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Power Generation, Sub-Station & Controlling
System of Summit Uttaranchol Power Co.Ltd.
(33MW Maona Power Plant)
MAONA POWER PLANT
ii
Practicum Report
On
Power Generation, Sub-Station & Controlling System of
Summit Uttaranchol Power Co.Ltd. (33MW Maona Power Plant).
Presented To
Prof. Engr. Abul Bashar
Associate Professor & Coordinator
Department of Electrical and Electronics Engineering
Presented By
Md: Saiful Islam
ID #13105135
Program: BSEEE
IUBAT- International University of Business Agriculture and Technology
December 15, 2016
iii
15th
December, 2016
Prof. Engr. Abul Bashar
Associate Professor & Coordinator
Department of Electrical and Electronics Engineering
CEAT- College of Engineering and Technology
IUBAT- International University of Business Agriculture and Technology
4, Embankment Drive Road, Uttara Model Town, Sector 10, Dhaka 1230, Bangladesh.
Subject: Letter of Transmittal.
Dear Sir,
With due respect, I would like to submit this report titled “Power Generation, Substation &
Controlling System of Summit Uttaranchol Power Co.Ltd. (33 MW Maona Power Plant)”
as partial fulfillment of Bachelor of Science in Electrical and Electronics Engineering. It was
undoubtedly a splendid opportunity for me to work on this topic to actualize my theoretical
knowledge in the practical area and to have an enormous experience in power generation &
transmission system of a plant with related switchgear equipments. Also I observe the operation,
maintenance and troubleshooting from close during my training period.
I tried to accommodate as much information as I could to make this report informative and
worthwhile to the best extent. Now I am looking forward for your kind assessment regarding this
report.
I would be very kind of you, if you please take the trouble of going through the report and
evaluate my performance regarding this report.
Sincerely Yours
--------------------------
(Md. Saiful Islam)
ID # 13105135
Program BSEEE
iv
v
I, Md. Saiful Islam, am a student of Bachelor of Science in Electrical and Electronics
Engineering, in the College of Engineering and Technology (CEAT) at the IUBAT-International
University of Business Agriculture and Technology and declaring that, this practicum report on
the topic of “Power Generation, Substation & Controlling System of Summit Uttaranchol
Power Co.Ltd. (33 MW Maona Power Plant)”” that only been prepared for the fulfillment of
the course of EEN-490, Practicum as the partial requirement of BSEEE.
It has not been prepared for any other purpose, reward, or presentation
……………………….
Md. Saiful Islam
ID # 13105135
Program:BSEEE
vi
I hereby declare that I have uniquely prepared this report which is entitled as “Power
Generation, Substation & Controlling System of Summit Uttaranchol Power Co.Ltd. (33 MW
Maona Power Plant)” after completion of three months practical work in Maona 33 MW Power
plant, Gazipur, a power plant of Summit Power Limited.
All praise is to the Supreme Being; creator and ruler of the universe, Almighty Allah, whose
mercy keeps us alive and to pursue my education in Electrical and Electronics Engineering and
to complete the Report.
This Report which is entitled as “Power Generation, Substation & Controlling System of Summit
Uttaranchol Power Co.Ltd.(33 MW Maona Power Plant)” is the concrete effort of a number of
people. In the process of conducting this Internship and preparing this report, I would like to
express my gratitude and respect to some generous persons for their immense help and enormous
cooperation.
First of all I would like to pay gratitude to Honorable Vice Chancellor Prof. Dr. M. Alimullah
Miyan, to provide me such nice environment for learning Engineering discipline and allow me to
prepare this report on this splendid topic.
I am very much grateful to respected Prof. Engr. Abul Bashar, Associate Professor &
Coordinator(Department of Electrical and Electronics Engineering), for his cooperation to
arrange my internship and do this report. I would like to special thank my respected faculty and
my supervisor “Md. Naz Niamul Islam” for his painstaking guidance to do this report properly.
After that I would like to thank Md. Abu Hanif (Plant In-charge) for accepting me in the plant
as an Internship student and then express my special gratitude to Engr. Shamim Hossain and
Engr. Rafiul Islam, (Assistant Deputy Manager (ADM)),Maona Power Plant for sharing their
knowledge regarding plant. I am very much grateful to respected Md. Kamrul Islam (Sr.ADM)
and Md.Abdul Bari (ADM) of Maona Power Plant for their guidance, and their diligent struggle
for my practical experience and encourage me to do this work.
Last but not the least, I would like to thank my parents who have been a constant source of
encouragement & inspiration during my studies & have always provided me support in every
walk of life.
vii
Main Text Of the Report
Chapter 1 (Introductory part)
Topic Page No:
1.1Origin of the report 2
1.2 Back ground 2
1.3 Objective 3
1.3.1 Broad Objectives 3
1.3.2 Specific Objectives 3
1.4 Scope 3
1.5 Methodology 3
1.6 Limitations 3
Preparatory Part
Topic Page No:
Title Fly i
Title Page vii
Letter of Transmittal iii
Letter of Authorization iv
Student Declaration v
Acknowledgement vi
Table of Content vii
Executive Summary vii
viii
Chapter 2- (Organizational Overview)
Topic Page No:
2.1 SUMMIT Power Plant at a galance 02
2.2 Aim 02
2.3 Vision 02
2.4 Mission 02
2.5 Commitment 02
2.6 Objective 03
2.7 Operational Power Plants 03
2.8 Power Plant Under Development 04
2.9 Recent International Award 04
2.10 Corporate governance 05
2.11 Organ gram Of Plant Employee 05
2.12 Corporate Social Responsibility 06
2.13 The client/ consumer/ customer of SPL 06
2.14 Maona Power Plant at a Glance 06
2.15 Plant Layout (Maona 33MW Power Plant) 08
Chapter 3 - ( Power Generation)
Topic Page No:
3.1 Introduction 2
3.2 Components of a Power System 2
3.3 Electricity Generation theory 03
3.4 Plants in Maona Power Plant 03
3.4.1 Single Line Diagram of 33 MW Maona Power Plant: 03
3.5 Power Generation 04
3.5.1 Engine 04
3.5.1.1 Wartsila 20V34SG Engine Specificatio 05
3.5.1.2 W20V34SG Engine Fundamentals 06
ix
3.5.1.3 The Lean-burn Concept 06
3.5.1.4 Components of Wartsila 20V34SG Engine 07
3.5.1.5 The engine block 07
3.5.1.6 Crankshaft 07
3.5.1.7 The connecting rods 08
3.5.1.8 The pistons 09
3.5.1.9 Camshaft 09
3.5.1.10 Flywheel 10
3.5.1.11 Pre-chamber 10
3.5.1.12 Ignition System 11
3.5.1.13 Ignition System 11
3.5.1.14 Instrument Air 11
3.5.2 Alternator 12
3.5.2.1 Alternator Working Principle 12
3.5.2.2 Specification of ABB Alternator for Wartsila 20V34SG 13
3.5.2.3 Components of ABB Alternator 13
3.5.2.5 Purpose of Excitation 14
3.5.2.6 Alternator Excitation System 14
3.5.2.7 Brushless Exciters General Description 15
3.5.2.8 Brushless Exciters for ABB Alternator (8 poles) 16
3.5.2.9 Automatic Voltage Regulator (AVR) 17
3.6 Auxiliary system of Maona Power Plant 18
3.6.1.1 Lubricating oil cooling 20
3.6.1.2 Lubricating oil filters 20
3.6.1.3 Pre-lubrication: 21
3.6.1.4 Lube oil thermostatic valve 21
3.6.1.5 Lube oil suction strainer 22
3.6.2 Cooling water systems 22
x
3.6.2.1 Preheating unit 23
3.6.2.2 Expansion vessel 23
3.6. 2.3 Radiator 23
3.6.2.4 Frequency Converter 24
3.6.3 Compressed air system 25
3.6.3.1 Compressed air system arrangement) 26
3.6.3.2 Compressed Air System Classification) 26
3.6.3.2.1 Starting Air Compressor: 26
3.6.3.2.2 Instrument air system 28
3.6.4 Charge air system: 28
3.6.4.1 Charge air filter 29
3.6.4.2 Charge air silencer V1 29
3.6.4.3 Turbocharger 30
3.6.4.4 Charge air compressor 30
3.6.4.4.1 Compressor function 31
3.6.4.4.2 Advantages of using Turbocharger 31
3.6.4.4.3 Disadvantages 32
3.6.5 Fuel Gas System 32
3.6.5.1 Main gas valve: 32
3.6.5.2 Gas regulating unit (GRU) 32
3.6.5.3 Working Principle 33
3.6.5.4 Main Gas Admission valve 34
3.6.5.5 Pre-chamber gas injection: 34
3.6.5.6 Main gas injection 34
3.6.6 Exhaust Gas system 35
3.6.6.1 Exhaust gas ventilation unit 35
3.6.6.2 Exhaust Waste 36
3.6.6.3 Air/fuel ratio control 37
3.6.6.4 Main Control Module 38
xi
3.6.6.5 Cylinder Control Module 38
3.6.6.6 WECS 8000 39
Chapter 04-(Control &Safety Zone)
Topic Page No:
4.1Introduction 02
4.2 Parallel operation 02
4.3 Island operation 02
4.4 Control functions 03
4.5 Engine Starting Condition 03
4.6 Automation System 04
4.7 PLC (Programmable Logic Controller) 05
4.8 WOIS (Wartsila Operator Interface System) 06
4.9 WISE workstation 06
4.10 CRP (Control Relay Panel) 07
4.11 Synchronization 08
4.12 Engine speed and load control 09
4.12.1 Speed droop control 09
4.12.2 KW Control 09
4.13 Voltage droop control 10
4.14 Power factor control 10
4.15 Control of Auxiliary Systems: 10
4.16 Alarm Handling1 11
4.17 Safety Functions 11
4.18 Engine Control System 11
4.18. 1 Speed Control 12
4.18. 2 Air Fuel Ratio Control 12
4.18. 3 Waste-gate Control 13
4.18. 4 Cylinder Balancing Conditions 13
4.18. 5 Knock Control 13
4.18. 6 Gas Pressure Control 13
xii
4.18. 7 Safety Control 14
Chapter 5-(Sub-Station & Protection Part)
TOPIC Page No:
5.1 Substation 02
5.2 Switchyard 02
5.3 Single Line Diagram 03
5.4 Equipments of Switchyard Used in Maona Power Plant 04
5.4.1 Power Transformer 04
5.4.1.1 Power Transformer Specification 05
5.4.1.2 On Load Tap Changer 06
5.4.2 Auxiliary/Station Transformer 07
5.4.2.1 Auxiliary Transformer Specification 08
5.4.3 Lightning Arrester 08
5.4.3.1 Working Principle of Lightning Arrester 09
5.4.3.2 Lighting Arrester Specification used in Maona Plant 09
5.4.4 Isolator 10
5.4.4.1 Isolator Specification used in Maona Power Plant 10
5.4.5 Potential Transformer (PT) 11
5.4.5.1 Potential Transformer Specification of Maona Power Plant 11
5.4.6 Current Transformer (CT) 12
5.4.6.1 Current Transformer Specification used in Maona Power Plant 12
5.4.7 Outdoor Vacuum Circuit Breaker (VCB) 13
5.4.7.1 Specification of Outdoor VCB 13
5.4.7.2 Components of Vacuum Circuit Breaker 14
5.5 Earth switch
14
5.6 Bus coupler 14
xiii
TOPIC Page No:
5.7 Protections of Power/Auxiliary Transformer are as follows 14
5.8 Medium Voltage (MV) or 11KV Protection at MV Room 15
5.8.1 Single Line Diagram of MV 15
5.8.2 Breaker Used for Medium Voltage (MV) Protection 15
5.8.3 Components of MV Room 16
5.8.4 Sulphur Hexafluoride (SF6) Circuit Breaker 16
5.8.4.1 Construction of SF6 Circuit Breaker 16
5.8.4.2 Specification of Sulphur Hexafluoride (SF6) Circuit Breaker 17
5.8.4.3 Advantages of SF6 Circuit Breaker 17
5.9 Neutral Grounding Resistance (NGR) 17
5.10 Low Voltage Protection and Control at Switchgear Room 18
5.10.1 Components of LV Room 18
5.10.2 Air Break Circuit Breaker 18
5.10.3 MCCB and MCB Breaker 19
5.10.4 Magnetic Contactors 20
5.10.5 Fuse 20
5.10.6 Relay 20
5.11 Transformer/Alternator Differential Protection 21
5.12 Distance/Impedance Relay Protection 22
5.13 Buchholz Relay 23
5.14 MV (11 kV) Buhs-bar Protection: 24
5.15- 33 kV Line Protection 24
xiv
Chapter 6 ( Troubleshooting & Supplementary)
TOPIC Page No:
6.1 Maintenance Tools 02
6.2 Personal Protective Equipments 02
6.3 Troubleshooting Activities and Observation of Maintenance Methods 03
Supplementary Part 06
TOPIC Page No:
6.4 Limitations 07
6.5 Recommendation 07
6.6 Conclusions 08
6.7 Appendix 09
6.7.1 Some Definitions 09
6.7.2 Acronyms 11
6.7.3 Elaboration 12
6.7.4 Annexure –Photograph during Practicum Sessions 13
6.7.4.1 Annexure-Some diagram of Wartsila Engine 15
6.8 References 16
xv
List of Figure
Chapter-02
Figure No. Page No.
Fig 01: Organ gram of Plant Employees 05
Fig 02: Maona Power Plant 07
Fig 03: Plant Layout 08
Chapter-03
Figure No. Page No.
Fig 04: Basic Structure of Electrical System 02
Fig 05: Single Line Diagram of 33 MW Maona Power Plant 03
Fig 06: Wartsila 20V34SG Engine 05
Fig.7: Lean burn Process of engine 06
Fig 8: The engine Blocks View
07
Fig.9: Crankshaft 08
Figure 10: Piston 09
Fig.11: Camshaft 09
Fig.12 : Engine Flywheel 10
Figure 13: Pre chamber Ignition. 10
Figure 14: Voltage production of Alternator 12
Fig 15: ABB Alternator components 14
Figure 16: Brushless Exciter Rotor 15
Figure 17: ABB Alternator excitation system (AVR) 16
Fig-18: Self-excitation system 17
Figure 19: Lube oil circulation system 18
Figure 20: Lube oil circulating system. 19
Figure 21: Lube oil flow inside the engine 19
Figure 22: Lube oil automatic filter and Centrifugal filter 20
Figure 23: Main lube oil pump and Pre-lube pump 21
Figure 24 : Lube oil thermostatic valve 21
xvi
Figure 25 : Cooling water system 22
Figure 26: Main features of standard frequency converter 24
Figure 27: Compressed air system layout 25
Figure 28: Compressed air system flow diagram 26
Figure29: Starting air pipe connections 27
Figure 2 : Starting air system on engine 27
Figure 3 : Charge air system overview 28
Figure 4 : Charge air silencer 29
Figure 21: Turbocharger functionality 30
Figure 22: Turbocharger assembly 31
Figure 23: Gas Regulating Unit (GRU) 32
Figure 24: GRU automation overview 33
Figure 25: Section view of Main gas admission (solenoid) valve 34
Figure 26: Gas injection control 34
Figure 27: Exhaust gas system overview 35
Figure 28 : Exhaust Wastegate 36
Figure 29 : Exhaust wastegate functional parts 36
Figure 30: Air/fuel ratio control process 37
Figure 31: Charge air pressure control by Exhaust wastegate 37
Figure 32: WECS 8000 38
Chapter-04
Figure No. Page No. Fig33: Control Room of MNPP 02
Figure 34: Cabling Interface Boxes (CIB) 03
Fig35: PLC Configuration 05
Fig 36: Relay and alarm indicator panel pictures from control room 07
Figure37: Synchronizing Control Unit 08
Chapter-05
Figure No. Page No. Fig38: Switchyard view of Maona power plant 02
Fig39: Single Line diagram of 33MW MnPP (Drawn by me Using AutoCAD) 03
Figure No. Page No.
xvii
Fig. 40: Power Transformer at MnPP Switchyard. 04
Fig 41: Tap Changer Panels with tap position chart 06
Fig. 42: Auxiliary Transformer 07
Fig 43: Lightning Arrester 08
Fig 44: Working Principle of Lightning Arrester 09
Fig 45: Isolator 10
Fig 46: Potential Transformer 11
Fig 47: Current Transformer 12
Fig 48: Outdoor Vacuum Circuit Breaker 13
Fig 49: Single Line Diagram of MV 15
Fig 50: Air Break Circuit Breaker 18
Fig 51: MCCB 19
Fig 52: Magnetic Contactors 20
Fig 53: Relay With Trip Circuit. 21
Fig 54: Differential Relay Operation Mechanism 22
Fig 55: Operation Principle of Distance/Impedance Relay 22
Fig 56: Buchholz Relay 23
Chapter-05
Figure No. Page No.
Fig 57: Face Shield, Helmet, Ear Muff, Hand Gloves, First Aid Box 02
Fig 58: Checking all parameters in GAS Regulating Meter Station (RMS). 03
Fig 59: CCM-10 03
Fig 60: Checking Spark Plug and Connection 04
Fig 61: Replacement of Cylinder head of wartsila gas engine 04
Fig 62: Bearing Change of Radiator Motor 05
Fig 63: Checking Radiator Control Panel 05
xviii
Electricity has played a pivotal role for the socio-economic development of the country.
Reliable, uninterrupted, safe and adequate power supply is a pre-requisite for the development of
the country. In this report, I have described the method of Power generation, Switchgear and
electrical Control system of 33 MW Maona Power Plant. As Maona power plant used gas
generator, gases are supplied from Titas gas company ltd. Natural gas are used as a raw materials
of the gas generator. Natural gas goes through the generator engine prime mover and from prime
mover mechanical energy goes through the alternator and its output is electrical energy The
generating voltage of Maona power plant is 11kv which is generated by plant generator. At first
the 11kv generating voltage is stepped up to 33 kv by using a unit step up transformer and this
step up voltage is supplied to grid. As 33 kv voltage is very high level voltage so it needs proper
protection system to continue its operation properly and to make the place riskless. The
equipment used for this power transmission purpose from generating unit to grid and to plant
itself without any risk is described in this report. For the operation of plant it also needs power
that is why a auxiliary step down transformer is also used with generating unit. Auxiliary
transformer stepped down voltage 11kv to 415v which is used for plant operation purpose. The
total procedure of electric power supply with related apparatus from the generating unit to REB
and plant itself is taken into consideration in this report.
This power station will not only play an important role to meet the demand but it will also
contribute significantly in reducing overloading of REB Sub Station, low voltage problem of the
adjacent losses of the system and will ensure quality power supply in the uttaranchol area of
Maymensingh and Gazipur. It has been established for supply of electricity to PBS(Palli Bidyut
Shamity) under 15 years power purchase agreement with REB(Rural Electrification Board).
xix
Chapter-01
Introductory Part
Page | 2
1.1 Source of the Report
My report entitled as “Power Generation, Substation & Controlling System of Summit
Uttaranchol Power Co.Ltd. (33 MW Maona Power Plant)” an elaborated representation of
twelve weeks long internship program with IUBAT- International University of Business
Agriculture and Technology as a partial requirement of my BSEEE program. The purpose of
this report is to actualize my theoretical knowledge in the practical area and to have an
enormous experience in power generation & transmission system of a plant with related
switchgear equipments. Also I observe the operation, maintenance and troubleshooting from
close during my training period. I have worked under the instruction of Engr. Shamim
Hossain (A.D.M), Engr. Md. Rafiul Islam (A.D.M) under Supervisory teacher Naz Niamul,
Faculty, IUBAT.
1.2 Background
Power plant is one of the few blooming industries in Bangladesh generating huge foreign
direct investment and also a significant number of employment opportunities have created.
This industry is one of the major driving forces of national economy and with the continuous
development of technologies worldwide. In the Power sector, Power industry of Bangladesh
promises to bloom further in the coming years. In today’s dynamic business environment, it
is even more challenging to run the technology based businesses in the right direction with
minimum cost which ultimately maximizes the profit. Such is the pace of technological
development & increase of cost in the current world, the technical companies have to
maintain a relentless focus on the Maintenance of Plant properly to keep track of all the
activities and do benefit by saving extra cost. Seeing an opportunity to cut costs, increase
productivity, and streamline its business-support system landscape, the companies began
investigating how it could implement a common global system in order to work with its
Technical Team in a more productive and uniform way. In our country the crisis of electricity
in national grid is a common problem where in industrial sector the electricity is required for
24 hours in a day. Summit Uttaranchol Power Co.Ltd. (33 MW Maona Power Plant)
under Summit Power Ltd. is one of the leading company which try to meet the country’s
electricity demand, where I have completed my practicum. They supplies electricity on
national grid. Summit Power Ltd. first established Maona 33 MW gas power plant in 2009.
Page | 3
1.3 Objectives
1.3.1 Broad Objective
The main objectives are to improve my theoretical knowledge to the practical field with
adequate conceptualization and understanding the performance of the parameters in case of
Power Generation, Operation, Maintenance and Troubleshooting of Engine, Radiator,
Control Panel, Transformer, Circuit Breaker etc.
1.3.2 Specific Objective
The specific objectives of this report include:
Study on Gas Generator, Transformer, Switchyards.
Maintenance of Electrical Machines (LV & MV) and Equipment’s
Identify the different types of problem which arise in generation and distribution
system.
Troubleshooting and isolate the probable problems occurred in power generation
and at substation.
Suggest probable solution of the identified problem.
1.4 Scope
This report will cover the types of machinery used in Maona 33MW Gas Engine Power Plant,
the operating and controlling of these machines, Transformer, troubleshooting, switchyards
and its protection systems, what equipment is placed in which zone, how the equipment has
been synthesized etc. The scope will be limited to only this type of power generation &
transmission system.
1.5 Methodology
Both primary and secondary data are being collected for the purpose of this report. The report
is concentrated of Summit Uttaranchol Power Co.Ltd. (33 MW Maona Power Plant) of
Summit Power Ltd.
Primary Data: Primary Data are collected from the books about power plants, the
Engineers through a face-to-face interview with a formal questionnaire, the User Manual
to the Engineers, official documents of the company and Plant Operation Manuals
Secondary data: Secondary data has been collected from the online resources, Journals
and Brochures.
1.6 Limitations
Three months are not enough time for an authentic study.
Some difficulties appeared during collecting information regarding internal data of
plant machineries like manual and protection details of equipments.
Chapter -03
Power Generation
Page | 2
3.1 Introduction:
In our country the crisis of electricity in national grid is a common problem where in
industrial sector the electricity is required for 24 hours in a day. Due to failure of national
grid private industry owners are using their own power plants combining with national grid to
meet the demand of electricity. The power system of today is a complex interconnected
network. Power is generated at generating stations, usually located away from the actual
users. The generated voltage is then stepped up to a higher voltage for transmission,
as transmission losses are lower at higher voltages. The transmitted electric power is then
stepped down at grid stations. The modern distribution system begins as the primary circuit,
leaves the sub-station and ends as the secondary service enters the customer's meter socket.
First, the energy leaves the sub-station in a primary circuit, usually with all three phases.
Fig 04: Basic Structure of Electrical System
The generating station supply electricity to the grid. For this purpose its need some apparatus
to supply and for protection. Generating station has its auxiliary supply also. The process of
generating electric power from mechanical power is discussed in this chapter.
3.2 Components of a Power System
A modern electric power system consists of six main components:
The power station.
A set of transformers used to step up the generated power for the transmission lines.
The transmission lines.
The substations at which the power is stepped down for the distribution lines.
The distribution lines.
The transformers that lower the distribution voltage to the level used by the consumer.
Page | 3
3.3 Electricity Generation theory:
Electricity generation is the process of creating electricity from other forms of energy. The
fundamental principles of electricity generation were discovered during the 1820’s and early
1830’s by the British scientist Michael Faraday. His basic method is still used today:
electricity is generated by the movement of a loop of wire, or disc of copper between the
poles of a magnet. For electric utilities, it is the first process in the delivery of electricity to
consumers. The other processes, electricity transmission, distribution, and electrical power
storage and recovery using pumped storage methods are normally carried out by the electrical
power industry. Electricity is most often generated at a power station by electromechanical
generators, primarily driven by heat engines fueled by chemical combustion of other fuel like
gas, HFO, diesel, coal, Etc...
3.4 Plants in Maona Power Plant
There are single plants in Maona Power Plant,WARTSILA Plant-(4×8.73= 34.92 MW)
3.4.1 Single Line Diagram of 33 MW Maona Power Plant:
Fig 05: Single Line Diagram of 33 MW Maona Power Plant (Drawn by me using AutoCAD)
Page | 4
3.5 Power Generation:
Power Generation done by the two main components:
Engine.
Alternator.
3.5.1 Engine
An Engine is one which converts the chemical energy of fuel into heat energy and heat
energy into mechanical energy is called engine. After that alternator use this mechanical
energy and converted it into electrical energy. The engine used in Summit Uttaranchal Power
Co.Ltd, Maona Power Plant is a four-stroke lean-burn gas engine, designed to operate on
natural gas. This four stroke engine have used as a prime mover. There are single type of
Engine (W20V34SG) used in Maona Power Plant.
In Maona power plant generally use 4-stroke spark ignited gas engine.
Engine Model: W20V34SG
The Wartsila 34SG is a 4-stroke spark ignited gas engine that works according to the Otto
process and the lean burn process. The engine runs at 720to 750 rpm for 60 to 50 Hz
application and produces 6950 to 9000 KW of mechanical power. The Wartsila 34SG
combines high efficiency with low emissions. This is achieved applying state-of-the-art
technology with features:
Use of a lean gas mixture for clean combustion
Individual combustion control & monitoring
Stable combustion, ensured by a high energy ignition system and pre-combustion
chamber
Efficient heat recovery design
Minimal consumables
W Wartsila
20 Number of Cylinders is 20 in one unit
V V type cylinder
34 Diameter of cylinder
S Spark ignited
G Gas engine
Page | 5
3.5.1.1 Wartsila 20V34SG Engine Specification
Engine type V-engine
Cylinder Bore 340mm
Stroke 400mm
Firing order A1-E1-A7-B7-A3-B3-A9-B9-A5-B5-A10-B10-A4-B4-A8-
B8-A2-B2-A6-B6
Speed 720/750 rpm
Piston speed 10 rn/s
Unit output 8.7 MW
Engine weight 86 tones
Genset weight 137 tones
Mean effective pressure 20 bar
Engine output 8700 KW
Electrical Efficiency 46.5%
Wartsila 20V34SG Engine
Fig 06: Wartsila 20V34SG Engine
Page | 6
3.5.1.2 W20V34SG Engine Fundamentals
The Wartsila W20V34SGengine used in Maona Power Plant is a V-type four-stroke, spark-
ignited gas engine that works according to the Otto cycle and lean-burn process. Ti
incorporates 20 cylinders and cylinder bore diameter is 34 cm. The engine runs at 750 rpm
for 50 Hz applications and procedure 9000 kW of mechanical power.
3.5.1.3 The Lean-burn Concept
In a lean-burn gas engine, the mixture of air and gas in the cylinder is lean, i.e. more air is
present in the cylinder than required for complete combustion. With leaner combustion, the
peak temperature is reduced and less NOx is produced. Higher output can be achieved with
lower knocking and higher efficiency. However, a too lean mixture will cause misfiring of
cylinders. Ignition of the lean air-fuel mixture is initiated with a spark plug located in the pre-
combustion chamber that provides a higher-energy ignition source for the main fuel
combustion in the cylinder. To obtain the best efficiency and lowest emissions, every
cylinder is individually
Fig.7: Too learn and too rich air/fuel mixture in the cylinder will introduce the troubles
stated above
Controlled by the engine control system to ensure operation at the correct air-fuel ratio and
corrected ignition timing. A well-controlled combustion also contributes to less mechanical
and thermal load on engine components and hence longer engine life. In the Wartsila 34SG
engine, the air-fuel ratio is very high and is uniform though the cylinder, due to premixing of
air and fuel before entering the cylinders. Therefore, maximum temperatures and subsequent
NOx formation are low.
Page | 7
3.5.1.4 Components of Wartsila 20V34SG Engine
The Engine Block Exhaust Valves
The Cylinder Liner Seal Ring
Main Bearing Camshafts
Crankshaft Turbocharger
Connecting Rods Charge Air Cooler
Pistons Oil Sump
The Piston Ring Set Automatic Filter
Cylinder Head Centrifugal Filter
Inlet Valves Pre Chamber
3.5.1.5 The engine block
is cast in one piece. The main bearings are hanging. The main bearing cap is supported by
two hydraulically tensioned main bearing screws and two horizontal side screws. The charge
air receiver is cast into the engine block as well as the cooling water header. The crankcase
covers, made of light metal, seal against the engine block by means of rubber sealing’s. The
lubricating oil sump is welded.
Fig 8: The engine Blocks View
3.5.1.6 Crankshaft
The crankshaft is forged in one piece and provided with counterweights fastened with
hydraulically tensioned screws. The counterweight counterbalances the crankshaft rotating
masses on the crank webs. At the driving end of engine, the crankshaft is equipped with a
combined flywheel/thrust bearing and a split gear wheel for driving the camshaft. At the free
Page | 8
Fig.9: Crankshaft
end, there is a gear for driving the water and lube oil pumps and usually a vibration damper.
The crankshaft is also equipped with oil drilling though which the oil drillings though which
the oil flows from main bearings to the connecting rod big end bearings. During maintenance,
the crankshaft can be turned by an electrically driven turning gear that operates the flywheel.
3.5.1.7 The connecting rods:
The connecting rods are of a three-piece design, so called “Marine type connecting rod”. The
combustion forces are distributed over a maximum bearing area. The relative movements
between mating surfaces are minimized. The connecting rod is forged and machined of
alloyed steel. The lower end is splitted horizontally in three parts to allow removal of piston
and connecting rod parts. All connecting rod bolts are hydraulically tightened. The big end
bearings are fully interchangeable tri-metal or bimetal bearings.
Page | 9
3.5.1.8 The pistons:
The Pistons are fitted with a Wärtsilä patented skirt lubricating system. The top ring grooves
are hardened. Cooling oil enters the cooling space through the connecting rod. The cooling
spaces are designed to give an optimal shaker effect. The piston ring set consists of two
chrome-plated compression rings and one chrome-plated, spring-loaded oil scraper ring.
Figure 10: Piston
3.5.1.9 Camshaft
The camshaft is built up of one-cylinder camshaft pieces and separate bearing
journals/supports. There are three cams in one camshaft piece, one for the inlet valves, one
for exhaust valves and one for the pre-chamber valve. The camshaft is driven by the
crankshaft though a camshaft drive (split gear coupling) at the driving end of the engine. At
the free end, the camshaft is equipped with an extension piece that operates the starting air
distribution.
Fig.11: Camshaft
Page | 10
3.5.1.10 Flywheel
A flywheel is a rotating mechanical device that stores the rotational energy during the power
impulses of the engine. It releases this energy between power impulses, thus assuring less
fluctuation in engine speed and smoother engine operation. It has a significant moment of -
inertia that resists the change in rotational speed. The amount of energy stored in a flywheel
is proportional to the square of its rotational speed.
Fig12: Engine Flywheel
3.5.1.11 Pre-chamber:
The pre-chamber is the ignition source for the main fuel charge and is one of the essential components
of a lean-burn spark-ignited engine. Gas is admitted to the pre-chamber through a mechanical
camshaft driven valve. This solution has proved to be extremely reliable and gives an excellent
mixture into the pre-chamber.
Figure 13: Pre chamber Ignition.
Page | 11
3.5.1.12 Ignition System:
The ignition module communicates with the MCM, which determines the global ignition
timing. The ignition coil is located in the cylinder cover and is integrated in the spark plug
extension.
The inlet valves: The inlet valves are satellite and the stems are chromium-plated. The valve
seat rings are made of a special cast iron alloy and are changeable.
The exhaust valves: The exhaust valves with starlit seats and chromium-plated stems, seal
against the directly cooled valve seat rings.
The seat rings: The seat rings made of a corrosion and pitting resistant material, are
changeable
Pre Lubricating Pump: It is used for lubricating purpose. When machine has been being
switched off for many days and starting is needed then turning gear is activated to flow the
lubricating oil around the engine including all the friction full area so that machine can start
and is operated smoothly.
3.5.1.13 Ignition System:
It is consisted with turbine, compressor, charge air chamber, waste-gate, exhaust line and
different kinds of control unit including ventilation system. Turbine and compressor both are
coupled. Firstly charge air is compressed (3 bar) by the compressor and passed into the air
chamber. Secondly 11:1 air fuel mixture is mixed into the cylinder and finally exhaust gas is
expelled out then some portion of this gas is passed through the turbine and rest passes
through the waste-gate depending upon the correct air fuel ratio. Exhaust gas temperature is
5400C. All things are controlled by MCM.
3.5.1.14 Instrument Air
It is also called control air (5.5bar-7 bar). It is a screw type oil cooled compressor and having
capacity of 3.11 M³/min. It maintains air pressure of 7 bar (max). An instrument air
compressor controls the application of air for operating valves in pneumatic (run by or using
compressed air) instruments. It is controlled by I/P converter consisting of the solenoid valve
that is driven by 4-20 mA electrical signals, followed by the MCM. Depending upon the
necessary condition, solenoid valve is opened and 6 bar air pressure is allowed to pass
through the actuator valve that eventually opens or closes the butterfly/ any sort of three-way
valve thereby by opening or closing system. The flow of any kind of system parameter like
water, lube oil etc is thus controlled in a power system.
Page | 12
3.5.2 Alternator
An alternator is an electromechanical device that converts mechanical energy to electrical
energy in the form of alternating current. Most alternators use a rotating magnetic field with a
stationary armature but occasionally, a rotating armature is used with a stationary magnetic
field; or a linear alternator is used. In principle, any AC electrical generator can be called an
alternator, but usually the term refers to small rotating machines driven by automotive and
other internal combustion engines. An alternator that uses a permanent magnet or residual
magnet for its magnetic field is called a magneto. Alternators in power stations driven by
steam turbines are called turbo-alternators.
3.5.2.1 Alternator Working Principle
The power generation operation based on phenomenon of electromagnetic induction
whenever a conductor moves relative to magnetic field Voltage is induced in the conductor.
Particularly if a coil is spinning in a magnetic field, then two sides of the coil move in
opposite directions, and the voltage induced in each side. Numerically the instantaneous
value of resulting voltage (called electromotive force, emf) is equal to the minus of the rate of
change of magnetic flux Φ times the number of turns in the coil.
Figure 14: Voltage production of Alternator
This relationship has been found experimentally and is referred to as Faraday’s law. The
minus sign here is due to Lenz law, which states that the direction of the emf is such that the
magnetic field from induced current opposes the change in the flux which produces this emf.
Lenz law connected to the conservation. For clarity in the above figure a single rectangular
conductor loop is shown instead of an armature with a set of windings on an iron core. Since
the rate of magnetic flux change through the coil that spins at a constant rate changes
sinusoidal with the rotation, the voltage generated at the coil terminals is also sinusoidal
(AC).If an external circuit is connected to the coil’s terminal, this voltage will create current
through the circuit, resulting in energy being delivered to the load.
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Thus the mechanical energy that rotates the coil is converted into electrical energy. The
higher the current, the larger force must be applied to the armature to keep it from fig the coil
is rotated by the hand crank.
3.5.2.2 Specification of ABB Alternator for Wartsila 20V34SG :
Name Synchronous AC Generator
Manufacture year 2008,Made in Germany
Rated Load 10913KVA
Power 8.73 MW
Phase 3
Stator Connection Y
Frequency 50 Hz
Voltage 11000V,AC
Current 573 A
Power Factor 0.8
Speed 750 rpm
Over speed 938 rpm
Excitation Voltage 52V
Excitation Current 4.4A
Direction of Rotation CW
Time phase sequence W V U
Weight 28.2 ton
Max and Min ambient Temp. 50 and 15 deg C
Driving Equipment 20V34SG
3.5.2.3 Components of ABB Alternator
Inlet Cooling Air Outlet Cooling Air
Line Terminals Air Filters
Exciter Fan
Diode Bridge End Sheild
Shaft D-end Bearing
CT, PT Rotor Poles
Neutral Point Rotor Windings
Stator Core Stator Windings
Detachable Feet AVR
Page | 14
Fig 15: ABB Alternator components.
3.5.2.4 Alternator Excitation
The injection of D.C in the field winding to produce magnetic field is called excitation.
3.5.2.5 Purpose of Excitation
The purpose of excitation system is to monitors line voltage and current constantly and
produces proper excitation voltage necessary to maintain terminal voltage constant under all
conditions of generator operation (no load, full load etc). At no load, the excitation system
should only supply that much amount of volts necessary to maintain the terminal voltage of
generator constant. When a sudden load is applied to a generator, its terminal voltage
decreases slightly, therefore an efficient excitation system senses the voltage dip and
increases the excitation volts immediately and thus maintains the terminal voltage.
3.5.2.6 Alternator Excitation System
The system which controls the excitation in order to maintain constant terminal voltage under
normal operating conditions, to vary the generation of reactive power and to maintain voltage
under fault conditions.
Types of Excitation System:
a) Exciter with Slip Rings
b) Brushless Excitation
Page | 15
The excitation system of Maona power plant is Brushless Excitation. Brushless Excitation
System is the most important part of modern day power generation concept, so I am going to
discuss it in detail.
In all the excitation systems discussed so far, the D.C. power generated or derived from
different means is fed to the generator fielded throw brushes to slip ring. The brush gear and
slip ring have become such a vital parts that required high maintenance and are a source of
failures,thus forming week links in the system. With the advent of mechanically robust
silicone diode capable of converting A.C. to D.C. at a high power levels, brushless excitation
system has become popular and being employed.
3.5.2.7 Brushless Exciters General Description
The brushless excitation system consists of a high frequency AC generator complete with
rotating, series redundant diode assembly and a lead assembly that connects the DC diode
output to the field windings of the main generator. The brushless design eliminates collector
rings, commentators, and brushes.
Figure 16: Brushless Exciter Rotor
These features contribute to a brushless excitation system with high reliability components
and trouble free low maintenance operation. It is also a relatively uncomplicated system, easy
to operate and inspect without extensive personnel training. Other advantages include:
The overhung design, shrink fit on the generator rotor shaft, requires no exciter
bearing
There are no carbon dust or contamination problems in the brushless exciter
system if it operates in a clean, controlled environment.
The brushless excitation system does not have the large field circuit breakers,
heavy field current control or bus interconnections components such static
systems require.
Page | 16
3.5.2.8 Brushless Exciters for ABB Alternator (8 poles)
This manual on the brushless exciter for 8 pole generators covers the general description,
construction, operation, initial inspection, alignment, maintenance, troubleshooting and
renewal parts. The main excitation of ABB Alternator takes part through residual magnetism.
By supplying DC source the excitation procedure starts. Through exciting the exciter stator
power is induced by the exciter rotor then this AC power is rectified and converted to DC and
supplied to the main rotor. Again rotating the main rotor power is induced in main stator then
it is supplied by the 3 phase supply.
Exciter Rating For Wartsila Generator
Voltage........................................................ 68V (DC)
Current........................................................ 9.3A (DC)
Figure 17: ABB Alternator excitation system (AVR)
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3.5.2.9 Automatic Voltage Regulator (AVR):
AVR is used to get a regulated output at the output terminal of the alternator. In addition to
regulating the generator voltage, the AVR circuitry includes under-speed and sensing loss
protection features. Excitation power is derived directly from the generator terminals.
Positive voltage build-up or regenerative voltage feedback from residual voltage level is
derived by the use of efficient semiconductors (IGBT) in the power circuitry of the AVR. The
AVR is connected to the main stator winding for actual voltage and current sensing and
voltage control purpose. It is also linked with the auxiliary exciter windings and the exciter
field windings to provide closed loop control of the output voltage with load regulation of +/-
1.0. Based on actual voltage level, the AVR controls the power fed to the exciter field, and
hence the power of the main field, to maintain the machine output voltage within the
specified limits.
Fig-18: Self-excitation system
Page | 18
3.6 Auxiliary system of Maona Power Plant
The auxiliary equipment is essential for the function of engine and must be in full operation
when the engine is running or standby. The auxiliary systems provide the engine with fuel,
lubricating oil, compressed air, cooling water and charge air. The auxiliary systems used in
Maona Power Plant are of following types:
3.6.1 Lubricating oil system
The lubricating oil circulation system provides the engine with clean lube oil at the correct
pressure and temperature. Besides lubricating the engine, the oil also removes the heat of the
engine. The oil is circulated through the filtering and cooling system by an engine-driven
pump.
Figure 19: Lube oil circulation system
Auxiliary
system
Page | 19
This lube oil pump is directly driven by the crankshaft of the engine. The pumps, the filters
and the temperature control circuits are built on the engine. The engine lube oil system also
lubricates the turbochargers. The circulation pump draws oil from the oil sump of the engine
and pumps it through lube oil cooler. A three-way valve in the lubricating oil circuit regulates
the oil flow to the cooler and controls the temperature of the oil. The oil flows through an
automatic filter before it enters the engine and the turbochargers. The back-flushing oil from
the automatic filter is cleaned in centrifugal filters and sent back to the sump.
A pressure control valve is used to adjust the oil pressure in the system. The oil from the
automatic filter flows through a number of paths as shown in Fig-3.
Lube oil system consists of the following components:
1. Circulation pump
2. Pre-lubrication pump
3. Lube oil cooler
4. Temp. control valve (thermostatic valve)
5. Automatic filter
6. Centrifugal filters
Figure 20: Lube oil circulating system.
The following fig- 5 shows the lube oil system components in details and the direction of
lube oil flow through the engine:
1. Centrifugal filter
2. Pre lube pump
3. Lube oil pump
4. Pressure Regulating valve
5. Thermostatic valve
6. Lube oil cooler
7. Lube oil filter
8. Pressure gauge
9. Oil dipstick
10. Camshaft bearings
11. Gudgeon pins
12. Rocker arm bearings
13. Lube oil pipe to T/C
14. Lube oil pipe from T/C
Figure 21: Lube oil flow inside the engine
Page | 20
3.6.1.1 Lubricating oil cooling:
The temperature of the lubricating oil circulating in the engine increases during operation and
the oil must therefore be cooled. The lubricating oil is cooled in a heat exchanger by water
from the low-temperature cooling water circuit of the engine. The cooler consists of a tube
stack inserted in a jacket. The oil flows through the cooler outside the tubes, while the
cooling water flows inside the tubes. Thus the heat of the lube oil is absorbed by the cooling
water. A temperature control valve directs the lubricating oil to the cooler according to the
temperature of the oil.
3.6.1.2 Lubricating oil filters: V1
The lubricating oil filtration system includes an automatic filter and a centrifugal filter. The
automatic filter includes a number of filter candles that clean the oil. Before leaving the filter
unit, the oil flows through a protective filter. The filter candles are cleaned by automatic
back-flushing. The back-flushing oil flows back to the oil sump through the centrifugal filter.
The automatic filter is equipped with a differential pressure indicator and overflow valves. If
the differential pressure rises too high (indicating inadequate cleaning of the filter candles),
the overflow valves open and the oil is filtered only through the protective filter.
Figure 22: Lube oil automatic filter and Centrifugal filter
The centrifugal filter cleans the back-flushing oil that comes from the automatic filter. Thus
the function of centrifugal filter is to gather the dirt particles out from the back-flashing oil
flow. The dirt deposited in the centrifugal filter gives information about the condition of the
lubricating oil circulating in the engine. In the centrifugal filter, the dirt is deposited on the
walls of the rotor due to the high centrifugal force.
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3.6.1.3 Pre-lubrication:
An electrically driven pre-lubrication pump is connected in parallel with the main circulation
pump. Pre-lubrication is done prior to starting the engine and during stand-by condition. It is
equipped with an adjustable pressure regulating valve.
When the pre-lube pump is set in automatic mode, it operates according to the operation of
the engine. The pump is automatically switched on when the engine stops, and switched off
when the engine has started by PLC. The figure- 07 shows the main lube oil pump and pre-
lube pump built on the engine.
Figure 23: Main lube oil pump and Pre-lube pump
3.6.1.4 Lube oil thermostatic valve:
Lube oil thermostatic valve is used so that the lube oil can by-pass the lube oil cooler when
the lube oil temperature is low.
From
From Cooler
Figure 24 : Lube oil thermostatic valve
Page | 22
3.6.1.5 Lube oil suction strainer:
Lube oil strainer is set up before the suction pipe to protect the lube oil pump and is provided
with high differential pressure alarm. The lube oil flow in the engine serves the following
functions:
Lubrication: It lubricates the moving parts in the engine to minimize wear and friction
Cooling: It acts as a cooling medium for bearings, pistons etc
Corrosion Protection: During combustion, it neutralizes the corrosive combustion acids
Cleaning: It transports harmful foreign particles away from bearings, pistons etc.
3.6.2 Cooling water systems
The cooling system of the engine uses chemically treated fresh water. The system is divided
into a low-temperature (LT) and a high-temperature (HT) cooling water circuit. The cooling
water is circulated in the system by directly driven centrifugal pumps mounted on the
crankshaft of the engine.
The LT cooling water is circulated through the charge air cooler and lube oil cooler. The HT
water cools the engine jacket. The temperature in the LT and HT circuits is controlled by
three-way valves. The temperature control valves direct the water to the cooling radiators or
back to the engine, depending on the temperature of the water. An expansion vessel is
installed in the system. The expansion vessel is connected to the cooling water circuits on the
engine by vent pipes. A preheating unit is used to heat the jacket cooling water before the
engine is started. The cooling water circuits include sensing equipments (sensors) for
monitoring the pressure and temperature of the system. Cooling system and its flow diagram
is given in Fig- 9.
Cooling system components:
1. Circulation pump
2. Charge air coolers
3. Lubricating oil cooler
4. Temperature control valve
5. Radiators
6. Expansion vessel
7. Preheating unit
Figure 25 : Cooling water system
Page | 23
3.6.2.1 Preheating unit:
The pre-heater keeps the engine jacket water heated when the engine is temporarily stopped.
This enables rapid start and loading of the generating set. The unit is also used for heating the
engine prior to start after a prolonged shutdown period.
The main components in the preheating unit are a circulation pump and an electric heater.
The unit is connected in parallel with the engine-driven HT water pump. The preheating
pump takes water from the outlet line of the engine and pumps it through the heater back to
the HT water circuit of the engine. The circulation pump is a centrifugal pump driven by an
electric motor. The preheating circuit is equipped with a non-return valve to prevent the water
from flowing in the wrong direction. A safety valve protects the circuit against too high
pressure. Temperature and level switches are installed to control the heater and protect the
heating elements from overheating. The unit is also equipped with automatic and manual vent
valves.
3.6.2.2 Expansion vessel
The expansion vessel compensates for water volume changes due to temperature variations in
the cooling water system. A level indicator and a level switch for low level alarms are
mounted on the vessel. The vessel has a drain and overflow line with a drain valve installed at
the bottom of the vessel. It is also equipped with connections for vent pipes. The expansion
vessel is connected directly to the external cooling water system. The level in the vessel rises
when water is added to the system.
3.6. 2.3 Radiator
The radiator removes heat from the cooling water. The main components of the air-cooled
radiator are copper tubes, aluminum fins and the cooling fans. The cooling fans are driven by
electric motors of 7.5 MW each, and the speed of the fans is controlled by a frequency
converter according to the amount of cooling required. Each fan is equipped with a safety
switch/ Motor protection circuit breaker (MPCB).
The rating of the radiator motor is-
Phase 3
Frequency 50Hz
Power 7.5KW
R.P.M 720
Current 17.6A
Page | 24
3.6.2.4 Frequency Converter:
Basic: Frequency converters are extensively used for accurate control of critical processes in
cooling system. The frequency converter generates variable frequency (in the form of PWM
sine wave) to drive the cooling motors at variable speed as per cooling requirements.
Microprocessor controlled gate-pulses to the IGBT inverters assist in generating variable
frequencies at precise level for proper cooling of the system irrespective of ambient
condition.
Figure 26: Main features of standard frequency converter
Motor Speed, N =
P= No. of motor pole
f = frequency which is proportional to motor speed
Page | 25
The Fig-26 presents the block diagram of the VACON Frequency converter. The frequency
converter mechanically consists of two units, the Power Unit and the Control Unit.
The three-phase AC-choke (1) at the mains end together with the DC-link capacitor (2) form
an LC-filter, which, again, together with the diode bridge produce the DC-voltage supply to
the IGBT Inverter Bridge (3) block. The AC-choke also functions as a filter against High
Frequency disturbances from the mains as well as against those caused by the frequency
converter to the mains. It, in addition, enhances the waveform of the input current to the
frequency converter. The entire power drawn by the frequency converter from the mains is
active power.
3.6.3 Compressed air system
The compressed air is used for starting the engine and operating the pneumatic valves in the
control system. The compressed air system includes two subsystems having separate
compressor units. The high-pressure air of about 30 bar required for starting the engine is
provided by the starting air unit, while the instrument air unit supplies air at lower pressure of
about 7 bar to pneumatically operated devices on the engine and in the auxiliary systems.
Components of compressed air system:
1. Starting air unit
2. Starting air vessel
3. Instrument air unit
4. Instrument air back-up line
Figure 27: Compressed air system layout
Page | 26
3.6.3.1 Compressed air system arrangement:
1. Main staring valve
2. Flame arrester
3. Starting air valve in cyl. head
4. Starting air distributor
8. Solenoid valve for starting
9. Blocking valve for turning gear
10. Safety valve
18. Pressure regulator
21. I/P converter for W/G positioner
22. Exh. W/G positioner
24. Solenoid valve for gas venting
25. Gas venting valve
27. Wastegate valve
301. Starting air inlet
311. Control air inlet to W/G &
Gas venting valve
Figure 28: Compressed air system flow diagram
3.6.3.2 Compressed Air System Classification:
It is classified as follows:
1. Starting air system
2. Instrument air system
3.6.3.2.1 Starting Air Compressor:
It is a piston type high pressure oil cooled compressor that maintains an air pressure of about
30 bar. This system has two air bottles to reserve air at 30 bar pressure. The engine is started
with compressed air of max 30 bar. The minimum pressure required is 22 bar and the WECS
engine control system gives an alarm for low starting air pressure at the level.
Page | 27
1. Engine control unit (WECS)
2. Pressure transducer
3. Drive valve
4. Main starting valve
5. Starting valve
6. Flame arrester
7. Connection piece
8. Air block
9. Blocking valve
11. End plate
13. Plate
14. Spring
15. Control piston
16. Liner
17. Plug
18. Connection piece
19. Safety valve
20. Pressure regulating valve
21. Starting air distributor
Figure29: Starting air pipe connections
Starting air system on engine:
1. Starting air delivery line
2. Main starting valve
3. Pressure regulator
4. Flame arrester
5. Safety valve
6. Pressure gauge
8. Solenoid valve
Figure 2 : Starting air system on engine
A - Starting air inlet from B-Bank
D- Air from blocking valve to starting air distributor
E -Air to blocking valve for turning gear
Page | 28
.
3.6.3.2.2 Instrument air system:
The instrument air is also called control air (5.5bar-7 bar). It is derived from a screw type oil
cooled compressor having capacity of 3.11 M³/min. The compressor maintains an air pressure
of 7 bar (max). An instrument air compressor controls the application of air for operating the
valves in pneumatic (run by or using compressed air) instruments.
3.6.4 Charge air system:
The Charge air system provides the engine with clean and dry combustion air. The charge air
is drawn into the engine from open environment of the power house. The air first passes
through the charge air filter and silencer units, then into the turbochargers mounted on the
engine. Before entering the charge air receiver inside the engine block, the compressed
charge air flows through the charge air cooler where it is cooled in two stages by water from
the cooling water system of the engine. Charge air system consists of the following
components:
(1) Charge air filter
(2) Charge air silencers
(3) Turbochargers
(4) Charge air coolersV1
Air inlet Engine
Figure 3 : Charge air system overview
Page | 29
3.6.4.1 Charge air filter
The charge air filter prevents water and particles from entering the engine. The dry air filter
unit consists of bag filters fixed into a box unit. Before entering the bag filters, the air flows
through a weather Louvre. A differential pressure indicator is installed to monitor the
condition of the charge air filter. The unit is also equipped with a pressure switch that
activates an alarm in case of too high pressure (>250 Pa) across the filter. Charge air filter is
installed before the engine to reduce the CAC differential pressure and the wear/corrosion of
turbocharger compressor and cylinder liner.
The highest permissible dust concentration in the charge air is 3 mg/m3. The filter should be
able to separate 70% of the particles above 5 mm. The dust concentration and particle size
must always be below this limit to turbocharger inlet.
3.6.4.2 Charge air silencer V1
The charge air silencer reduces the environmental noise spreading out from the turbocharger
and engine. The operation of the silencer is based on absorptive attenuation. The silencer is
equipped with a condensate drain.
Figure 4 : Charge air silencer
The charge air sound level after turbocharger is approximately 120 dB. This high sound level
pollutes the environment and is severely detrimental to human hearing. Therefore, charge air
silencer is incorporated to minimize the level of sound. A typical charge air silencer gives
about 35 dB attenuation.
Page | 30
3.6.4.3 Turbocharger
Turbocharger is a mechanical device which converts the thermal and kinetic energy of
exhaust gas into air pressure that can be fed into the cylinders to improve the engine
efficiency.
Construction: It consists of an exhaust driven turbine and a compressor mounted on the
same shaft. The rotational speed of T/C at full load for W20V34SG engine is about 23000
rpm.
Turbine: The turbine converts the exhaust gas into mechanical energy to drive the charger/
compressor. It consists of turbine wheel and turbine housing.
Turbine function: The flow of exhaust gas which is restricted by the turbine blades results
in a pressure and temperature drop between inlet and outlet. This pressure drop is converted
into kinetic energy to drive the turbine wheel.
3.6.4.4 Charge air compressor
The turbine compressors are centrifugal compressors which compress the charge air before it
has been fed into the cylinders to improve the engine efficiency. It consists of Compressor
wheel, Compressor housing and Diffuser.
Figure 21: Turbocharger functionality
Page | 31
3.6.4.4.1 Compressor function:
With the rotational speed of compressor wheel, the air is drawn in and accelerated to high
velocity into the receiver. The diffuser compresses and slows down the high velocity of air so
that both pressure and temperature increase.
Figure 22: Turbocharger assembly
3.6.4.4.2 Advantages of using Turbocharger:
1. As the combustion air is pre-compressed by the Turbocharger before being fed to the
engine, the charge air pressure increases and more air mass (consequently more fuel
in the same proportion) is fed into the combustion chamber (cylinder). The burning of
more air/fuel in the cylinder increases the power output of the engine.
2. The engine driven turbocharger improves the quality of combustion and thereby
improves the engine efficiency.
3. In a turbocharged engine, some of the exhaust gas energy which would be lost
normally is used to drive the Turbocharger without additional power losses
4. Engine torque can be adjusted by adjusting the charge air pressure (with a wastegate)
5. The T/C improves the engine torque at lower rpm.
6. It reduces the size and mass of the engine.
3.6.4.4.3 Disadvantages:
1. Turbocharger needs cooling and lubricating systems.
2. Mechanical stress on engine components will increase.
Page | 32
3.6.5 Fuel Gas System
The purpose of the fuel gas system is to ensure an uninterrupted and reliable supply of fuel
gas to the engine. The components in the system clean the gas and regulate the fuel pressure
according to the load of the engine. A flow metering unit (Flow-computer, flow-chart etc) is
installed at the R.M.S before gas regulating unit. The main shut-off valves in the gas line to
the engine hall are located before the flow meter.
3.6.5.1 Main gas valve: V
A manual shut-off valve is installed at the gas inlet pipe to the power house. This valve allows the gas
to enter the fuel system (GRU & Engine) in the power house. In an emergency situation, such as a
gas leak alarm or a fire alarm, the valve is closed to stop the supply of fuel gas to the power house.
3.6.5.2 Gas regulating unit (GRU):
The gas regulating unit is a vital auxiliary component that controls the flow of gas to the
engine together with the main gas admission valves at the engine. The unit ensures that clean
gas be fed to the engine at the correct pressure, depending on the load of the engine. The gas
regulating unit includes manual and automatic shut-off valves, venting valves, gas regulating
valves and a filter. The gas is cleaned in a cellular filter which is equipped with a differential
pressure indicator. A filter is also installed in the instrument air line. The instrument air is
used to operate the gas regulating valves, automatic shut-off valves and venting valves. The
automatic electro-pneumatic valves close upon loss of power or control air. The solenoid
(shut-off) valves remain open as long as the control voltage is present, whereas the venting
valves remain closed as long as the control voltage is present.
Gas inlet
MCC
PCC
Figure 23: Gas Regulating Unit (GRU)
The GRU has two gas outlet lines to the engine: one for the main combustion chambers,
MCC and another for the pre-combustion chambers, PCC. A gas regulating valve is installed
in each line. The regulating valves regulate the outlet gas pressure based on the control signal
Page | 33
of the engine control system (MCM700). The operation of automatic shut-off/ solenoid
valves and venting valves are controlled by PLC (external automation) during the start and
stop sequences. A manual venting valve is also installed in both MCC and PCC lines. The
unit has a connection for inert gas, used for purging the air of the fuel system after
maintenance work in order to avoid explosive mixtures of fuel gas and air in the system. The
unit includes temperature sensors and pressure sensors (pressure transmitter) for monitoring
the temperature and pressure of the gas. The pressure is measured at several locations in the
unit.4Components of GRU as shown is Fig-26 are as follows:
(1) Manual shut-off valve
(2) Gas filter
(3) Gas regulating valves
(4) Automatic shut-off valves
(5) Venting connection
(6) Inert gas connection
3.6.5.3 Working Principle:
The gas supply pressure reference from the MCM is set depending on the engine load. The
actual pressure is measured and set according to a reference pressure map. If the deviation is
too high an alarm will be initiated and sent to the PLC. If the deviation increases more, the
safety (shut-off) valves on the gas regulating unit will cut the gas supply to the engine
immediately. Both references and actual pressures are sent to the PLC for the main gas
system.
Figure 24: GRU automation overview
Page | 34
3.6.5.4 Main Gas Admission valve:
Main gas admission valves function as a speed regulator and can be adjusted individually
during operation. It has short opening/ closing time (stroke 0.2 mm) and first response time.
Its operation is controlled by the engine control system
Figure 25: Section view of Main gas admission (solenoid) valve
3.6.5.5 Pre-chamber gas injection:
The pre-chamber gas injection valves are mechanically operated by the cam-shaft of engine.
3.6.5.6 Main gas injection:
The amount of main gas admitted to each cylinder is controlled by the main gas solenoid
valves (Fig-3) which are connected to the CCM. The amount of gas admitted into the cylinder
depends upon the gas supply pressure and the duration of main gas admission. The gas is
admitted further away or closer to TDC by changing the main gas solenoid valve opening
moment (timing) in order to obtain an optimum air/gas mixture.
Figure 26: Gas injection control
Page | 35
The WECS system uses pre-set values to optimize this mixture during the operation. Valve
duration and timing are sent to the CCM from the MCM via the Control Area Network
(CAN)-bus. Valve duration and timing can be controlled individually for each cylinder. The
timing depends on engine speed and load. The duration is controlled by the load/speed PID-
controller, so that speed or load always matches their references. The CCM uses the pulses
from speed and phase sensor to calculate engine angular position and engine speed in order to
open the valve according to the duration and timing references.
3.6.6 Exhaust Gas system
The exhaust gas system leads the exhaust gases out of the power house. The system also
includes equipment for noise reduction (Exhaust silencer). The exhaust gas from the engine
passes through the turbochargers to the exhaust gas silencer and the stack. Explosion relief
element (Rupture disk) protects the system in the event of a sudden pressure rise. The exhaust
gas system includes a ventilation unit, which is used for removing any explosive gases/
unburned gases from the exhaust gas system after the engine is stopped.
Exhaust system components:
1. Exhaust gas silencer and stack
2. Exhaust gas ventilation fan
3. Turbochargers
Figure 27: Exhaust gas system overview
3.6.6.1 Exhaust gas ventilation unit:
The exhaust gas ventilation unit ensures that any explosive gas in the exhaust gas system
must be removed after the engine is stopped. The exhaust gas system has to be ventilated
properly in order to prevent gas explosions in the system during startup.
The main components of the ventilation unit are a fan, a flow switch and a shutoff valve. The
flow switch is installed to monitor the operation of the fan. The pneumatically operated shut-
off valve prevents back-flow of exhaust gases into the unit when the fan is not running.
The ventilation unit is automatically started and stopped by the PLC. The engine cannot be
started until exhaust gas ventilation has been performed successfully.
Page | 36
3.6.6.2 Exhaust Wastegate
Wastegate valve works as a charge air pressure regulator (controller) that controls the charge
air pressure in the charge air receiver. The exhaust gas wastegate valve, when opened, by-
passes partly exhaust gases over turbocharger thus reducing turbocharger speed and charge
air pressure in the air receiver.
The exhaust wastegate system is built on the engine and
consists of an actuator connected to the butterfly valve that
controls the exhaust by-pass flow to the turbocharger exh-
gas outlet as much as required to keep the correct charge
air pressure.
Figure 28 : Exhaust Wastegate
Function of Exhaust Wastegate:
The wastegate control system gets control air from the compressed air system. The control
pressure is approx. 4 - 6 bar. The instrument air needs to be clean, dry and oil free to secure
proper function of the components
The wastegate system works as follows:
When the engine is running, air is supplied to
the I/P converter (8) and the positioner (9)
in the actuator unit (1). The I/P converter
supplies a 0.2-1.0 bar control air pressure to
the positioner depending on the incoming 4-20 mA
control signal from the MCM.
The positioner pilot valve (11),
supplies the actuator (1) with air pressure (4 to 6 bar)
according to the control air pressure from the
I/P converter. Figure 29 : Exhaust wastegate functional parts
Page | 37
3.6.6.3 Air/fuel ratio control:
It is apparent from above discussion that the charge air pressure in the receiver is controlled
by a wastegate valve, located on the turbocharger support. The valve can be either an exhaust
wastegate valve, or an air by-pass valve. Both types of valve systems control the turbocharger
speed and thereby control the air pressure in the receiver. For this pressure control, a
continuous receiver air pressure, alternatively an average exhaust gas temperature
measurement is carried out and calculated in the MCM. The reference for the PID controller
is a load dependent receiver pressure table, or alternatively a load dependent average exhaust
gas temperature table.
Exhaust Gas Was
Figure 30: Air/fuel ratio control process
The following Fig-23 shows how the exhaust wastegate controls turbocharger speed and the
charge air pressure in the charge air receiver.
Figure 31: Charge air pressure control by Exhaust wastegate
Page | 38
36.6.4 Main Control Module.
The main control module, the core of the Engine Control System, reads the information
sent by all the other modules. Using this information it determines reference values for
the main gas admission to control the engine’s speed and load. The main control module
also uses the information sent from the different distributed modules to control the global
air-fuel ratio and global ignition timing in order to obtain the best performance and
reliable operation in different site conditions, such as varying ambient temperature and
methane number. The main control module automatically controls the start and stop
sequences of the engine and the engine safety. It also communicates with the plant control
system (PLC).
3.6.6.5 Cylinder Control Module
Each cylinder control module monitors and controls three cylinders. The cylinder control
module controls the cylinder-specific air-fuel ratio by adjusting the gas admission
individually for all cylinders. This ensures optimal combustion in all cylinders. The
cylinder control module also measures the knock intensity i.e. uncontrolled combustion in
all cylinders. Information on knock intensity is used to adjust the cylinder-specific
ignition timing by the cylinder control module. Light knocking leads to automatic
adjustment of the ignition timing and air-fuel ratio. Heavy knocking leads to load
reduction and ultimately to shut-down of the engine if heavy knocking does not
disappear. The cylinder control module also monitors the exhaust gas and cylinder liner
temperatures of all cylinders.
Figure 32: WECS 8000
Page | 39
3.6.6.6 WECS 8000
The WECS8000 is distributed engine control system for monitoring and control of all engine
functions. The system monitors and controls gas, air, ignition, knock, speed, load, diagnostics
and communication with plant control system. It comprises air/fuel ratio control, cylinder
balancing control, hardware I/O control, ignition control, knock control, load control, main
gas ignition control, gas pressure control, safety system control, speed control, speed
reference control etc.
The main parts of WECS system are:
MCM700: Main Control Module. The MCM is responsible for all engine control functions
and communicates with the plant systems external to the engine.
ACQ700: Acquisition Module collecting data from sensors in the free end of the engine and
used for waste-gate control.
CCM10: Cylinder Control Module, used as a cylinder control unit. The CCM10 handles
cylinder specific sensors and actuators like gas admission valves, knock sensor and cylinder
specific temperature sensor. One module controls three cylinders.
WCD10: Wartsila coil driver. Ignition control module drives up to 10 ignition coils as
commanded from CCM10.
CAN Repeater: Extends and galvanic ally isolates the CAN link outside the engine. Used to
connect to the program (WECS explorer) running on a PC. It is used to strength weak signals
and retransmit.
ESM: Engine safety module. Handling fundamental engine safety and interfacing to the
engine shutdown device and back up instruments.
EGW: Ethernet Gat Way graphical panel with indication of the most important engine
measurements. It process data between WECS and external automation systems over
Ethernet.
P-MOD: It handles power and fusing on the engine.
C-MOD: It comprises MCM700, ESM and EGW. It handles also external I/0 and
Communication Module.
Chapter-04
Control & Safety Zone
Control Room
Page | 2
4.1Introduction:
The generating set can be operated in automatic or manual mode. The control mode selection is
made with the "generating set control" switch on the manual control unit. In automatic mode, the
control system selects the engine and generator control methods according to the "parallel with
grid" signal. In manual mode, the engine and generator control modes are selected with switches
on manual control unit. Some control modes are enabled only when the generating set is in
parallel with the grid.
4.2 Parallel operation
If the generating set is in parallel with the grid, the grid will determine the frequency and
voltage. Any fluctuation in grid voltage or frequency is followed by the generating set. An
increase or decrease in the output of the generating set does not affect the network frequency or
voltage, provided that the power plant is relatively small compared to the total network capacity.
Parallel operation requires that the generating set is synchronized with the grid.
4.3 Island operation
In island operation mode, the power plant feeds an isolated network. The control system of the
power plant controls the frequency and voltage in the network.
Fig33: Control Room of MNPP
Control Room
Page | 3
4.4 Control functions
The main functions of the control system are:
Start and stop of the generating set
Synchronization
Engine speed and load control
Generator output control
Control of auxiliary systems
Monitor and alarm handling
Safety functions, such as start blocking, shutdown and load reduction.
The generating set can be controlled in automatic or manual mode. In automatic mode, which is
the normal operating mode, the control system takes care of start and stop, loading and
unloading, and generator output control.
In manual mode, the loading and unloading as well as the generator output control must be done
manually by the operator. The safety functions, such as checking of the start conditions, work in
the same way as in automatic mode
4.5 Engine Starting Condition Engine start is enabled when the following starting conditions are to be met.
1. Lube oil pressure >0.6 Bar
2. HT- water temperature >450C
3. Engine speed=0
4. Valve power supply>18vdc
5. Safety wire ok
6. Turning gear disengaged
7. External start block
8. WECS ready for start
9. Exhaust gas ventilation
10. Engine is not running
11. Stop command inactive
12. Shutdown alarm inactive
13. Tripping alarm inactive
14. Earthing disconnector open
15. Breaker truck in service
16. PLC- WECS communication
Page | 4
4.6 Automation System
The Engine Control System is an engine-mounted distributed system. The various electronic
modules are dedicated to different functions and communicate with each other via a CAN data
bus. All parameters handled by the Engine Control System are transferred to the operator
interface and the plant control system. Its features are:
1. easy maintenance and high reliability due to rugged engine-dedicated connectors, CIB´s
(cabling interface boxes) and high quality cables
2. less cabling on and around the engine
3. easy interfacing with external system via a data bus
4. digitized signals giving immunity from electromagnetic disturbance
5. built-in diagnosis for easy troubleshooting
Figure 34: Cabling Interface Boxes (CIB)
It is the Work Station of the Power house which incorporates the following major control units:
PLC (Programmable Logic Controller)
WOIS (Wartsila Operator Interface System)
WISE workstation
CRP (Control Relay Panel)
Energy Metering Panel
CFA901 Panel
CFC Panel
Auto-Synchronizer
Differential Relay
Distance Relay
U/f Relay
AVR (Automatic Voltage Regulator)
DC Charger Panel
Speed droop control
Page | 5
4.7 PLC (Programmable Logic Controller)
The programmable logic controller (PLC) system is the core of the control system.
The PLC system includes a PLC for each generating set, and a common PLC. Each PLC
includes a central processing unit (CPU), which contains the control functions, and a
number of I/O cards for collecting and transmitting process signals. The PLC system
controls the operation of the generating sets and some of the auxiliaries. It collects data,
executes controls, generates alarms and performs measurement scalings for the WOIS
terminal. The main control functions of the generating set PLC are engine start and stop,
engine speed and load control, generator output control, synchronization and control of
auxiliary systems. The engine speed is controlled by the PLC together with the engine
control system. The common PLC collects data and controls operations that are common
for the generating sets in the power plant. The WOIS reads values from the PLC memory.
Control commands and setting values from the WOIS workstation are automatically
transferred to the PLC.
The PLC system consists of one common PLC, one engine vice PLC and one WECS per
Gen-set and one operator’s station. For this system Ethernet is used for communication
between the PLCs and the operation’s station. The WECS system controls and monitors
the engine while the PLC controls and monitors engine auxiliaries and common systems.
The WECS and PLC system collect and scale data from the inputs and sends the data to
the operator’s station through the Ethernet.
Fig35: PLC Configuration
Page | 6
4.8 WOIS (Wartsila Operator Interface System)
The Wärtsilä Operator's Interface System (WOIS) provides a user interface to the PLC system. It
consists of a computer with the necessary software, connected to the control system of the power
plant.The WOIS workstation is mainly used for monitoring the generating sets and the auxiliary
systems, while most of the operations are performed at the control panels. At the WOIS
workstation, the operator can view the present status of the processes in the power plant and send
commands to the PLC, for instance to acknowledge alarms and change parameters and set points.
The WOIS workstation is used for monitoring the power plant by visualizing essential digital and
analog information, such as:
Active control mode
Active engine running status (for instance starting, loading or unloading)
Generator power output
Breaker positions
Temperature and pressure readings and set points for auxiliary systems
Start conditions and whether they are fulfilled or not.
The WOIS includes various displays for supervision of the plant. Graphic pictures showing
status information and continuously measured values are available for processes related to
different generating sets and common systems. Trend displays are available for analogue values,
and various reports can be used for long-term supervision of the power plant. The WOIS
workstation is also used for alarm handling. An alarm list shows all active alarms and allows the
operator to acknowledge the alarms. An event list shows events in the power plant, such as
changes in breaker positions or in the running status of pumps and motors.
The WOIS presents information on several display levels. The most important information about
the status of the main components in the plant is presented in the overview display. The process
displays give more information about the different processes and systems, using graphical
symbols and numerical values.
4.9 WISE workstation
The Wärtsilä Information System Environment (WISE) is used for follow-up of the power
production and the engine condition, as well as for long-term diagnostics of the engine. The
WISE calculates and saves important measurement values, and allows the operator to view and
print reports. The WISE gets the information from the WOIS.The reporting system calculates
and shows daily, monthly and yearly production reports of the generated power and the fuel
consumption. The production reports include minimum, maximum and average values.
Page | 7
4.10 CRP (Control Relay Panel)
Responsible for controlling, monitoring and measuring of the parameters of substation
equipments
Energy Metering Panel – Responsible for measurement of delivered/ received power units
CFA901 Panel– Synchronization and Common control panel
CFC Panel – Gen-set control Panel controls and monitors the generator & engine operation.
Auto-Synchronizer – automatically synchronizes the two independent power sources for mutual
load sharing
Differential Relay – Responsible for Over current and Earth fault protection
Distance Relay – Responsible for line fault (I>, E/F) protection
U/f Relay – used for under/ over voltage and frequency protection
AVR (Automatic Voltage Regulator) – Regulates the generator terminal voltage at desired
level at no-load condition and controls the reactive power while delivering load to the grid.
DC Charger Panel – Responsible for charging the dc batteries. The dc batteries supply dc
voltage for biasing and activation of electronic equipment.
Some Relay and alarm indicator panel pictures from control room:
Differential Relay panel Distance Relay panel Alarm Indicator panel
Fig 36: Relay and alarm indicator panel pictures from control room
Page | 8
4.11 Synchronization
Closing a generator breaker or a common circuit breaker when there is voltage on both sides of
the breaker requires that the breaker is synchronized. During the synchronization, the frequency
and the voltage are adjusted to bring the generating set into synchronism with other generating
sets on the same bus-bar or the public grid. The synchronization can be performed manually by
the operator or automatically by the control system. The synchronization mode is selected from
the synchronizing control unit on the common control panel. When the generating set is operated
in automatic mode, the synchronization is automatically activated after the start of the engine. In
manual mode, the synchronization must be activated manually. A generator breaker is selected
for synchronization with the "synchronization" switch in the manual control unit. A common
circuit breaker is selected with the corresponding button in the mimic diagram on the common
control panel. The PLC system checks that the conditions for synchronization are fulfilled.
During automatic synchronization, the automatic synchronizer performs the necessary
adjustments. To adjust the frequency and the phase, the automatic synchronizer orders engine
speed changes, and to equalize the voltages, it changes the generator excitation. As soon as these
parameters are matched within preset tolerances, a breaker close command is given. If manual
synchronization is selected, the frequency and the voltage are adjusted by the operator. Before
the breaker can be closed, the frequency, voltage and phase deviations have to be within preset
limits. The synchronizing control unit is used for making the adjustments and giving the breaker
close order. The common control panel includes frequency and voltage meters and a
synchronoscope for checking that the synchronization conditions are fulfilled.
Figure37: Synchronizing Control Unit
Sync. Control Unit
Page | 9
4.12 Engine speed and load control
The following engine control modes are available:
Speed droop control
KW control.
When the "generating set control" switch on the manual control unit is in position "auto", the
control mode is selected by the control system. When the switch is in position "manual", the
control mode selection is made with the "engine control" switch. The PLC prohibits selections
that would result in conflicting operation modes.
4.12.1 Speed droop control
Speed droop mode is the typical control mode for smaller grids or island operation. In the speed
droop control mode, the generating set shares the load with the grid or other generating sets
according to a linear speed droop curve. The speed droop curve specifies the speed reduction
(droop) at increased engine load. At load changes, the engine speed reference is adjusted in
accordance with the speed droop curve to maintain the nominal frequency. The engine load is
determined by the system load. In automatic mode, the PLC calculates the speed reference (the
operator can change it from the WOIS terminal). In manual mode, the speed is regulated by
increasing or decreasing the fuel supply with the "fuel" switch on the manual control unit.
4.12.2 KW Control:
kW control is enabled only in parallel operation. In the kW control mode, the active power of the
generating set is maintained at a preset level irrespective of system load or frequency. In
automatic mode, the operator can enter the power set point at the WOIS terminal. The active
power will be slowly increased to the set value after the breaker has been closed. In manual
mode, the power is regulated by increasing or decreasing the fuel supply with the "fuel" switch
on the manual control unit.
The output of the generator is controlled by the generator excitation system along with the
automatic voltage regulator (AVR). The AVR controls the DC field current in the rotor and
adjusts the excitation as required to compensate for load changes.
The following generator control modes are available:
Voltage droop control
Power factor control.
Page | 10
The control mode selection is made with the "generator control" switch on the manual control
unit when the "generating set control" switch is in position "manual". In automatic mode, the
control system selects the generator control mode based on the “parallel with grid” signal.
4.13 Voltage droop control
In the voltage droop control mode, the generating set shares the reactive load with other
generating sets and the grid in relation to the sizes of the units. This is the typical operating mode
for smaller grids or island operation. The sharing of the reactive load is done by adjusting the
reference voltage of the generator according to a linear voltage droop curve. In automatic mode,
the voltage is automatically regulated, while in manual mode, the operator may adjust the voltage
with the "excitation" switch on the manual control unit. A control method called voltage droop
compensation enables the reactive power to be shared equally between generators connected in
parallel while maintaining a constant voltage in an island system.
4.14 Power factor control
In the power factor control mode, the power factor of the generating set is kept constant at a
preset level. The power factor control mode is enabled in parallel operation only. In automatic
mode, the PLC sends increase or decrease commands to the AVR in accordance with the set
value. The AVR adjusts the generator excitation current to keep the power factor constant,
independent of changes in the active power. In manual mode, the operator can give increase or
decrease commands with the "excitation" switch on the manual control unit.
4.15 Control of Auxiliary Systems:
Automatic start and stop of auxiliary units: V1
Units in the auxiliary systems are normally set into automatic mode. In automatic mode, the units
are started and stopped by the control system or by local instrumentation equipment. The "engine
running" signal controls the pre-heater, the pre-lubrication pump and the generator ant
condensation heater. These units are switched on when the engine is stopped, and
correspondingly switched off when the engine starts.
The gas regulating unit operates according to the load of the engine, and it is activated when the
engine starts. The control system also controls the exhaust gas ventilation unit, which is operated
in connection with the stopping sequence of the engine.
Page | 11
Radiator control: V1
The motors of the radiator fans are controlled by a frequency converter. The fans are started and
stopped based on the operation of the engine. The set point to the frequency converter is based
on the cooling water temperature in the return line from the radiators.
4.16 Alarm Handling: V1
An alarm condition arises if an analogue value exceeds the alarm limits or if a binary alarm
signal is received. The WOIS workstation is used for handling alarms from the generating set
and auxiliary units. Alarms are shown in the alarm list of the WOIS workstation. Analogue
values exceeding the alarm limits are also indicated by a red background colour in the process
displays. All alarms have to be acknowledged by the operator, even if the alarm condition has
been removed. Acknowledged alarms remain in the alarm list until the alarm condition is
removed.
4.17 Safety Functions:
V1Engine start conditions:
Starting the engine is possible only if a number of start conditions are fulfilled, for instance:
Generator breaker is open.
Starting air and control air pressure is high enough.
Lubricating oil inlet pressure is high enough.
HT water outlet temperature is high enough.
If any of the start conditions are not fulfilled, the start command is not accepted.
Automatic shutdown and engine stop:
Highly critical situations activate an immediate shutdown of the engine without first unloading,
for instance:
Emergency stop
Low lubricating oil pressure
High cooling water temperature
Over speed.
The reason for the shutdown is indicated at the WOIS terminal. Less critical situations, for
instance a generator breaker trip, activate a controlled stop of the engine.
Load reduction alarm: Poor operating conditions that do not require an engine stop activate a
load reduction alarm. When this alarm is activated, the operator must reduce the load.
Page | 12
Automatic load reduction: Automatic load reduction (derating) takes place when required by
the ambient conditions.
4.18 Engine Control System:
i. Speed control
ii. Air fuel ratio control
iii. Cylinder balancing control
iv. Knock control
v. Gas pressure control
vi. Ignition control
vii. Safety control
a. Start block
b. Alarm
c. Shutdown
d. Emergency stop
4.18. 1 Speed Control:
a) The desired speed is set from WOIS(550-780rpm)
b) The speed is kept by a PID controller that adjusts the opening
c) Time of the main gas valves
d) Fixed duration at start of the engine
e) The speed PID controller is activated 20 rpm below speed set point
f) Hardwired signals from encoder to all CCU’s
g) Each cylinder sends the engine speed on CAN bus to MCU
h) The MCU calculates average value and sends main gas duration reference on CAN bus to
CCU’s.
4.18. 2 Air Fuel Ratio Control:
a) The Waste gate lets part of the exhaust gases beside the oversized turbochargers
b) A 4-20mA set point is sent by the MCU to the WG I/P-converter which controls the WG
actuator with instrument air
c) A PI controller adjusts the WG so a certain charge air pressure is kept
d) Open loop control- no feedback signal from WG position
e) Alarms when WG cannot keep AFR set point
f) Linear correction for charge air temperature
Page | 13
High charge air temperature--- more pressure
Low charge air temperature--- less pressure
g) Compensation for exhaust gas average temperature
Exhaust gas average temperature too high--- more pressure
Exhaust gas average temperature too low--- less pressure
The engine is operating in the optimum operating point, regardless of changing site ambient
conditions. Exhaust waste gate valve used on high load. Air by-pass valve used on high loads.
Charge air pressure and temperature combined with exhaust gas average temperature
compensation used for waste gate control giving same engine performance regardless of
changing ambient conditions.
4.18. 3 Waste-gate Control:
a) Used on high loads to obtain correct air flow into the cylinder
b) One throttle valve used for both exhaust banks
c) Charge air pressure used as main input parameter
d) Correction to pressure point if exhaust gas average temperature is not within specified
values
4.18. 4 Cylinder Balancing Conditions:
a) The exhaust gas temperature after each cylinder is controlled
b) Main gas duration is adjusted 1% at a time so the reference temperature is kept within a
window of
c) Reference value for each cylinder is average temperature + an offset value (T_Adjust)
d) Measurement + T_Adjust = temperature seen by MCU
Positive T_Adjust→ less gas, temperature down
negative T_Adjust→ more gas, temperature up
4.18. 5 Knock Control:
a) At knock vibration, certain frequency is formed
b) Detected by knock sensors mounted in each cylinder head
c) The piezoelectric knock sensors send a mV signal to the KDU
d) KDU sends the knock value on CAN bus to MCU
4.18. 6 Gas Pressure Control:
a) The pressure set point is sent by MCU to gas regulating unit
b) Analog 4-20mA signal equals 0-1 bar
c) The pressure is adjusted so a certain main gas duration is obtained
Page | 14
d) Main gas duration 0,5ms too long → pressure up
e) Main gas duration 0,5ms too short → pressure down
4.18. 7 Safety Control:
a) Start block:
A. MCU restarted
B. Low lube oil pressure, air pressure & HT water temperature
C. Turning gear engaged
D. Engine speed not zero
E. Power supply failure CCU
b) Alarm:
A. Low control air pressure & start air pressure
B. Low HT & LT water pressure
C. Low lube oil pressure
D. High HT water outlet temperature
E. High cylinder liner temperature
F. High main bearing temperature
G. High exhaust gas temperature
H. Too lean air/fuel ratio
I. High internal temperature CCU
J. Low lube oil level
K. Nominal speed not reached
c) Shutdown :
A. Heavy knock
B. High crankcase pressure
C. Main gas duration max time
D. High load at current speed
E. CAN bus failure CCU
d) Emergency Stop:
A. Over speed from encoder
B. Speed deviation
C. Degassing failure
D. Power supply failure
Page | 15
Chapter-05
Sub-Station & Protection Part
Sub-Station at MnPP
2
5.1 Substation
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. Electric power may flow through several substations between generating
plant and consumer, and its voltage may change in several steps. A substation that has a step-up
transformer increases the voltage while decreasing the current, while a step-down transformer
decreases the voltage while increasing the current for domestic and commercial distribution. The
word substation comes from the days before the distribution system became a grid. The first
substations were connected to only one power station, where the generators were housed, and
were subsidiaries of that power station.
5.2 Switchyard: The area in a substation where outdoor equipments are installed is called switchyard. The
outdoor equipments are connected systematically in a switchyard. In a substation, the
switchyard performs an important role for switching of the incoming & outgoing power. This is
the main workhouse of the station. The control room gets the required data about voltage, current
and fault levels from the switchyard. Systematic and simple design of the switchyard helps in
obtaining reliability of supply without any disturbance.
Fig38: Switchyard view of Maona power plant
3
5.3 Single Line Diagram
In power engineering, a single-line diagram (SLD) is a simplified notation for representing
a three-phase power system. The diagram has its largest application in power flow studies.
Electrical elements such as circuit breakers, transformers, capacitors, bus bars, and conductors
are shown by standardized schematic symbols. Instead of representing each of three phases with
a separate line or terminal, only one conductor is represented. It is a form of block diagram
graphically depicting the paths for power flow between entities of the system. Elements on the
diagram do not represent the physical size or location of the electrical equipment, but it is a
common convention to organize the diagram.
Fig39: Single Line diagram of 33MW MnPP (Drawn by me Using AutoCAD)
Here,
L.A = Lightning Arrestor
C.T =Current Transformer
P.T = Potential transformer
OVCB = Outdoor vacuum Circuit Breaker
PBS
PBS
4
5.4 Equipments of Switchyard Used in Maona Power Plant
The following equipments are generally installed at substation:
Power Transformer
Auxiliary/Station Transformer
Lightening Arrester
Isolator
Potential Transformer (PT)
Current Transformer (CT)
Vacuum circuit breaker (VCB)
Now these types of equipments are discussed in brief.
5.4.1 Power Transformer
Power Transformer transmits the power at high voltage without change in frequency. A
transformer is a stationary device by means of which electric power in one circuit is transformed
into electric power of the same frequency in another circuit.
Fig. 40: Power Transformer at MnPP Switchyard.
5
Alternatively, a transformer is a device that transfers electrical energy one circuit to another
through inductively coupled conductors—the transformer’s coils. A varying current in the
primary winding creates a varying magnetic flux in the transformer’s core and thus a varying
magnetic field through the secondary winding. This varying magnetic field induces a varying
electromotive force (EMF), or “voltage”, in the secondary winding. This effect is called mutual
induction. If a load is connected to the secondary, an electric current will flow in the secondary
winding and electrical energy will be transferred from the primary circuit through the
transformer to the load.
5.4.1.1 Power Transformer Specification
POWER TRANSFORMER
Job Description
20/25 MVA,33/11 KV,3-
phase,50Hz
Vector Group YNd1
Connections Three-Phase
Type of Tap Changer ON-Load Tap Changer
Winding Description HV LV
Terminal Notation A B C N a b
Rated Capacity in MVA
ONAN 20 20
ONAF 25 25
Rated Voltage(in Kv) 33 11
Rated Current(in Ampere)
ONAN : 349.91 1049.73
ONAF : 437.39 1312.16
LV Voltage : 11000 Volts in all Tap Positions
Serial No : 20/25 MVA-14
Year of Manufacture : 2008
6
5.4.1.2 On Load Tap Changer
A tap changer is a connection point selection mechanism along a power transformer winding that
allows a variable number of turns to be selected in discrete steps. A transformer with a variable
turn ratio is produced, enabling stepped voltage regulation of the output.
The tap selection may be made via an automatic or manual tap changer mechanism. The
generation voltage is 11KV and it can be controlled. The rated high voltage is 33kv (that PBS is
taking from the plant).But sometimes due to increasing/decreasing load voltage also changes
consequently.
We cannot control high voltage (33kv) but low voltage (11kv).
We know, turns ratio, TNR
In order to maintain /balance the TNR of transformer we need to change the turn or tap of the
primary side (11kv).This is where Tap changer is used.
Fig 41: Tap Changer Panels with tap position chart
In power generation, tap-changing has to be performed on load so that there is no interruption in power
supply.
7
5.4.2 Auxiliary/Station Transformer
Station Transformer transmits the power at low voltage without change in frequency. These
transformers help to run the internal devices of this Power Plant. This transformer step down
voltage 11kv to 415 V. This low voltage also uses to run the auxiliary system of the Engines.
Fig. 42: Auxiliary Transformer
When Power plant tripped, the power from grid at 33KV comes to Power transformer and
stepped down to 11KV and reaches to 11KV bus bar and hence further stepped down to 415 V
through Auxiliary Transformer and this will help to run the auxiliary system of the plant. And
when plant is on ON mode and provides Power to the grid, same time one line comes from 11
KV bus to the Auxiliary transformer to run the auxiliary system of the plant
8
5.4.2.1 Auxiliary Transformer Specification
Auxiliary Transformer
Rated power : 750 KVA
Standard : BS-171/IEC-76
Class : A
Rated frequency : 50 Hz
Type of cooling :ONAN
Ambient Temperature : 40 deg C
Insulation level : LI 75 AC28
Rated no load voltage : HT-11000/LT-415 Volts
Rated current : HT-39.36/LT-1043.43 Amp
Vector group :DYN11
Total weight :2800 kg
oil weight : 850 kg
Winding temp rise : 65 deg C
Year of Manufacture : 2008
5.4.3 Lightning Arrester
Lightning arresters are protective devices used to divert the surge voltage due to lightning. It is
used in electrical power system to protect the insulation on the system from the damaging effect
of lightning. In times of lightening, it conducts the high voltage surges on the power system to
the ground.
Fig 43: Lightning Arrester
9
5.4.3.1 Working Principle of Lightning Arrester
The figure shows a basic form of a surge arrester. It consists of a spark gap in series with a non-
linear resistor. One end of the diverter is connected to the terminal of the equipment to be
protected and the other end is effectively grounded. The length of the gas is so adjusted that
normal line voltage is not enough to cause an arc across the gap but a dangerously high voltage
will break down the air insulation and form an arc.
The property of the non-linear resistor is that its resistance decreases as the voltage/current
increases and vice-versa. Power circuit
Spark gap
Non-linear Resistance
Fig 44: Working Principle of Lightning Arrester
5.4.3.2 Lighting Arrester Specification used in Maona Plant:
A. Type : Y10W5-126/315Kv (proclaim bushing type)
B. Rated voltage : 126kV
C. Rated current : 50Hz
D. Rated discharging current : 10kA
E. Rated discharging current : 10kA =<3015kV (peak)
F. Standard discharging current : 1.0kA (peak)
G. Continuous operating voltage : 100.8kV
H. Leave factory data : 1050
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5.4.4 Isolator
Isolator is used to disconnect any section or unit from all live parts of a substation. It is normally
a knife switch designed to open a circuit under no load. The main purpose of using isolator is to
isolate one portion of a circuit from the other. It should never be opened until the circuit breaker
in the same circuit has been opened and should always be closed before the circuit breaker is
closed. Isolators are usually placed on either side of the circuit breakers for safety during
maintenance and troubleshooting.
Based on the position of the isolator in the system, it can be classified in three ways:
1. Line Isolator : Isolates an incoming or outgoing line from the bus
2. Bus Isolator : Isolates two section of the bus
3. Transformer Isolator : Isolates the transformer from the bus or the lines
Fig 45: Isolator
5.4.4.1 Isolator Specification used in Maona Power Plant
a. Type : GW4-145TH
/1250(earthlings switch in both sides)
b. Rated voltage : 145kV
c. Rated current : 1250A
d. Rated frequency : 50HZ
e. Short time current/peak current : 40kA for 4s/80kA (peak)
f. Power frequency withstand voltage: 275kV
g. Operating mechanism : Manual derived CS19 for earthling switch
h. Circuit resistance : =<150µΩ
i. Earthling loop resistance :=< 290µΩ
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5.4.5 Potential Transformer (PT)
Potential transformer (PT) is used for voltage measurement and power system protection. They
are widely used in the power system for over voltage, under voltage, directional and distance
protection. The primary of the potential transformer is connected to the power circuit whose
voltage has to be measured. The secondary output gives a lower voltage which is very easy to
measure by the common voltmeter. The secondary winding turns of PT is designed to produce
110V irrespective of the primary voltage rating. For example, if a voltage of 33 kV is to be
measured, the PT will have a turns ratio of 33000/110 = 300:1. Fig 39 shows the voltage
measurement by PT. The number of primary turns in a PT is much greater than the number of
secondary turns.
Fig 46: Potential Transformer
5.4.5.1 Potential Transformer Specification of Maona Power Plant
a. Type : JDCF-145THW2 (electromagnetism, oil immersed)
b. Serial number : 04J02031-1
c. Device maximum operating voltage : 145kV
d. Rated voltage : 132/√3kV/100/√3V/100V
e. Level : 0.5/3P
f. Rated output : 200/75VA
g. Rated frequency : 50HZ
h. Maximum output : 2000VA
i. Technique standard : IEC60044-2:1997
j. Manufacturer : Dalian NO 1 instrument transformer factory
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5.4.6 Current Transformer (CT)
A current transformer (CT) is used for measurement of electric current. When current in a circuit
is too high to be measured directly by measuring instruments, a current transformer produces a
reduced current accurately proportional to the current in the circuit, which can be conveniently
connected to measuring and recording instruments. Current Transformer steps down the current
from high value to a low value that can be measured by a measuring instrument or fed to a
protective relay for system protection and monitoring. CTs are used extensively for measuring
current and monitoring the operation of the power system.
Fig 47: Current Transformer
5.4.6.1 Current Transformer Specification used in Maona Power Plant
a. Type :LCWB-145THW2(outdoor, oil immersed type )
b. Serial number :04L01024-1
c. Device maximum operating voltage :145kv
d. Rated voltage :132kV
e. Rated current :1000/1A
f. Level group :5P20/5P20/5P20/5P20/0.5/0.2S
g. Rated output :60/60/60/60/30/30VA
h. Power factor :0.8
i. Rated frequency :50Hz
j. Technique standard :IEC60044-1:1996
k. Manufacturer :Dalian NO 1 instrument transformer factory
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5.4.7 Outdoor Vacuum Circuit Breaker (VCB)
VCB are being employed for outdoor applications ranging from 22kv to 66kv. For a country like
Bangladesh where distances are quite large and accessibility to remote areas is difficult, the
installation of such outdoor VCB is used. In Maona power plant there are five outdoor Vacuum
Circuit breakers. Out of this five VCB 2 are in CAT Substation (1 is for transformer breaker and
other is for line breaker) and other three are in WARTSILA substation (2 for TX, the other for
line breaker)
5.4.7.1 Specification of Outdoor VCB
Rated System Voltage 33KV
Rated Maximum Voltage 36KV
Current 600A
Making Current 66kAp
Auxiliary Supply 220V (AC)
Frequency 50Hz
1 min Power Frequency Withstand (KV rms) 70
System Breaking Current (KA rms) 264
Closing Coil 110 VDC
Tripping Coil 110 VDC
Fig 48: Outdoor Vacuum Circuit Breaker
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5.4.7.2 Components of Vacuum Circuit Breaker
VCB Column Closing Spring
Vacuum Interrupter Tripping Spring
Fixed Contact Auxiliary contact
Moving Contact Liver
Push Rod Mechanical Push Button
Closing Coil Electrical Push Button
Tripping Coil Limit Switch
5.5 Earth switch: It is used to bypass the extra stored charge in the line although line is inactive by the main
isolator into the earth by making a short circuit path from line to ground for extra safety purpose.
When line is inactive then earth switch must be closed on the other hand when line is active then
earth switch must be opened.
5.6 Bus coupler: It is normally open. When any fault is occurred or maintenance is needed in one bus then to
transmit whole power through another bus at that time bus coupler is activated by making close
contact.
5.7 Protections of Power/Auxiliary Transformer are as follows: a) Differential protection
b) Buchholz Relay protection
c) Protection Winding and Oil Temperature Protection
d) Restricted Earth Fault Protection
e) PRV Protection
f) Oil surge Protection
15
5.8 Medium Voltage (MV) or 11KV Protection at MV Room In Summit Power Ltd, Maona Power Plant considers 11KV as medium voltage. The generating
voltage is 11KV. The generated power first comes at Medium Voltage Room (MV Room),
where different protection system for the medium voltage is arranged. Power from alternator
comes to the MV room through underground cable. Protection against 11KV fault and for the
controlling purpose MV room components are used.
5.8.1 Single Line Diagram of MV
Fig 49: Single Line Diagram of MV
5.8.2 Breaker Used for Medium Voltage (MV) Protection
1. Sulphur Hexafluoride (SF6) Circuit Breaker
Beside the SF6 Circuit Breaker Neutral Grounding Resistance (NGR) is used as protective
equipment at MV Room.
G2 G3
11 KV BUS
Station Transformer
11KV Breaker
NGR
G. Breaker
G4
11 KV BUS
11/0.415KV
Transformer
HT Breaker
G1
G. Breaker G. Breaker
NGR
Power transformer
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5.8.3 Components of MV Room
The components of MV room are below:
Station Transformer Breaker-1 (Incoming) (SF6)
Station Transformer Breaker-2 (Incoming) (SF6)
Generator Breaker-1 (SF6)
Generator Breaker-2 (SF6)
Generator Breaker-3 (SF6)
Generator Breaker-4 (SF6)
11KV Outgoing Breaker-1 (SF6)
11KV Outgoing Breaker-2 (SF6)
Neutral Grounding Resistance
After completing the required condition for synchronization, Generator Breaker is closed
automatically. Then synchronization takes place.
5.8.4 Sulphur Hexafluoride (SF6) Circuit Breaker
In this circuit breaker, Sulphur Hexafluoride (SF6) gas is used as the arc quenching medium. The
SF6 gas is an electro negative gas and has a strong tendency to absorb free electrons. The
contacts of the breaker are opened in a high pressure flow of SF6 gas and an arc is struck
between them. The conducting free electrons in the arc are rapidly captured by the gas to form
relatively immobile negative ions. This loss of conducting electrons in the arc quickly builds up
enough insulation strength to extinguish the arc. The SF6 circuit breakers are very effective for
high power and high voltage service.
5.8.4.1 Construction of SF6 Circuit Breaker
SF6 circuit breaker consists of fixed and moving contacts enclosed in a chamber called arc
interruption chamber containing SF6 gas. This chamber is connected to SF6 gas reservoir. When
the contacts of breaker are opened the valve mechanism permits a high pressure SF6 gas from the
reservoir to flow towards the arc interruption chamber. The fixed contact is a hollow cylindrical
current carrying contact fitted with an arc horn.
17
The moving contact is also a hollow cylinder with rectangular holes in the sides to permit the SF6
gas to let out through these holes after flowing along and across the arc The tips of fixed contact,
moving contact and arcing horn are coated with copper-tungsten arc resistant material. Since SF6
gas is costly, its reconditioned and reclaimed by a suitable auxiliary system after each operation
of the breaker.
5.8.4.2 Specification of Sulphur Hexafluoride (SF6) Circuit Breaker
Circuit Breaker Gas SF6
SF6 Reactive Pressure at 20ºC 2.3bar
Voltage 12KV
Breaking Capacity 25KA
Making Capacity 63KA
Short Time Current 25KA-1s
Mass of SF6 480g
Current In 630A
Impulse Voltage 75KVp
Mass 170kg
Frequency 50Hz.
5.8.4.3 Advantages of SF6 Circuit Breaker
Due to the superior arc quenching property of SF6 such circuit breakers have very short
arcing time.
Since the dielectric strength of SF6 gas is 2 to 3 times that of air, such breakers can
interrupt much larger currents.
The SF6 circuit breaker gives noiseless operation due to its closed gas circuit and no
exhaust to atmosphere unlike the air blast circuit breaker.
The closed gas enclosure keeps the interior dry so that there is no moisture problem.
There is no risk of fire in such breakers because SF6 gas is non-inflammable.
5.9 Neutral Grounding Resistance (NGR)
Neutral grounding resistance (NGR) are used to restrict the earth fault current during fault
condition below a certain value. This is done for high voltage generators because due to high
voltage & low winding resistance fault current is very high and the windings are not designed to
carry such a large current so it is the place where NGR comes to play. NGR used in 11KV
generating station is to limit the fault current within the specified limit. Generator is connected
with grid (Synchronized Condition) heavy fault current may occurred in line, that fault current
may damage winding insulation that is why NGR is used to protect the generator from heavy
fault current.
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5.10 Low Voltage Protection and Control at Switchgear Room
The generation power from the engine room comes to the switchgear room through underground
cable. All protection system against low voltage is arranged here in LV room.
5.10.1 Components of LV Room
Air Break Circuit Breaker
Molded Case Circuit Breaker (MCCB)
Miniature Circuit Breaker (MCB)
Change Over Switch
DC Distribution Box
Frequency Converter
Battery Charger- 110V
Battery Charger- 24V
Magnetic Contactor
Fuse
5.10.2 Air Break Circuit Breaker
These circuit breakers employ high resistance interruption principle. The arc is rapidly
lengthened by means of the arc runners and arc chutes and the resistance of the arc is increased
by cooling, lengthening and splitting the arc. The arc resistance increases to such an extent that
the voltage drop across the arc becomes more than the supply voltage and the arc extinguished.
Air breaker circuit breakers are used in DC circuits and AC circuit upto 12 kV. Magnetic field is
utilized for lengthening the arc in high voltage air break circuit breaker. The arc resistance is
increased to such an extent that the system voltage cannot maintain the arc and the arc get
extinguished.
Fig 50: Air Break Circuit Breaker
19
The operating mechanisms are generally operating spring. The closing force is obtained from the
following means:
a. Solenoid
b. Spring charged manually or by motor
The solenoid mechanisms drive power from battery supply or rectifiers. The solenoid energized
by the direct current gives the necessary force for the closing of the circuit breaker.
The springs used for closing operation can be charged either manually or by motor driven gears.
At the time of closing operation the energy stored in the spring is released by unlatching of the
spring and is utilized in closing of the circuit breaker.
5.10.3 MCCB and MCB Breaker
MCCB is a mechanical device to be used to connect and disconnect the circuit in normal and
abnormal. It is commonly used in the distribution panel. Rated current up to 2500 A. It works to
break the circuit caused by a short circuit and over current. Its operating system is based on the
temperature resulting from the current flow in the core conductor. When the current through the
core conductor is very high, then high temperatures will be produced. Two metals in the core
conductors will react and will enable the system to determine the mechanism of the circuit. This
system is active with the interval of time and can be adjusted to suit the circuit.
MCB (Miniature Circuit Breaker)- It’s rated current not more than 100 A. Trip
characteristics normally not adjustable. Thermal or thermal-magnetic operation. Breakers
illustrated above are in this category.
Fig 51: MCCB
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5.10.4 Magnetic Contactors
As the name suggest, the magnetic contactor works by means of a magnet. Not the ordinary
magnets we see but an electro-magnet. An electro magnet is something that can become a
magnet when it is energized with current. When current is switch off, it becomes an ordinary
piece of metal with no magnetic properties. The magnetic contactor is a switch that is activated
by the magnet. When current passes through the coil, it energizes it and the piece of metal
becomes a magnet which in turn attracts the contacts point and pulls the contacts together,
allowing current to pass through.
Fig 52: Magnetic Contactors
4.10.5 Fuse
In electronics and electrical engineering a fuse (from the Latin "fuses" meaning to melt) is a type
of sacrificial over current protection device. It is essential component is a metal wire or strip that
melts when too much current flows, which interrupts the circuit in which it is connected. Short
circuit, overload or device failure is often the reason for excessive current. A fuse interrupts
excessive current (blows) so that further damage by overheating or fire is prevented. Over
current protection devices are essential in electrical systems to limit threats to human life and
property damage. Fuses are selected to allow passage of normal current and of excessive current
only for short periods. In general, there are two categories of fuses viz.
1) Low voltage fuses. 2) High voltage fuses.
5.10.6 Relay
The relays detect the abnormal conditions in the electrical circuits by constantly measuring the
electrical quantities which are different under normal and fault conditions. The electrical
quantities which may change under fault conditions are voltage, current, frequency and phase
angle. A protective relay is a device that detects the fault and initiates the operation of the circuit
breaker to isolate the defective element from the rest of the system.
21
Fig 53: Relay With Trip Circuit.
Having detected the fault, the relay operates to close the trip circuit of the breaker. This results in
the opening of the breaker and disconnection of the faulty circuit.
Why Maona Power Plant Uses Relay
Protective relays connected in a particular fashion for giving protection against certain abnormal
condition. According to the abnormal condition against which the relays are uses as follow:
Over-current Protection
Earth Fault Protection
Reverse Power Protection
Under Voltage Protection (UVP)
Under Frequency Protection (UFP)
According to based on principle of operation relays are uses as follow:
Differential Protection
Distance Protection
5.11 Transformer/Alternator Differential Protection
A differential relay is a device that operates when the vector difference of two of more similar
electrical quantities (I1& I2) exceeds a predetermined valve. It compares the current entering a
section of a system with the current leaving the system. For differential protection, two identical
CTs having same turn’s ratio are placed on either end of the section to be protected. The
operating relay coil is connected across the CT’s secondary circuit. Under normal operation, the
incoming and outgoing currents of the section are equal and therefore, CT’s secondary currents
are equal. As a result, no resultant current flows through the relay coil, but as soon as a fault
occurs within the protection zone, the differential current through the relay coil is no longer zero.
A differential current (that is, the difference between incoming and outgoing current) is fed to the
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relay operating coil. If this differential current is equal to or greater than a pre-set value, the relay
will operate to close the trip circuit that finally opens the circuit breaker. Thus the faulty section
is isolated from the healthy system.
Transformer/ Generator
CT CT CB
I1 I2
IF
I1 I2
I2-I1 Relay Battery
I1 I2 Trip circuit
Fig 54: Differential Relay Operation Mechanism
5.12 Distance/Impedance Relay Protection Distance relay is a protective device in which the operation is governed by the ratio of the line
voltage to line current. In an impedance relay, the torque produced by a current element is
opposed by the torque produced by a voltage element. The relay will operate when the ratio V/I
is less than a pre-determined value. Fig-13 shows the operation principle of a distance relay. The
voltage element of the relay is excited by a potential transformer (PT) and current element is
excited by a current transformer (CT). The portion AB of the line is the protected zone. Under
normal condition, the impedance of the protected zone is ZL. The relay is so designed that it
closes its contacts whenever impedance of the protected zone falls below a pre-determined value.
Generator CB A CB CT F1 CB B CB F2
Distance Relay IF IF
Fig 55: Operation Principle of Distance/Impedance Relay
Now when a fault occurs at point F1 in the protected zone, the impedance Z= V/I between the
point the relay is placed and the point of fault will be less than ZL and the relay will operate. If
the fault occurs beyond the protected zone (say at point F2) the impedance Z will be greater than
ZL and the relay will not operate.
23
5.13 Buchholz Relay
Buchholz relay is a gas- actuated relay installed in oil-immersed transformers for protection
against all kind of faults. It is used to gives an alarm in case of slow developing faults or
incipient faults in the transformer and to disconnect the transformer from the supply in the event
of severe internal faults. It is installed in the pipe between the conservator and main tank. This
relay is used in oil-immersed transformers of rating above 750 KVA. It consists of a domed
vessel placed in the pipe between the conservator and main tank of the transformer. The device
has two elements. The upper element consists of a mercury type switch attached to a float. The
lower element contains a mercury switch mounted on a hinged type flap located on the direct
path of flow of oil from the transformer to the conservator. The upper element closes an alarm
circuit during slow developing faults whereas the lower element is arranged to trip the circuit
breaker in case of severe internal faults. In case of slow developing faults within the transformer,
the heat due to the fault causes decomposition of some transformer oil in the main tank. The
products of decomposition mainly contain 70 % of hydrogen gas. The hydrogen gas being light
tries to go into the conservator and in the process gets trapped in the upper part of the relay
chamber. When a predetermined amount of gas gets accumulated, it exerts sufficient pressure on
the float to cause it to tilt and close the contacts of mercury switch attached to it. This completes
the alarm circuit to sound an alarm. If serious fault occur in the transformer, an enormous
amount of gas is generated in the main tank. The oil in the main tank rushes towards the
conservator via the Buchholz relay and in doing so it tilts the flap to close the contacts of
mercury switch. This completes the trip circuit to open the circuit breaker controlling the
transformer.
Fig 56: Buchholz Relay
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5.14 MV (11 kV) Bus-bar Protection:
The Bus-bar in the generating station and Sub-stations forms important link between the
incoming and outgoing circuits. If a fault occurs on a bus-bar, considerable damage and
disruption of supply will occur unless some form of quick acting automatic protection is
provided to isolate the faulty bus-bar. The bus-bar zone, for the purpose of protection, includes
not only the bus-bar themselves but also the isolating switches, circuit breakers and the
associated connection. In the event of fault on any section of the bus-bar, all the circuit
equipments connected to that section must be tripped out to give complete isolation.
The two most commonly used schemes for bus-bar protection are:
Differential Protection:
The basic method for bus-bar protection is the differential scheme in which current entering
and leaving the bus are totalized. During normal load connection, the sum of these currents
is equal to zero. When a fault occurs, the fault current upsets the balance and produces a
differential current to operate relay.
Fault bus protection:
It is possible to design a station so that the faults that develop are mostly earth faults.
5.15-33 kV Line Protection
1. Under Voltage, under frequency protection
2. Over Voltage, over frequency protection
3. Distance Protection Relay
4. Directional Earth fault Relay
5. Over current IDMT Relay
6. Earth Fault IDMT Relay
7. Phase sequence Relay
8. Power Swing Detection Relay
Chapter: 06
Troubleshooting & Supplementary
2
6.1Maintenance Tools
a) Multi-meter (AVO Meter) b) Process Calibrator
c) Insulation Resistance Tester d) Star Screwdriver
e) Screwdriver f) Linesman Pliers
g) Hammer h) Channel Lock Pliers
i) Wire Strippers j) Pliers
k) Side Cutter Pliers l) Flashlight
m) Allen Wrench Set (Hex Set) n) Utility Knife
o) Wire Crimpers p) Hot Gun
q) Spanner r) Adjustable Wrench
6.2 Personal Protective Equipments Safety Goggles High temperature Hand Gloves
Ear Muff Dust mask
Helmet Dust Mask Cartridge
Safety Belt Face shield
High Voltage hand Gloves Gum boot
Chemical Hand Gloves
Fig 57: Face Shield, Helmet, Ear Muff, Hand Gloves, First Aid Box
3
6.3 Troubleshooting Activities and Observation of Maintenance Methods:
Alarm: Gas Pressure is not sufficient for Fed to Engine.
Alarm indication: Engine is in an emergency condition.
Symptoms: If this alarm comes then engine will automatically shutdown.
Solution: Plant Shift Engineer Contact with Titas Gas Transmission Authority of Dhanua,
Maona and they Send and Resource Person to check all parameters and they fixed this problem.
Fig 58: Checking all parameters regarding gas fuel in GAS Regulating Meter Station (RMS).
Alarm: Emergency Stop Safety Wire MCM700-1. NSZ805
Alarm indication: Engine is in an emergency condition.
Symptoms: If this alarm comes then engine will automatically shutdown.
Solution: We have changed the Cylinder Control Module-10 (CCM-10).
Fig 59: CCM-10
4
Alarm: Sparking Fail of a Cylinder
Probable Cause: sparking Plug may damage or connection problem to Source.
Solution: Plant Maintenance Engineer Check the problem and take necessary steps to fix it.
Fig 60: Checking Spark Plug and Connection
Problem: Cylinder Head not working properly
Probable Cause: Exhaust temperature might be so high and it damages some parts of it.
Solution: Plant Maintenance Engineer Check the problem and replace the Cylinder Head.
Fig 61: Replacement of Cylinder head of wartsila gas engine
5
Problem: Radiator Motor not running.
Probable Cause: Winding short circuit or burn out, bearing jam, problem in switch and in
magnetic contactor.
Solution: First we have tried to ensure whether the winding is short circuited or not. It ensured
by “Megger” test. Sometimes we found the winding short circuit and sent the motor to the
workshop for rewinding. If the winding is okay then the problem could be in bearing. Sometimes
we found that the bearing is jam and we changed the bearing. Sometimes we showed that
winding and bearing is okay but the motor was not running, then we checked the switch. If the
problem was there then we changed the switch.
Fig 62: Bearing Change of Radiator Motor
Alarm: Radiator Control Panel’s Relay problem
Probable Cause: Problem in Alarm circuit, relay and fault signal.
Solution: We checked the relay and alarm circuit. We found the problem in a relay. Then we
changed the relay.
Fig 63: Checking Radiator Control Panel
6
Supplementary Part
7
6.4 Limitations
During the period of my internship at MnPP and from my experience it is clear to me that ---
They do not have sufficient manpower especially in maintenance section. Sometimes
wartsila engine is suddenly tripped and it takes 2 or 3 days.
The exhaust gas coming out through the chimney has a temperature of 540ºc. The heat
that is being lost to the atmosphere also pollutes the environment and causes global
warming.
Due to low gas supply in Bangladesh, the engines of this plant cannot give full load as
they can produce.
During my internship a good number of breakdowns have already occurred in the plant.
The time of the replacement of any fault equipment is very high.
The distribution line connects only with PBS line. When the 33 KV line feeder of PBS
tripped then the whole plant will be shut down and under ingenerated condition.
No more standby engine for back up full capacity, when regular running engine has
scheduled or unscheduled maintenance
6.5 Recommendation
On the basis of above limitations of the plant, the following recommendations are suggested.
MnPP should increase the manpower especially in maintenance section for smooth
operation of the plant.
Necessary measures should be taken for extracting the heat energy from the exhaust gas
and recycle it for any other purpose and save the environment from global warming.
The plant incoming gas line from Titas which is 4 bars and sometimes it become less than
3 bars. It should be raised to 12 bars for getting high pressure.
Replacement of faulty and frequent failing equipments should be done with equipment of
better performance and quality.
It should keep standby engine for back up full capacity, when regular running engine has
scheduled or unscheduled maintenance.
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6.6 Conclusion
Summit Power Limited, Maona Power Plant is one of the very few private power plants in
Bangladesh. Considering the current electricity crisis in Bangladesh it is very much important
that private investment in power sector takes place at a rapid rate. In this regard the government
has a lot to do to ensure smooth running of the power sector in private sector.
My experience during the short time stay at Summit Power Plant, Maona has not only increased
my depth of knowledge, but also has given me the feeling of challenges faced in engineering
profession. Thanks to Summit Power Limited for providing me with the opportunity to conduct
my internship in their plant. I am also thankful to all the engineers and employs of Summit
Power for their heartiest support.
This report contains the power generation system, electrical protection of different parts of
electrical machines and apparatus used in MnPP Power Plant, Summit Power Limited. During
three months of my practicum session, I have learned practical knowledge about how to generate
power, how to supply power in main grid, what was the purpose of transformer, how to improve
power factor and so on. I am also elucidated the various ways of protecting electric machines
against various electrical faults.
9
6.7 Appendix
6.7.1 Some Definitions
Ampere (amp): A unit used to define the rate of flow of electricity (current) in a circuit; units
are one coulomb (6.28 x 1018
electronics) per second.
Auxiliary Transformer: Local distribution transformer used for the local electrical supply of
the diesel power plant.
Bus bar: The metal (often copper) bar system which is the distribution media for the 3 phase
high voltage system in the power plant.
Circuit breaker: When looking at the engine from the driving end the shaft rotates counter-
clockwise.
Conductor: A wire or cable for carrying current.
Current Transformer: In electrical engineering, a current transformer (CT) is used for
measurement of electric currents. Current transformers are also known as instrument
transformers.
Exciter Voltage: The voltage required to cause exciter current to flow through a field winding.
Exciter Current: The field current required producing rated voltage at rated load and frequency.
Feeder: The temperature to which oil must be heated in order to give sufficient vapor to form a
flammable mixture with air under the conditions of the test. The vapor will ignite but will not
support combustion.
Frequency: Number of cycles over a specified time period over which an event occurs.
Generator: A device that produces electric current, usually by rotating a conductor in a
magnetic field, thereby generating current through electromagnetic induction.
Ground: A connection, either intentional or accidental, between an electric and the earth or
some conducting body
Impedance: The total opposition to electrical flow (resistive plus reactive).
Isolation: The reduction of the capacity of a system to respond to an external force by use of
resilient isolating materials.
Isolator: A passive attenuator in which the loss in one direction is much greater than that in the
opposite direction, a ferrite isolator for waveguides is an example.
Kilowatt Hour (kWh): 1000 watt hours. Kilovolt amperes (kva): 1000 volt amps.
Lightning Surge: A transient disturbance in an electric circuit due to lightning.
10
Maximum Power Rating: The maximum power in watts that a device can safely handle.
Open Circuit: The lack of electrical contact in any part of the measuring circuit.
Phase Difference: The time expressed in degrees between the same reference point on two
periodic waveforms.
Potential Transformer: An instrument transformer whose primary winding is connected in
parallel with a circuit in which the voltage is to be measured or controlled. It is also known as
potential transformer (PT).
Power Supply: A separate unit or part of a circuit that supplies power to the rest of the circuit or
to a system.
Relay: An electromechanical device that completes or interrupts a circuit by physically moving
electrical contacts into contact with each other.
Resistance: The resistance to the flow of electric current measured in ohms (1/2) for a
conductor. Resistance is function of diameter, resistivity (an intrinsic property of the material)
and length.
Rotor: A rotor is a rotating body whose journals are supported by bearings.
Reactive Power: The part of the generated power in an electrical network which cannot be used
at the consumer’s appliances (cf. active power).
Rectifier: A device for changing alternating current into direct current or unidirectional current.
Stator: The portion of an electrical machine which contains the stationary parts of the magnetic
circuit and their windings.
Synchronization: Refer to the way in which a power generating source is connected to another
at the exact point in time when they both have the same frequency and period.
Thermal Conductivity: The property of a material to conduct heat in the form of thermal
energy.
Transformer: A device used to transfer electrical energy from one circuit to another. With an
alternating current, a transformer will either raise or lower the voltage
Volt: The (electrical) potential difference between two points in a circuit.
Voltage: An electrical potential which can be measured in volts.
Voltmeter: An instrument used to measure voltage.
Voltage Drop: The difference in voltage at no-load and full-load expressed as a percent of the
full-load value
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Voltage Regulation: The difference between maximum and minimum steady state voltage
divided by the nominal voltage expressed as a percent of the nominal voltage.
Voltage Regulator: A device which maintains the voltage output of a generator by other
electrical equipment.
6.7.2 Acronyms
A
AC Alternating Current
AVR Automatic Voltage Regulator
C
CCM Cylinder Control Module
D
DC Direct Current
E
EMF Electromotive force.
H
HRC High Rupturing Capacitor
Hz Hertz (cycles per second)
HT High Temperature (cooling water circuit)
K
KHz Kilo Hertz (1000 cycles per second)
KVA Kilo Volt Amperes
KWH Kilo Watt Hours
L
LT Low Temperature (cooling water circuit).
P
PIV Peak Inverse Voltage
PLC Programmable Logic Controller
PCB Printed Circuit Board.
R
RPM Revolutions Per Minute.
S
SF6 Sulfur Hexa Fluoride Gas
V
VCB Vacuum Circuit Breaker
W
WECS Wartsila Engine Control System.
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6.7.3 Elaboration:
MCM Main Control Module
WECS Wartsila Engine Control System
CIB Cabling Interface Boxes
CCM Cylinder Control Module
WCD Wartsila Coil Driver
ESM Engine Safety Module
PCV Pressure Control Valve
WOIS Wartsila operator Information system
WISE Wartsila Information System and Environment
AVR Automatic Voltage Regulator
CRP Control and Relay Panel
RTCC Remote Tap Changer Control
LV Low Voltage
HV High Voltage
MV Medium Voltage
ACB Air Circuit Breaker
RMS Regulating and Metering Station
MCB Miniature Circuit Breaker
MCCB Molded Case Circuit Breaker
NGR Neutral Grounding Resistor
CT Current Transformers
PT Potential Transformers
VCB Vacuum Circuit Breaker
HT High Temperature
LT Low Temperature
NTC Negative temperature coefficient
CAN Communication Area network
PLC Programmable Logic Controller
P-MOD Power Module
C-MOD Communication Module
GRU Gas Regulating Unit
TDC Top Dead Center
BDC Bottom Dead Center
PID Proportional plus Integrator plus Derivative
CCU Cylinder Control Unit
MCU Main Control Unit
WG Waste Gate
RMS Regulating and Metering Station
RTCC Remote Tap Changer Control
OLTC On Load Tap Changer
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SF6 Sulfur Hexafluoride
MVA Mega Volt Ampere
ONAN Oil natural Air natural
ONAF Oil natural Air force
LAN local area network
PCC Pre-combustion chamber
MCC Main- combustion chamber
6.7.4 Annexure –Photograph during Practicum Sessions:
14
15
6.7.4.1 Annexure-Some diagram of Wartsila Engine
8. Start/Stop Sequence:
Engine Ready For
Start
Start Preparation
Starting
Idle Running
Synchronizing
Loading
Normal Operation
Unloading
Shutdown, Waiting
For Reset
Engine Stopped
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6.8 References
Company Profile: www.summitpower.org
Company Relevant Information: www.summitcentre.com
Excitation:
http://www2.emersonprocess.com/siteadmincenter/PM%20Power%20and%20Water%20
Documents/PWS_005075.pdf
Generation Details : Plant manual and Wartsila engine manual and tutorials.
Synchronization: http://electriciantraining.tpub.com/14177/css/14177_78.htm
NGR: http://www.allinterview.com/showanswers/161958.html
VCB: http://www.electrical4u.com/vacuum-circuit-breaker-or-vcb-and-vacuum-
interrupter/
Transformer: http://www.electrical4u.com/what-is-transformer-definition-working-
principle-of-transformer/
Air Break Circuit Breaker:
http://www.oocities.org/hemant_thermal/airbreakcircuitbreaker.htm
The End
