Tarining Report on Siemens

Prepared by:-
RATHOD NIKUNJSINH D.
From:-
ELECTRICAL ENGINNERING
(VISHWAKARMA GOVERNMENT ENGINEERING COLLEGE,
CHANDKHEDA)

Siemens Ltd., Maneja V.G.E.C., Chandkheda
ELECTRICAL ENGG. (N.$.) Page 2
INDEX
1.Preface_____________________________________________
2.Abstract___________________________________________
3. History of Siemens________________________________
4. Siemens Business Segments_____________________
5. Manufacturing Process in Siemens, Maneja____
6. Industrial Training Report_______________________
1) Introduction of Energy Available in Nature……………………….
2) Sensors & Transducers…………………………………………………….
I. pH Meter…………………………………………………………………………….
II. Hydrogen Sensors……………………………………………………………….
III. Temperature Detecting Transducers……………………………………
i. Resistance Temperature Detector (RTD)…………………….
ii. Thermocouple……………………………………………………………
iii. Pyrometer…………………………………………………………………
IV. Flow Sensor…………………………………………………………………………….
i. Electro Magnetic Flow meter……………………………………
V. Pressure…………………………………………………………………………………
ii. Pressure Gauge………………………………………………………….
VI. Proximity Sensors……………………………………………………………………
3) Pumps……………………………………………………………………………
1. Positive-Displacement Pump…………………………
i. Reciprocating Pump…………………………………………………...
2. Centrifugal Pump………………………………………………………………..
3. Cavitation…………………………………………………………………………...
4). Turbine………………………………………………………………………

I. Compounding of Turbines…………………………………………………
i. Pressure Compounding……………………………………………..
ii. Velocity Compounding……………………………………………….
iii. Pressure-Velocity Compounding………………………………..
iv. Reaction Compounding……………………………………………..
v. Siemens SST Turbine…………………………………………………
vi. SST-300…………………………………………………………………….
vii. SST-600……………………………………………………………………
5). Thermal Power Plant………………………………………………….
i. Introductory Overview………………………………………………
ii. Diagram of a typical coal-fired thermal power station…
iii. Principal……………………………………………………………………
iv. Components of Coal Fired Thermal Power Station………
6). Electrical Substation…………………………………………………...
I. Classification of Substations……………………………………….
II. Equipments in Substations…………………………………………
III. Gas Insulated Substation……………………………………………
i. Components of Gas Insulated Substations………….
ii. Advantages of GIS……………………………………………..
iii. Disadvantages of GIS…………………………………………
7). Alternator…………………………………………………………………..
I. General Structure of a generator capability………
II. Cylindrical Rotor……………………………………………..
III. Brushless alternators………………………………………
8). Synchronization of Alternator to Infinite Bus-bar…………
I. Equality of Voltage…………………………………………
II. Equality of Frequency……………………………………
III. Phase Sequence……………………………………………….
IV. Phase Difference Angle (Phase Displacement)…..
9). Switch gear & Protection……………………………………………

10.) Protection of Alternator………………………………………………
I. Alternator Faults…………………………………………….
A. Stator Winding Faults……………………………
B. Field Winding or Rotor Circuit Faults………
C. Normal Operating Conditions………………….
II. Protection Provide to Alternators……………………
III. Automatic Field Suppression and use of Neutral
Circuit Breaker……………………………………………….

PREFACE
It gives me great pleasure to present this Report to the new trainee. My
Report Gives you more visualization and more Information about Turbines,
Alternators and It’s Auxiliaries. Some content is not given in details. There are
Illustrative Figures is given into this Report so you can easily Grasp.
I am Thankful to Malhar Thakar Sir and Jainil Bhagat Sir
(Mechanical Engineering), thank you sir for sharing information and
Knowledge regarding Turbine and It’s Auxiliary System.
I am also Thankful to Satyam Dave Sir and Ravi Patel Sir (Electrical
Engineering), thank you sir for sharing Information and Knowledge regarding
Alternator and It’s Protection System.
I am very very Thankful to Snehal Patel Sir (Design Depart.-SIEMENS).
Thank you sir for arranging this Training sessions, giving Opportunity to
improve our skill and updated with today’s World Class Technology and giving
us Confidence.
And thank you to all my Friends (Traineemates).
Hope, this Report will be found useful to the students in their Study.
August, 2014 -Rathod Nikunjsinh D.
Ahmadabad

Abstract
The Purpose of this report to give some more information about this
Company. I have include the Illustrative Description of Lectures and Seminar
regarding Sensors, Transducers, Turbines, Thermal Power Station, Condenser,
Pump and some General aspects of Steam Power Plant.
Then, I have include 66/11kV Air Insulated Substation and Gas Insulated
Substation(66kV). In this Substation we have visited 66/11kV Crompton
Greaves Transformer, Microcontroller Relay, SCADA interface with the whole
Substation, 11 kV Indoor Switch Gears, Capacitor Bank for power factor
Correction, 11/.43kV Transformers and Two Diesel-Generator(DG) Sets of
1500kVA.
After that we have gate more and deep study of Alternator, It’s Protection
System and It’s Auxiliaries. Which types of Protection used all the things I have
described.

Siemens & Halske was founded by Werner von Siemens on 12 October 1847. Based
on the telegraph, his invention used a needle to point to the sequence of letters, instead of
using Morse code. The company, then called Telegraphen Bauanstalt von Siemens & Halske,
opened its first workshop on October 12.
In 1881, a Siemens AC Alternator driven by a watermill was used to power the
world's first electric street lighting in the town of Godalming, United Kingdom. The
company contin light bulbs. In 1890, the founder retired and left the company to his brother
Carl and sons Arnold and Wilhelm. Siemens & Halske (S & H) was incorporated in 1897, and
then merged parts of its activities with Schuckert & Co., Nuremberg in 1903 to become
Siemens - Schuckert.
In 1907, Siemens (Siemens & Halske and Siemens 34,324 employees and was the
seventh -largest company in the German empire by number of employees. (seeList of
German companies by1907)
In March 2011, it was decided to list Osram on the stock market in the autumn, but
CEO Peter Löscher said Siemens intended to retain a long-term interest in the company,
which was already independent from the technological and managerial viewpoints
In September 2011 Siemens, which had been responsible for constructing all 17 of
Germany's existing nuclear power plants, announced that it would exit the nuclear sector
following the Fukushima disaster and the subsequent changes to German energy policy.
Chief executive Peter Loescher has supported the German government's planned
Energiewende, its transition to renewable energy technologies, calling it a "project of the
century" and saying Berlin's target of reaching 35% renewable energy sources by 2020 was
feasible.

The Business Segment
The business of Siemens is divided into four different segments (also called as sectors).
Siemens and its subsidiaries employ approximately 360,000 people across nearly 190 countries
and reported global revenue of approx. 73.5 billion Euros for the year of 2011. The sectors are as
follows.
Energy
Healthcare
Industry
Infrastructure and Cities.
Energy Sector
Siemens consolidates its innovative offerings in the Energy sector by combining its
full range expertise in the areas of Power Generation (PG) and Power
Transmission & Distribution (PTD). Utilizing the most advanced plant diagnostics
and systems technologies, Siemens provides comprehensive services for complete
power plants and for rotating machines such as gas and steam turbines, generators
and compressors.
Power Generation Special Applications
Gas Turbines Fans
Steam Turbines Mechanical Drives
Generators Services
Power Plants Expansion Turbines
Renewables Compressor Packages
Environmental Systems
Fuel Gasifier
Power Transmission
Power Distribution
Automation, Controls, Protection & Electricals
Compression, Expansion & Ventilation
Turbo compressors
The Siemens Plant inManeja, Vadodara manufacture the steam turbine, the Condenser unit and
the Designing of the power plant for controlling the turbine and Designing Alternator and It’s
Auxiliaries component in the power plant

1) The Process compressor consists of various parts as,
 Project Engineering.
 Core Engineering.
Energy Oil and Gas Steam
Unit
Gas Turbine
Sales
Marketing
Project
Engineering
Core
Engineering
Project
Management
B.O.P.(Bill of Project)
Mechanical
B.O.P.(Bill of Project)
Electrical
Lubricating Oil
Mechanism
Steam jet ejection
Bearing
Gearbox
Pump sets
Electrical Panel Design
Alternator Specifications
M.C.C. Specifications
Metering Panel
Single Line Diagram
LA, SC, PT, CT
Neutral Grounding
Turbine
Condenser
SIEMENS
BARODA

2) Project management.
3) The project Engineering consists of B.O.P. (bill of project) of the mechanical as well as
electrical.
4) In the B.O.P. Electrical department the alternator, control panels, M.C.C. Metering Section
etc. are being designed.
5) In the B.O.P. mechanical department the turbine, lubrication, oil mechanism, pump sets,
bearing mechanism, gear box etc. are being designed.
6) Core Engineering consists of the turbine as well as the condenser Technology which is the
base of the total power plant.
7) B.O.P. also consists three things:
1. S.L.D. ( Single line diagram )
2. L.A, S.C, C.T. & P.T. (lighting arrestor, Surge Capacitor, Current transformer, potential
transformer )
3. N.G.R. ( Neutral grounding resistance )
The process of the project management has three step are being carried out initially
S.L.D. is being drawn. After it L.A. S.C. C.T. & P.T. being Selected then the N.G.R. is being
selected
.

1) Introduction of Energy Available in Nature:-
Energy is defined as “The capacity to produce a change from Existing
conditions.”
The Energy Available from following natural resources:
1) Fuels:
a) Solids-Coal,Wood,etc.
b) Liquids-Petroleum
c) Gases-Natural Gas
2) Energy stored in water-Hydraulic energy
3) Nuclear Energy-Energy from fission chain reaction of nuclear fuel
4) Solar energy-Energy from Sun
5) Geothermal energy-Natural heat generated within the earth
6) Wind power-Kinetic energy of wind
7) Tidal energy-Energy from tides of ocean water
(1) Electrical Energy:-
 The Electrical energy occupies the top position in the energy grades ranking.
 The electrical energy is a convenient form of energy because it can be generated centrally
in bulk and transmitted economically over long distances and is almost pollution free at
the consumer level.
 Electrical Energy is Generated from converting Upper 7 energy into Electrical Energy.
 Electrical Energy cannot be stored.
 Electrical Energy is stored by Chemical Energy (i.e. Battery)
 By using Non-Conventional Sources we can Generate Electrical Energy without any
pollutions.
 And also without any Operating Cost.
 Electrical Energy Sources are classified in two types.
(1) Conventional Energy Sources:-
(i) Thermal Power Plant
(ii) Nuclear Power Plant
(iii) Diesel Power Plant
(iv) Hydro Power Plant
(2) Non- Conventional Energy Sources:-
(i) Wind Energy
(ii) Small-Mini-Micro Hydro Power Plant
(iii) Solar Energy
(iv) Tidal Energy
(v) Geo-Thermal Energy
(vi) Bio-Gas
(vii) Bio-Mass

2) Sensors & Transducers:-
Sensor:-
A device which detects or measures a physical property and records, indicates, or
otherwise responds to it is called Sensor.
Transducer:-
A device that converts variations in a physical quantity, such as pressure or
brightness, into an electrical signal, or vice versa.
The List of Sensors & Transducers:-
 Acoustic, sound, vibration
 Automotive, transportation
 Chemical
 Electric current, electric potential, magnetic, radio
 Environment, weather, moisture, humidity
 Flow, fluid velocity
 Ionizing radiation, subatomic particles
 Navigation instruments
 Position, angle, displacement, distance, speed, acceleration
 Optical, light, imaging, photon
 Pressure
 Force, density, level
 Thermal, heat, temperature
 Proximity, presence
Here we in Siemens Turbine Assembling of SST 200,300, & 600. We are using only Few
Sensors.
(1). pH Meter:-
An acidic solution has far more positively charged hydrogen ions in it than an
alkaline one, so it has greater potential to produce an electric current in a certain
situation—in other words, it's a bit like a battery that can produce a greater voltage.
A pH meter takes advantage of this and works like a voltmeter: it measures the
voltage (electrical potential) produced by the solution whose acidity we're interested in,
compares it with the voltage of a known solution, and uses the difference in voltage (the
"potential difference") between them to deduce the difference in pH.

(2). Hydrogen Sensors:-
The Palladium(pd) is used in many of these, because it selectively absorbs hydrogen
gas and forms the compound palladium hydride(pdH2). Palladium sensors have to be
protected against carbon monoxide, sulfur dioxide and hydrogen sulfide.
Thin films of chromogenic materials, such as WO3, NiOx, V2O5, are deposited on the
end of a fiber-optic cable and used to indicate the presence of hydrogen. At concentrations
above 0.02% hydrogen in air, these materials undergo optical changes, either changing color
or changing the transmittance through the film as atomic hydrogen is incorporated. When a
beam of light is propagated down the cable, the intensity of either the reflected beam or the
transmitted beam is monitored to indicate the presence of hydrogen gas. Research is focused
on developing a better understanding of the service lifetime and performance issues that will
enable the commercialization of thin film hydrogen sensors.

(3). Temperature Detecting Transducers:-
( i) Resistance temperature detector:
Resistance temperature detectors (RTDs), are sensors used to measure
temperature by correlating the resistance of the RTD element with temperature. The significant
characteristic of metals used as resistive elements is the linear approximation of the resistance
versus temperature relationship between 0 and 100 °C. This temperature coefficient of
resistance is called alpha, α. The equation below defines α; its units are ohm/ohm/°C.
the resistance of the sensor at 0°C
the resistance of the sensor at 100°C
Pure platinum has an alpha of 0.003925 ohm/ohm/°C in the 0 to 100 °C range and is used in
the construction of laboratory grade RTDs.
(ii) Thermocouple:
A thermocouple is a temperature-measuring device consisting of two dissimilar
conductors that contact each other at one or more spots.
It produces a voltage when the temperature of one of the spots differs from the
reference temperature at other parts of the circuit.
Thermocouples are a widely used type of temperature sensor for measurement and control, and
can also convert a temperature gradient into

electricity.
(iii) Pyrometer:-
Pyrometer is used for sensing High Temperature. A radiation pyrometer
determines the temperature of an object from the radiation (infrared and, if present,
visible light) given off by the object.
The radiation is directed at a heat-sensitive element such as a thermocouple,
a device that produces an electric current when part of it is heated. The hotter the
object, the more current is generated by the thermocouple. The current operates a
dial that indicates temperature. A steam boiler may be fitted with a pyrometer to
measure the steam temperature in the super heater.

(4). Flow Sensor:-
(i) Electro Magnetic Flow meter
A magnetic field is applied to the metering tube, which results in a potential
difference proportional to the flow velocity perpendicular to the flux lines.
The physical principle at work is electromagnetic induction. The magnetic flow meter
requires a conducting fluid, for example, water that contains ions, and an electrical insulating
pipe surface, for example, a rubber-lined steel tube.
Usually electrochemical and other effects at the electrodes make the potential
difference drift up and down, making it hard to determine the fluid flow induced potential
difference.
To mitigate this, the magnetic field is constantly reversed, cancelling out the static
potential difference.

This however impedes the use of permanent magnets for magnetic flow meters.
(5). Pressure:-
(i) Pressure Gauge:- Pressure Gauge is used to measure pressure on
liquid.
When Pressure is applied on the Pressure Gauge the Burden Gauge is compressed so link
rotate the Pointer.
(6). Proximity Sensors:-
A proximity sensor is a sensor able to detect the presence of nearby objects without any
physical contact.
(i) Inductive Sensor
When any material comes in metal sensing region there is flux linkage so there is burden on
oscillator so it sensed by Current Sensor.

(ii) Capacitive Sensors
The Shape of Capacitive and Inductive is same but capacitive Proximity sensor can detect Insulators
as well as Conductor.

3) Pumps:-
Pump:- A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical
action.
Types of Pumps
1. Positive-Displacement Pumps:-
Positive-displacement pumps operate by forcing a fixed volume of fluid from the inlet
pressure section of the pump into the discharge zone of the pump.
These pumps generally tend to be larger than equal-capacity dynamic pumps.
Positive-displacement pumps frequently are used in hydraulic systems at pressures ranging
up to 5000 psi.
A principal advantage of hydraulic power is the high power density (power per unit
weight) that can be achieved. They also provide a fixed displacement per revolution and,
within mechanical limitations, infinite pressure to move fluids.
i) Reciprocating Pump:- In a reciprocating pump, a volume of liquid is
drawn into the cylinder through the suction valve on the intake stroke and is
discharged under positive pressure through the outlet valves on the discharge stroke.
The discharge from a reciprocating pump is pulsating and changes changes only
when the speed of the pump is changed. This is because the intake is always a constant
volume.

Often an air chamber is connected on the discharge side of the pump to provide a
more even flow by evening out the pressure surges. Reciprocating pumps are often used for
sludge and slurry.
2. Centrifugal Pump:-
A centrifugal pump converts mechanical energy from a motor to energy of a moving
fluid. A portion of the energy goes into kinetic energy of the fluid.
Fluid enters axially through eye of the casing, is caught up in the impeller blades, and
is whirled tangentially and radially outward until it leaves through all circumferential parts
of the impeller into the diffuser part of the casing.
The fluid gains both velocity and pressure while passing through the impeller. The
doughnut-shaped diffuser, or scroll, section of the casing decelerates the flow and further
increase the pressure.
where:
is the input power required (W)
is the fluid density (kg/m3)
is the standard acceleration of gravity (9.80665 m/s2)
is the energy Head added to the flow (m)
is the flow rate (m3/s)
is the efficiency of the pump plant as a decimal
Inlet of Fluid
in Pump
Outlet of Fluid
in Pump
Four Non-
Returning Valves
Cylinder
Piston

3) Cavitation:-
Cavitation is the formation of vapour bubbles in a liquid in pump, Valve & Turbine.
Due to this Blades & impeller gets damaged.
Due to Cavitation the net positive suction head (NPSH) of the system is too low for
the selected pump.
How Cavitation Occurred:-
 Consider one Centrifugal Pump, When it’s in running condition the impeller of pump
giving centrifugal force to the water on impeller so water leaves through all
circumferential parts of the impeller into the diffuser part of the casing with
increasing pressure.
 So that low pressure creates on impellers and its try to suck water from suction pipe.
 And then water coming in impeller & the vacuum bubbles are formed on impeller.
 When this bubbles are collapsed the Cavitation occurred.
 These hammer-like blows against the impeller can cause physical destruction within
a short time.
 When it collapsed it give 3Hz Shock wave.

you need to know its vapor pressure to prevent boiling and the formation of bubbles. In the
charts section of this web site you will find a vapor pressure chartfor several common liquids.

4) Turbine:-
A steam turbine is a device that extracts thermal energy from pressurized steam and uses it
to do mechanical work on a rotating output shaft.
A steam turbine is a prime mover which continuously converts the energy of high pressure,
high temperature steam supplied by a steam generator into shaft work with the low temperature
steam exhausted to a condenser.
This Energy conversion essentially occurs in two steps:
(i) The high pressure, high temperature steam first expands in efficient nozzles and comes out at a
high velocity.
(ii) The high velocity jets of steam coming out of the nozzles, impinge on the blades mounted on a
wheel, get deflected by an angle and suffer a loss of momentum which is absorbed by the rotating
wheel in producing torque.
A steam turbine is basically an assemblage of nozzles and blades.
Nozzle:- It is a duct by flowing fluid through which the velocity of a fluid increases at the expense of
pressure drop.
Convergent:-

Divergent:-
Impulse & Reaction Turbine:-
 Compounding of Turbines:-
In a single stage of turbine, high velocity steam is allowed to flow through moving blade, it
produces a 30,000 rpm which is too high and also steam leaving velocity of the turbine Stage
or blade is also very high which is known as carey over losses.

To avoid this difficulties we increase number of stages in turbine so the leaving velocity of
steam become less. This process is called Compounding of turbines.
The main types of compounding:-
1. Pressure Compounding

2. Velocity Compounding

3) Reaction Turbine

4. Pressure – Velocity Compounding

(Siemens SST Turbine)
Thrust Bearing Collar:-
It is used to absorb the Axial Thrust. There is a Pressurized oil in Thrust Bearing Collar about
2 to 7 bar. Which absorbs Axial Vibrations in Turbine.
Seal Shell:-
It is Used for sealing from atmosphere air to turbine Steam.
Gear Wheel:-
For high output turbines the weight is increases with so we can’t use ball or roller bearing we
have to used hydraulic bearing. for lifting the shaft in the centre of Turbine Gear Wheel is used.
Control Stage Wheel :-
Most of Steam Pressure is Drop in this Stage.

Steam Turbine SST-300:
The SST-300 is a single casing steam turbine, providing geared drive to a 1,500 or
1,800 rpm generator and packaged in a base frame-mounted design. Its modular package design
allows a wide variety of configurations to satisfy the industrial customer’s individual needs in the
most economical way.
Typical applications of the SST-300 are in:
Industrial power plants, e.g. captive power plants, chemical, petrochemical, sugar
and textile industry, pulp and paper mills, steel works and mines
• Cogeneration and district heating plants
• Waste to energy, e.g. waste incinerators; biomass plants
• Combined-cycle applications
• Petrochemicals, refineries, FPSO applications
Technical Specifications
Power output up to 50MW
Inlet pressure 120bar/1,740psi
Inlet temperature 540°C/1,004°F
Rotational speed up to 12,000rpm
Controlled extraction up to 25bar/363psi and
up to 350°C/662°F
Bleed up to 60bar/870psi
Exhaust pressure (back pressure) up to 16bar/232psi
Exhaust pressure (condensing) up to 0.3bar/4.4psi
Exhaust area 0.28–1.6m2/3.0– 17.2sq.ft.

Steam Turbine SST-600:
The SST-600 is a single casing steam turbine, designed for operation with speed ranging
from 3,000 to 18,000 rpm for generator or mechanical drives up to 150 MW. The turbine is used
for both condensing and back-pressure applications, either geared or directly coupled.
Typical fields of application are chemical and petrochemical industry, pulp and paper
mills, steel works, mines, power plants, seawater desalination plants and waste-to-energy, e.g.
waste incinerators.
The SST-600 is used as:
Compressor drive
Generator drive
Boiler feed water pump drive

The innovative, improved Enhanced Platform technology is now standard design
for the SST-600. The turbine with front steam admission offers the possibility of
up to eight bleeds with various pressure levels, or up to five bleeds in combination
with two controlled extractions up to 45 bars for internal controlled extraction and
72 bars for external controlled extraction.
Technical Specifications:
Power output up to 150MW
Inlet pressure up to 165bar/2,393psi
Inlet temperature up to 565°C/1,049°F
Rotational speed 3,000–18,000 rpm
Up to 2 controlled extraction with pressure up to 72bar/1,044psi
Up to 7 bleeds at various pressure levels
Exhaust pressure (back pressure) up to 72bar/1,044psi
Exhaust area 0.2–8.0m2/1.938sq.ft.

5) Thermal Power Plant:-
At present 59.51% or 148478.39 MW (as per CEA on 31/06/2014) of total electricity
production in India is from Coal Based Thermal Power Station.
A coal based thermal power plant converts the chemical energy of the coal into electrical
energy. This is achieved by raising the steam in the boilers, expanding it through the turbine and
coupling the turbines to the generators which converts mechanical energy into electrical energy.
 Introductory overview:-
1) In a coal based power plant coal is transported from coal mines to the power plant by railway in
wagons or in a merry-go-round system.
2) Coal is unloaded from the wagons to a moving underground conveyor belt. This coal from the
mines is of no uniform size. So it is taken to the Crusher house and crushed to a size of 20mm.

3) From the crusher house the coal is either stored in dead storage( generally 40 days coal supply)
which serves as coal supply in case of coal supply bottleneck or to the live storage(8 hours coal
supply) in the raw coal bunker in the boiler house.
4) Raw coal from the raw coal bunker is supplied to the Coal Mills by a Raw Coal Feeder. The Coal
Mills or pulverizer pulverizes the coal to 200 mesh size.
5) The powdered coal from the coal mills is carried to the boiler in coal pipes by high pressure hot
air.
6) The pulverized coal air mixture is burnt in the boiler in the combustion zone.
7)
Generally in modern boilers tangential firing system is used i.e. the coal nozzles/ guns form
tangent to a circle. The temperature in fire ball is of the order of 1300 deg.C.
8) The boiler is a water tube boiler hanging from the top. Water is converted to steam in the boiler
and steam is separated from water in the boiler Drum.
9) The saturated steam from the boiler drum is taken to the Low Temperature Super heater, Platen
Superheater and Final Superheater respectively for superheating.
10) The superheated steam from the final super heater is taken to the High Pressure Steam Turbine
(HPT). In the HPT the steam pressure is utilized to rotate the turbine and the resultant is
rotational energy.
11) From the HPT the out coming steam is taken to the Reheater in the boiler to increase its
temperature as the steam becomes wet at the HPT outlet.
12) After reheating this steam is taken to the Intermediate Pressure Turbine (IPT) and then to the
Low Pressure Turbine (LPT).
13) The outlet of the LPT is sent to the condenser for condensing back to water by a cooling water
system.
14) This condensed water is collected in the Hot well and is again sent to the boiler in a closed cycle.
15) The rotational energy imparted to the turbine by high pressure steam is converted to electrical
energy in the Generator.

 Diagram of a typical coal-fired thermal power station:-

Principal:-
Coal based thermal power plant works on the principal of Modified Rankine Cycle.
Components of Coal Fired Thermal Power Station:
Coal Preparation
i)Fuel preparation system: In coal-fired power stations, the raw feed coal from the coal
storage area is first crushed into small pieces and then conveyed to the coal feed hoppers at the
boilers. The coal is next pulverized into a very fine powder, so that coal will undergo complete
combustion during combustion process. pulverizer is a mechanical device for the grinding of many
different types of materials. For example, they are used to pulverize coal for combustion in the
steam-generating furnaces of fossil fuel power plants.
Types of Pulverisers:
(1) Ball and Tube mills
(2) Ring and Ball mills
(3) MPS
(4) Ball mill
(5) Demolition.

ii)Dryers: they are used in order to remove the excess moisture from coal mainly
wetted during transport. As the presence of moisture will result
in fall in efficiency due to incomplete combustion and also result in CO emission.
iii)Magnetic separators: coal which is brought may contain iron particles. These iron
particles may result in wear and tear. The iron particles may include bolts, nuts wire fish
plates etc. so these are unwanted and so are removed with the help of magnetic separators.
The coal we finally get after these above process are transferred to the storage site.
Purpose of fuel storage is 2 –
Fuel storage is insurance from failure of normal operating supplies to arrive.
Storage permits some choice of the date of purchase, allowing the purchaser to take
advantage of seasonal market conditions. Storage of coal is primarily a matter of protection
against the coal strikes, failure of the transportation system & general coal shortages.
There are 2 types of storage:-
(1) Live Storage(boiler room storage):-
storage from which coal may be withdrawn to supply combustion equipment with little or no
remanding is live storage. This storage consists of about 24 to 30 hrs. of coal requirements of
the plant and is usually a covered storage in the plant near the boiler furnace. The live
storage can be provided with bunkers & coal bins. Bunkers are enough capacity to store the
requisite of coal. From bunkers coal is transferred to the boiler grates.
(2) Dead storage:-
stored for future use. Mainly it is for longer period of time, and it is also mandatory to keep a
backup of fuel for specified amount of days depending on the reputation of the company and
its connectivity.There are many forms of storage some of which are –
Stacking the coal in heaps over available open ground areas.
As in (I). But placed under cover or alternatively in bunkers.
Allocating special areas & surrounding these with high reinforced concerted retaking walls.
Boiler and auxiliaries:-
A Boiler or steam generator essentially is a container into which water can be fed and steam can be
taken out at desired pressure, temperature and flow. This calls for application of heat on the
container. For that the boiler should have a facility to burn a fuel and release the heat. The functions
of a boiler thus can be stated as:-
(1) To convert chemical energy of the fuel into heat energy

(2) To t http://www.xvideos.com/video8379299/juelz_ventura_-_juelz_droolsransfer this heat
energy to water for evaporation as well to steam for superheating.
The basic components of Boiler are: -
(1) Furnace and Burners
(2) Steam and Superheating
a. Low temperature superheater
b. Platen superheater
c. Final superheater
Economizer:-
It is located below the LPSH in the boiler and above pre heater. It is there to improve the efficiency of
boiler by extracting heat from flue gases to heat water and send it to boiler drum.
Advantages of Economiser include
1) Fuel economy: – used to save fuel and increase overall efficiency of boiler plant.
2) Reducing size of boiler: – as the feed water is preheated in the economiser and enter boiler tube at
elevated temperature. The heat transfer area required for evaporation reduced considerably.
Air Preheater:-
The heat carried out with the flue gases coming out of economiser are further utilized for preheating
the air before supplying to the combustion chamber. It is a necessary equipment for supply of hot air
for drying the coal in pulverized fuel systems to facilitate grinding and satisfactory combustion of
fuel in the furnace
Reheater:-
Power plant furnaces may have a reheater section containing tubes heated by hot flue gases outside
the tubes. Exhaust steam from the high pressure turbine is rerouted to go inside the reheater tubes
to pickup more energy to go drive intermediate or lower pressure turbines.
Steam turbines:-
Steam turbines have been used predominantly as prime mover in all thermal power stations. The
steam turbines are mainly divided into 2 groups: -
(1) Impulse turbine
(2) Impulse-reaction turbine
The turbine generator consists of a series of steam turbines interconnected to each other and a
generator on a common shaft. There is a high pressure turbine at one end, followed by an

intermediate pressure turbine, 2 low pressure turbines, and the generator. The steam at high
temperature (536 ‘c to 540 ‘c) and pressure (140 to 170 kg/cm2) is expanded in the turbine.
Condenser:-
The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be
pumped. If the condenser can be made cooler, the pressure of the exhaust steam is reduced and
efficiency of the cycle increases. The functions of a condenser are:-
1) To provide lowest economic heat rejection temperature for steam.
2) To convert exhaust steam to water for reserve thus saving on feed water requirement.
3) To introduce make up water.
We normally use surface condenser although there is one direct contact condenser as well. In direct
contact type exhaust steam is mixed with directly with D.M cooling water.
The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be
pumped. If the condenser can be made cooler, the pressure of the exhaust steam is reduced and
efficiency of the cycle increases.
Diagram of a typical water-cooled surface condenser
The surface condenser is a shell and tube heat exchanger in which cooling water is circulated
through the tubes. The exhaust steam from the low pressure turbine enters the shell where it is
cooled and converted to condensate (water) by flowing over the tubes as shown in the adjacent
diagram. Such condensers use steam ejectors or rotary motor-driven exhausters for continuous
removal of air and gases from the steam side to maintain vacuum.
Ejectors:- Ejector is a type of pump that uses the Venturi effect of a converging-diverging nozzle
to convert the pressure energy of a motive fluid to velocity energy which creates a low pressure zone
that draws in and entrains a suction fluid.

After passing through the throat of the injector, the mixed fluid expands and the velocity is reduced
which results in recompressing the mixed fluids by converting velocity energy back into pressure
energy. The motive fluid may be a liquid, steam or any other gas. The entrained suction fluid may be
a gas, a liquid, a slurry, or a dust-laden gas stream.
Boiler feed pumpL:-
Boiler feed pump is a multi stage pump provided for pumping feed water to economiser. BFP is the
biggest auxiliary equipment after Boiler and Turbine. It consumes about 4 to 5 % of total electricity
generation.
Cooling tower:-
The cooling tower is a semi-enclosed device for evaporative cooling of water by contact with air. The
hot water coming out from the condenser is fed to the tower on the top and allowed to tickle in form
of thin sheets or drops. The air flows from bottom of the tower or perpendicular to the direction of
water flow and then exhausts to the atmosphere after effective cooling.
The cooling towers are of 4 types: -
1. Natural Draft cooling tower
2. Forced Draft cooling tower
3. Induced Draft cooling tower
4. Balanced Draft cooling tower
Fan or draught system:-
In a boiler it is essential to supply a controlled amount of air to the furnace for effective combustion
of fuel and to evacuate hot gases formed in the furnace through the various heat transfer area of the
boiler. This can be done by using a chimney or mechanical device such as fans which acts as pump.
i) Natural draught

When the required flow of air and flue gas through a boiler can be obtained by the stack (chimney)
alone, the system is called natural draught. When the gas within the stack is hot, its specific weight
will be less than the cool air outside; therefore the unit pressure at the base of stack resulting from
weight of the column of hot gas within the stack will be less than the column of extreme cool air. The
difference in the pressure will cause a flow of gas through opening in base of stack. Also the chimney
is form of nozzle, so the pressure at top is very small and gases flow from high pressure to low
pressure at the top.
ii) Mechanized draught
There are 3 types of mechanized draught systems
1) Forced draught system
2) Induced draught system
3) Balanced draught system
Forced draught: – In this system a fan called Forced draught fan is installed at the inlet of the boiler.
This fan forces the atmospheric air through the boiler furnace and pushes out the hot gases from the
furnace through superheater, reheater, economiser and air heater to stacks.
Induced draught: – Here a fan called ID fan is provided at the outlet of boiler, that is, just before the
chimney. This fan sucks hot gases from the furnace through the superheaters, economiser, reheater
and discharges gas into the chimney. This results in the furnace pressure lower than atmosphere and
affects the flow of air from outside to the furnace.
Balanced draught:-In this system both FD fan and ID fan are provided. The FD fan is utilized to draw
control quantity of air from atmosphere and force the same into furnace. The ID fan sucks the
product of combustion from furnace and discharges into chimney. The point where draught is zero is
called balancing point.
Ash handling system:-
The disposal of ash from a large capacity power station is of same importance as ash is produced in
large quantities. Ash handling is a major problem.
i) Manual handling: While barrows are used for this. The ash is collected directly through the ash
outlet door from the boiler into the container from manually.
ii) Mechanical handling: Mechanical equipment is used for ash disposal, mainly bucket elevator, belt
conveyer. Ash generated is 20% in the form of bottom ash and next 80% through flue gases, so called
Fly ash and collected in ESP.
iii) Electrostatic precipitator: From air preheater this flue gases (mixed with ash) goes to ESP. The
precipitator has plate banks (A-F) which are insulated from each other between which the flue gases
are made to pass. The dust particles are ionized and attracted by charged electrodes. The electrodes
are maintained at 60KV.Hammering is done to the plates so that fly ash comes down and collect at

the bottom. The fly ash is dry form is used in cement manufacture.

Generator(Alternator):-
Generator or Alternator is the electrical end of a turbo-generator set. It is generally known as the
piece of equipment that converts the mechanical energy of turbine into electricity. The generation of
electricity is based on the principle of electromagnetic induction.
Advantages of coal based thermal Power Plant
 They can respond to rapidly changing loads without difficulty
 A portion of the steam generated can be used as a process steam in different industries
 Steam engines and turbines can work under 25 % of overload continuously
 Fuel used is cheaper
 Cheaper in production cost in comparison with that of diesel power stations
Disadvantages of coal based thermal Power Plant
 Maintenance and operating costs are high
 Long time required for erection and putting into action
 A large quantity of water is required
 Great difficulty experienced in coal handling
 Presence of troubles due to smoke and heat in the plant
 Unavailability of good quality coal
 Maximum of heat energy lost
 Problem of ash removing

Electrical Substation
 Substation is a place where the characteristic of electric energy is changed
from one form in to the other required form.
 It is the link between the generation and utilization of electrical power.

Classification of Substation:-
(a) Step up Substation
or Switch yard(11kV)
(b) Primary grid station
Transformer Or Receiving station
Substation (440 or 765 kV)
Industrial
Function Switching (c)Secondary Substation
Power Factor (132kV or 220 kV)
Correction
Frequency (d)Distribution
Substation Changer Substation (33 or 11 kV)
Manual
Control Automatic
Supervisory
Indoor
Outdoor
Mounting Pole mounted
Foundation mounted
Under gorund
(Classification of Substation)

Equipments in Substation:-
(1)Incoming Line:-
Power is received by the substation with the help of coming. There may be two or three many more
incoming Lines.
(2)Bus Bar:-
Bus bar is hollow pipe conductor by using this the reliability is more than strained conductors.
(3)Wave Trap:-
Wave Trap is used to catch PLCC(Power Line Communication Line) Signal by tuning LC Circuit.
(4)Insulators:- Insulators are used to support the live conductor, Bus bar & Equipment.
Porcelain Material is used for Insulators.
(5)Lightening Arrester:-
L.A. is used for protection of all Equipments of Switchyard against Surges and lightening
Discharges.

In L.A., numbers of thyrite discs are mounted one above the other depending upon the voltage.
Its electric resistance at normal voltage or system voltage is very high but when high voltages
occur on line its resistance is decreases to very low value, so the high voltage is grounded and all
equipments are protected.

(6)Instrument Transformers:-
The Instrument type Transformer is used for two purposes
 For Measuring
 For Proection
There are two type of Instrument type Transformer
I. Current Transformer(C.T.)
II. Potential Transformer(P.T.)
(Figure of CT) (Figure of PT)

Current Transformer (C.T.):-
Current Transformer is used to step-down the current for measuring & Protection Purpose.
Potential Transformer (P.T.):- Potential Transformer is used to step-down the voltage for measuring &
Protection Purpose. As a Design Point of view there is difference between Power & Instrument
Transformer. In Instrument Transformer we have to minimize Ratio error & Phase Error.
(7)Circuit Breaker:- Circuit Breaker is working as a Switch. Circuit Breaker is used to make or Break
the Circuit. Circuit Breaker is operating by pneumatic , Hydraulic or motor mechanism.
In recent, the Vacuum, SF6 and somewhere Oil Circuit Breaker and air blast Circuit Breaker is
used.

Fixed Contact
Moving Contact
SF6 Gas
Surrounding
the Contacts

(8) Isolators:- Isolator is used to isolate the equipment from the live part of the other
equipment during maintenance and repairing the system.
Isolator is a air break switch but it is not used for a break or make the circuit if it tries it for
the arc is produced and the isolator damaged.
So there is interlocked between circuit Breaker & Isolators.
(9) Earth Switch(E.S.):-When Transmission line is trip due to any fault the circuit Breaker
from both ends of substation is tripped so that result there is static charge in to the line
because a long ACSR conductor is a inductor which store energy of 1/2LV2 Energy. So if any
ne touch the line at the time of maintenance and repairing so he or she affect the high voltage
electric shock.
To avoid this condition there is earth switch connected top the Isolator.
So when isolator is ON the E.S. is OFF and when Isolator is OFF the E.S. is ON
For this in substation there is a Interlock between Circuit Breaker,Isolator & Earth Switch.
Isolator
Operating
Mechanism
By Motor

(10) Transformer:- three phase Transformer is used for converting one Voltage level to another
voltage level. In substation Step down Transformer is used.
In Siemens, There is Four to five Transformer is used
1. 66/11 kv at Incoming (CG)
And others are 11/.43kv is used.
Off Load Tap Changer:- It is used in Transformer for changing the voltage level by increase or
decrease the no. of turns in transformer by shut down of Transformer

On Load Tap Changer:- It is used in Transformer for changing the voltage level by increase or
decrease the no. of turns in transformer without shut down of Transformer.
(11) Reactor:- Reactor is used to increase or decrease the reactance of line.
It is used to control the power flow in the Transmission line.
(12) Capacitor Bank:- Capacitor Bank is used to supply reactive power to Inductive load. By
using Capacitor we can get unity power factor. It decreases the value of current by supplying the
reactive current to inductive load.
(13) Earthing Transformer:- For Neutral Earthing in Transformer there is another Earthing
Transformer is used to detect the earth Fault.
(14) Indicating and Metering instruments:- Ammeters, voltmeter, wattmeter, kWh meters,
kVARh meters, power factor meters, reactive-volt-ampere meters are installed in substations to
control and maintain a watch over the currents flowing through the circuits and over the power
loads.
(15) Lead Batteries:- In Substations, the operating and automatic control circuits, the protective
relay systems, as well as emergency lighting circuits, are supplied by station batteries. This are
independent sources of operative dc power and guarantee operation in any Fault condition.

(16) Neutral Grounding(NGR):- NGR is Required to the Transformer for the protection of it
from Earth Fault and High AC Voltage.
Consider one X’mission Line The R-Y-B phase has capacitance with each other as well as with
earth(Ground). So when Earth fault occurs in R phase so for return path it goes from the Y and B
phase so there is Voltage rise in both Healthy Phase & the arc is Produced between the Ground and
two phase which damage the Whole Line. so neutral Grounding Provides return path. So when
Fault occurs we can put relay in the neutral grounding so we can detect the earth Fault.
(17) Carrier Current Protection:- Carrier current protection is used for communication, relaying,
telemetering and supervisory control. It is called power line communication System(PLCC). Radio
Signal is transmitted from one substation to the other through Power line.
(18) Neutral Grounding:- InThree- Phase wire System Neutral Terminal is buried in Ground it’s
called Neutral Grounding. It is used to sense the any earth fault as well as it restrict Arcing Ground
in the Fault Condition and it provides protection to the system against Unbalance System.
(19) Control Cables:- It is used to control All Switch gears in Substation, Transformer tap-
changing, etcetera. It generally operates at 110 V or 220 V.
(20) Outgoing line:- After changing the voltage level the lines are taken out of the substation to
different regions.

Gas Insulated Substation
Siemens Gas Insulated Substation
(145kV)

Components of Gas Insulated Substation:-
1. Bus bar 7. Maintenance Earthing Switch
2. Diconnector 8. Diconnector
3. Maintenance Earthing Switch 9. Earthing Switch
4. Current Transformer 10. Voltage Transformer
5. Circuit Breaker 11. Bushing
6. Current Transformer
Rated voltage 550kV

 Advantages of Gas Insulated Substation:-
1. It occupies very less space (1/10th) compared to ordinary substations
2. Most reliable compared to Air Insulated Substations, number of outages due to the
fault is less.
3. Maintenance Free
4. Can be assembled at the shop and modules can be commissioned in the plant easily
 Disadvantages of Gas Insulated Substation:-
1. Cost is higher compared to Ordinary Conventional Substations
2. Care should be taken that no dust particles enter into the live compartments which
results in flash over.
3. When fault occurs internally, diagnosis of the fault and rectifying this takes very long
time (outage time is high)
4. SF6 gas pressure must be monitored in each compartment, reduction in the pressure
of the SF6 gas in any module results in flash over and faults

Alternator
An alternator is an electrical generator that converts mechanical energy to electrical energy in the form
of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with
a stationary armature
Cylindrical Rotor
Stator

Smooth cylindrical Rotor
It is used for steam turbine driven alternator. The rotor of this generator rotates in very high speed. The
rotor consists of a smooth solid forged steel cylinder having a number of slots milled out at intervals along
the outer periphery for accommodation of field coils. These rotors are designed mostly for 2 pole or 4 pole
turbo generator running at 3000 rpm or 1800 rpm respectively.
A conductor moving relative to a magnetic field develops an electromotive force (EMF) in it, (Faraday's
Law). This emf reverses its polarity when it moves under magnetic poles of opposite polarity. Typically, a
rotating magnet, called the rotor turns within a stationary set of conductors wound in coils on an iron core,
called the stator. The field cuts across the conductors, generating an induced EMF (electromotive force), as
the mechanical input causes the rotor to turn.
The rotating magnetic field induces an AC voltage in the stator windings. Since the currents in the stator
windings vary in step with the position of the rotor, an alternator is a synchronous generator.
The rotor's magnetic field produced by a field coil electromagnet.
Alternators used in central power stations also control the field current to regulate reactive power and to
help stabilize the power system against the effects of momentary faults. Often there are three sets of stator
windings, physically offset so that the rotating magnetic field produces a three phase current, displaced by
one-third of a period with respect to each other.
One cycle of alternating current is produced each time a pair of field poles passes over a point on the
stationary winding. The relation between speed and frequency is , where is the
frequency in Hz (cycles per second). is the number of poles (2,4,6...) and is the rotational speed
in revolutions per minute (RPM).

Brushless alternators:-
A brushless alternator is composed of two alternators built end-to-end on one shaft. Smaller brushless
alternators may look like one unit but the two parts are readily identifiable on the large versions. The larger
of the two sections is the main alternator and the smaller one is the exciter. The exciter has stationary field
coils and a rotating armature (power coils). The main alternator uses the opposite configuration with a
rotating field and stationary armature. A bridge rectifier, called the rotating rectifier assembly, is mounted
on the rotor. Neither brushes nor slip rings are used, which reduces the number of wearing parts. The main
alternator has a rotating field as described above and a stationary armature (power generation windings).
Varying the amount of current through the stationary exciter field coils varies the 3-phase output from the
exciter. This output is rectified by a rotating rectifier assembly, mounted on the rotor, and the resultant DC
supplies the rotating field of the main alternator and hence alternator output. The result of all this is that a
small DC exciter current indirectly controls the output of the main alternator.

PMG: It is a part of the generator excitation system where the rotor of the
PMG is mounted on the main generator extended shaft. Output of the PMG is
connected to Generator AVR Panel.
Space Heaters: They are fitted in the machine to avoid condensation in the event
of long storage, also when machine is not in operation. Care should be
taken such that it is switch on when not in operation, and switch off before the
machine is commissioned into operation.
Cooler: The cooler are used in alternator for its cooling purpose. They provide
cooling by air or by water medium. In CACW (Closed Air and Circulating Water) the
circulating air absorbs the heat loss of the machine and dissipates in to the cooling water
through the heat exchanger/tube bundle.
Fans are assembled on the shaft facilitate the effective cooling by circulating the air
from cold air to hot air & vice versa. There are three types of cooler.
Top Mounted Cooler
Side Mounted Cooler
Bottom Mounted Cooler
Basic Requirements to Design Alternator:
Ratings
Cooling System
Reactance
Efficiency
Stator (field)
Rotor (armature)
Power Capability Curve
Rotor Heating Limit

Synchronization of Alternator to Infinite Bus bar:-
Synchronization is the process to connect Alternator in Parallel with Infinite Busbar(Grid) which are
connected with no. of Alternators.
For synchronization, following conditions must be satisfied:
(1) EQUALITY OF VOLTAGE
(2) PHASE SEQUENCE
(3) EQUALITY OF FREQUENCY
(4) PHASE Difference Angle
Voltage:-
Voltage can be checked with the help of Potential Transformer.
If the Alternator Voltage More than Grid Voltage we can equal it by giving less Excitement to Rotor of
Alternator or Vice versa.

SYNCHRONIZING BY SYNCHROSCOPE:
Frequency:-
If the Frequency of Grid and Alternator is not same there is some resultant voltage is Produced between
them which tends to flow circulating current.
If the Frequency of generator is greater than Grid so by Decreasing speed of rotor or Vice versa. We can
get same Frequency as Grid.
Synchroscope is a device that shows the correct instant of closing the synchronizing switch with the help of
a pointer which will rotate on the dial. The rotation of pointer also indicates whether the incoming machine
is running too slow or too fast.

If incoming machine is slow then pointer rotates in anticlockwise direction and if machine is fast then
pointer rotates in clockwise direction.
Fig. 3 Synchronizing by Synchroscope
Phase Sequence:-
It is for knowing Three Phase Sequence (R, Y, B or U, V, W) It is for ensured to that the three phase (R,
Y, B or U, V, W) of Alternator is connected to Grid three phase. If there is interchanging of R-Y’ instead
of R-R’ there is 240o
or 120o
Phase difference which result to voltage difference so the circulating current
flow between them. And it can be measured by Phase Sequence Indicator.
We have to give three phase signal of both P.T. to
this Phase Sequence Indicator.
If the Phase Sequence is(Rg-Ra, Yg-Ya, Bg-Ba)
Correct it will Rotate in a Arrow Direction.
If it rotate in another direction the Phase Sequence
is incorrect (Rg-Ya, Yg-Ra, Bg-Ba) so we have to
interchange Generator terminal.

Phase Displacement:-
When there is equal Voltage, Frequency and same Phase Sequence but there is small phase
Displacement it can result in a flow of circulating Current between Alternator and Grid.
For complete minimization of Phase displacement We have to see both waveforms then
increase frequency of alternator when it catch the grid voltage phasor then we have to
dercrease it’s frequency to rated frequency.
(Figure of Grid and Alternator phasor diagram)
Note:- In Synchronization of 11 kV Alternator to Grid Tolerance of 10o is acceptable.
Phase Displacement Between two waveform of
Alternator and Grid
The Value of Vg and Va is
Different for time t1
Valternator
rnator
Vgrid
t1
Grid Voltage Phasor
Alternator Voltage Phasor
Phase Displacement

Switch gear & Protection:-
As a switch gear the Circuit Breaker is used. There are two function of Circuit Breaker
1. It switches ON and OFF the circuit in healthy condition.
2. It breaks the circuit in abnormal condition such as short circuit or fault.
Normal Operation of Power System:-
1. Voltages and currents are balanced i.e. the three-phase voltages are equal and the three-phase
currents are also almost equal.
2. Frequency of the supply is equal to the rated frequency. There is very little change in the
frequency.
3. There is no change in the voltage beyond some limit.
4. Power flow is in the desired direction.
5. Value of current is equal to the rated value or less than it.
Abnormal Condition of power system:-
1. Overloading of Equipment:-
2. Unbalanced loading:-
3. Failure of prime mover in power station
4. Failure of exciter in power Station
5. Loose Contacts
Fault:-
Abnormalities is the result of Fault. It means the defect developed in electrical system due
to which flow of current is diverted from its desired path.
When there is change in voltage, current, frequency, power factor or temperature beyond
some limit, the condition of the power system is called the abnormal condition.
Cause of Fault:-
1. Defect in insulation of the winding of electrical equipment :
i. Ageing
ii. Voltage surge
2. Defect in underground cable :
3. Defect in overhead line :
4. Defect in the bus bars of control panel of the substation :

Various types of Faults occurred in Power System:-
No Fault Chances
1. Over head Fault 50%
(i) Line to Ground Fault 85%
(ii) Line to line Fault 8%
(iii) Line to line Ground Fault 5%
(iv) Line to line Fault 2%
2. Underground Cables 10%
3. Switchgear 15%
4. Transformer 12%
5. CT & PT 2%
6. Control Equipment 3%
7. Miscellaneous 6%
Function of a protection System:-
When fault or abnormal condition is produced in power system. The faulty component should be
immediately isolated or should be isolated as quickly as possible from the system because otherwise the
faults spreads in the healthy system and more damage occurs to the system so the reliability becomes
lesser.And there is always Backup Protection is used at Primary Protection.

If High Voltage or High Current passes through the instrument transformer gives signal to the relay and
relay operates the circuit breaker.

In a new Trend of Power System there is continuously data transferred of Voltage level, current, frequency,
power factor, active power and reactive power between all the substation of National Grid of India through
Power Line Communication Line so by this PLCC line we can operate any Circuit Breaker.
Functional Requirements of Protection Relay:-
(1) Reliability
The most important requisite of protective relay is reliability. They remain inoperative for a long
time before a fault occurs; but if a fault occurs, the relays must respond instantly and correctly.
(2) Selectivity
It is the ability of the relay to sense the fault in its own zone and to operate the circuit breaker to
isolate the faulty component without affecting other healthy sections which are not in its zone.
(3) Sensitivity
The relaying equipment must be sufficiently sensitive so that it can be operated reliably when level
of fault condition just crosses the predefined limit.
(4) Simplicity
Relay have to be designed so simple that anyone can interference with them.
(5) Discrimination
The relay should have the power of discrimination which means that it should operate only when fault
occurs in its own zone and should not operate when there is through fault.
Thus it should be capable to sense whether the fault is in its own zone or it is the through fault.
So the relay should be capable to discriminate between overload and Fault.
(6) Speed
The protective relays must operate at the required speed. There must be a correct coordination provided in
various power system protection relays in such a way that for fault at one portion of the system should not
disturb other healthy portion. Fault current may flow through a part of healthy portion since they are
electrically connected but relays associated with that healthy portion should not be operated faster than the
relays of faulty portion otherwise undesired interruption of healthy system may occur.

Zones of Protection:-

Protection of Alternator:-
Protection of Alternator is the most complex because of following
results:
 Alternator is a costly equipment and one of the major links in a power system.
 Alternator is not a single equipment but is associated with unit-transformers, auxiliary transformer,
station bus-bars, excitation system, prime mover, voltage regulating equipment, cooling system
etcetera. The protection of alternator, is therefore, to be coordinated with the associated equipment.
 The alternator capacity has sharply risen in recent years from 30 MW to 500 MW with the result
that loss of even a single machine may cause overloading of the associated machines in the system
and eventual system instability.
Alternator Faults:-
A. Stator Winding Faults
Such faults occur mainly due to the insulation failure of stator winding coils.
The main types of stator winding faults are
(i) Phase to Earth Faults
(ii) Phase to Phase Faults
(iii) Inter turn Faults inter turn involving turns of same winding.
The stator windings of Big Alternators are hollow copper bars type so stator faults are the most
dangerous faults and also it is very expensive to repair and in some case there is need of
replacement of alternator stator.
There may be to possibility in the above Fault:
(1) Arcing to core, which welds lamination together causing eddy current hot spots on subsequent
use. Repairs to this condition involve expenditure of considerable money and time.
(2) Severe heating in the conductors damaging them and the insulation with possible fire breaks.
B. Field Winding or Rotor Circuit Faults
Faults in the rotor circuit may be either earth faults (conductor to earth faults) or inter turn
faults, which are caused by severe mechanical and thermal stresses.
The faults due to short ckt of rotor core and bits winding not lead to Earth fault but earth fault
will short circuit of rotor winding and may thereby develop an unsymmetrical field system, giving
unbalanced force to rotor. This can cause severe vibration of the rotor with possible damage to Bearing
and may bend the shaft.
Also Failure of Excitation may occur due to open ckt or short ckt in the field. so due to this the
rotor rpm increases and whole machine act as a induction generator and supplying leading power
factor. So there is loss of synchronism as bad as system stability.

C. Abnormal Operating Conditions
1. Failure of prime mover resulting in synchronous motor.
2. Failure of field
3. Unbalanced loading and subsequent heating of alternator
4. Overloading
5. Over voltage at Alternator terminals
6. Over speed
7. Ventilation failure
8. Current leakage in the body of the alternator

PROTECTION Provide to Alternator:-
Different Relay for Alternator Protection:-
21 (Phase Distance Protection)
24 (Over Fluxing Protection)
27 (Under Voltage Protection)
32 R (Low Forward Power Protection)
32R (REVERSE POWER PROTECTION)
40 (LOSS OF FIELD/EXCITATION PROTECTION)
46 (Negative Phase Sequence Protection)
50 (INSTANTANEOUS OVERCURRENT PROTECTION)
50/27 (INADVERTANT ENERGIZATION PROTECTION
50 BF (BREAKER FAILURE PROTECTION
51 (VOLTAGE CONTROLLED INVERSETIME OVERCURRENT PROTECTION)
59 (OVERVOLTAGE PROTECTION
51 N (STANDBY/SENSITIVE EARTH FAULT PROTECTION)
59 N (NON-DIRECTIONAL EARTH FAULT PROTECTION)
60 FL (FUSE FAILURE OR PT FAILURE PROTECTION)
78 (POLE SLIPPING)
81 (OVER/UNDER FREQUENCY PROTECTION)
81 R (RATE OF CHANGE OF FREQUENCY PROTECTION)
87G (DIFFERENTIAL PROTECTION)

(1) 21 (Phase Distance Protection) :
The distance relay applied for this function is intended to isolate the
generator from the power system for a fault which is not cleared by the
transmission line breakers.
(2) 24 (Over Fluxing Protection) :
Over fluxing damage to the stator core is likely to occur towards each end of the core. It may
reveal overheating on the tops of the core teeth. Increased core losses will release heat into the
core, and the temperature will increase with time. Core temperatures can rapidly increase to the
point where the interlaminar insulation breaks down, allowing circulating currents to flow
axially within the core, further increasing the heat input. Temperatures can then continue to
increase until the core steel melts. If this area of the core is adjacent to a stator winding
conductor bar, the bar insulation may become heat-damaged and break down, possibly
resulting in a stator earth fault.
To Prevent this, The AVR of Excitation System has to be set to trip on overfluxing voltage.
(3) 27 (Under Voltage Protection) :
If Alternator voltage goes down below rated voltage there is circulating current flow and
beyond some limit it falls from synchronism from the grid.
To prevent Under voltage, We use AVR in Excitation system which will give more voltage to
field system so we can get rated voltage at terminal Voltage.
(4) 32 R (Low Forward Power Protection) :
The generator will not develop output power when turbine input is less than the no load losses
and motoring action develops on the turbine. The generator is able to generate power, usually
55 to 10% of generator capacity, within pre-determined time after closing of breaker.
(5) 32R (REVERSE POWER PROTECTION) :
Turbo generators are run by steam turbines. In case of turbine trip, if the generator remains
connected to the grid, the generator will run as motor and rotate the turbine.
With no steam in turbine, there will be air in the turbine casing. Turbine blades, specially low
pressure turbine blades will offer heave windage loss thereby increasing the temperature of
blades to very high value which will damage the turbine.
When turbine is run by steam, temperature is limited to that of the steam. But when steam is
not there, temperature will go dangerously high. So forward power relay is used to trip the
generator thereby preventing the motor operation of the set.
This saves the turbine from high temperature. Some utilities prefer reverse power relay over
forward relay.
(6) 40 (LOSS OF FIELD/EXCITATION PROTECTION) :

When there is a reduced or lost of excitation of the synchronous generator, conceptionaly it
will start functioning like an induction generator. Otherwise, if the system cannot provide
adequate reactive power support for induction generator mode of operation, then synchronism
is lost. The change is a gradual one and if the field is tripped by accident, an alarm can be used
to alert the operator. However, if the field is not quickly restored, then the unit should be shut
down.
(7) 46 (Negative Phase Sequence Protection):-
The most common causes are system asymmetries
(untransposed lines), unbalanced loads, unbalanced system faults, and open
phases. These system conditions produce negative-phase-sequence components
of current that induce a double-frequency current in the surface of the rotor, the
retaining rings, the slot wedges, and to a smaller degree, in the field winding.
These rotor currents may cause high and possibly dangerous temperatures in a
very short time., the melting of the wedges in the air gap. ANSI standards have established that
the limits can be expressed as 2
2i dt k where 2i is the negative sequence current flowing.
The machine designer establishes constant k. It can be in the range of 5 – 50. An inverse-time
overcurrent relay excited by negative sequence current can be used for this protection.
(8) 50 (INSTANTANEOUS OVERCURRENT PROTECTION)
When there is suddenly increase of current due to any external fault in switchyard or in grid so
to protect alternator form overcurrent we have to give instantaneous overcurrent protection.
(9) 50/27 INADVERTANT ENERGIZATION PROTECTION
Inadvertent or accidental energizing of off-line generators has occurred often enough to
warrant installation of dedicated protection to detect this condition. Operating errors,
breaker head flashovers , control circuit malfunctions, or a combination of
these causes has resulted in generators being accidentally energized while off-line.

When a generator is off-line on turning gear and is inadvertently energized from the
power system, it will develop an inrush current (similar to an induction motor start) that
can be as high as 300 percent to 400 percent of the generator name plate (rating). This
inrush current subjects the turbine shaft and blades to large forces, and with rapid
overheating of the stator windings and potential for damage due to the excessive slip
frequency currents. The impedance of the transformer and the stiffness of the system
dictates the level of inrush current.
This protection is required when the unit is off-line and may or may not be armed when
the unit is in service and connected to the system.
(10) 50 BF BREAKER FAILURE PROTECTION
For most of the faults, the generator breaker involves tripping the generator from the system.
Failure of the breaker to open probably results in loss of protection and other problems such as
motoring action or single phasing, If one or two poles of the generator breaker fail to open due
to mechanical failure in breaker mechanism, the result can be a single phasing and negative
phase sequence currents inducted on the rotor. The LBB protection is energized when the
breaker trip is initiated after a suitable time interval if confirmation of the confirmation of
breaker tripping from three poles is not received. The energized tripping signal from LBB
protection will trip all generator breakers and all feeder breakers through Bus-bar protection.
(11) 51 (VOLTAGE CONTROLLED INVERSETIME OVERCURRENT PROTECTION)
(12) 59 OVERVOLTAGE PROTECTION
First, one should raise an alarm if the over voltage is above 110% of rated value. There would
a subsequent trip if it persists for 1 min or more. Very large over voltages of the order of
120% of rated value or above, will lead to trip within approximately 6 seconds.
Why this protection is necessary?
Terminal voltage of a generator is controlled by an automatic voltage regulator (AVR). If the
load current (I) on the generator reduces, the AVR would automatically reduce the field
current so as to reduce open circuit emf E to maintain constant terminal voltage V. However,
loss of a VT fuse, incorrect operation or setting of AVR etc can lead to over voltage which is
detrimental to the generator. Steady state over voltage will lead to saturation of iron, both for
generator and the unit transformer connected to it. This will lead to large magnetizing currents,
unacceptable flux patterns, over-heating, which can damage the power apparatus. Hence,
generators have to be protected against overvoltage.
(13) 51 N (STANDBY/SENSITIVE EARTH FAULT PROTECTION)
It is similar to generator differential protection in working. It protects the high voltage winding
of Alternator against internal faults.
One set current transformers of the Alternator on neutral and phase side, is exclusively used for
this protection. The protection can not detect turn-to-turn fault within one winding. Upon the
detection of a phase-to-phase or phase-to-ground fault in the winding, the unit to be tripped
without time delay.

(14) 59 N (NON-DIRECTIONAL EARTH FAULT PROTECTION)
(15) 60 FL (FUSE FAILURE OR PT FAILURE PROTECTION)
(16) 78 POLE SLIPPING
When a generator loses synchronism, the resulting high current peaks and off-frequency
operation may cause winding stresses, pulsation torques and mechanical resonances that have
the potential danger to turbine generator. Therefore, to minimize the possibility of damage, it is
generally accepted that the machine should be tripped without time delay preferably during the
first half-slip cycle of the loss of synchronism condition. The electrical center during loss-of-
synchronous conditions can oc
The point at which the apparent impedance swing crosses the impedance line between
the generator and the system is referred to as the electrical center of the swing and
represents the point at which zero voltage occurs when the generator and the system
are 180 degrees out-of-phase. During pole slipping the voltage magnitude between the
generator and the system reaches two per unit when the angle difference reaches 180
degrees, which can result in high currents that cause mechanical forces in the generator
stator windings and undesired transient shaft torques. It is possible for the resulting
torques to be of sufficient magnitude to cause the shaft to snap or damage turbine
blades.

(17) 81 OVER/UNDER FREQUENCY PROTECTION
If alternator frequency is changed so its fall out from synchronism. For this Speed Governor of
Turbine may be Faulty.
(18) 81 R (RATE OF CHANGE OF FREQUENCY PROTECTION)
It is also called V/f protection. During start-up or shut down, the speed of the generator will
deviate significantly from the nominal speed. As per the emf equation (E = 4.44f mN),
overfluxing of the core is not simply a consequence of over voltages with respect to nominal
voltage. Rather overfluxing occurs when V/f ratio exceeds its nominal value.
Per unit voltage divided by per unit frequency commonly called Volts/Hertz is a measurable
quantity that is proportional to flux in the generator cores. Moderate over fluxing (105-110%)
increases core loss resulting in increase of core temperatures due to hysterics & eddy currents
loss. Long term operation at elevated temperatures can shorten the life of the stator insulation.
Severe over fluxing can breakdown inter-laminar insulation followed by rapid local core
melting.
Over fluxing normally can be caused by over speed of the turbine or over excitation during
Off-line condition, and load rejection or AVR mal-functioning during On-line condition.
(19) 87G DIFFERENTIAL PROTECTION
Some form of high-speed differential relaying is generally used for phase
faultprotection of generator stator windings.
Differential relaying will detect threephase faults, phase-to-phase faults, double-phase-to-
ground faults, and some single-phase-to-ground faults, depending upon how the generator is
grounded.
Differential relaying will not detect turn-to-turn faults in the same phase since there is no
difference in the current entering and leaving the phase winding.
Where applicable, separate turn fault protection may be provided with the split phase relaying
scheme.
This scheme will be discussed subsequently. Differential relaying will not detect stator ground
faults on high-impedance grounded generators.
The high impedance normally limits the fault current to levels considerably below the practical
sensitivity of the differential relaying.
Three types of high-speed differential relays are used for stator phase fault detection:
percentage differential, high-impedance differential, and self-balancing differential.
Percentage Differential Protection

Automatic Field Suppression and use of Neutral Circuit Breaker
In the event of a fault on a generator winding even though the generator circuit breaker is tripped, the fault
continues to be fed as long as the excitation will exist because emf is induced in the generator itself.
So it is necessary to discharge excitation magnetic field in the shortest possible interval of time. Hence, it is
to be ensured that all the protection system not only trip the alternator circuit breaker but also trip
automatic field discharge switch.
The Schematic Diagram for Automatic Field Suppressing and opening of the neutral Circuit Breaker
In the event of fault the circulating relay contact is closed and so trip coils TC1, TC2, TC3 and TC4 are
energized.
The trip coil TC1 opens the main Circuit Breaker while TC2 and TC4 opens the upper contacts, shorts the
lower contacts so as to short-circuit the field winding through resistor R1 and R2.
This Process of discharging consists of the isolation of the exciter from the alternator rotor field winding
and involves the dissipation of magnetic energy stored in the inductive reactance of the rotor and the main
exciter windings.

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