is easily disconnected from
the circuit.

various types of busbar arrangement are used in the power system-

Single Bus-Bar Arrangement: The arrangement of such type of system is very simple and
easy. The system has only one bus bar along with the switch. All the substation equipment like
the transformer, generator, the feeder is connected to this bus bar only.

Main and transfer Bus arrangement: Such type of arrangement uses two type of busbar
namely, main busbar and the auxiliary bus bar. The busbar arrangement uses bus coupler which
connects the isolating switches and circuit breaker to the busbar. The bus coupler is also used
for transferring the load from one bus to another in case of overloading.

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Double bus Double breaker arrangement: This type of arrangement requires two bus bar
and two circuit breakers. It does not require any additional equipment like bus coupler and
switch.

6.9 Circuit Breaker

Circuit breakers are used to open and close circuits. They can be operated manually to perform
maintenance or will automatically trip if a short circuit occurs. This function in the power
system is similar to that of the fuses or breakers in a household distribution panel.

Fig.6.6: A photograph of Circuit breaker

6.10 Isolator:

Isolator is a manually operated mechanical switch that isolates the faulty section of substation.
It is used to separate faulty section for repair from a healthy section in order to avoid the
occurrence of severe faults. It is also called disconnector or disconnecting switch. There are
different types of isolators used for different applications. They are: single break, double break,
bus isolator, and line isolator. The isolator will be a horizontal double break central rotating
type with an earth switch. Isolators and earth switches can be hand operated. Earth switches
and Isolators (in closed position) are designed to withstand thermal effects and other conditions
due to short circuit current.

6.11 Lightning arrester

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The device which is used for the protection of the equipment at the substations against
travelling waves, such type of device is called lightning arrester or surge diverter. In other
words, lightning arrester diverts the abnormal high voltage to the ground without affecting the
continuity of supply. It is connected between the line and earth, i.e., in parallel with the
equipment to be protected at the substation.

Fig.6.7: A photograph of Lightning arrester

6.12 Insulators

An insulator gives support to the overhead line conductors on the poles to prevent the current
flow toward earth. In the transmission lines, it plays an essential role in its operation. The
designing of an insulator can be done using different materials like rubber, wood, plastic, mica,
etc. The special materials used in the electrical system are glass, ceramic, PVC, steatite,
polymer, etc. But the most common material used in the insulator is porcelain and also special
composition, steatite, glass materials are also used.

6.13 Capacitor Bank

As the name implies, a capacitor bank is merely a grouping of several capacitors of the same
rating. Capacitor banks may be connected in series or parallel, depending upon the desired
rating. As with an individual capacitor, banks of capacitors are used to store electrical energy

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and condition the flow of that energy. Increasing the number of capacitors in a bank will
increase the capacity of energy that can be stored on a single device.

6.14 Protective Relay

A relay is automatic device which senses an abnormal condition of electrical circuit and closes
its contacts. These contacts in turns close and complete the circuit breaker trip coil circuit hence
make the circuit breaker tripped for disconnecting the faulty portion of the electrical circuit
from rest of the healthy circuit.

Chapter 7

Switchgear and Control Room

7.1 Introduction to Switchgear

The apparatus used for controlling, regulating and switching on or off the electrical circuit in
the electrical power system is known as switchgear.The switches, fuses, circuit breaker,
isolator, relays, current and potential transformer, indicating instrument, lightning arresters and
control panels are examples of the switchgear devices.

The switchgear system is directly linked to the supply system. It is placed in both the high and
low voltage side of the power transformer. It is used for de-energizing the equipment for testing
and maintenance and for clearing the fault.

When the fault occurs in the power system, heavy current flow through equipment due to which
the equipment get damaged, and the service also get interrupted. So to protect the lines,
generators, transformers and other electrical equipment from damage automatic protective
devices or switchgear devices are required.

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 Fig.7.1: Switchgear Room of Sirajgonj NWPGCL CCPP

7.2 Control room of Sirajgonj NWPGCL CCPP

The various supervision, control and protection functions are performed in the substation
control room. The relays, protection and control panels are installed in the controlled room

Control room of Sirajganj NWPGCL is located at 2nd floor of Unit 2.

7.3 Control Panel

The substation control panel is designed to form automated control systems (SCADA) of the
traction substations, using digital protection and programmable logic controllers.

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 Substation control panel provides:

• Telemechanical control of the substation (sending/receiving signals of telecommands,

telemetry and telesignaling)
• Remote control of the substation (using integrated controls and indicating devices)
• Collection and transmission of the telemetry and diagnosing data via digital channels
of the data transmission network (DTN)

With the substation control panel any traction substation may be reconstructed with gradual
connection of the new smart controllers and bay terminals, while the unmodified equipment is
still controlled with the existing telecommunications panel.

Substation control panel includes:

• An operator station for remote equipment control.

• A controller of the overall substation signaling.
• A substation controller functioning as a concentrator of the substation information-
control network.
• An uninterruptible power system.
• Interface convertors with galvanic separation.

Fig.7.2: PLC installed I/O Cards room Fig.7.3: Electrical switch of Control panel
room

7.4 UPS Panel

A UPS is typically used to protect equipment such as computers, data centres,

telecommunication apparatus or other electrical equipment where an unexpected power outage
could cause injuries, fatalities, serious disruption to business or loss of data. UPS is an
uninterruptable power supply which uses converter inverter set. AC input is first converted to

39
DC and again converted to AC. The battery bank installed for UPS is connected in between
converter inverter set so that if AC supply to converter fails, battery comes on load and supplies
DC to inverter for maintaining the AC power supply at output end.

Fig.7.4: A photograph of UPS Panel

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 Chapter 8
Safety Rules

8.1 Introduction
In the past several decades, power plant owners and industry in general have vastly improved
employee safety. Numerous organizations that hand down safety requirements and regulations
have been established, creating a safer work environment. Although power plants are much
safer than they once were, plant employees still encounter many hazards, and it is up to
employers to implement programs and policies aimed at eliminating accidents. Comprehensive
training, detailed pre-job planning, and proper and well-maintained safety equipment are key
to accident prevention, regardless of the hazard.
Hazard are classified into 3 types-
1. Electrical Hazard
2. Chemical Hazard
3. Boiler Hazard

8.2 Protection for complex requirements

In complex environments like power plants, having a comprehensive fire protection plan and
reliable extinguishing systems is essential to ensure the safety of workers and for the
continuous supply of electrical power.

Fire extinguisher chart may help to protect from fire.

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 Fig.8.1: Fire Extinguisher chart

Chapter 9

Conclusion

9.1 Conclusion

The industrial training at NWPGCL, Sirajgonj was a great opportunity for me to gain practical
knowledge about the overall operation of a power plant and checking all the procedures of
power generation which we studied in different courses of our academic session. The training
was highly successful. We received insight of the whole plant right from the fuel procurement,
processing, combustion, generation and transmission of electricity. The whole process of
power generation was explained in detail by the engineers working in NWPGCL with detailed
description about each equipment with their specifications. The authorities of NWPGCL are
very considerate about all kinds of safety and security of the plant. During the training we
experienced a lot of things about power plant and power system practically. This training
program helped me absorbing the theoretical aspects of power system more efficiently. I hope
this training will play an important role in my future life to apply my knowledge and experience
in the related field efficiently and I would really appreciate more such visits in the future.

REFERENCES

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1. V.K. Mehta and R. Mehta; ‘Principles of power system’, S. Chand & Company LTD.,
4th edition, 2014-2015.
2. .https://www.earthreminder.com/water-treatment-plant-its-importance/
3. https://solarland.com.bd/projects/7-6-mwp-ongrid-solar-project/
4. https://en.wikipedia.org/wiki/Electrical_substation
5. https://peaksubstation.com/the-importance-of-substation-design
6. https://www-power--technology-com.translate.goog/analysis/feature1915
7. https://www.tutorialspoint.com/what-is-potential-transformer-p-t-and-how-it-works
8. https://circuitglobe.com/electrical-bus-bar-and-its-types.html
9. https://www.sciencedirect.com/topics/engineering/isolators
10. https://circuitglobe.com/lightning-arrester.html
11. https://www.elprocus.com/types-of-insulators-and-their-applications/
12. https://www.arrow.com/en/research-and-events/articles/capacitor-banks-benefit-an-
energy-focused-world
13. https://circuitglobe.com/switchgear.html
14. https://www.power-eng.com/news/power-plant-safety/#gref
15. https://fireandsafetyaustralia.com.au/resources/free-fire-extinguisher-selection-charts/

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