64001972-copy-of-training-report-gail-ms-word-2003-format (1).doc

Training,GAIL(PATA)

ACKNOWLEDGEMENT

Inplant

I wish to place on record my deep sense of reverence & gratitude to

Mr. JAIVINDER SINGH, HOD-CM(Electrical),for his keen interest,

and help which have sustained my efforts at all stages of this

undertaking. Also I would like to thank Mr. M.K.PRASAD(MGR),

Mr.NIKHILKUMAR(MGR),Mr.VIKAS SRIVASTAVA(Sr.ENG),

Mr.S.P.DWIVEDI(Sr.ENG), Mr.DHEERAJ GOEL (Sr.ENG),

Mr. KUMAR RAHUL(Sr.ENG) and Mr.RISHIKESH ROY(MGR)

Mr.SOMEN MANDAL(CM) for their constant guidance and great

support.

It gives me great pleasure to acknowledge my humble & sincere

indebtness to Mr. AJAY SHARMA (finance) for providing

encouragement and all help needed despite of his multifarious

responsibilities.

This work bears the impact of many persons who made significant

contribution in formal or informal way.

I am thankful to all of them.

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Training,GAIL(PATA)Inplant

VEDANT.

PREFACE

Knowledge of something useful can become redundant. The difference

between a successful and an unsuccessful professional lies not only in

the amount of knowledge one has, but how much he can actually use in

various situations.

It is with this objective that every student of B.Tech has to undergo four

to six weeks of summer training in the corporate world to get the first

hand experience of working in an organization.

I was fortunate enough in doing my summer training at GAIL, PATA

which is a prestigious “NAVARATNA STATUS” company.

V EDA NT

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Training,GAIL(PATA)

TO WHOM IT MAY CONCERN

Inplant

This is to certify that Vedant, student of GLA Institute of

Techonology & Management,Mathura has undergone a

Vocational Training in Electrical System at

Gail(PATA)Unit from 17th june, 2011 to 16th July,

2011(4 weeks duration) .

He has prepared the project report under my guidance.

Date:

Mr. Jaivinder Singh HOD-CM

(Electrical) GAIL, PATA

Training,GAIL(PATA)

I N D E X

Inplant

Introduction

GAIL at a glance

History and importance

Vision

Plant description

GAIL’s pipeline network

GAIL UPPC(PATA) Complex

Introduction to Electrical Section

Page 6

Page 8

Page 9

Page 10

Page 15

Page 16

Page 16

Power Distribution System Page 18

Switchyard Page 19

Protection and Security

Transformer

Motors

Steam Turbine Generator

Emergency Power Supply

Variable Speed Drives

Cathodic Protection

Page 20

Page 24

Page 30

Page 34

Page 38

Page 40

Page 42

Energy saving Page 45

Page 4 of 53

Training,GAIL(PATA)

Conclusion Page 46

G A I L , P AT A P ETR O C H E MI C A L

C O MP LE X

Inplant

IN TR ODU CT ION

GAIL (India) Ltd., PATA Petrochemical Complex is located at

District Auraiya in Uttar Pradesh. It is based on natural gas as

feedstock from GAIL’s HVJ pipeline, which has been set up in

accordance with GAIL’s mission to maximize the value addition from

each fraction of natural gas.

The Plant consists of five major units i.e. Gas Processing Unit (GPU), Gas Cracker Unit

(GCU), HDPE unit, LLDPE Unit and LPG unit. Current capacity of the cracker plant is

440,000 tones per annum of Ethylene. This acts as a feedstock for the

two downstream units with an annual production capacity of 100,000

TPA HDPE and 210,000 TPA of LLDPE/HDPE respectively.HDPE

and LLDPE are used by plastic processors to manufacture a large

variety of products for industrial, agricultural and domestic uses. The

Plant also has an LPG recovery plant.

The Upstream (GPU & GCU) and Downstream (LLDPE & HDPE)

plants of GAIL, PATA are based on the best technologies available in

the world. The technology for the GCU has been licensed by Stone

and Webstar, USA and the GPU by TFE. The technology for the

HDPE unit has been licensed by Mitsui of Japan and Nova Chemicals,

Canada for Swing plant of HDPE & LLDPE unit. Ethane, a constituent

of natural gas is converted into ethylene as its main product in the

GCU using the latest technology from USA. Ethylene is feedstock for

downstream units

Page 5 of 53


namely, HDPE plant and Swing LLDPE/HDPE Plant. Butene-1 used

as co-monomer in the production of HDPE & LLDPE is produced in

Butene-1 Plant licensed by M/s Axens, USA.

GAIL AT A GLANCE

GAIL is India’s flagship natural company, integrating all aspects

of natural gas value chain(including Exploration &

Production, Processing, transmission,

distribution and Marketing)and its related services. It is

outstanding public sector enterprises in the country. In rapidly

changing scenario, it is spearheading the move to new era of clean fuel

industrialization, creating a quadrilateral of green energy corridors

that connect major consumption centers in India with major gas fields

,LNG terminals and other cross border gas sourcing points. GAIL is

also expanding its business to become a player in the International

market.

GAIL is one of the NAVARATNA enterprises and ranks among the top

ten companies in India. Today, GAIL’s Business Portfolio includes:

5,800 km of natural gas high pressure trunk pipeline with a capacity to carry 130

MMSCMD of natural gas across the country.

7 LPG gas processing units to produce 1.2 MMTPA of

LPG and other liquid hydrocarbons.

North India’s only gas based integrated Petrochemical

complex at PATA with a capacity of producing 3, 10, 00 TPA

of polymers.

1,922 km of LPG transmission pipeline network with a capacity to transport 3.8

MMTPA of LPG.

30 oil and gas Exploration blocks and 3 coal bed methane blocks.

Page 6 of 53


13,000 km of OFC network offering highly dependable

bandwidth for telecom service providers.

Joint venture companies in Delhi ,Mumbai, Hyderabad,

Kanpur, Agra, Lucknow, Bhopal and Pune, for supplying piped

natural gas (PNG) to households and commercial users, and

compressed natural gas (CNG) to transport sector.

Participating stake in the Dahej LNG terminal and the upcoming

Kochi LNG Terminal in Kerala..

GAIL has been entrusted with the responsibility of reviving the

LNG terminal at Dabhol as well as sourcing LNG.

Established presence in the CNG and City Gas sectors in

Egypt through equity participation in 3 Egyptian

companies:Fayum Gas Company SAE, Shell CNG SAE and

National Gas Company SAE.

Stake in China Gas Holding to explore opportunities in the CNG sector in mainland

China.

A wholly-owned subsidiary company GAIL Global(Singapore) Pte Ltd in singapore.

Training,GAIL(PATA)

HISTORY AND IMPORTANCE

Inplant

GAIL (INDIA) Ltd. is one of the outstanding public sector

enterprises (PSE) in the country today.

GAIL today handles about 95% of the natural gas business in India through its 4000 km of pipelines in the country supplying about 60 million cubic meters (MMSCM) of gas per day asfuel to power plants

for generation of over 4000 MW of

power as

feedstock for gas based

fertilizer plants to produce about 10 MMTPA of Urea and to several other industrial units to meet their requirements.

GAIL was established by the Government of India in August

1984 for handling post

exploration activities

relating to the natural gas with the

objectives of accelerating and

optimizing the effective use of national economy. It was dedicated to

the nation on 10th June’99 by the Honorable Prime Minister of India

Shri Atal Bihari Vajpayee. The 2800 km Hazira Vijaypur

Jagdishpur(HVJ) pipeline become operational in 1991.

During 1991-93, three LPG plants were constructed and some regional

pipeline were acquired, which enabled GAIL to begin its regional gas

distribution in various parts of India. GAIL began its city gas

distribution in 1997 in Delhi by setting up nine CNG stations, catering

to city’s vast public transport fleet.

Page 8 of 53


In 1999, GAIL set up northern India’s only Petrochemical plant at

PATA. GAIL become the first Infrastructure Provider Category II

license and signed the country’s first Service Level Agreement for

leasing bandwidth in the Delhi-Vijaypur sector 2001, through its

telecom business GAILTEL. In 2001, GAIL commissioned world’s

longest and India’s first cross country LPG Transmission from

Jamnagar to Loni.

GAIL today has reached new milestones with its strategic

diversification into Petrochemicals, Telecom and Liquid Hydrocarbons

besides gas infrastructure. The company has also extended its

presence in power, LNG regasification, City Gas Distribution

and exploration and production through equity and joint ventures

participations. Incorporating the new found energy into its corporate

identity, GAIL (India) ltd on Nov 22,2002.

Within the period of 15 years GAIL has emerged and maintained its

position as the no.1 gas company in India. It has won the excellent

performance awards for the past five years consecutively and also

safety awards from the Oil Industry Safety Directorate (OISD) and

British Safety Council. It has an ISO-9002 certification for its pipeline

system. LPG plants and Gas Technology Institute and also ISO-14001

certification for its LPG plants at Vijaypur, Vaghodia and along the

HVJ Pipeline making it the 1st Indian company in the petroleum

sector to secure this certification.

Recently the running LPG plant at UPPC PATA was dedicated to the

nation on 20th June’01 by the Honorable Oil and Petroleum minister

Mr.R.Naik. As a GAIL subsidiary, UPPC PATA is an integrated

Petrochemical Complex with an investment of Rs.2500 Crore itself and

LPG plant is installed with a capital investment of Rs.460 Crore. This

complex recovers ethane, propane (C2/C3) from natural gas.

V ISION

Page 9 of 53


Be the leading company in natural gas and beyond with global focus

,committed to customer care, value creation for all stake

holders and environmental responsibility.

PLANT DESCRIPTION

Gas Sweetening Unit

The gas from the HVJ pipeline contains about 5 to 6 %

CO2 by volume which interferes

with C2-C3 recovery in GPU where deep cryogenic conditions are involved.

In view of

this it is necessary to remove CO2 from the feed gas down to 50 PPM level.

The sour

feed gas enters the bottom of the absorber where it

contacts counter currently with the

descending lean solution. The acid gas component in the

gas is absorbed by the solvent

and the sweet gas leaves from the top of the

absorber. The rich solvent solution

loaded with acid components is drawn from the

absorber bottom and flashed in to the

flash drum to recover dissolved heavy hydrocarbons.

The flashed rich solution is then

Page 10 of 53


fed to the regenerator through a lean/rich exchanger. In

the regenerator the acid

components are stripped off by the reboiled vapor

generated through the regenerator

reboiler and the solvent is recovered as lean solvent

which is recycled as absorber top.

C2-C3 Extraction Unit

The sweetened gas is compressed and cooled in feed gas

cooler to separate moisture.

This gas is then passed through molecular sieve dryer

for drying the gas further. The

dehydrated gas is next cooled in three stages. In the

first stage, the gas is cooled by

de-methaniser bottom reboiler, chillier 1 and side

rebolier. The liquid produced is

separated in separator I. In the second stage, gas is

sent to chillier 2 for further cooling

and the liquid produced is separated in separator II. In

the third stage, the gas is

expanded in an expander to cool down to 100°C. The cold

gas is then fed to de-methaniser column for recovery of

ethane (C2) and propane (C3).

Liquids produced in

separator I and separator II are also fed to this column

for distillation. The liquid from

bottom of the de-methaniser column is pumped to C2

and C3 storage. The gases from

the top of the de-methaniser column are cooled down in

condenser and the condensate

Page 11 of 53


is separated in reflux drum and pumped back to the

column. The vapor from the

reflux drum is expanded in the de-methaniser

overhead gas expander compressor to

result in temperature reduction in the plant to -117°

C. The cold gas is utilized in the

process. A part of the exit gas from intermediate

stage of the exit gas compressor is

used for molecular sieve regeneration, recompressed and recycled back to

HVJ pipeline.

Gas Cracker Unit (GCU)

In gas cracking unit, the feed C2/C3 is cracked in

hollow furnace tubes at high

temperature in the presence of steam. The furnace

output is cooled in quench tower by

direct water quench and the cooled gas is sent to cracked gas compressor

(CGC) for

pressure boost up. The cracked gas is scrubbed for

carbon dioxide using caustic wash

and then sent for dehydration in molecular sieve dryers.

The dry gas is next passed on

to de-methaniser section where all gases other than

methane and hydrogen are

condensed into liquid. Uncondensed methane and

hydrogen mixture from the de-methaniser is expanded

to achieve the low temperature required for hydrocarbon

separation. Methane is recycled back to fuel gas system,

while hydrogen is used for the production of pure H2,

which is required for hydrogenation reaction terminator.

The liquid from de-methaniser is sent tode-ethaniser,

which splits up the feed to ethane and ethylene products

at

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the top and the heavier at the bottom. The ethane-

ethylene mix from de- ethaniser top is processed for

removal of acetylene and is thereafter sent to ethylene

column for further separation. In the etheylene column,

the

ethane-ethylene mixture is separated into ethylene

product at the top and ethane at the bottom which is

again recycled back to furance for cracking. The heavier

bottoms from de-ethaniser is fed to de-propaniser which

separates the propane-propylene mixture at the top and

all the heavier fractions at the bottom. The propane

propylene mixtures are separated in the propylene

column where by-product propylene goes as the top

product and propane is obtained at the bottom. This

propane is again recycled back to furnace for production

of ethylene and

propylene. The heavy fraction from de-propaniser

bottom is fed to the de- butanisser,

which separates the feed into C4 mix byproduct at the

top and gasoline by product at

the bottom.

High density polyethylene plant (HDPE)

The high-density polyethylene plant (HDPE) uses the

slurry process for making

polyethylene (PE). The process consists of feeding

ethylene to reactors containing

catalyst, hydrogen and propylene or butene-1 along with

hexane for making tailor made

PE product to suit customer application

requirements. The slurry from reactors

(polymerizers) is fed to centrifuge where the solvent

hexane gets separated from the

polymer powder. This powder is next fed to a dryer

for drying. The dry powder is fed to

Page 13 of 53


an extruder to get pellets of required size, which are

subsequently bagged for shipment.

The recovered hexane from centrifuge and dryer is sent

to hexane recovery section,

where the hexane is stripped to yield byproduct low

polymer. The stripped hexane is

next dehydrated for removal of moisture and recycled back for reuse.

Linear Low Density Polyethylene/High Density

Polyethylene

(LLDPE/HDPE) Swing Plant.

The process in linear low-density polyethylene/high

density polyethylene (LLDPE/HDPE) swing plant

utilizes solution phase reaction system for

polyethylene manufacture.

Solvent cyclohexane and co-monomer butene-1 are

pumped to absorber- cooler where ethylene is fed to

form reactor feed solution. The reactor operates at high

pressure and temperature to yield PE. The control of

the properties of the polymer is normally achieved by

varying the feed quantity and injection of catalysts and

hydrogen. The catalysts present in the solution in

excess is next deactivated by deactivator addition.

The solution is then preheated before passing through an

adsorber for the removal of the deactivated

catalysts. The adsorbed material

is depressurized in two stages, at intermediate

pressure separator (IPS) and low-pressure separator

(LPS) for flashing off of unreacted ethylene, solvent and

co-monomers, which are recycled for recovery. The

polymer melt from LPS is next passed through extruder

to form pellets which is steam stripped, dried, blended

and bagged for dispatch. The recycle vapor stream from

IPS and LPS is fed to low boiler (LB) column to yield

unrecovered ethylene, co- monomer, extra product and

cyclohexane as bottom product. The solvent

Page 14 of 53


stream from LB column is then fed to high boiler (HB)

column from where recycle solvent is available as top

product and high boilers (low molecular weight

polymers) as the bottom product. The ethylene

stream from LB column is sent to the ethylene column

from where ethylene vapor obtained from the top is

recycled back to cracker for recovery. The bottom

product from ethylene column is sent to the co-

monomer column from where pure comonomer is

obtained as top product and solvent is recovered as

bottom product.

The bottom product from the HB column is sent to

the RB column from where low molecular weight

polymer is taken out as grease.

Butene - 1 plant

The process in Butene-1 plant involves dimerisation of ethylene into butene-

1. It is

used as co-monomer in LLDPE/HDPE swing plant. Feed

ethylene along-with recycled

ethylene is fed to the reactor where reaction is takes

place in presence of catalyst and

butene-1 is produced. The reactor outputs are

vaporized in steam exchangers and sent

to flash drum. Liquid from flash drum is taken to

catalyst waste removal section for

waste catalyst recovery. The vapor from flash drum is

sent through cooler to surge

drum and liquid separated in surge drum is taken to

recycle column. Vapor ethylene

from recycle column is recycled back to reactor,

while liquid from the bottom of recycle

column is fed to butene-1 column. The product butene-

1 is available from the top of the

Page 15 of 53


butene-1 column while heavier hydrocarbons are

available as by-product from the

bottom of the same column.

Liquid Petroleum Gas (LPG) plant

Liquid hydrocarbon from gas processing unit (GPU) is fed

to LPG plant C2-C3 distillation column to have C2-C3 as

top product and propane (C3) and heavier hydrocarbons

as bottom withdrawal. This bottom liquid is fed to propane

recovery column where top product is propane and

bottom withdrawal is C3 and heavier hydrocarbons. This

bottom hydrocarbon mixture is then fed to LPG column to

have LPG (C3/C4) as top product and natural gasoline

(NGL) as bottom product. NGL comprises pentane (C5)

and heavier hydrocarbons (C6 and above) which can be

termed as special

boiling point solvent (SBPS). Based on the

demand/supply scenario of propane, the propane

column is used for the production of pentane and

SBPS by fractionating NGL, which is available as

bottom product of LPG column. The SBPS column can

be reverted back to propane column whenever

propane production is required.

Utilities

The utilities requirement for the GAIL, PATA include

power, raw water, steam, cooling

water, DM water, fire water, plant air, instrument air,

and nitrogen. The solid/semisolid

wastes are also generated from various utility units viz. DM water plant

(spent

Cation/Anion samples), Nitrogen plant (spent

alumina balls and spent molecular sieve).

Page 16 of 53


Wastewater Treatment Plant

A number of effluent streams are generated from various sources

viz, process waste stream (GSU, GPU, GCU, HDPE, LLDPE

units), spent caustic waste stream, cooling water blow down, DM

plant effluent, boiler blow down and sanitary waste stream. The

total quantity of wastewater generated from the above mentioned

sources amounts to

150 m3/hr. M/s GAIL have installed a combined wastewater

treatment plant (WWTP) for the treatment of these effluents.

Apart from this a substantial quantity of storm water is also

generated during monsoon season and gets mixed up with the

plant effluent. To handle this additional quantity of wastewater

during monsoon, and to

prevent the shock loading to various units of WWTP, M/s GAIL

have installed two surge ponds where the incoming effluent is

stored and released at controlled rate to the

WWTP. The major units of WWTP are Grit Chamber, Oil

Separator, Equalization Tank, Neutralization Tank, Flocculation

Tank, Biotower, Aeration tank, Clarifier, and Sludge Thickener.

The treated effluent is discharged to Sengar River.

GAIL’S PIPELINE NETWORK

GAIL operates over 4000 km of pipeline in all the four regions of the country supplying about

60 million cubic meters of gas per day. In the area of pipeline GAIL

is currently working on expansion of the capacity of HVJ Pipeline from

33.4 MMSCMD.

In the area of LPG pipelines GAIL proposes to construct two more

LPG pipelines in southern India. one form Vizag to Secunderabad in

Andhra Pradesh 600 km and other from Mangalore to Madurai 700 km

in the stats of Karnataka and Tamil Nadu.

Page 17 of 53


GAIL UPPC (PATA) COMPLEX

GAIL (INDIA) Ltd. U.P Petrochemical Complex is situated at PATA

in distt. Auraiya in Uttar Pradesh. It is 55 km away from Etawah and

110 km away from Kanpur. UPPC is also located near by Sengar

River so that disposal of waste water etc. can be easily done. UPPC

use Ruradhana Canal for taking raw water. Another project named

AuGPS of NTPC (National Thermal Power Corporation) is also near

GAIL UPPC PATA. This ground (on which UPPC plant is

constructed) is barren so by constructing the plant it is the best use of

the ground. According to the view of transportation it is well connected

through rail as well as road route to Kanpur and Auraiya. Another

major aspect is that it is situated near HVJ pipeline. So it is one of the

best possible locations.

ELECTRI CAL SECTI ON UPPC,PATA

Page 18 of 53


Two Incomers are coming from NTPC AuGPS which are at 220 KV.

At switchyard they are stepped down to 33 K V by two transformers of 40 MVA.

220 KV SF6 type CGL(five in number) make out door circuit breakers are used.

Vacuum Circuit Breakers are used at 33 KV side of transformer.

This power is fed to SS#1, and there are 4 section of 33 KV bus.

All the bus bars are connected in parallel so that in case one incomer fails other

can take full load.

15.6 MW STG is connected to 33 KV bus section 2.

25.5 MW STG is connected to 33 KV bus section 3.

At SS#1, 33 KV voltage is stepped down to 6.6 KV with the help of 4 transformers of

33/6.6 KV 25/31.5 MVA.

Power at 6.6 KV level is fed to various substation all over the plant through cables.

The Substations are –

IOP – SS#1,2,3,4A,4B,5,6,7

LPG – SS#8

UP stream- SS#11

Down Stream –SS#12

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SS#18

This power is fed to HT motors and Transformer for plant operation.

For LT load 6.6 KV is step down to 415 v.

SS#1 act as a main distribution substation where all the downstream plant are fed from.

SS#11 caters to the upstream plants namely GCU and GPU.

SS#12 caters to the downstream plants namely LLDPE/HDPE.

For fire protection purpose fire water pipeline is laid all over the plant.They have the following main equipments–

4 no. of HT motor (310 KW) driven water pumps

5 no. of diesel engine driven pumps .

3 no. of jockey pump (45 KW) for maintaining fire water pressure at around 10 Kg/cm sq.

Circuit breaker used at various voltage level panel are-

220 KV SF6 circuit breaker made by CGL.

33 KV Vacuum circuit breaker made by Siemens.

6.6 KV SF6 circuit breaker made by Voltas.

In switchyard we use wave trap for communication purpose. This is known as PLCC. The full form of PLCC is Power Line Conductor Communication.

Page 20 of 53


In switchyard we have 2 bus bars.Bus bar 1 is energised by incomer 1 and bus bar 2 is energised by Incomer2 . We have done this for the reliability of the system.

In Switchyard we can experience ‘Corona Effect’ .There we can hear hissing sound due corona. We use hollow conductor to reduce ‘Skin Effect’.


Page 22 of 53

Training,GAIL(PATA)

SWITCH YARD

Inplant

1) It is a medium for exchange of power from source to load or

from one source to another.

2) It consists of switching equipment, measurement,

protection and control equipment required for power

generation and utilization.

3) The main components are:

Circuit breaker (CB),

Isolator,

Earth Switch,

Current Transformers (CT),

Capacitive Voltage Transformers (CVT),

Lightening Arrester (LA),

Wave Trap,

Potential Transformers (PT),

Line matching unit (LMU),

Lightening Mast (LA).

Training,GAIL(PATA)

P R O TECT I O N AN D S ECUR I T Y G en e ra t or pr o t e c ti on

Inplant

D i ff e re n t i al p r ot e c t i on :1. Ge n er a t or d i ff ere nt ial ( agai n s t s h o r t c ir c u i t ) -A direct short circuit between differential phases of the winding can cause highly extensive damage due to flowing of heavy current. The relay used is 87G and GAG34type.2. GT overall differential -GT is connected to the stator winding, bus duct, UAT’s HV side.

Earth fault protection :1. Stator earth fault protection-The secondary of the transformer is shorted through loading resistance (0.42 ohm). If insulation is damaged then earth fault occurs. Generator earth fault current flows in theprimary of the neutral grounding transformer. As a result, the voltage across the resistoris developed which activates stator E/F sensing relay. In this relay, 95% is used for phases and 5% for neutral so that it may confirm fault from the neutral side or from the phase side.---- S tator s tand by E / F :

The relay is connected across an open delta of the generator PT secondary windings. When there is no E/F, the sum of the phase voltages of the generator and hence the voltage across the relay is zero.---- Stator inter turn fault:When leakage occurs between the turns in the same phase of a winding, the induced voltage is reduced and there will be a voltage difference between the centre of the terminal voltage triangle and neutral of the machine. If inter turn fault occurs in the machine, the CT carries a transient current and thereby pick up the relay and trips

the generator.2. Ro t or e a r t h f a u l t -Earth fault may be developed in rotor circuit due to failure of insulation occurring due to stresses offered by the centrifugal forces. It is of 2 types:---Single rotor E/F,---Double rotor E/F.Single rotor earth fault is not harmful because no earth current circuit is completed. But double rotor earth fault is harmful because immediately E/F is completed, the internal turns which can burn the conductor causing severe damage to the rotor. Due to double E/F leakage current flows through brushes which may be damaged.

Page 24 of 53


N e gat i v e ph a s e s e qu e n c e :Three phase balanced load produces a reaction field which is constant and rotates synchronously with the rotor field system. Any unbalanced condition could be resolved into positive, negative and zero sequence components. The +ve sequence is similar to the balanced load. The zero sequence component does not produce armature reaction. The -ve sequence component is similar to that of the +ve sequence but the resulting reaction field rotates in the opposite direction. Hence the flux produced by the negative phase sequence current cuts the rotor at double the rotational speed thereby inducing double frequency currents. As a result, eddy currents produced are very large and cause severe heating of the rotor windings particularly damper windings. The losses in the rotor are proportional to the square of the degree of the unbalance.

Generator back up impedance protection :Impedance relay sensing (back up) is up to the busbars. A three phase zone impedance relay is provided for the backup protection of generator against external three phase and phase to phase faults in the 400/220 kV system. It should be connected to trip the generator after a time delay of 1 to 1.5 seconds so that the generator is tripped only when 400/220 kV protection has not cleared the faults even in the second zone.

Loss of excitation protection :Sudden loss of excitation in an alternator makes the generator to run as an induction generator. Generally all the generators should be designed to run as induction generator with a reduced load for a short period but the rotor will get overheated from the induced current flowing in the rotor iron, particularly at the retaining rings of the rotor. Due to loss of excitation it will draw the reactive power from the grid (MVAR) or takes excitation from system and there may be a voltage dip in the system which is not desirable from system

point of view. When loss of excitation is accompanied by undervoltage, it will initiate Class A trip otherwise Class B trip if the grid is able to sustain the voltage dip.

P o l e sl i pp i n g :Pole slipping may occur in the generator due to instability. It causes severe shock to both machine and grid due to violent oscillations in both active and reactive power. The angular displacement of the rotor exceeds the stability limit the rotor will slip a pole pitch usually known as pole slipping.

O v e r vo l ta g e o r o v er f l u x i n g :The generator can develop dangerously high voltage in the event of maloperation of AVR or load throws off while generator excitation is under manual control. Since voltage generated is directly proportional to flux, quantity of flux increases at

Page 25 of 53


overvoltage. Due to increase of flux, losses in the stator increases due to which core will get heated up and thus reducing the life of the generator.

Low fo r w a r d p o we r p r o t ec t i on :When a generator is synchronized with the grid, it loses its driving force and the generator remains in synchronization. The generator should be isolated from the grid after the steam flow ceases and the flow of power to grid reduces to minimum i.e. the point when the generator starts drawing power from the grid and acts as motor. If the turbine tripped or ESV closed, the generator trips with a time delay of 2 seconds.

Reverse power protection :When the input to the turbine suddenly goes off and generator is in service delivering power to the system, turbine will be subjected to excessive thermal overstress, vibration and distortion causing damage to the turbine. So there is a back up arrangement to trip the generator if it does not trip within 2 seconds. Reverse power protection acts in 2 stages----1 st s tag e - Reverse power relay operates after 5 sec time delay and includes stop value closing/turbine trip.--- 2 n d s ta g e - Reverse power relay acts after 60 sec time delay.

Local breaker back up protection :When the main generator breaker fails either due to---- Mechanical failure,--- Trip circuit not healthy.This protection acts as back up to the main generator by tripping all the breakers connected to that particular bus.

Under minimum frequency :

In case of under frequency excitation will be loaded. Under frequency is also dangerous for turbine as it may damage the HP blades.

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Generat o r transformer protection 1 . B u c kh o l z p r ot e c t i o n :Any internal fault in the generator transformer causes the winding temperature to increase rapidly resulting in vaporization of oil. The generated gas is utilized for relay operation (B u c k h olz r e la y ).2. Thermal overload protection:Vapour pressure thermometer resistance temperature are used for this purpose. When the winding temperature and oil temperature reaches a certain value, it will give indication that the load on the transformer has to be reduced. If the temperature rises further, tripping will take place.3. F i r e p r ot e c t i o n : Sprinkler system is utilized to protect the transformers from fire hazards.4. High oil temperature protection.5. High winding temperature protection.6. Pressure relief valve (PRV).7. Overfluxing protection:The condition of overfluxing could arise in case the voltage at the machine terminal rises or its frequency drops or both occurring simultaneously.


T RANSFO RMER

A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors — the transformer's coils. Except for air-core transformers, the conductors are commonly wound around a single iron-rich core, or around separate but magnetically-coupled cores. A varying current in the first or "primary" winding creates a varying magnetic field in the core (or cores) of the transformer. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the "secondary" winding. This effect is called mutual induction. If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will flow from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary to the number of turns in the By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making NS less than NP.

PRINCIPLE OF OPERATIONThe transformer is based on two principles: firstly, that an electric

current can produce a magnetic field (electromagnetism) and secondly that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil.The voltage induced across the secondary coil may be calculated

from Faraday ' s l aw of i nduc ti o n , which states that:

where VS is the instantaneous vo lt ag e , NS is the number of turns in

http://en.wikipedia.org/wiki/Faraday's_law_of_induction

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Faraday's_law_of_induction

the secondary coil and Φequals the m agne t i c f l ux through one turn of the coil.If the turns of the coil are oriented perpendicular to the magnetic field lines, the flux is the product of the m agne t i c f i e l d s trength B and the area A through which it cuts. The area is constant, being equal to the cross-sectional area of the transformer core, whereas the magnetic field varies with time according to the excitation of the primary. Since the same magnetic flux passes through both the primary and

secondary coils in an ideal transformer,[ 1 2] t he instantaneous voltage across the primary winding equals

Taking the ratio of the two equations for VS and VP gives the basic equation for stepping up or stepping down the voltage

Page 28 of 53

http://en.wikipedia.org/wiki/Transformer#cite_note-flanagan_p2.1-11

http://en.wikipedia.org/wiki/Magnetic_field

http://en.wikipedia.org/wiki/Magnetic_flux

Training,GAIL(PATA)

CONSTRUCTION

Inplant

The construction of the transformer basically includes the following: CORE RADIATORS CONSERVATOR BREATHER OIL LEVEL INDICATOR EXPLOSION VENT WINDING COOLANT TAP CHANGER HV/LV BUSHINGS BUCKHOLZ RELAY

CORE:Transformers for use at power or audio frequencies typically have cores made of high permeability silicon steel. The steel has a permeability many times that of free space , and the core thus serves to greatly reduce the magnetizing current, and confine the flux to a path which closely couples the windings The effect of laminations is to confine eddy currents to highly elliptical paths that enclose little flux, and so reduce their magnitude. Thinner laminationsreduce losses, but are more laborious and expensive to construct. Thin laminations are generally used on high frequency transformers, with some types of very thin steel laminations able to operate up to 10 kHz.

RADIATORS:The radiators are the fins that are attached to the main body of the transformer ,hence increasing the contact surface area by providing a circulatory path to the oil. Now it circulates in a convection cycle and cooling becomes more efficient. Since the heat can be dissipated more easily and efficiently now, the rating of the transformer can be increased.

CONSERVATOR:

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The oil is filled through the opening in conservator at the top. The conservator is never filled fully since the oil volume varies according to the temperature. The oil either expands or contracts according to the heating Hence conservator acts as a supplementary space for the oil in case of expansion.

EXPLOSION VENT:In case of some fault, there can be a sudden passage of huge amount of charge through the transformer. This produces immense heat resulting in the vaporization of oil and production of gas. In order to avoid any possible explosion in the body of the transformer a pressure release vent or explosion vent is provided. The end of it capped by a brittle material that is destroyed and the gas is released.

BREATHER:The breather is used to suck in the air whenever the oil contracts so as to maintain the inside pressure equal to the outside pressure .In order to avoid the sucking of moisture along with air, SILICA GEL is provided along with oil to absorb the moisture. The absence of moisture is so much important because even a small amount of its presence reduces the dielectric constant of the oil considerably.

OIL LEVEL INDICATOR:As the name suggests, oil level indicator is used to indicate the level of oil in the transformer.

WINDING:The conducting material used for the windings depends upon the application, but in all cases the individual turns must be electrically insulated from each other to ensure that the current travels throughout every turn. Larger power transformers operating at high voltages may be woundwith copper rectangular strip conductors insulated by oil-impregnated paper.Both the primary and secondary windings on power transformers may have external connections, called taps, to intermediate points on the winding to allow selection of the voltage ratio. The taps may be connected to an automatic ON LOAD TAP CHANGER(OLTC) for voltage regulation of distribution circuits. Certain transformers have the windings protected by epoxy resin. The OLTC is always connected on the HT side since sparking is less, reason being the current which is also less on the HT side.

COOLANT:High temperatures will damage the winding insulation. Power transformers rated up to several hundred KVA can be adequately cooled by natural convective air- cooling, sometimes

assisted by fans. In larger transformers, part of the design problem is removal of heat. Some power transformers are immersed in transformer oil that both cools and insulates the windings. The oil is a highly refined mineral oil that remains stable at transformer operating temperature.

It is also required to keep a check on the increase in the rise in oil’s temperature.Similarly winding temperature also needs to be looked after. Hence we install OTI (Oil Temperature Indicator) and WTI (Winding Temperature Indicator).

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HV/LV BUSHINGS:The bushings are provided to isolate the live wire from the main body and hence the energisation of the transformer casing. The conductor passes through the bodyof the bushing.

BUCKHOLZ RELAY:In the field of electric power distribution and transmission, a Buchholz relay, also called agas relay or a sudden pressure relay, is a safety device mounted on some oil-filled power transformers The Buchholz Relay is used as a protective device sensitive to the effects of dielectric failure inside the equipment. The relay has two different detection modes. On a slow accumulation of gas, due perhaps to slight overload, gas produced by decomposition of insulating oil accumulates in the top of the relay and forces the oil level down. A float operated switch in the relay is used to initiate an alarm signal.

If an arc forms, gas accumulation is rapid, and oil flows rapidly into the conservator. This flow of oil operates a switch attached to a vane located in the path of the moving oil. This switch normally will operate a circuit breaker to isolate the apparatus before the fault causes additional damage.

In GAIL (PATA) there are various type of transformer used. Now total no. of transformer in

Gail (PATA) are –

In switchyard there are two 40 MVA Transformer are used. They step-down 220 KV to

33 KV.

In SS#1 there are 4 ,25/31.5 MVA Transformer which are use to step-down 33 KV to

6.6KV.

There is one 20 MVA and one 30 MVA Transformer which are connected to STG

.They are use to Step-up 11KV to 33 KV.

Low rating Transformer are used for distribution purpose. The distribution transformers are generally connected in delta-star configuration, providing a neutral on the secondary side. The delta on the other hand makes sure that the harmonics, basically

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the third harmonic current which are zero sequence currents get captured in the delta and do not cause losses in the system(Since DO NOT CIRCULATE IN THE SYSTEM ANYMORE). Also it is deemed necessary to provide a path to the third harmonic without its suppression so as to get a sinusoidal voltage on the secondary side.

Lightning Transformer in SS#1 are used to protect system from lightning fault.

The lighting transformer or the isolation transformer are used to increase the impedance of the system so that any fault on the secondary side(lighting side) is not manifested severely on the primary side i.e. the PANELS causing any major outage.

TRANSFORMER CONSTRUCTION(DISTRIBUTION TRANSFORMER)


Page 33 of 53

Training,GAIL(PATA)

RELAY USED FOR PROTECTION OF TRANSFORMER

Tripping relay type VAJ

Trip current supervision relay Type VAX MK-2

Auxiliary relay

type: Buckholz

alarm

Oil temperature

Alarm Oil level low

alarm Auxiliary

relay type VAA :

PRV valve

WDG Temp Alarm

PRV Trip

Auxiliary Relay type VAA :

Buch relay

Oil trip

WDG trip

Overcurrent Relay (Inverse)

type CDG Instantaneous earth

f

a

u

l

t

R

e

l

a

y

t

y

p

e

C

A

G

Over curre

nt Relay (Inverse) type CDG Inplant

Page 34 of 53

Training,GAIL(PATA)

MOTORS

Inplant

An electric motor is a device using electrical energy to produce mechanical energy, nearly always by the interaction of magnetic fields and current-carrying conductors. The reverse process, that of using mechanical energy to produce electrical energy, is accomplished by a generator or dynamo. Traction motors used on vehicles often perform both tasks.Electric motors are found in myriad uses such as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and computer disk drives, among many other applications. Electric motors may be operated by direct current from a battery in a portable device or motor vehicle, or from alternating current from a central electrical distribution grid. The smallest motors may be found in electric wristwatches. Medium-size motors of highly standardized dimensions and characteristics provide convenient mechanical power for industrial uses. The very largest electric motors are used for propulsion of large ships, and for such purposes as pipeline compressors, with ratings in the thousands of kilowatts. Electric motors may be classified by the source of electric power, by their internal construction, and by application. Here the main load in the plant ins mainly of motors . The two biggest motor in the plant are in Downstream-2350 KW main LLDPE extruder and 710 KW for gear pump in HDPE plant. The most of the motors in plant are Induction motor.

INDUCTION MOTORAn induction motor (IM) is a type of asynchronous AC motor where power is supplied to the rotating device by means of electromagnetic induction. Commonly used motor in industry is squirrel cage motor (the rotor bars with short circuit rings resemble a squirrel cage (hamster wheel)).

WORKING PRINCIPLE OF INDUCTION MOTORBy way of contrast, the induction motor does not have any direct

supply onto the rotor; instead, a secondary current is induced in the rotor. To achieve this, stator windings are arranged around the rotor so that when energised with a polyphase supply they create a ro t a ti ng m agne ti c f i e l d pattern which sweeps past the rotor. This changing magnetic field pattern induces current in the rotor conductors with the rotating magnetic field created by the stator and in effect causes a rotational motion on the rotor.

Three phase supply provides rotating magnetic field in Induction motor. However, for these currents to be induced, the speed of the physical rotor and the speed of the rotating magnetic field in the stator must be different, or else the magnetic field will not be moving relative to the rotor conductors and no currents will be induced. This difference between the speed of the rotor and speed of the rotating magnetic field in the stator is called slip. Due to this an induction motor is sometimes referred to as an asynchronous machine.

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http://en.wikipedia.org/wiki/Rotating_magnetic_field

http://en.wikipedia.org/wiki/Rotating_magnetic_field


CONSTRUCTIONThe stator consists of wound 'poles' that carry the supply current to induce a magnetic field that penetrates the rotor. In a very simple motor, there would be a single projecting piece of thestator (a salient pole) for each pole, with windings around it; in fact, to optimize the distribution of the magnetic field, the windings are distributed in many slots located around the stator.

There are three types of rotor:Squ i rre l - cage ro t o r : The most common rotor is a squirrel-cage rotor. It is made up of bars of either solid copper (most common) or aluminum that span the length of the rotor, and are connected through a ring at each end. The rotor bars in squirrel-cage induction motors are not straight, but have some skew to reduce noise, harmonics and magnetic locking as well. Most of the motors in the plant are squirrel cage type.

S li p r i ng ro tor: A slip ring rotor replaces the bars of the squirrel-cage rotor with windings that are connected to s li p r i ng s . When these slip rings are shorted, the rotor behaves similarly to a squirrel-cage rotor; they can also be connected to resistors to produce a high-resistance rotor circuit, which can be beneficial in starting

So li d core ro t or : A rotor can be made from a solid mild steel. The induced ED D Y Current causes the rotation.

STARTING OF INDUCTION MOTOR

Starting of induction motor depend upon following facts :

1. Size and design of motor.

2. Capacity of power lines.

3. Type of driven load

http://en.wikipedia.org/wiki/Slip_rings

http://en.wikipedia.org/wiki/Slip_ring

http://en.wikipedia.org/wiki/Squirrel-cage_rotor

In plant starting of induction is done by direct on line starting(DOL Starter).We do not use any other method for the starting of the Induction motor such as the Star-Delta starter method or Resistance starting.

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DIRECT ON LINE STARTING METHOD The simplest way to start a three-phase induction motor is to connect its terminals to the line. This method is often called "direct on line" and abbreviated D O L .

In an induction motor, the magnitude of the induced e m f in the rotor circuit is proportional to the stator field and the s li p s peed ( the difference between synchronous and rotor speeds) of the motor, and the rotor current depends on this emf. When the motor is started, the rotor speed is zero. The synchronous speed is constant, based on the frequency of the supplied AC voltage. So the slip speed is equal to the synchronous speed, the slip ratio is 1, and the induced emf in the rotor is large. As a result, a very high current flows through the rotor. This is similar to a transformer with the secondary coil short circuited, which causes the primary coil to draw ahigh current from the mains.

When an induction motor starts DOL, a very high current is drawn by the stator, in the order of5 to 9 times the full load current .The motor which are operated at 415 V are called L.T. motors. Motors which are operated at high voltage are called H.T. Motors. In the plant we are using DOL method of starting to start the motors. This method does not effect the performance of other motors connected to the line.

In the induction motor there is a super heater that will evaporate the moisture present inside motor insulation.

The preventive maintenance of motor is done to save the motor from fault. In preventive maintenance of motor we do following process :

We do the dusting of the motor.

http://en.wikipedia.org/wiki/Slip_ratio

http://en.wikipedia.org/wiki/Electromotive_force

http://en.wikipedia.org/wiki/Direct_on_line_starter

We measure the insulation resistance of the motor.

Page 37 of 53

Training,GAIL(PATA)

Abnormal conditions of Motor

Inplant

1. Mechanical overload.2. Supply voltage changes - The most important consequence of a

line voltage change is its effect on the torque speed curve of motor. If stator voltage decreases then torque also decreases. If line voltage will be too high, flux per pole will be too high and iron losses and magnetizing current increases due to which temperature increases and power factor decreases. If voltage and frequency both vary, sum of two in % must not exceed 10%.

3. Unbalanced loading - A slight unbalance of three phase voltages produce a serious unbalance of the three line currents.

4. S i n g l e ph a s i n g - If one line is accidentally opened, current drawn from the remaining two lines will almost double leading to overheating of motor.

5. Frequency variation - Frequency change leads to changing in speed of the motor.

6.6 KV Motor protection

All 6.6 KV motors used in plant would be squirrel cage induction motor and would beDOL started through circuit breaker.

1. Sh o r t c i rc u i t p r ot e c t i on - Instantaneous over current relays will

beconnected in all three phases to trip motor. The relay setting is such that they do not operate due to inrush of starting current.

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2. O v e rl oad p r o t ec t i o n .3. S ta lli n g p r o t ec t i on - The motor would also have a

speed switch to detect stalling if the current relay remains picked up and speed switch continues to indicate stalling.

4. Ea r th fa u l t p r ot e c t i on .5. Und e r vo l ta g e p r o t ec t i o n .

STEAM TURBINE GENERATORIn GAIL (PATA)

power is taken from NTPC and power is also

generated here .For power

generation there are two generator which are synchronized with Grid .There are two steam turbine generator (STG).

STG 1 have extraction type turbine in this turbine VHP steam at 105 Kg/cm sq. is fed and

HP steam at 40 Kg/cm sq. is extracted. This steam is used in plant operation.

STG 2 have Condensate type turbine in which output steam is condensate and water is re- circulated to DM water plant.

Power is generated at STG at 11Kv level and then stepped to 33KV with the help of a 20

MVA and a 30 MVA transformer. STG is helpful in maintaining the power factor of plant load above 0.95. The speed of STG-1 turbine is upto 8580 rpm and generator’s

speed is 3000 rpm(speed reduced using GEARS) but in STG-2 speed of both turbine and generator is same.

Frequency of Exciter is 1500 rpm.

RATING O F STG

STG -2

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Page 40 of 53


Page 41 of 53


S t a t o r F r a m e The stator frame is fabricated structure made out of mild steel plates. It houses and support core together with the winding. Dovetail shaped steel guide bar are welded to the inside surface of the frame on to which core is assembled .The stator is fixed to the foundation frame at the footing.

Stator Core The stator core is made of segments of insulated punching of non-grain oriented high quality silicon steel to give minimum electrical losses .These punching are assembled in a interleaved manner on the machine guide bars and are separated into packet of appprox- 50 mm .Ventilation ducts are provided between them .The core is then sprayed with insulation varnish in the slots and subjected to magnetization test.

Rotor BalancingRotor is balanced with the help of balancing weights are fitted in dovetail grooves providing in hubs and fan . The rotor is dynamically balanced and subjected to an over speed of 20% for two minute.

BearingThe turbo generator rotor is supported in two journal bearing .The pedestals are gray iron casting and the bearing shell is manganese steel casting in two halves There is resistance thermometer provide in lower part of shell for measurement of temperature of bearing shell .The bearing lubrication is done by circulation oil under pressure .The oil pressure is to be maintained at 1.0 bar .The maximum permissible temperature for the bearing oil is 64 degree Celsius.

Ventilation ArrangementThe turbo generator is cooled by air circulation by mean of two axial fans. The air after circulation is cooled by air cooler .The air is drawn through suction ducts by axial fans mounted on either side of rotor. The warm air flows out through exhaust at the bottom of the stator frame.

B rush l ess E xc i t a t i on Sy s t em The brushless excitation system mainly consist of mainly an A.C exciter, rotating rectifier , Permanent magnet generator and automatic VR Equipment

The A.C Exciter comprise of revolving armature and stationary yoke with field winding .The alternating voltage generate by A.C exciter is rectified by the rotating diodes and rectified voltage is fed to the field winding of the generator .The field excitation of exciter is controlled by A.V.R. as per requirement of the generator voltage and load .To increase reliability of the system

Page 42 of 53


power supply to the A.V.R is taken from the permanent magnet generator directly coupled to the main exciter. The A.C exciter, P.M.G and rotating rectifier wheels are cooled by air.

The Diode use rotating rectifiers are mounted on heat sinks made of cast aluminium. Cooling of diode is achieve by integral fins on the heat sink. Snubber circuit with capacitors and resistors are housed in the carrier ring and are connected in parallel to damp the over voltage spikes arising out of Commutation and hole stage effect. Permanent magnet Generator power supply of 220 V. AVR is a thyristorised, solid state, fast response, dual channel type. The output of AVR is fed to the field of main exciter which is of revolving armature, stationary field type.

POWER PLANTA power station (also referred to as a generating station, power plant, or powerhouse) is an industrial facility for the generation of electric power. Some prefer to use the term energy center because it more accurately describes what the plants do, which is the conversion of other forms of energ y , like che mi cal energy, grav it a t i onal po t en ti al energy or heat energy into electrical energy.At the center of nearly all power stations is a generator, a rotating machine that converts mechanical energy into electrical energy by creating relative motion between a magnetic field and a conductor .In Gail (PATA) there is Thermal power plant .There steam is used to rotate the turbine. There are three boiler in Power plant .The steam is then fed to the steam turbine.The steam is the process requirement and not basically produced for the plant requirement.

THERMAL POWER PLANTIn thermal power stations, mechanical power is produced by a heat engine that transforms thermal energy, often from combustion of a fuel, into rotational energy. Most thermal power stations produce steam, and these are sometimes called steam power stations.

In GAIL ( PATA ) there are

http://en.wikipedia.org/wiki/Gravitational_potential_energy

http://en.wikipedia.org/wiki/Gravitational_potential_energy

http://en.wikipedia.org/wiki/Chemical_energy

http://en.wikipedia.org/wiki/Energy

three boiler – Utility Boiler 1Utility Boiler 2Utility Boiler 3

Page 43 of 53


E M ER G EN C Y P O W E R S U PP L Y Uninterrupted power supply is required in various application like PLC’s DCS remote operated valve ,critical local panel ,level gauges transducer .For this we have UPS system with lead acid battery back upto 200 KVA capacity. It is of HIREL. Two models are there- Accupower which is thyristor based and 7400 series which is IGBT base .There are battery chargers for charging battery. Battery charger is designed to supply a constant voltage for any load within it’s rating. With battery connected to the output , the charger will supply sufficient current to maintain the battery at full charge regardless of variation in line or load within rating.Silicon controlled

rectifiers (thyristor) are employed and operated by a solid state firing circuit

to maintain constant voltage. A full wave bridge half controlled using three controlled rectifiers and three silicon diode provides rectification. Battery chargers are of CHABBI and UNILEC. For catering the emergency load of plant in case of complete power failure , we have DG set of250KVA to 1000KVA capacity. All these DG set are in auto mode.

The number of Diesel Generator Sets at GAIL(PATA)are:

Location NO. of DG set

Upstream 2Downstream 1IOPS 4Hdpe2 1

DG sets are of BHEL/Cummins make.


UN I N TERRU P TED P OWER S U PP LY UPS is used to ensure absolute continuity of power to the computerized control system thereby protecting critical equipment from electrical supply failure. The main flow of energy is from the rectifier to the inverter with the standby battery kept in float. If system voltage fall below a certain level or fails the battery output to the inverter maintain the clean a.c. supply. When the main supply restore ,the main energy flow starts from rectifier to the inverter but in addition rectifier recharge the battery.

UPS are available of various capacities – 80 KVA ,60 KVA,45KVA Input supply – 3 phase , 415vDC intermediate – 405 V AC output – 110v , 50 Hz

Standby batteries used normally are lead-acid battery. At some place

Ni-Cd batteries are used. Battery bank capacity are of different

capacity and power fed to HT emergency panel andlighting. The capacity is in AmpereHour.

Specific gravity of electrolyte is maintained

from 1200 to 1250. Voltage of the Battery

should not be less than 2.23 V.

BATTERY CHARGER

The system consists of dual float cum battery charger 125v ,50 A built in single panel .Both charger are rated to supply the load as well as carry out the OFF-LINE boost charging of the battery. On A.C. side two chargers are supplied through the different incoming feeder.

Each charger is provided with input ON switch,fuses, contractor, thermal over current relay,input surge suppressors. Different mode of operation of chargerFloat Mode – When cells are charged only small amount of current flows to keep it fully charged as with time it get discharge.

In Boost Mode – When cells are being charged output DC voltage ranges fromapproximately float voltage to maximum output voltage.Initial charging mode – Output DC voltage range is approximately Float voltage to maximum Output voltage.Total number of chargers in different area of plant :

Area No. of chargersUpstream 6Downstream 4

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IOPS 15HDPE2 1

VARIABLE SPEED DRIVES ( VSD) The AC induction motor is the main stay for energy conversion. It is found in industry, in commerce, in home. It is the major converter of electrical energy into usable form. For this purpose about two third of the electrical energy is fed to the motors. Much of the power that is consumed by A.C. motor goes into the operation of fans, blower, and pump. Basically fans and pumps are design to meet the maximum demand of the system. There are several types of variable speed drives that could be used with fans and pumps running at various speed so that they can consume optimal power. These include adjustable frequency drives, DC drives, eddy current drives, variable pitch drives and wound rotor motors.

ADJUSTABLE FREQUENCY AC DRIVES Adjustable frequency drives are also known as inverters. They are available at range of horsepower from 1000 HP. they are design to operate induction motors. This allows them to be easily added to an existing system. The basic drive consist of the inverter itself which convertthe 60 htz incoming power to a variable frequency and variable voltage. The variable frequencyis the actual requirement which will control motor speed. These are of three major type :

CSI Inverter (Current Source Inverter)The CSI inverter control the current output to the motor. The actual speed of the motor issensed by other circuits. This is then compared to the reference speed and an error is generated a demand for more or less current to the motor. The output switching devices, usually SCR are switched at desired frequency to steer the current to the motor. Current source inverter are available in a wide range of horse powers but most often are found in range of 50 HP and above

VSI Inverter (Variable Voltage Inverters)These inverters control the voltage and frequency to the motor to

produce variable speed operation. The main difference is the scheme

used to control the voltage. This inverter control the voltage in a separate section than the other section is used for the frequency generation. Usually the voltage control is done by using a phase controlled input bridge rectifier circuit at the input of the inverter. These drives are available from fraction horse power to about 500 Hp.

Pulse Width Modulation (PWM) inve r ters The down stream plants are having V/F controller, sensor less drive and close loop flux vector control drives. The total 54 no. of drives are of above type. The V/F is general purpose constant torque scalar inverter and sensor less vector control drives are the drive having no feedback signal from the motor(i.e. open loop system). The closed loop flux vector control are having feedback signal from motor through encoder. The various advantages are as follows:

Energy saving

Page 46 of 53

Training,GAIL(PATA)

Improve process control

Reduce mechanical stress through soft starting

Improve electrical system power factor

Inplant

The plant has VSD drive in the range of 0.25 KW to 2350 KW. The maximum VSD drive rating is for 2350KW main LLDPE extruder supplied by ABB Finland. In the HDPE plant maximum VSD drive rating is 710KW for gear pump motor supplied by ANSALDO, Italy.Both are closed loop flux vector control drive. Most of the VSD drive are single unit and need lot of care for continuous polymer production. The microprocessor based drives are sophisticated one and to be handled carefully.

Pulse Width Modulation inverter are available from 1 to 1000 HP.

PWM inverter features :

Uses standard motors-The standard induction motor are easily available.

Good Efficiency –The inverter can achieve efficiency of

90% at full speed, full load.

Power factor- The diode rectifier is used to rectify the incoming current. This permit good power factor throughout the full operating speed range of the inverter.

By Pass – If the inverter fails, motor can be

operated directly across the incoming line for continuous operation.

High inertia- The inverter can adapt its operation to prevent the overload caused by accelerating the high inertia load found in some applications

Multi motor – More than one motor can be operated from the same inverter. Also the inverter is not sensitive to changing the combination of motor operated as long as the total load current does not exceed the inverter rated current

Page 47 of 53


VARIABLE PITCH DRIVES This method of speed control uses the mechanical means of belts and variable pitch sheaves of pulley to change speed. The power source is a standard induction motor. Often these units are enclosed and have a gear reducer built in for reduced speed ranges. The horse power range is generally limited from 5 to 50 HP with not much available outside this range.

WOUND ROTOR AC MOTOR DRIVES They are specially constructed motor to accomplish speed control. The motor rotor is constructed with the winding which are brought out of the motor through the slip ring on the motor shaft. The torque performance of the motor can be controlled using these variableresistors. They are most common in range of the range of 300 HP and above.

CATHODIC PROTECTIONCorrosion is the electrochemical process through which loss of metal

due to interaction with environment. Cathodic protection (CP) is a technique to control the corrosion of a metal surface by making it work as a cathode of an electrochemical cell. This is achieved by placing in contact with the metal to be protected another more easily corroded metal to act as the anode of the electrochemical cell. Cathodic protection systems are most commonly used to protect steel, water or fuel pipelines and storage tanks, steel pier piles, ships, offshore oil platforms and onshore oil well Casings.

The pipeline will act as cathode and no corrosion will take place on it’s surface but occurs on metal being used for protection .Current flow from cathode to anode.

Interim pipeline storage facility for LPG is being protected by permanent impressed current C.P. system using anode flex conductive polymer anode (24 no. of pipes of 36 diameters having 301.1 meters length).Mounded storage bullets (7 no.) for LPG and (2 no.) for propane being commissioned by permanent impressed current C.P. system using anode flex conductive polymer anode (93m. length and 63 m. diameter).In length from wastewater treatment are being protected by

permanent impressed current C.P. system using high silicon chromium anode.

Impressed Current Cathodic Protection

For larger structures, galvanic anodes cannot economically deliver enough current to provide complete protection. Impressed current cathodic protection (ICCP) systems use anodes connected to a DC power source TR unit (transformer rectifier). Anodes for ICCP systems are tubular and solid rod shapes or continuous ribbons of various specialized materials .The metal use for anode are silicon cast iron, graphite, mixed metal oxide, platinum and niobium coated wire and others. A typical ICCP system for a pipeline would include an AC powered rectifier with a maximum rated DC output of between 0 and 75 amperes and 0-75 volts. The positive DC output terminal is connected via cables to the array of anodes buried in the ground (the anode ground bed). A cable rated for the expected current output connects the negative terminal of the rectifier to the pipeline.

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CRITERIA FOR CATHODIC PROTECTION

Following Cathodic protection criteria are normally followed for underground steel pipeline: The pipe-to electrolyte potential measurement for steel structure in soil will be between -0.85 and -1.5 volts with respect to copper/copper sulphate reference electrode.The pipeline to be considered protected when a minimum -300 milivolt potential shift has been achieve from the initial native potential to the ‘ON’ potential.A minimum polarization shift of -100 milivolts will indicate adequate level of cathodic protection of pipeline.With the relative cathodic protection system cycled on and off ,any positive potential shift (with the system only) in excess of 20 milivolts will be investigated for interference.

Corrosion control measures, though adequately designed, can only be effective if maintained properly. Without a suitable maintenance program, money spend on designing & installation can be wasted . Monitoring of CP system mainly involve the following:

S No ACTIVITY FREQUENCY

1 Monitoring of Transformer rectifier Monthl2 Monitoring of pipe to soil

potential(ON)Quarterly3 Monitoring of Pipe to soil

potential(ON-OFF)Yearly

4 Monitoring of ALJB & anode ground bed

Yearly5 Current measurement of pipeline Yearly

6 Monitoring of Cased crossing Quarterly

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ELECTRICAL ENERGY SAVING Improve power factor by installing capacitor banks to reduce KVA

demand chargers and line losses within the plant.

Avoid repeated rewinding of motors .Rewound motors show efficiency loss of up to 5% .

Use of variable frequency drives ,slip power recovery systems and fluid coupling for variable speed applications like fans , pumps help to minimize the consumption.

Replacing aluminium or fabricated steel fans by moulded FRP fan with aerofoil design result in electrical saving upto 15 to 40 % .

Improper selection of pumps can lead to wastage of energy . A pump with 85% efficiency at rat flow may only have 65 % efficiency at half flow rate.

Loose belts between pumps and motors can save between 15-20%

energy.

Training,GAIL(PATA)

CO NCLUSIO N

Inplant

Industrial experience is deemed necessary for an engineering student. It is through an industrial training that one learns how to see the theoretical fundamentals in practical and how to apply the principles learned. We not only learn the engineering basics required but also get introduced to the latest trends in the industry.

The industrial training at GAIL(PATA) lasted for four weeks, but in this four weeks itself I was able to earn a lot of practical knowledge. Also I got a chance to clear many concepts as well. It was through interaction with the highly proficient and experienced professionals that I understood the industrial culture and how they work, running such a huge Plant successfully. This interaction has not only brought knowledge to me but also introduced me to the industrial environment and the work culture.

All in all the training session was quite interesting, all credit goes to the GAIL management and officials. I have hugely benefitted and believe that this will help me in becoming a better professional.

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64001972-copy-of-training-report-gail-ms-word-2003-format (1).doc

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