all about ONGC Hazira. Mainly i discussed ONGC in view of electrical engineer.

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SUMMER TRAINING REPORT
OIL & NATURAL GAS CORPORATION
LTD. HAZIRA PLANT SURAT
BY.
RAGHAV CHUG
ANKIT SAINI
PURUSHOTTAM KUMAR
B.TECH. (ELECTRICAL ENGG.)
S.V.NATIONAL INSTITUTE OF TECHNOLOGY,
SURAT
MENTORED BY : GUIDANCE BY : THANKS TO:
Mrs. C. BHARATHI Mr. RUTVIK Mr. ARUN DATTA
Mr. K.V. SUBBARAO

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Table of contents:
1 .Overview of ONGC
2. HGPC Electric Power System
3. CO-Generation Unit:
3.1 What is Co-Generation?
3.2 overview of COGEN Unit
3.3 Objectives of COGEN
3.4 Advantages of GT Based CPP
3.5 COGEN Power Efficiency
3.6 Major Systems of COGEN Plant
3.7 Gas Turbine
3.7.1 Theory of operation
3.7.2 Gas Turbine Construction Details
3.7.3 GT System & Components
3.7.4 GT Protection
3.7.5 GT Generator System
3.8 Boilers
3.8.1 Working Principle
3.8.2 Basic details of Boiler
3.9 Switchyard Rating
3.10 Two 11kV bus as S/S-I

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3.11 Power & Steam Demand
3.12 HRSG (Heat Recovery Steam Generator)
3.13 Power Generation
3.14 Modes of operation
3.15 Generator Protection
3.16 Benefits of COGEN
4. Electrical Repair Shop
4.1 UPS (Unintrupted Power Supply)
4.1.1 UPS Applications
4.1.2 UPS Components
4.1.3 Operation Mode
4.1.4 Working Principle
4.1.5 UPS Attributes
4.1.6 UPS Topology
4.1.7 UPS Protection
4.2 Air Conditioning
4.3 Lighting
5. Pipes color code
6. Production Process
7. Process Units

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Acknowledgement
Trainings for giving me a chance to come at ONGC Hazira
plant for training.
. BHARATHI who guided
me throughout my project .
thanks to Mr. VIPUL MANDILIYA, Mr. K. V.
SUBBARAO , Mr. A.B.JAGUWALA , Mr. RUTVIK who have
explained me each and every thing , so that I could corelate
the theoretical and technical aspects of all the practical
machines and instruments I see in the plant .
grateful to Mr. J. DAVE, TIWARI Sir for their
open hearted support and sharing their valuable technical
knowledge.
ankful to all ONGC
staff members of HAZIRA plant for their kind cooperation
and valuable guidance throughout the process of work.

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Overview of ongc hazira plant
oil and gas company headquartered in Dehradun,India. It is a Public Sector
Undertaking (PSU) of the Government of India, under the administrative control
of the Ministry of Petroleum and Natural Gas.
largest oil and gas exploration and production company. It
produces around 69% of India’s crude oil (equivalent to around 30% of country’s
total demand) and around 62% of its natural gas.
added products such as Natural Gas Liquids
(NGL), Aromatic Rich Naphtha(ARN) and Kerosene. Internationally its wholly
owned subsidiary ONGC Videsh Limited has number of existing and up-coming
interest in selected Oil patches including development of large gas field in
Vietnam offshore.
and Asia’s largest gas processing facility.It is situated near Bhatpore Village ,on
Surat-Dumas Road, 18 km to the western side from Surat Railway Station.
Tapti River connecting Kuchchh track pipeline originating from the South Basin
in off shore Vasai gas fields of ONGC Mumbai and Panna,Mukta &Tapti fields
operating under joint venture.
working inside the Plant. The Plant was set up in September 1985.
l, Condensate
and Fractionation Units. Liquefied Petroleum Gas Plant, Gas Sweetening Unit,
Unit for Gas Dehydration, Dew Point Depression. Sulphur Recovery Unit,
Kerosene recovery unit and Co-Generation Unit.

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t of Rs 1337 Crores approx.
including Phase-III (A). In view of ageing of Phase-I & Phase-II facilities
(commissioned in 1988 & 1990 respectively) and likely to increase of gas
production from ONGC’s Western Offshore fields, as part of Phase-IV of
expansion of Hazira Complex, ONGC has installed Additional Gas Processing
Facilities (AGPF Project).
Mukta and other fields of the Bombay Offshore region.
ceive sweet gas from Bombay High, but with time it
was seen that there were concentrations of sour gas coming in the line. Hence
the plant was converted into a sour gas plant.
of the gas fields in Mumbai offshore are producing sour natural gas
containing poisonous Hydrogen Sulfide Gas (also known as acid gas/sour gas)
in varying amount. Sour natural gas containing H2S require special treatment
for removal of the poisonous gas.
rise to production of sour LPG which requires additional treatment for making it
sweet, marketable and safe for use.
s from South Basin
Gas Fields which is subsea reservoir. The gas is transported from South Basin
field to HGPC through subsea pipelines.
containing HC condensate, moisture and chemicals (like corrosion inhibitors)
are separated. Gas and associated Condensates are sent further in separate
system for processing.
Places visited during training
Gas Turbine,
Boilers, HRSG
in S/S-4

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/S-1, S/S-4, S/S-14
-Conditioning Unit
Lighting Unit
HGPC ELECTRICAL POWER SYSTEM
To feed the electricity to the entire Hazira Gas Processing Complex and the
residential townships for the employees ONGC Nagar-1, ONGC Nagar-2 and
Bachelor’s Colony at Magdalla, Surat with cumulative requirement to feed
approximate 31MW of Electrical load, ONGC HGPC is capable of generating 61.5
MW of power at full capacity from the Co-Generation Plant. This power is fed to
the various processing units by the network of the total 17 substations
consisting of more than 60 transformers throughout the palnt.
The HGPC consist various electrical devices, machines and apparatuses at
various process and utility units. These includes electrical machines like HT
motors, LT motors, EOT Cranes, Illumination and Air-conditioning utilities and
other minor apparatuses in large number of amounts. The regular preventive
maintenance and breakdown maintenance is handled by Field Maintenance
Group throughout the year.
Thus, Electrical Power System of HGPC is divided
into three units.
1.COGEN Unit
2.Substations
3.Field Maintenance Group
Cogeneration unit:-
What is Cogen Plant?.
The generation of Power and Steam is done simultaneously at the same time
is known as cogeneration. COGEN unit fulfills the Steam and Electricity
requirement of ONGC,HGPC. Thus is called Cogeneration Plant. And the use of
exhaust gas from gas turbine to produce steam increases its efficacy.

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PRINCIPLE OF COGENERATION
Cogeneration or combined heat and power (CHP) is the use of a heat engine or
power station to simultaneously generate electricity and useful heat. Tri-
generation or Combined cooling heat and power (CCHP) refers to the
simultaneous generation of electricity and useful heating and cooling from the
combustion of a fuel or a solar heat collector.
Cogeneration is a thermodynamically efficient use of fuel. In separate production
of electricity some energy must be discarded as waste heat but in cogeneration
this thermal energy is put to use.
Objectives of COGEN,HGPC:
, LP & MP Steam to the
process
Mehsana Asset & Sale to State Electricity Board.
The COGEN unit can generate maximum of 61.5 MW of Power from the 3
Generator units coupled with the Gas Turbines. Out of all the Power generated,
approximately 28-31 MW Power is utilised within the HGPC itself. 25 MW of
Power is exported to Mehsana Asset through wheeling with State Electricity
Board and the rest of the surplus power is exported to the State Electricity Board
for Sale.
OVERVIEW OF COGENERATION,HGPC

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In cogeneration unit we have 3 GTs
GT1 and GT2 are BRUSH make while GT3 is BHEL make
All GTs have rating as : 19.25 KW,11KV
Incoming power of GT1,2 is on 11KV Bus from there it is transmitted 11KV SS1.
After power is transferred to 11KV Bus of S/S-1 via 3 incomers each of GT1,GT2
AND GT3(either section A or section B of 11KV S/S-1).Power is distributed to all
over the plant for process requirement, residential complex of ongc and wheeled
to other ongc installations via state grid network. After being stepped upto 66KV.
Four incomers from from 11KV Bus bring power to phase 1 and 3. In phase 3
we have 415 V bus which gets power from 11 KV Bus through 2 transformers.
415 V Bus of phase 3 is called PMCC Bus and supplies power to HP pumps of
HRSG 3 Boiler and also two various local loads like station Battery Charger and
various Boilers auxiliaries.
Two incomers from S/S-1 to phase1 supplies power to 11KV Cogen Bus from
where it is distributed to 2 other Buses of 6.6KV and 415V.
Two 750 KVA transformers step-down the voltage from 11KV to 6.6 KV.
Now this 6.6KV Bus is source to FD fan motors of HRSG 1 and 2.
IMPORTANT MOTORS USED IN CO-GEN PLANT
Load shed scheme of HAZIRA PLANT

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Purpose of load shed scheme is to minimise total power blackout probability
by shedding pre-defined load. This is done under following four condition:
(1) NO GEB Condition + system frequency less than 47.55 HZ
(2) NO GT Condition : this is met when breakers of all the GTs are in off
condition
(3) GEB available with only one GT condition
(4) NO GEB condition + only one GT available
Operation of GTs:
(a) Solo operation of GT:- Single GT should run in either of the two
modes
1.isochronous mode
2.droop mode :part load
(b) Parallel operation of GTs without Grid
When two generators are operating in parallel one should be in
‘ISO’ mode (i.e. it will take care of load variation and will maintain
the frequency at 50 Hz).
And the other GT should be in ‘droop mode’
(c) Operation of GTs with Grid
When GTs are operated in parallel with grid they have to be in
‘Droop Mode’(preselect or base load).In this mode frequency will
not change.

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o Most reliable & trouble free.
o Quick starting & loading time.
o More compact.
o Cheaper overhauling cost.
o Quality power within minimal tolerance limit.
o Flexibility in use of fuel.
o Waste heat of gas turbines used for steam generation in HRSGs.
o Open cycle efficiency: 30-35%
o Combined cycle efficiency: 50-60%
o Cogeneration cycle efficiency: 75-80%.
DEMINERALIZATION PLANT(DM WATER PLANT)
This plant is used to remove dissolved salts from the water. When salts dissolve
in water, the molecular constituents of the salt form ions which have either
positive(+) electrical charge or negative(-) electrical charge.
Ion exchange De-mineralisation is accomplished using resins that exchange one
ion for another.
Water Plant Rating:
o Cat-ion exchanger: 3 numbers(80m³/hr. each)
o Weak base anion exchanger:3 numbers(80m³/hr. each)
o Strong base anion exchanger:3 numbers(80m³/hr. each)
o Degasser tower, blowers & pumps.
o Mix bed exchanger:3 numbers(80m³/hr. each)
o DM transfer pumps: 4 numbers(135m³/hr. each)
o DM water consumption:1500m³/day

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GAS TURBINE
A Gas Turbine also called a combustion turbine is a type of internal combustion
engine. It has an upstream rotating compressor coupled to a downstream turbine
and a combustion chamber in between.
The basic operation of the Gas Turbine is similar to that of the steam power plant
except that air is used instead of water. Fresh atmospheric air flows through a
compressor that brings it to higher pressure. Energy is added by spraying fuel
into the air and lighting it so the combustion generates a high-temperature flow.
This high-temperature, high-pressure gas enters turbine where it expands down
to the exhaust pressure, producing a shaft work output in the process. The
turbine shaft work is used to drive the compressor and other devices such as
electrical generator that may be coupled to the shaft. The energy that is not used
for shaft work comes out in the exhaust gases, so these have either a high
temperature or high velocity. The purpose of the gas turbine determines the
design so that the most desirable energy is maximized.
Compressor section:
-17 stage axial-flow compressor
-It consists of rotor and casing along with the inlet guide vanes and three rows
of exit guide vanes.

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FUNCTION -
It develops a highly compressed air with PRESSURE 8.1 Kg/cm2 and
temperature of 343 Degree.
COMPRESSOR STATOR ASSEMBLY CASINGS :
-It directs the flow of outside air into the compressor.
-It consists of the inlet guide vanes, journal bearing no.1 and sealing surface to
prevent bearing oil ingress.
-Inlet section of the compressor is connected to the air inlet duct to convey air
into compressor zero stage.
-It consists of the compressor stages blades 0 to 3aft casing -It contains of
compressor stages blades from 4 to 9.
-It contains stator blading from 10th to 16th stage and the exit guide vanes.
Bleed air from the 4th and 10th stages of the rotor is extracted
for various uses like sealing, cooling and preventing start -up surges through
bleed valve.
PROBLEM OF START UP SURGES:
startup, the air density changes through the machine to a lesser
degree than it does at full speed and causes stalling of the compressor with
reduction or virtual break down of the flow lending to start up trouble.

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SOLUTION :
prevent such a phenomenon, which is damaging to the equipment, the 10th
stage bleed valve remains open below 95% speed to ensure a minimum air mass
flow.
guide vanes are operated in conjunction with the bleed valve to
ensure fast and smooth starting of the gas turbine.
-up inlet vanes are set at 44 degree and when the turbine accelerates
to 95% speed, the vanes are rotated to the 80 degree position to increase flow of
air .
THEORY OF OPERATION
air is compressed isentropic ally combustion occurs at constant pressure, and
expansion over the turbine occurs isentropic ally back to the starting pressure.
In practice, friction and turbulence cause:
1. Non-isentropic compression: for a given overall pressure ratio, the compressor
delivery temperature is higher than ideal.
2. Non-isentropic expansion: although the turbine temperature drop necessary
to drive the compressor is unaffected the associated pressure ratio is greater,
which decreased the expansion available to provide useful work.
3. Pressure losses in the air intake, combustor and exhaust: reduces the
expansion available to provide useful work.
heat engines, higher combustion temperature means greater
efficiency. The limiting factor is the ability of the steel, nickel, ceramic or other
materials that make up the engine to withstand heat and pressure. Considerable
engineering goes into keeping the turbine parts cool. Some turbines also try to
recover exhaust heat, which otherwise is wasted energy. Recurpertators are heat
exchangers that pass exhaust heat to the compressed air, prior to combustion.
Combined cycle designs pass waste heat to steam turbine systems and combined
heat and power (co-generation) uses waste heat for hot water production.
Mechanically, gas turbines can be considerably less complex than internal
combustion piston engines. Simple turbines might have one moving part: the
shaft/ compressor/ turbine/ alternative-rotor assembly not counting the fuel
system. However, the required precision manufacturing for components and
temperature resistant alloys necessary for high efficiency often makes the
construction of a simple turbine more complicated than piston engines.

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have multiple shafts (spools), hundreds of turbines blade top speed determines
the maximum power possible independent of the size of the engine.
they have been hydrodynamic oil bearings or oil-cooled ball bearings. These
bearings are being surpassed by foil bearings, which have been successfully used
in micro turbines and auxiliary power units.
This also has three components:
-A Gas compressor
-A burner (or combustion chamber) --An
expansion turbine
chamber-pressure process since the chamber is open to flow in and out.
expanding through a turbine (or series of turbines). Some of the work extracted
by the turbine is used to drive the compressor.

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Actual Brayton cycle:
– Compression
– Heat addition
– Expansion
– Heat rejection
Gas turbine construction details:
o Compressor stages :17
o Turbine stages:2
o Number of combustors:10
o Pressure ratio:10:3
o Firing temperature:963˚C
o Load gear box rating:31500KW
o Load gear design: Single helical
Gas turbine system & components:
o Starting system:
o Compressor- (17 stage, axial flow)
o Fuel gas system
o Air inlet system
-cleaning air filters
o Combustion chamber: 10 nos.
o Turbine-2 stages

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o Lube oil & hydraulic oil system
o Temperature & Vibration monitoring system
o Gas/ fire detection & control system
o Accessory gear & auxiliaries
o Load gear & generator
o Water wash & line cleaning system
SPEEDTRONIK CONTROL (MK VI) FOR TURBINE CONTROL:
o Pre start-up checks & sequencing
o Start-up acceleration & shutdown
o Synchronising & loading of turbine
o Load & speed control
o Temperature control
o High vibration
o Over speed
o Fire detection
o High temperature
o Loss of flame
:
o The 31.25 MVA generators have Brushless excitation system.
o Winding temperature monitoring system.
o Generator protection system.
o Rotor earth fault monitoring system.
o Synchronising circuits
o GTG 1&2 –Forced open air cooling system
o GTG 3-closed air- water cooling system

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TRANSFORMER DETAILS
GRID TRANSFORMER 1/2
Make : VOLTAMP
MVA RATING : 25/31
HV VOLT : 66 KV
LV VOLT : 11 KV
HV AMP. : 218.69/271.8 AMP.
LV AMP. : 1312.16/1627.08 AMP.
IMP % Voltage : 10.54(ONAF)/13.02(ONAN)
COOLING : ONAN/ONAF
FREQUENCY : 50 Hz
WEIGHT OF OIL : 11500 Kg

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WEIGHT OF CORE & WINDING : 21000 Kg
TOTAL WEIGHT : 49000 Kg
RATED CURRENT AT NO LOAD : 0.75 % FLRC
NO LOAD LOSS : 17.1 KW
INSULATION LEVEL : HV – 325 KVP HVN – 95 KVP
LV & LVN --75KVP
UNIT AUXILLARY TRANSFORME (3 No.)
Make : BHEL ( DRY TYPE )
RATING : 400 KVA
HV VOLT : 11 KV
LV VOLT : 433 V
HV AMP. : 21 A
LV AMP. : 533 A
COOLING : AN
FREQUENCY : 50 Hz
INSULATION CLASS : F
WEIGHT : 3600 Kg
INSULATION LEVEL : 75 KNP
IMPEDANCE % VOLTAGE : 4.5

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# In ONGC Hazira Plant:
-Approximate 1500 LT Motors
-Approximate 105 HT Motors
o 66 kV switchyard with:
-4 number of MOCBs
-2 number of 25/31.5 MVA, 66/11kV transformers with OLTC
-Bus PTs
-CTs
-Lightening Arrestors
-GEB Metering System
o Two GEB grid feeders with contract demand of 8MVA
-1 with:

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o A Bus Coupler
o A reactor connecting both Buses
o Numerous feeders supplying the total load of HGPC through VCBs
Pipes Color-Code in Plant
Grey :- Water
Yellow :- Gas
Red :- Fire water
Blue :- Instrumented Air
Green :- DM Water
DURATION OF MAINTAINENCE OF VARIOUS ELECTRICAL MACHINES:
1.LT MOTORS:ONCE IN EVERY 3 MONTHS
2.HT MOTORS:ONCE IN EVERY 6 MONTHS
3.GTS:ONCE IN EVERY 5 YEARS
4.TRANSFORMER: ONCE IN EVERY 6 MONTHS

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ELECTRICAL POWER SYSTEM:
11 KV cubicle of Generator is provided at the Cogen switchgear room for
Generator’s power input and consists of:
 11 KV minimum Oil-circuit Breaker(Master Breaker)
 Fused tee-off connection suitable for connection to the unit auxiliary
transformer and a parallel connection to 11 KV Bus PT.
 Unit auxiliary transformer incomer.
 Terminating and connection of generator outgoing feeder cables.
 Bus PT for live bus incoming voltage sensing.
For supplying power to unit auxiliaries at 415V, one no. 315KVA, 11/.415KV,
Delta/Star transformer has been provided. The transformer is oil immersed type.
The power tapping is taken from the 11KV system by a tee-off provision inside
the line side cubicle.
GT MCC:
This provides control of electrical auxiliaries through motor controllers. Each
motor controller includes OFF/HEAD/AUTO Switch Control, Power
Transformer, Control Circuit, Power Contactor, ON/STANDBY Duty Selector
Switch and Indicating Lights. Each turbine has various accessory motors and
other auxiliary supply modules housed in MCC. In Cogen plant each GT has a
MCC module of its own. MCC receives power from two sources:
(1) UAT breaker and
(2) Section C of PCC(415 V) bus
In case if supply from UAT breaker fails or if UAT is under maintenance then,
power could be harnessed from Section C of PCC panel.GT-MCC module boxes
supply of 125V DC, 110V AC, 230V AC used for various auxiliaries . 125V DC is
used for Emergency oil pump, Ratchet motor and aux. supply for GCP panel of
Generator and TCP panel of turbine. All the auxiliaries of GT have their power
supply from MCC panel. E.g.-vent fans of turbine, Auxiliary Lube oil pump,
Auxiliary Hydraulic oil pump, Emergency Lube oil pump, Battery Charger supply
etc.
GT PCC:
In one way or the other PCC is called the heart of the distribution system of
Cogen Plant as, it boxes all important
LT loads of the Cogen. All the pumps of Boilers (HP & LP), AC and Ventilation,
415V supply to UPS of mother substation S/S-1 etc. are all fed by PCC panel of

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Cogen plant. PCC gets its incoming supply as 415V from two incoming 2 MVA
Transformer each fed by 11KV from Cogen 11KV Bus.
Active/Reactive Power Control and Capacitor Bank
The demand of active power is expressing Kilo Watt (kw) or mega watt (mw). This
power should be supplied from electrical generating station. All the
arrangements in electrical pomes system are done to meet up this basic
requirement. Although in alternating power system, reactive power always comes
in to picture. This reactive power is expressed in Kilo VAR or Mega VAR.
The demand of this reactive power is mainly originated from inductive load
connected to the system. These inductive loads are generally electromagnetic
circuit of electric motors, electrical transformers, inductance of transmission and
distribution networks, induction furnaces, fluorescent lightings etc. This reactive
power should be properly compensated otherwise, the ratio of actual power
consumed by the load, to the total power i.e. vector sum of active and reactive
power, of the system becomes quite less.
This ratio is alternatively known as electrical power factor, and fewer ratios
indicates poor power factor of the system. If the power factor of the system is
poor, the ampere burden of the transmission, distribution network,
transformers, alternators and other equipments connected to the system,
becomes high for required active power. And hence reactive power compensation
becomes so important. This is commonly done by capacitor bank. we know that
active power is expressed = VIcosθ
Where, cosθ is the power factor of the system. Hence, if this power factor has got
less valve, the corresponding current (I) increases for same active power P.
As the current of the system increases, the Ohmic loss of the system increases.
Ohmic loss means, generated electrical power is lost as unwanted heat originated
in the system. The cross-section of the conducting parts of the system may also
have to be increased for carrying extra ampere burden, which is also not
economical in the commercial point of view. Another major disadvantage, is poor
voltage regulation of the system, which mainly caused due to poor power factor.
The equipments used to compensate reactive power.
There are mainly two equipments used for this purpose.
(1) synchronous condensers
(2) Static capacitors or Capacitor Bank
1.static capacitor bank
Static capacitor can further be subdivided in to two categories,

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(a) Shunt capacitors
(b) Series capacitor
These categories are mainly based on the methods of connecting capacitor bank
with the system. Among these two categories, shunt capacitors are more
commonly used in the power system of all voltage levels. There are some specific
advantages of using shunt capacitors such as,
1.It reduces line current of the system.
2.It improves voltage level of the load.
3.It also reduces system Losses.
4.It improves power factor of the source current.
5.It reduces load of the alternator.
6.It reduces capital investment per mega watt of the Load.
Where, SR – 7KVAR, 6.6KV (Series Reactor)
RVT –Residual Voltage Transformer
F –Expulsion type unit fuses
Final power factor is 0.92

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Human Machine Interface (HMI)
(Human Machine Interface) The user interface in a manufacturing or process
control system. It provides a graphics-based visualization of an industrial control
and monitoring system. Previously called an "MMI" (man machine interface), an
HMI typically resides in an office-based Windows computer that communicates
with a specialized computer in the plant such as a programmable automation
controller (PAC), programmable logic controller (PLC) or distributed control
system (DCS).
Boilers
not necessarily boil (Furnace is normally used if the purpose is not actually to
boil the fluid). The heated or vaporized fluid exists the boilers for use in various
processes or heating applications.
(which are relatively new and of more capacity) and fire tube boilers (which are
relatively order and of less capacity and efficiency). Working principal of fire tube
boiler is hence mentioned.
The working principle of water tube boiler: It consists of mainly 2 drums, one is
upper drum called Stream Drum other is lower drum called Mud drum. These

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upper drum and lower drum are connected with two tubes namely down-comer
and riser tubes as shown in picture.
Water in the lower drum is the riser connected to it, is heated and stream is
produced in them which comes to the upper drums naturally. In the upper drum
the stream is separated from water naturally and stored above the water surface.
The colder water is fed from feed water inlet at upper drum as this water is
heavier than the other water of lower drum and that in the riser. So there is one
conventional flow of water in the boiler system.
More and more steam is produced the pressure of the closed system increases
which obstructs this conventional flow of water and hence rate production of
steam becomes slower proportionately. Again if the steam is taken through steam
outlet, the pressure inside the system falls and consequently the conventional
flow of water becomes faster which result in faster steam production rate. In this
way the water tube boiler can control its own pressure. Hence this type of boiler
is referred as self-controlled machine.
to produce power. As both steam and power is produced in this unit so the name
COGENERATION is given.
rated steam is being produced and used in various processes. Steam
having high latent heat vaporization is the best medium to generate heat as it
maintains its temperature as constant till all the steam is cooled to water. This
is the main advantage of using steam for heating purposes in plant.

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approximately 20MW due to some damaged machineries.
The steam produces in three types i.e. LP (Low pressure), MP (Medium
pressure), and HP (High pressure).
BASIC DETAILS OF THE BOILER
o Gas Turbines 57 MW at 35˚C
o Generators 31.25 MVA
o HRSG 1,2& KTI boilers
o HP 18.5T/Hr,37kg/cm²
o LP 105T/Hr,9kg/cm²
o HRSG-3(HP) 50T/Hr,37kg/cm²
o Dumping facility
o Grid feeders with contract demand of 8MVA
o 04 Gas Fired Boilers(MP) 32T/Hr.
o Average power demand of 30 to 31MW
o HP Steam demand of 45-65 Ton/Hr. at 26 kg/cm²

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o MP Steam demand of 60-85 Ton/Hr. at 18kg/cm²
o LP Steam demand of 140-180 Ton/Hr. at 6kg/cm²
Heat recovery steam generator (HRSG)
The form and size depends on the application: mobile steam engines such as
steam locomotives, portable engines and steam powered road vehicles typically
use a smaller boiler that form an integral part of the vehicle; stationary steam
engines, industrial installations and power station will usually have a larger
separate steam generating facility connected to the point-of-use by piping. A
notable exception is the steam-powered fireless locomotive, where separately-
generated steams are transferred to a receiver (tank) on the locomotive.
ry steam generator (HRSG) is an energy recovery heat exchanger
that recovers heat from a hot gas steam. It produces steam that can be used in
a process or used to drive a steam turbine. A common application for an HRSG
is in a combined-cycle power station where hot exhaust from a gasturbine is fed
to an HSRG to generate steam which in turn drives a steam turbine. This
combination produces electricity more efficiently than either the gas turbine
alone. Another application for an HRSG is in diesel engine combined cycle power
plants, where hot exhaust from a diesel engine, as primary source of energy, is
fed to an HSRG to generate steam which in turn drives a steam turbine.
Cogeneration plant typically has a higher overall efficiency in comparison to a
combined cycle plant. This is due to loss of energy associated with the steam
turbine.
exhaust gases flow or number of pressure level. Based on the flow exhaust gases,
HRSGs are categorized into single pressure and level. Based on the flow exhaust
gases, HRSGs are categorized into vertical and horizontal types. In horizontal
type HRSGs exhaust gas flows horizontally over vertical tubes whereas in vertical
types HRSGs exhaust gas flow vertically over horizontal tubes. Based on
pressure levels, HRSGs can be categorized into single pressure and multi
pressure. Single pressure HRSGs have only steam drum and steam is generated
at single pressure level whereas multi pressure HRSGs employ two (double
pressure) or triple pressure steam drums. As such triple pressure HRSGs consist
of three sections LP section, a reheat/IP (intermediate pressure) section. Each
section has a steam drum and an evaporator section where water is converted

29. 29
to steam. This steam then passes through super heaters to raise the temperature
and pressure past the saturation point.
POWER GENERATION
Grid Feeders Isolated.
-Availability of the Two Gas Turbines System is synchronised
with Grid to meet Power demand.
of Sudden Shortfall in Generation due
to some Abnormality.

30. 30
- AVR:
o AVR maintains the terminal voltage within the capacity of the generator.
o The AVR also does the protective actions of :
tage Monitoring
:
o The synchronising of all generators and the grid feeders is done at 11kV level
only.
o The generators synchronising can be done either in Auto or Manually.
o Load Shedding is done whenever there is load-generation mismatch.
o This scheme is operated by frequency sensing.
o Winding Temperature Protection through RTDs.
o Overcurrent Protection.
o Voltage Restrained Overcurrent Protection
o Reverse Power Protection Stage 1 & Stage 2
o Negative Sequence Current Protection

31. 31
o Under Voltage Protection
o Over Voltage Protection
o Differential Protection
o Pole slipping protection
o Loss of Field
o Under Frequency
o Turbine under speed trip.
OBJECTIVE OF PROTECTION:
The objective of power system protection is to isolate a faulty section of electrical
power system from rest of the live system so that the rest portion can function
satisfactorily without any severer damage due to fault current.
COMPONENTS OF POWER SYSTEM PROTECTION:
1.SWITCHGEAR
2.BATTERY STATION
1.SWITCH GEAR
A switchgear or electrical switchgear is a generic term which includes all the
switching devices associated with mainly power system protection. It also
includes all devices associated with control, metering and regulating of electrical
power system. Assembly of such devices in a logical manner forms switchgear.
The switchgear has to perform the function of carrying, making and breaking the
normal load current like a switch and it has to perform the function of clearing

32. 32
the fault in addition to that it also has provision of metering and regulating the
various parameters of electrical power system. Thus the switchgear includes
circuit breaker, current transformer, voltage transformer, protection relay,
measuring instrument, electrical switch, electrical fuse, miniature circuit
breaker, lightening arrester or surge arrester, electrical isolator and other
associated equipment.
PARTS OF SWITCH GEAR
(A) CIRCUIT BREAKER
The modern power system deals with huge power network and huge numbers of
associated electrical equipments. During short circuit fault or any other types of
electrical fault these equipment as well as the power network suffer a high stress
of fault current in them which may damage the equipment and networks
permanently.
For saving these equipment and the power networks the fault current should be
cleared from the system as quickly as possible. Again after the fault is cleared,
the system must come to its normal working condition as soon as possible for
supplying reliable quality power to the receiving ends. In addition to that for
proper controlling of power system, different switching operations are required
to be performed.
So for timely disconnecting and reconnecting different parts of power system
network for protection and control, there must be some special type of switching
devices which can be operated safely under huge current carrying condition.
During interruption of huge current, there would be large arcing in between
switching contacts, so care should be taken to quench these arcs in circuit
breaker in safe manner. The circuit breaker is the special device which does all
the required switching operations during current carrying condition. This was
the basic introduction to circuit breaker.

33. 33
There are different types of breaker depending upon handling of power:
(a) DOL(Direct ON-Line starter): 1-60 KW
(b) Air Circuit Breaker : 60-160 KW
(c) Vacuum/SF6 Breaker : above 160 KW
(B) ELECTRICAL ISOLATOR
Circuit breaker always trip the circuit but open contacts of breaker cannot be
visible physically from outside of the breaker and that is why it is recommended
not to touch any electrical circuit just by switching off the circuit breaker. So for
better safety there must be some arrangement so that one can see open condition
of the section of the circuit before touching it. Isolator is a mechanical switch
which isolates a part of circuit from system as when required. Electrical isolators
separate a part of the system from rest for safe maintenance works.
(C)PROTECTION RELAY
A relay is automatic device which senses an abnormal condition of electrical
circuit and closes its contacts. These contacts in turns close and complete the
circuit breaker trip coil circuit hence make the circuit breaker tripped for
disconnecting the faulty portion of the electrical circuit from rest of the healthy
circuit
(D)LIGHTENING ARRESTOR OR SURGE ARRESTER
A surge arrester is a device to protect electrical equipment from over-voltage
transients caused by external (lightning) or internal (switching) events.

34. 34
2.BATTERY STATION
All the circuit breakers of electrical power system are DC (Direct Current)
operated. Because DC power can be stored in battery and if situation comes
when total failure of incoming power occurs, still the circuit breakers can be
operated for restoring the situation by the power of storage station battery.
Hence, the battery is another essential item of the power system. Some time it is
referred as the heart of the electrical substation. An electrical substation battery
or simply a station battery containing a number of cells accumulate energy
during the period of availability of AC supply and discharge at the time when
relays operate so that relevant circuit breaker is tripped at the time failure of
incoming AC power.
DISTRIBUTION NETWORK DIAGRAM :

35. 35

36. 36

37. 37
Benefits of cogeneration
Provide the cogeneration is optimized in the way described above( i.e. sized
according to the heat demand), the following benefits can be obtained:
-Increased efficiency of energy conversion and use.
-Lower emissions to the environment, in particular of CO₂, the main
greenhouse gas.
process or agricultural wastes (either anaerobically digested or gratified) are
used.
which serve as fuels for cogeneration schemes, increases
the cost effectiveness and reduces the need for waste disposal. Large cost
savings, providing additional competitiveness for industrial and commercial
users while offering affordable heat for domestics’ users also.
generation where plants are designed to meet the needs of local consumers,
providing high efficiency, avoiding transmission losses and increasing flexibility
in system use.
opportunity to increase the diversity of generation plant, and provide competition
in generation. Cogeneration provides one of the most important vehicles for
promoting liberalization in energy markets.
UPS(uninterrupted power supply)
battery/flywheel backup, is an electrical apparatus that provides emergency
power to a load when the input power source or mains power fails. A UPS differs
from an auxiliary or emergency power system or standby generator in that it will
provide near-instantaneous protection from input power interruptions, by
supplying energy stored in batteries, super capacitors, or flywheels. The on-
battery runtime of most uninterruptible power sources is relatively short (only a
few minutes) but sufficient to start a standby power source or properly shut
down the protected equipment.
ch as computers, data centres,
telecommunication equipment or other electrical equipment where an
unexpected power disruption could cause injuries, fatalities, serious business
disruption or data loss. UPS units range in size from units designed to protect a
single computer without a video monitor (around 200 voltampere rating) to large

38. 38
units powering entire data centres or buildings. The world's largest UPS, the 46-
megawatt Battery Electric Storage System (BESS), in Fairbanks, Alaska, powers
the entire city and nearby rural communities during outages.
An Uninterrupted Power Supply is employed for critical loads which cannot be
powered by utility supply (mains) directly. An UPS system protects the critical
loads from utility supply problems such as the following:
-
This unit is already a part of our installation. It distributes the Mains (utility)
and/or Generator power to your facility and will also supply input to your UPS
system. The safety “earth” connection for the UPS system is also considered to
be a part of the Mains distribution unit.

39. 39
An Auxiliary module generally comprises a Voltage Stabilizer (static type or servo
type) to provide a stable Alternate supply to the UPS.
Consists of the UPS (without Battery).Depending upon the configuration
selected, one or more UPS modules can be employed.
This module comprises the battery pack for supplying power to the UPS module
in the event of a mains failure. There are various types of batteries- SMFB (Sealed
Maintenance Free Battery), LATB, NI-CD etc. Battery module may either be in
the form of an enclosure or may be supplied as a rack. Vented batteries such as
LATB can emit acidic fumes & requires a special room.
Output of the UPS system needs to be distributed to various loads. Such a
module generally comprises switches, fuses, etc. The coordination of fuses is
important to avoid faults from affecting the other loads supported by the UPS.
OPERATION MODE
The Modular UPS is an on-line, double-conversion UPS that permits operation
in the following mode
• Normal mode
• Battery mode
• Bypass mod
• Maintenance mode (manual bypass)
The inverter of power modules continuously supply the critical AC load. The
rectifier/charger derives power from the AC mains input source and supplies DC
power to the inverter while simultaneously FLOAT or BOOST charging its
associated backup battery.
y Mode or Mains Failure:
Upon failure of the AC mains input power, the inverter of power modules, which
obtain power from the battery, supply the critical AC load. There is no
interruption in power to the critical load upon failure. After restoration of the AC
mains input power, the” Normal mode” operation will continue automatically
without the necessity of user intervention.

40. 40
:
If the inverter overload capacity is exceeded under Normal mode, or if the inverter
becomes unavailable for any reason, the static transfer switch will perform a
transfer of the load from the inverter to the bypass source, with no interruption
in power to the critical AC load. Should the inverter be asynchronous with the
bypass, the static switch will perform a transfer of the load from the inverter to
the bypass with power interruption to the load. This is to avoid large cross
currents due to the paralleling of unsynchronized AC sources. This interruption
is programmable but typically set to be less than 3/4 of an electrical cycle, e.g.,
less than 15ms (50Hz) or less than 12.5ms (60Hz). The action of transfer/re-
transfer can also be done by the command through monitor.
A manual bypass switch is available to ensure continuity of supply to the critical
load when the UPS becomes unavailable e.g. during a maintenance procedure.

41. 41
Working principles of ups:
The UPS consisting of four major sections:
nverter
#UPS Front panel:
Rectifier/charger section:
The rectifiers operate according to the constant voltage current limiting principle
and shall incorporate a “Soft Start” feature to gradually accept load on initial
energizing.
The rectifier section of the UPS system is capable of precise regulation to
prevent damage to the battery.
the initial battery rapid charge operation is provided by Manual & Automatic
means.
voltage to maintain the charging current limit to a present level. A separate
current sensing circuit provides for adjustment of battery current.

42. 42
Inverter:
is of the PMW (Pulse Width Modulation) type.
depending upon the rating. By switching a train of pulse through one IGBT
bridge circuit and alternatively through second IGBT circuit at the required
output frequency the output sine wave build up.
a frequency decided by the control card. By switching a train of pulses through
one transistor bridge circuit and alternatively through second transistor circuit
at the required output frequency the output AC is developed.
waveform than near to the cross-over point. By varying the pulse width in this
way the output AC waveform can be controlled very accurately.

43. 43
of single phase inverter having 4 switches
Static switch:
static bypass switch is provided to ensure that even in the event of an
inverter failure the supply of power to the load will maintained automatically and
without break by connecting it to the incoming Bypass supply.
static switch employs a pair of back-to-back thyristors. One set is in series
with the inverter output and another in series with Bypass supply.

44. 44
BATTERY:
When mains fail the battery takes over the DC supply of the inverter without any
interruption. The voltage of the battery is supervised by the control card. Right
before the battery voltage reaches its end an alarm (LOW BATT) is generated.
When the battery voltage reaches its end the UPS is switched-off automatically,
to prevent an abnormal discharging of the battery. Battery is supporting the
charger in case of transient surge and dip at the inverter.
Role of battery in ups
• To provide reliable emergency DC power to the inverter when the normal power
fails or degrades.

45. 45
Ups attributes
• Excellent Transient Response
• High Crest Factor Load Handling Capability
• High Fuse clearing Capability
• Low Noise
• Wide Frequency Synchronization Window
• Connectivity
Ups topology:-
• Static UPS
– Single Conversion
– Double Conversion
– Delta Conversion
• Rotary UPS
Basic element of static ups:-
Double conversion-

46. 46
UPS are available in following configuration:
- Single alone system
- Cascaded Reductant System
- Parallel Reductant System
- Split Reductant System
• RFI/EMI filter protection
• Input voltage surge protection using GMOV
• Input current spikes protection through Line chokes and Semiconductor fuses.
• Input under voltage & over voltage protection.
• Soft start feature for Charger and Inverter.
• Battery protection through current limit
• Battery reverses polarity protection.
• DC over-voltage and under voltage protection.
• Inverter Short circuit and over temperature Protection.
• Di/dt and dv/dt protection for power devices.

47. 47
AIR CONDITIONING
The principle behind working of A.C. is same as that of refrigerator. A.C. works
on the mechanism of refrigerant liquid. Any A.C. will comprise of three parts i.e.
a compressor, a condenser and an evaporator. Compressor and condenser are
usually kept outside the house where as an evaporator is kept inside the house.
Types of Air-Conditioner
There are different types of air conditioners available. Which type of the AC
should be used depends upon the size of the area which has to be cooled. The
following are few types of AC used:
1. Window Air-Conditioning System
2. Split Air-Conditioning System
3. Central Air-Conditioning System
4. Package Air-Conditioning System
As there are large buildings in ONGC Hazira Plant so the most efficient cooling
system which can be used for cooling purposes are Central Air-Conditioning
System as they are used for cooling of large building areas and are efficient also
as only single system have to be installed in it as compared to Split AC.
CENTRAL AIR-CONDITIONING UNIT:
Central air conditioner unit is an energy moving or converted machines that are
designed to cool or heat the entire house. It does not create heat or cool. It just
removes heat from one area, where it is undesirable, to an area where it is less
significant.

48. 48
Central air conditions has a centralize duct system. The duct system (air
distribution system) has an air handler, air supply system, air return duct and
the grilles and register that circulates warm air from a furnace or cooled air from
central air conditioning units to our room. It returns that air back to the system
and starts again.
It uses Ac refrigerant (we may know it as Freon) as a substance to absorb the
heat from indoor evaporator coils and rejects that heat to outdoor condenser
coils or vice versa.
Central air conditioner units used a blown, which is mounted indoor to a furnace
to circular that cold air to the entire house through air distribution system (duct).
It uses the same duct system for heating and cooling.
THE OPERATION PRINCIPLE OF CENTRAL AC:
Central air conditioner unit is simply a matter of removing heat from indoor
(evaporator coil) to outdoor (condenser unit) by using the four basic mechanical
components:
The compressor, the condenser, the expansion device, the evaporator and the
refrigerant copper tube that connects these components.
If we understand how the basic refrigeration cycle works, we understand how
any air conditioner units work. Since all air conditioner units have the same
basic components, refrigeration cycle and air conditioning theory.
It doesn’t matter if it’s window ac, packed air conditioner, ductless air
conditioner, portable air conditioners or central air conditioning units.The basic
operation is always the same.

49. 49
BASIC MECHANICAL COMPONENTS OF CENTRAL AC:
1. COMPRESSOR:
The air conditioner compressors, located outdoor within the condenser unit is
responsible for providing the pressure difference in an air conditioner system.
The compressor pulls in low-pressure, temperature from the evaporator and
compresses that gas to high-pressure, high temperature superheats to the
condenser.
2. CONDENSER:
Air conditioner condenser, it’s a square (or round) metal box located outdoor. It
receives the high-pressure, temperature vapour refrigerant from the compressor
and rejects that heat to the surrounding air (medium).
As a result of condensing the hot vapour heat, the refrigerant turns to liquid.
3. EVAPORATOR:
The air conditioner evaporator, located indoor within the air handler or furnace
is responsible for absorbing heat from whatever places that needs to be cool.
4. REFRIGRANT:
Air Conditioner Refrigerant copper tube- Its copper tube that connects the
compressor, the condenser, the metering device, and the evaporator.
Once the refrigerant’s tube connects to these components, and we add
refrigerant in it. It is now known as refrigeration cycle (close- loop air conditioner
units).The copper tube comes in many differences sizes, purpose and some of it
comes with an insulator.
5. EXPANSION VALVE:
The air conditioner expansion valve (meter devices) is located indoor in the air
handler or furnace. The meter devices are near the evaporator coil which is
within the air handler. It acts as a restriction. It’s responsible for providing the
correct amount of refrigerant to the evaporator coil.

50. 50
THE PRODUCTION PROCESS
The plant receives gas in 36” and 42” pipelines through 217 km long submarine
pipes from South Bassein to Umbrhat and then 14 km long lines from Umbrhat
to the Gas Terminal. Here gas and any condensates formed are seperated. The
gas goes to Gas Sweetening Unit or GSU and the condensate is sent to
Condensate Fractionation Unit or CFU. In GSU the feed gas is freed of hydrogen
sulphide and is hence “sweetened”. Thee hydrogen sulphide recovered is sent to
Sulphur Recovery Unit or SRU, where it is converted into elemental sulphur and
dried into bricks.Commercial production of the same is not done. Sweet gas is
sent to Gas Dehydration Unit or GDU for removal of any moisture. Product of
GDU is sent to the Dew Point Depression Unit or DPDU, where the sweet and
dry fuel gas is freed any condensates, and then is sent for packaging and
dispatch. A part of sweet gas from GSU is taken within the plant and sent to the
LPG recovery unit to obtain LPG and Propane, latter being required to
refrigeration within the plant. The condensate sent to the CFU is seperated into
Naphtha and Natural Gasoline Liquid or NGL. The former is packed and
dispatched. The latter is sent to Kerosene Recovery Unit or KRU where value
added products like Superior Kerosene Oil(SKO), Aviation Turbine Fuel(ATF) and
Hight Speed Diesel (HSD) are formed. The LPG, SKO and ATF from CFU and KRU
are passed through a Caustic Wash Unit to remove hydrogen sulphide. Additives
are added to the same before their packaging and dispatch. A COGEN unit is
also in function to fulfill plant power requirements. Systems of effluent disposals
along with air, inert gas and water supply are also setup. The output of the plant
sustains the HBJ or Hazira-Bijapur-Jagdispur by supplying fuel gas to GAIL.
Other customers include IOCL, BPCL, HPCL, RIL, KRIBHCO, NTPC, ESSAR etc
Process units:-
It receives & separate sour gas & associated condensate from offshore.
Removal of H2S from sour gas by selective absorption in Methyl Di- Ethanol
Amine.
Removal of Moisture by Absorption in Tri-Ethylene Glycol.
Removal of liquid hydrocarbon by chilling to make it suitable for transportation
through 2300 km long HBJ pipe line any formation of hydrates

51. 51
Fractional distillation of associated Sour condensate to produce LPG & NGL.
Production of LPG & ARN from sweet Gas by Cryogenic Process.
nit
Fractionation of NGL to produce Naphtha, SKO/AFT &HSD.
LIGHTING
An electric lamp is a conventional light emitting component used in different
circuits, mainly for lighting and indicating purposes. The construction of lamp
is quite simple, it has one filament surrounding which, a transparent glass made
spherical cover is provided. The filament of the lamp is mainly made of tungsten
as it has high melting point temperature. A lamp emits light energy as the thin
small tungsten filament of lamp glows without being melted, while current flows
through it.
Types of Electric Lamps
1.incandescent lamp

52. 52
2.fluorescent lamp
3.tungsten halogen lamp
4.high pressure sodium lamp
1.Incandescent lamp:
The electrical light source which works on the principle of incandescent
phenomenon is called Incandescent Lamp. In other words, the lamp works due
to glowing of the filament caused by electric current through it, is called
incandescent lamp.
WORKING:
When an object is made hot, the atoms inside the object become thermally
excited. If the object is not melt the outer orbit electrons of the atoms jump to
higher energy level due to the supplied energy. The electrons on these higher
energy levels are not stable they again fall back to lower energy levels. During
falling from higher to lower energy levels, the electrons release their extra energy
in a form of photons. These photons then emitted from the surface of the object
in the form of electromagnetic radiation.This radiation will have different
wavelengths. A portion of the wavelengths is in the visible range of wavelengths,
and a significant portion of wavelengths are in inferred range. The
electromagnetic wave with wavelengths within the range of inferred is heat
energy and the electromagnetic wave with wavelengths within visible range is
light energy. Incandescent means producing visible light by heating an object.
An incandescent lamp works in the same principle. The simplest form of the
artificial source of light using electricity is an incandescent lamp. Here we use
electric current to flow through a thin and fine filament to produce visible light.
The current rises the temperature of the filament to such extent that it becomes
luminous.

53. 53
2.FLUORESCENT LAMP:
A fluorescent lamp or a fluorescent tube is a low weight mercury vapour lamp
that uses fluorescence to deliver visible light. An electric current in the gas
energizes mercury vapor which delivers ultraviolet radiation through discharge
process which causes a phosphor coating of the lamp inner wall to radiate visible
light. A fluorescent lamp changes over electrical vitality into useful light a great
deal more proficiently than incandescent lamps. The normal luminous viability
of fluorescent lighting frameworks is 50-100 lumens for every watt, a few times
the adequacy of incandescent lamps with equivalent light yield.
WORKING:
When the switch is ON, full voltage will come across the tube light through
ballast and fluorescent lamp starter. No discharge happens initially i.e. no lumen
output from the lamp.
At that full voltage first the glow discharge is established in the starter. This is
because the electrodes gap in the neon bulb of starter is much lesser than that
of inside the fluorescent lamp.
Then gas inside the starter gets ionized due to this full voltage and heats the
bimetallic strip that is caused to be bent to connect to the fixed contact. Current
starts flowing through the starter. Although the ionization potential of the neon
is little bit more than that of the argon but still due to small electrode gap high
voltage gradient is appeared in the neon bulb and hence glow discharge is started
first in starter.
As voltage gets reduced due to the current causes a voltage drop across the
inductor, the strip cools and breaks away from the fixed contact. At that moment
a large L di/dt voltage surge comes across the inductor at the time of breaking.
This high valued surge comes across the tube light electrodes and strike penning
mixture (mixture argon gas and mercury vapor).

54. 54
Gas discharge process continues and current gets path to flow through the tube
light gas only due to low resistance as compared to resistance of starter.
The discharge of mercury atoms produces ultraviolet radiation which in turn
excites the phosphor powder coating to radiate visible light.
Starter gets inactive during operation of tube light.
3. TUNGSTEN HALOGEN LAMP:
a halogen gas (basically Iodine) inside the incandescent lamp. Basically, without
halogen gas, incandescent lamp filament gradually losses its performance
because of its filament evaporation at higher temperature of operation.
The evaporated tungsten from the filament of normal incandescent lamp gets
deposited inside the bulb surface gradually. Thus lumens get obstructed from
its way to come out from the bulb. So the efficacy i.e. lumen/watt of the
incandescent lamp goes down gradually.But the insertion of halogen gas into the
incandescent lamp overcomes this difficulty in addition to different advantages.
Because this inserted halogen gas helps the evaporated tungsten to form
tungsten halide which never gets deposited on the inner bulb surface at bulb
surface temperature between 500oK and 1500oK.So the lumens never face
obstruction. So Lumen per watt of the lamp does not deteriorate. Again due to
insertion of pressurized halogen gas, the rate of evaporation of the filament goes
down.
4. HIGH PRESSURE SODIUM LAMP:
It has an inner PCA arc tube that is filled with xenon gas. This xenon gas is used
for starting purpose of the lamp as ionization potential of xenon gas is lowest
among all other inert gases used for this purpose. In addition to xenon gas
sodium mercury amalgam is present in this arc tube, too. In each end, back

55. 55
wound and coated tungsten electrodes are mounted. To seal the tube monolithic
seal is used instead of niobium end cap.
The arc tube is inserted into a heat resistant outer bulb. It is supported by an
end clamp that is floating. This end clamp permits the entire structure to expand
contract without distorting. The space between the tube and the bulb is a
vacuum space. This vacuum space is needed to insulate heat from the arc tube.
Because it is necessary to keep the arc tube at required temperature to sustain
arc during normal operation.
High pressure sodium lamp has very small diameter (3/8 inch). So there is no
enough space to provide any starting electrode in the arc tube. So higher voltage
is required to initiate arc. A ballast with igniter is used for this purpose. High
voltage is fed to the lamp from the ballast by using the phenomenon of
superimposing a low energy high voltage pulse. Generally a typical pulse has a
peak voltage of 2500V and it has durability for only 1 microsecond only. This
high voltage pulse makes the xenon gas ionized sufficiently. Then it initiates and
maintains the xenon arc. The initial arc has sky blue color. Amalgam used in the
reservoir formed inside the arc tube. It is in the back of one of the electrodes. It
is normally vaporized during lamp operation. As the xenon arc has started
temperature of arc tube is increased which first vaporizes mercury and the lamp
start glowing with bluish white color. This color represents the effect of the xenon
and mercury mixture at excitation. Gradually the temperature again rises, and
sodium becomes vaporized lastly and becomes excited, a low pressure
monochromatic yellow sodium spectrum results. During the period of sodium
spectral line becomes at 589 nm. With temperature the sodium pressure
increases from 0.02 atm in the monochromatic discharge to over 1 atm in the
final steady state, broad spectrum condition. Also presence of excited mercury
and xenon gives bluish effect to the lamp radiation and finally pleasant golden
bright light comes out.

56. 56
LED:-
The pn junction diode, which is specially doped and made of special type of
semiconductor, emits light when it is forward biased is called light emitting
diode.
Advantages of LED or Light Emitting Diode:
If anybody compares LEDs to other illumination methods present in the market
now days it will be found that LED lighting in by far the most saving solution. In
modern era of technology, there is an up gradation from analog to digital. You
can say LED is digital light which has huge advantages over conventional analog
lights. The main advantages are briefly described below.
1.Size :-
Sizes of Light Emitting Diodes are from 3 mm to 8 mm long. The small size allows
them to be used in small spaces where tube lights cannot be used. Because of
its small size, various designs can be made very simply.
2.Larger lifetime :-
This is the number one benefit of LEDs lights. As an example a high power white
LEDs life time is projected to be 35,000 to 50,000 hours. Where as an
incandescent bulbs life time is 750 to 2,000 hours. For compact fluorescent
bulbs, the life time is 8,000 to 10,000 hours. Actually unlike standard lighting
LEDs do not burn out. They just gradually fade.
3.Lower Temperature :-
LED's mechanism does not consists of any step to produce heat. In conventional
lights, the production of heat are very common fact. They waste most of their
energy as heat. They remain cool.
4.Energy Efficiency :-
Light Emitting Diode is today’s most energy efficient way of lighting its energy
efficiency is nearly 80% to 90% whereas traditional lights have 20% energy
efficiency, 80% is lost, as heat. More over the quality of lighting is very good.

57. 57
5.Design Flexibility :-
LEDs can be merged in any shape or combination. They can be used in singly as
an irony. Single LED can be operated, resulting in a dynamic control of light.
Superb lighting effects of different colors can be achieved by well designed LED
illumination system.
6.Ecologically Friendly:-
LED lights do not contain any toxic chemical. They do not leave any toxic
material and 100% recyclable. Their illuminations are close to no UV emission.
The solid package of it can be designed to focus its light also.
7.Color:-
LEDs can be emit light of intended color this is done by charging the
compositions of the solid state materials doping without using any color filter.
8.On/Off Time:-
Light Emitting Diodes can be operated very quickly. They can be used in frequent
on/off operation in communication devices.