A BRIEF PROFILE OF THE COMPANY

PROJECT REPORT

During summer training Programme Bhilai Jaypee Cements Limited,

Unit- BabupurSubmitted by: -

Chandra Prakash Gupta

IInd Year (4th Semester),

G.L.A.Instituite of Technology & Management

MATHURA

ACKNOWLEDGEMENT

I wish to express my gratitude to those who generously helped to color the mosaic during summer training in M/S Jaypee Cements Limited Unit- Babupur Distt- Satna (Madhya Pradesh) of their knowledge & expertise.

I pay my special thankful to the Management of M/s BJCL, Unit- Babupur for allowing me to conduct my training programme for 30 days i.e. from 24.06.11 to 24.07.11 accordingly.

I am also thanks to Mr.K.C.Sharma, General Manager, H.O.D (E & I), and other plant officers Of M/s JCL, Babupur, who provided my necessary information about the company and guided me at every step whenever required while working on this project work.

With regards,

Chandra Prakash Gupta

IInd Year (4th Semester),

SITE FALLODI

CONTENTS

#1 Introduction

#2 Company profile

#3 Clinker manufacturing process of Bhilai Jaypee cements Ltd. Unit- Babupur.

#4 Sections under training

1) 132KV Switchyard

2) Main receiving SubStation

3) Secondary Sub-stations

4) 6.6KV Motors, Motor Protections, Power Control Circuit

,DC motors, Motor Control Circuit

5) Battery Bank, Battery Charger

6) Work Permits, Safety of personnel & equipments, Earthing, Lightning Protections

7) Erection of Electrical Equipment

Introduction

WHAT IS CEMENT

Cement is a generic name for powdered material, which initially have plastic flow when mixed with water or other liquid, but from a solid structure in several hours with varying degree of strength and bonding property, which continue to improve with age. The most common is Portland cement, which is the basis for number of cement product. Specifically, Portland cement is identified as finely ground calcium aluminates and silicate of varying composition which hydrate when mixed with water to a rigid continues structure with good compressive strength.

ACL, Rabriyawas is making PPC.

ORDINARY PORTLAND CEMENT (O.P.C)

Portland cement are made by grinding a mixture of lime stone and clay material, burning the material at a very high temperature, cooling the resultant product, called clinker and grinding the same to an unpalatable powder. This type of cement develops enough compressive strength at 3 days, 7 days & 28 days to be suitable for all types of moderate civil engineering constructions.

POZZOLONA PORTLAND CEMENT (P.P.C)

Fly ash mixed with Portland cement clinker and ground with the addition of 5% to 6% gypsum the resultant cement is called Portland Pozzolona Cement. PPC should not contain more than 25% Pozzolona or fly ash. PPC has a much lower heat of hydration and is also fairly sulphate resistant. It has all the physical properties of OPC, but has lower shrinkage, and can be used for all construction work for which OPC is used.

COMPANY PROFILE

BHILAI JAYPEE CEMENTS LIMITED Unit- Babupur, is one of the leading company in the field of clinker production. Today in India M/s BJCL organization occupies a place of pride in industrial and commercial fields. The M/s BJCL organization is contributing a lot to the economic and social growth of India over the last decades.

The honorable chairman of this enterprise “Mr.Manoj Gaur ” and the managing director “ Mr.Sunny Gaur “ are the persons who had established this great firm by there talents and abilities.

The cement manufacturing units are located at

1. M/s BJCL Bhilai (Chattisgharh )

2. M/s BJCL Babupur (M.P.)

The clinker production capacity of the Babupur unit is 1.09 million tones per annum.

The clinker shell be sent by Rail dispatch to Bhilai wherein the split Grinding Unit of ISPAT CEMENT Project is located for manufacture for PSC.

PROFILE

M/S BJCL Babupur is situated in north part of Madhya Pradesh. The location of the clinkerisation plant is at village Birahauli of Tahsil Raghuraj Nagar ,District satna,Madhya Pradesh and the cement grinding plant is in Bhilai Steel Plant at Slag End Road.

MILE STONES OF GROWTH

The erection of the plant was started in 2008.It gets completely installed in December 2009. In 2010 the plant was commissioned and the production was started in July.

BRIEF PROCESS OF CLINKER MANUFACTURING

Firstly identified captive lime stone after assessing the required quality are drilled, blasted and transported to single impact crusher hopper, where 1m3 LS boulder is crushed by 400TPH impact crusher and converted to 70-100mm sizes. The crusher is being driven by a 6.6KV (500KW, 965 rpm) motor. The crushed lime stones are transported to lime stone yard through a series of belt conveyors and store in a pile through an automatic stacker machine .once a pile of known quantity and quality is achieved then reclaimer is used to reclaim stoke pile material. By using stacker and reclaimer machines, pre blending takes place to minimize fluctuation in crusher lime stone quality. Reclaimed pile LS stake is continuously reclaimed and sends to row mill.

When Raw mill is in operation and store in hopper at Raw mill section. Magnet separators are installed over the belt conveyors to remove any foreign materials if reported.

Additive materials like china clay purchased high-grade limestone and iron dust is also used as corrective material. The additive material are stored in separate identified yard and fed to feeding hopper through pay loader and then materials are transported in hoppers via a series of belt conveyers. All additives are stored in separate hoppers.

The proportionate ratio of LS and other additive materials after electronically weighing conveyed to a vertical raw mill (capacity 340TPH), however 70-100 mm size LS materials are ground to very fine powder and residue of 90 miocron&212 micron is mainted

at 18%and3% with the help of high efficient dynamic separator. Pre –condiitioned hot gases from kiln pre heater are utilized to dry up the material and swept the material to next conveying system.

Controlled flow silo can store 11000MT fine powder, which is also known as kiln feed. In CF silo feeding, blending and extraction process took place simultaneously. Due to good halogenations in CF silo fluctuations in input is minimized. The required feed to kiln for burning is being measured by an electronic weighing system and fed to kiln PH cyclones. Half of the kiln feed is in one string and remaining is in other string. Each string has six nos. of cyclones thus made total 12 nos. of cyclones in pre heater. Material that are fed from top cyclone finally entered in cyclone #5 and then from both string cyclone #5 it enters in inline calcimine and after achieving degree of calcinations it again fed to cyclone #6from where it entered in kiln for next process.

Hot gases when leaving cyclones#1 are having around 340 degree. Hot gases are re-conditioned (reduction in temperature) for further utilization in raw mill& coal mill section. All gases after heat utilization enter in bag house, where fine dust particles are collected and again fed back to system.

Indigenous coal is ground in vertical mill and being used in kiln & pre-calciner s a fuel. Around 60%pulverized fine coal is being fired at calciner where material is 90% calcined before entering into rotary kiln. 40%pulverized fine coal is fired in kiln through multi channel smilax burner. Typically 1400-degree temp. is being performed ideally. The burnt powder is converted into black pieces known as clinker.

When clinker leave the kiln it fall on the grate cooler where calculated fresh air is pumped with the help of 121 nos. fans and clinker temp. Brought down from 1400 to 250 degree. Hot gases are used in kiln and remaining excess air after filtration through ESP passes through, clean air emit to the atm.

The whole process of control and operation is centralized from a single place called CCR. The process control and instrumentation are taken care by modern DC system the process control and instrument care are taken cared by modern DC system. At every stage of process, on line quality parameters are checked through X-Ray analyser.

Technical capacity of plant

(1) Plant has single impact crusher of hazemag make of capacity 400TPH.

(2) Vertical Raw mill is of 340TPH capacity and its feed rate is controlled with electronic weigh feeder

(3) The kiln is of 64 meter length and 4.15 meter dia., having design capacity of 3300 TPD.

(4) Refectories are installed inside the kiln to protect kiln shell and to avoid heat losses.

(5) Generally 1200-1400 degree temp. is being maintained in the kiln to complete clinkerization reaction.

(6)12 nos. of cooler fans supply ambient air to cool clinker.

SECTIONS UNDER TRAINING

1) 132KV SWITCH-YARD

The total power consumption of the plant is as

S.No

SECTION

MW

1

Crusher

2

2

Raw mill and Coal mill

7

3

Kiln

6

Equipment used in 132KV sub-station

The various equipment which are used in the sub-station are as below-

1) Lighting arrester

2) Isolator and Earthing Switch

3) Current Transformer

4) Potential Transformer

5) Circuit Breaker

6) NGR

7) Power Transformer

(1) Lighting arrester

A wave of short duration appearing in electrical power is known as surge. These surges cause the failure of insulation of transformer & other equipment & motors. To over come these surges we have to use lighting arrester.

Details of Lighting Arrester are as:

120KV, 10KA station class gapless type lighting arrester

(2) Isolator and earthing switch

It is used for isolating the system from the power supply at normal condition. Whenever we have to work on the line or in substation then we must have to isolate the system. Isolators can be operated manually or may be of motorized type with and without earthing switch. Earth switch are used for ground the system or for discharge the equipment. Whenever we have to work on the line then it is required to discharge the system so the earthing switch is provided. These are generally used at isolator for discharging the line whenever work is done is required.

(3) Current transformer

Current transformers are used for the reducing/stepping down the A.C. of higher value to lower value for measurement/protection/control. These are used for measuring purpose so they are called instrument transformer. As current transformer ratting VA is very low so it is not used in power transfer. This is the main difference between instrument and power transformer.

a) Measuring current transformer

These are used with ammeters, Wattmeter, KVA meters and to reduce line current nearby 1 Amp.

b) Protective current transformer

These are used with over current protection, earth fault protection, differential protection etc.

Details of current transformer are as:

Make-

Mehru

Rated S.T.C.

31.5KA for 1 sec

Insulation level

275/650KV

Rated burden in V.A.

30

Current ratio

150/1

(4) Potential transformer

Potential transformers are used for stepping down A.C. voltage form higher level to lower level value for measuring/protection/control etc. This is also known as instrument transformer. Potential transformers are necessary for voltage, directional, distance protection. In the plant 1:2 type potential transformer is used.

Details of potential transformer are as:

Make

Mehru

Type

Out door oil cooled

Highest voltage

145KV

Primary voltage

132KV/1.732

Secondary voltage

110V/1.732

Insulation level

275/650KV

Burden

100VA

(5) Circuit breaker

Circuit breaker is a mechanical device, which is used for opening or closing electrical circuit under normal & abnormal condition. In 132KV Switchyard SF6 circuit breakers are provided.

Details of circuit breaker are as:

Make

Siemens

Type

3APIFG

Working voltage

145KV

Normal current

3150A

Lighting impulse with standing voltage

275KV

Short circuit breaking current

31.5KA

Short time with stands current & duration

40.0KA, 3s

Gas pressure of SF6/20 degree

6Bar

Closing & opening device supply voltage

110V DC

Auxiliary supply voltage

110V DC

Total weight

1700Kg

a) Operating principle

A circuit breaker is a switching &current interrupting device. It consists of fixed and contact. Which are touching each other and carry current in normal operating condition.

Whenever faults occur the trip coil of breaker get energized and the moving contact pulled apart and open the circuit. When ever the circuit is disconnected then heavy spark is produced this may damage the circuit breaker. So to over this fault SF6 circuit breaker is used. SF6 gas absorbs the spark as fast as possible because SF6 gas has good arc quenching properties& good dielectric strength.

Circuit breaker perform these operation-

(1) It carries full load current continuously without over heating.

(2) It opens or closes the circuit on no load condition.

(3) It makes or breaks the short circuit current of magnitude up to which it is designed.

The main basic difference between the circuit breaker & isolator is that

Circuit breaker works on the abnormal condition or in fault condition but isolator works whenever operator wanted.

Circuit breaker works ON load condition but isolator works on off load condition.

SF6 circuit breaker is used for high current lines or high voltage driven equipments.

b) Properties of SF6 Gas

Sulpher hexafluoride is an inert, heavy gas having good dielectric and arc extinguishing properties. Following are the properties of SF6 gas.

Chemical properties of SF6 gas are

(1) Stable up to 500degree centigrade

(2) Inert

(3) Electronegative gas

(4) Does not react with structural material up to 500 degree

Dielectric property

Dielectric strength of SF6 at atmospheric pressure is 2.35 times that of air. At higher pressure the strength is increases. At the pressure about 3Kg/cm2 the dielectric strength is more then dielectric oil. This property permits smaller clearance and small size of equipment.

Heat transferability

The heat transferability of SF6 gas is 2to2.5 times that of air at same pressure so the current carrying capacity of same conductor size is relatively more.

(6) NGR

Neutral ground resistance is being connected to the power transformer neutral point.

Its resistance is on the value of voltage applied & current with standing capacity of the transformer here the capacity is 100amp.so the resistance is-

V=6.9*1000/1.713 =3810

R=3810/100=38.10

These are connected between the star point & ground point.

(7) Power Transformera) Principle of transformer

A transformer is consisting of a closed magnetic core and two winding. When one of the winding is connected to a.c. supply magnetic flux is produced in the core .As per the rule of mutual inductance E.M.F. of same frequency is induced in the other winding.

b) Constructional details

The power transformer is constructed of many parts. These are –

1. Tank

2. Core

3. Conservator

4. Radiator

5. Bushing

6. Carriage

7. Thermometer

8. Oil

(1) Tank

Tank is an iron box in which the whole winding& oil is immersed. This is made of iron.

(2) Core

Core is a group of soft iron strips, which the winding is assembled. These are of three-lag type, which is insulated from winding through paper & air.

(3)Conservator

It is large cylinder connected by pipe to the transformer. Transformer oil is filled up to certain level in the conservator. Remaining upper portion is filled with air. conservator oil is in communication with tank oil.

(4) Radiator

Radiators are hollow strips in which oil is flowing for cooling. in these the oil is circulated and gets cooled.

(5) Bushing

Bushings are provided for connecting the transformer winding to external supply with insulating the tank.

(6) Carriage

On the carriage the whole transformer is constructed at this wheels are provided for moving transformer from one place to another place.

(7) Thermometer

Thermometer is used for measuring the temp. of oil and winding.

(8) Oil

Oil is used in the transformer for cooling & providing insulation to the winding.

Details of power transformer are as:

Make

AREVA

Vector group

YNyn0

KVA

25/31.5MVA

Hz

50

Amb. Temp

50 degree centigrade

Volts HV

132KV

Volts LV

6.9KV

Amps HV

109.3/137.8A

Amps LV

2091.8/2635.7A

Phase

3

Cooling

ONAF

Max temp rise

40 degree C

% Impedance volts AT

12.1

c) Protection of transformer

For the protection of transformer these equipments are used-

(1) Lighting arrester

(2) Over current relay

(3) Buchholtz relay

(4) Earth fault relay

(5) Oil temp. & Winding temp relay

(6) Oil level indicator

(6) Over fluxing relay

(2)MAIN RECEIVING SUBSTATION

MRSS have 6.6KV 40KA DOUBLE BUSBAR MV SWITCH BOARD and 2 VCB. Power distribution for various sections of plant is given through individual breakers (detail of which is given as below). This switchboard has isolator system with interlocking arrangement for transferring load on DG bus.

Protective relay:

Protective relay is an electric device designed to initiate isolation of a part of an electrical installation or to operate an alarm signal in the event of an abnormal condition or a fault.

A good protective relay must contains these feature-

(1) Reliability

(2) Selectivity

(3) Sensitivity

(4) Simplicity

(5) Speed

(6) Economic

In general following protective relays are used. Brief descriptions of various types of protective relays are as

(1) Over current relay

(2) Earth fault relay

(3) Differential relay

(4) Reverse power relay

(5) Low power relay

(6) Over voltage/under voltage

(7) Over frequency/under frequency relay

(8) Time lag relay.

Over current relay

This relay provides a safety from the current exceeding then the rated or value provided by them to this relay. When the current exceeding then it breaks the circuit and stop the power supply flowing in the circuit.

.

Details of over current relay used at HT panel

This relay is being used in all the three-phase supply at the HT panels. These relay are (IDMT+INST.) relays.

Make

Siemens

Type

7SJ

Current ratio

150/1

Operating voltage

110V

Differential relay

Differential protective relay is most positive in selectivity and in action. It operates in the principle of comparison between the phase angle and magnitude of two or more similar electrical quantities.

A differential relay is defined as the relay that operates when the phaser difference of two or more similar electrical quantities exceeds a pre-determined amount.

Reverse power relay

Reverse power relay is used for the avoiding the return of the supply to the grid sub station. As both the supply generated and the RSEB are in one bus bar so there may be chance of supply to in reverse direction.

This relay works on the principle of max torque angle. The torque-developed on the disc is suspended between the two magnets is proportional to the VI. When the power flows in the normal direction the torque developed on the disc is assisted by the spring tends to turn away the moving contact form the fixed trip circuit contact. Thus the relay remains in the operate condition. A reversal of current in the circuit reverses the torque produces on the disc and when this torque is large enough to over come the control spring torque, the disc rotate in the opposite direction and moving contact breaks the circuit.

Earth fault relay

Whenever the supply is due to any fault is comes in contact with the earth then higher current is flows in the circuit this may damage the equipment. To overcome this earth fault relay is used. This is connected between the earth switch and the earth strip.

Whenever current flows through the relay coil this coil breaks the circuit and save the circuit form damage.

Details of Earth fault relay are as

Make

Siemen

Type

7UT

Current ratio

150/1

Low forward power relay

This relay is used for protection of the system form low supply. In this relay a minimum power is possible to flows in the normal direction.

3) Secondary sub-station

There are four nos. of secondary sub-station, which are as follows

a) Crusher sub-station.

b) Raw mill sub-station.

c) Kiln sub-station.

Brief description of Kiln sub-station is as follows.

There is 6.6KV switch board having 10 nos. of panels

1) Incomer

2) Bag House Fan motor (1200KW)

3) Pre-Heater Fan motor -1 (1810KW)

4) Kiln Main Drive (Thyristor drive 2400KVA)

5) Cooler Exhaust Fan motor (310KW)

6) Transformer

7) Spare Feeder

6.6KV supply is then stepped down to 433V by Distribution Transformers and their secondary supply is feeded to incomers of Power Control Center.

Distribution transformer

The transformer whose capacity is is less then the 10 MVA is known as distribution transformer. There supply voltage is low as compare to the power transformer. The distribution transformers are used in the distribution of the supply. These gives the 415V supply to the system. The distribution transformer is generally used in industries for driving the low voltage supply. As per the working and construction the distribution and power transformer are same.

As per the connection power transformer are generally connected in star-star connection, but the distribution transformer are connected in delta –star connection. Using of star connection one neutral point comes with this single-phase supply is also used.

Details of Distribution Transformer are

Make

EMCO

Vector group

DYN11

Rating

2MVA

No load voltage

HV- 6.6 KV

LV- 433V

Cooling

ONAN

Amb temp

50 degree

Details of Kiln Thyristor Drive Transformer

6.6KV, 2400KV, ratio 6.6KV/690V, 3 phase,

Power control center

At the power control center the secondary supply of Distribution Transformer is feeded to incomers of PCC. PCC is having outgoing feeders to MCC, Capacitor panels having Air circuit breakers.

Following equipment are provided at PCC panel

(1) Air circuit breaker

(2) Current transformer

(3) Over current relay

(4) Earth fault relay

(5) Tripping relay

(6) Energy meter

(7) Over voltage relay

(8) Auxiliary relay

Air circuit breaker

In the air circuit breaker air at atmospheric pressure is used as an arc-extinguishing medium. Arc is quenched by the high resistance interruption principle. The arc is rapidly lengthened by means of the arc runners and arc chutes and cooling, lightning and splitting the arc increase the resistance of the arc. The arc resistance increases to such an extent that the voltage drop across the arc becomes more than the supply voltage and the arc gets extinguished.

Air circuit breaker are used in low voltage unto 1000KV.these circuit breaker are widely used in low voltage at motor control centers or indoors drown out type switch gear.

Construction& operation of air circuit breaker

There are two sets of contacts;

(1) Main contacts

(2) Arcing contacts

Main contacts

Main contacts conduct the current in closed position of the breaker. They have low contact resistance and are silver-plated.

Arcing contact

These are hard, heat resistant and are usually of copper alloy. While opening the contacts the main contacts dislodge frist.the current is sifted to arcing contacts the arcing contacts dislodge and arc is drawn between them. This arc is forced upward by the electromagnetic forces and thermal action. The arc moves upwards and is split by the arc splitter plate. The arc is extinguished by lengthening, cooling, splitting etc. Air circuit breaker is widely used in the plant for switchgear and circuit breaker.

Motor Control Center

1) Constructional Features

1) Motor Control Center (MCC) have double front, indoor, floor mounting, MCC have series of panels of uniform height placed side by side. Each vertical panel of MCC is provided with space heaters. . Each compartment is provided with a neoprene gasket all along the perimeter in the front. The thickness of sheet steel used is 2 mm

The base channels is of minimum 3 mm thick sheet steel, painted black to prevent corrosion of sheet steel cubicles and to facilitate cleaning of floors.

2) MCC is extendable on either side at site.

3) All doors and covers are provided with double lipped Neoprene gaskets to ensure positive dust proofing. The door hinges are concealed.

4) MCC is divided into a number of shipping sections with facilities for assembling them at site.

5) The switching module is of draw out type up to 75 KW and fixed type for higher rating.

6) Vertical sections

Each vertical section is provided with main horizontal bus bars at the top and cable entry is from bottom. Each vertical section is divided by horizontal sheet steel partitions into independent cells / compartments..

7) The compartment door is so interlocked that it shall not be possible to open the door with the switch in closed position. However, it is possible for an authorized person to defeat this interlock for inspection and testing. After the interlock has been defeated it is not possible to close the door unless the interlock defeat has been set to normal.

8) Facility is provided to padlock the switches in OFF position.

9) Chassis

The chassis is made of cold rolled sheet steel. All equipments viz., switch fuse, contactor, overload relay, control fuse and control link, MCB`s, indicating lamps, ammeters etc as may be required for a particular feeder shall only be mounted on the withdrawable chassis.

2) Busbars

1) Horizontal Main Busbars

2) Vertical busbars

3) Control supply Busbars

4) Ground Busbars

3) Wire ways and wiring

4) Terminals

5) Termination arrangement

6) Equipment mounted in the MCC

The brief technical specification of the components are given as under

1) Circuit Breaker

2) Switches and Fuses

3) Contactors

a) Contactors are 3-pole air break type suitable for making and breaking stalling current of the motor at 0.30 power factor of the motor. The stalled current of the associated motor shall be considered as 6 – 8 times the full load motor current. Each contactor has potential free spare 1 NO + 1 NC auxiliary contacts.

b) The contactor coils is replaceable from front. The coil voltage is being 240 VAC.

The minimum size of the contactor in the power circuit is of 30 Amps.

The contactors are chosen from the standard sizes i.e. 30, 73, 110, 140, 200, 300, 450, 550 and 630 amperes.

The rating of a contactor shall not be less than 125 % of the rated full load current of the motor to be controlled.

4) Protection Relays

These are comprise of a three element positive acting, ambient temperature compensated, time lagged, hand reset type thermal overload relays with adjustable settings for motors. Hand reset button is flush with the front door of the starter and suitable for resetting the relay with the starter module door closed. Thermal relays are either direct operated or saturable CT operated depending on the rated motor current and have one no. changeover contacts.

5) Current Transformers

Current transformers for metering and protection are of epoxy moulded to achieve compactness and ease of replacement and are complete with shorting links. CT`s are be with 1 Ampere secondaries.

6) Lockable Stop Push Button

One no lockable key type stop push button is provided on MCC module in each motor feeder.

7) Control Transformers

The control voltage shall be 240 VAC fed through 2 nos control transformers of either 5 KVA capacity, each 100 % rated (one of them standby unit) of 415 +/- 10 % / 240 V. Manual changeover switch for selecting any one of the control transformers shall be provided. Protective fuses shall be provided on both primary & secondary circuits of the transformers.

8) Ammeter with Selector Switches

9) Illumination Lamp

Screw type illumination lamp with door interlock to be provided in the cable alley. The lamp shall be suitable for 240 VAC, 50 Hz single phase supply.

10) Potential Transformer

It is of Cast Resin type, rated 100 VA and shall have voltage ratio 415 +/- 6 % / 110 V, class of accuracy 1.0

7) Design Data and Technical Specification of Field Mounted Push Button Stations

The push button station is housed in totally enclosed, dust proof with IP 55 protection suitable for wall / pedestal mounting.

a) Push Button Station for Unidirectional Drive

The Push Button Station shall have start and stop push buttons. The stop push button is mushroom-headed stay put type, red colour and key lockable in pressed condition.

b) Push Button Station for Reversible Drive

The Push Button Station shall have three push buttons – Forward, Reverse and Stop. The stop push button shall be mushroom-headed stay put type, red colour and key lockable in pressed condition.

4) 6.6KV motors

The induction motor is chosen for most of the industrial applications for their simplicity, reliability and low cost. Induction motor have good efficiency, good over-load capacity and require minimum maintenance.

In three-phase induction motors the generated torque is proportional to applied voltage so where higher torque is required higher voltage motors are used. In the plant total 13 nos. of 6.6 KV motors are employed.

Operating principle

A three-phase induction motor has two main sub assemblies: stator and rotor. Stator has a three-phase distributed winding supplied from a 3-phase 50Hz, balanced A.C.supply. The 3-phase current in the distributed windings produces magnetic field revolving at synchronous speed. The rotor has a closed short-circuited winding. The induced emf in the rotor produces short-circuited rotor current.

A current carrying conductor placed in the magnetic field experiences torque. There fore the rotor conductor carrying induced currents placed in the rotating magnetic field experience a torque the rotor rotates at nearly the same speed as that of the rotating magnetic field. During loaded condition rotor speed drops slightly. Since the torque is due to the induced currents, the motors are called induction motors.

Slip

The rotor speed of an induction motor is slightly less then the synchronous speed. The speed at which the rotor conductor moves relative to stator revolving magnetic field is equal to the difference Ns-N. The ratio of this difference and synchronous speed is called the slip.

Starting device of MV motors

Since MV motors are provided at high inertial loads, so it requires high starting torque. In order to get smooth start of these high inertial drives and to limit starting current, MV slip-ring motors are started by (L.R.S) liquid resistance starter.

Protection of 6.6KV motors

Large motor requires protection against various abnormal conditions. Several relays are provided for sensing the abnormal condition and trip the circuit of motor circuit breaker.

Earthing

For the protection purpose motor is earthen to 6 points

(1) 2-stator

(2) 2-rotor

(3) 2-body

Liquid resistance starter (L.R.S.)

In this type of starter water is used as resistance in order to get maximum torque and better power factor at starting. This is working on the resistance method of speed controlling of induction motor. This water resistance is connected in series with rotor winding.

In LRS there are 6 electrodes, 3 electrodes are star connected which are known as moving electrodes, lying at zero position in starting i.e. maximum resistance remains in circuit. Three electrodes are fixed, which are connected to rotor circuit. A final shorting contactor is provided, which bypasses the LRS after reaching of moving electrodes at final position i.e. resistance is minimum.

Three water columns are provided by means of highly insulated sheets. Electrolyte concentration is adjusted as per motor operating characteristics.

In this LRS two limit switches are provided at max. and min. position. For driving the moving electrodes pilot motor is provided.

In fan drives LRS is used as LRC in order to control rpm. Due to flow of current, heat is produced, which evaporate the liquid, so it is required to maintain the water level. LLC (low level controller) is provided which generates alarm in case water level happens low. Water level is maintained through make up tank. A pump is provided which maintains temperature of liquid by circulating it through heat exchanger. A thermostat is provided as temperature controller.

At the LRS current relay is provided for the protection. A timer is provided with a time delay of 35sec, which trips the drive in case moving electrodes not reaches at final position due to any reason.

General maintenance of 6.6 KV motors

(1) Tightening of stator and rotor connection

(2) Blowering of slip ring

(3) Measurement of size of brushes.

(4) Vibration of motor

(5) LRS general maintenance.

Direct current motors

D.C. motors are being used even today because of their excellent characteristics particularly for variable speed drive and truncation duties. Their inherent characteristics give it high starting torque. Their speed range is wide, above and below rated speed. As there voltage are fixed so their current I also fixed so there speed is fixed at a fixed current. As in the case of AC for a particular fixed speed higher voltage are required then the rated voltage.

Principle of operation of a DC motor

A current carrying conductor placed a magnetic field experiences a mechanical force.

This phenomenon is used in electric motor.

F=BIL Newton’s

Several conductors are arranged on the rotor. The stator poles provide the magnetic field. The supply to rotor winding is through commutator. Force is developed due to electromagnetic action between the rotor and stator flux. It gives torque and causes rotation of the rotor.

Construction of DC motor

A general motor is consists of these essential parts

(1) Magnetic frame

It provides the mechanical support to the poles and acts as protective cover for the motor.

(2) Pole

These are works for the motor as field whenever they are connected to the supply they produces north and South Pole.

(3) Armature

In the armature slots are provided for the rotor winding. When current flows in them torque generated and it rotates the armature.

(4) Coils

Coils are copper wires closed circuit in which current flows.

(5) Commutator

The commutator converts DC supply to AC in DC motor

(6) Brushes

Brushes are used for providing the current to the armature. These are generally of carbon.

(5) Battery bank

Battery banks are used in all the applications requiring permanent need of steady, low voltage, low capacity DC power supply. DC supplies are used fro the trip circuit and control circuit in power station and sub station and these supply is for the computers in case of the power failure. These bank supplies 110V &220V as per the requirement of the system.

In the battery bank the batteries are connected in the series to form a higher capacity of the supply. Electrochemical cells are used for the battery bank. They are rated in term of voltage and ampere-hour capacity. The ampere-hour capacity means the number of ampere-hours that can be delivered under specified conditions temp. Rate of discharge and the voltage. For refilling the distilled water is used in place of ordinary water because ordinary water contains many minerals and salts, which have adverse chemical reaction on the plates.

Battery charger

Battery charger is designed for charging the batteries in float as well as in boost modes. In case of float-cum boost charger, one DC converter is provided to charge the batteries and to supply to the load as well. Voltage dropping with selector switch is provided as per the requirement.

In case of float and boost charger, two separate DC converters are provided, one is for float and another for boost charging. Float charger circuit provides the required out put DC filtered voltage. The battery in discharged condition is charged by the boost charger circuit, its voltage is approximately 25%more than the float voltage. External current control potentiometer is provided to keep the desired current required for charging the batteries. Also two separate potentiometer provided for controlling the boost voltage and float voltage as per requirement. In case of mains failure a DC contactor is provided to connect the full battery across the load. Under normal working conditions both boost and float circuit be on.

Equipment location

1) Locate all the equipment in a clean, dry atmosphere.

2) Max. Amb. Temp. Must not exceed 40 degree C

A damp room is dangerous due to possible earth leakage from the battery. The battery room should be well lit at all times of the day and night. Direct sunlight on the should be avoided. Suitable stands and supports are to be provided for the battery bank.

6) Work Permits, Safety of personnel & equipments, Earthing, Lightning Protections

SAFETY

Safety is one of the fundamental needs of all living beings. Accident is unwanted event and held due to carelessness so these can be minimized or prevented with it.

A worker can preserve himself by following the safety rules and precautions. To get best out of an individual his physical safety is essentials.

There are mainly two reasons, which induced to accident.

1) Unwanted Acts

2) Unwanted Condition

UNWANTED ACTS

In the accident induced by the unwanted acts the worker is directly responsible, these type of accident are held by improper acts, carelessness, short cut for completion of work, over confidence of the worker. These wanted acts can be minimize by keeping awareness patience in doing work one should not touch any machine or equipment, or should not do any work without having proper complete knowledge of procedure of the same.

UNWANTED CONDITIONS

Unsafe conditions also add to the accidents. To avoid such situations it is necessary to make workstation clean. These are indirect reasons and the unwanted acts are also involved directly, which results accidents.

For the protection from the accident before working on equipment person must have to take the work permit to safe form electric shock.

Work permit

The written permission of doing work on the equipment for supply disconnecting and safety is known as work permit.

Procedure for taking work permit

Before doing any work on the motor or equipment the person must take the work permit for his and equipment. the person have to go electrical dept. and fill the work permit and take the permission .there is three copy of work permit are of different colour.

(1) White

(2) Yellow

(3) Pink

White copy is known as original copy it is taken by the person who is taking the work permit.

Yellow copy is placed on the control panel of the equipment.

Pink copy is for the record of the electrical department.

After completing this work engineer have to do these work-

For 6.6KV motor

(1) Racking out the circuit breaker to test position for the isolation of power connects.

(2) Placing of danger board.

For 415v motor switch board-

(1) Switch of the switch fuse unit.

(2) Check that no out put voltage at

(3) Switch fuse unit

(4) Remove control fuses

(5) Switch off of MCB

(6) Placing of danger board

After completing of the work person should have to go electrical dept. ask to clear the permit. Engineer have to conform that no man on the motor. Then engineer will supply ON.

Safety of person

For the safety of the person he have to use these thinks.

(1) Rubber gloves.

(2) Rubber shoes.

(3) Insulating mats.

(4) Insulating supports.

(5) Insulating tools for repairing work.

(6) Always wear the helmet.

For the safety of equipment when work is in process then whole body of device should be grounded. Electrical supply should be disconnected.

Lightning

Lightning is a natural hazard, being the discharge of static electricity generated in storm clouds, some of them damage the buildings and a few kill or injure people and animals, either directly or indirectly by causing fire and explosion.

Current in the lightning stroke

Current in the lightning stroke ranges from about 2000 Amps to

2,00,000 Amps.

Voltage in clouds

Before the flash takes place, estimated potential of cloud is more than 100MV.

Protection

The need of protection should be on these places

(1) Where large numbers of people congregate.

(2) The area is in which lighting strokes are prevalent.

(3) In places where very tall and isolated structures.

For the protection from lightning, a lightning conductor is incapable of discharging a thundercloud without a lightning stroke. Its basic function is to divert to itself a lightning discharge, which might otherwise strike a vulnerable part of the structure to be protected. The range of attraction of lightning stroke is little affected by the configuration of the conductor

In general there is two type of configuration-

(1) Vertical configuration-for this conductor rising from ground level, the zone has been defined as a cone with its apex at the tip of the conductor, its base on the ground.

(2) Horizontal configuration-for this configuration the zone has been defined as the volume generated by a cone with its apex on the horizontal conductor moving from end to end.

7) Erection of Electrical Equipment

During my visit to plant I have attended the ongoing project work of Crusher screening plant. During my training I have seen the erection work of following electrical equipment.

HT cable

The power cable cables carry the main load current at medium and high voltage of main circuit. Power cables have higher normal current rating and there fore large cross-section of the conductors. In the plant mostly XLPE cables are used.

XLPE cables

Cross-linked poly ethylene (XLPE) is a synthetic insulating material being increasingly preferred for high voltage cable insulation. XLPE is ideal material for cables. It is technically superior economical over oil filled cables.

XLPE cable qualities

(1) Its thermal withstanding capacity is normally 1.5 times of PVC cables.

(2) Smaller thickness due to higher dielectric strength.

(3) Excellent moisture resistance

(4) High impulse strength.

Insulation resistance measurement

The insulation resistance is measured by means of megger. 5KV megger is used for HV cables. The insulation resistance is measured between each conductor and earth. Or conductor and other two conductors earthed.

Testing of power cable

After the installation, Hi-pot test is carried out. This test is done by high voltage test kit.Test voltage is applied between the conductor and earth. The test voltages are applied for 5 minute with a value of (2K+1) KV. Here K means voltage, which is supplied in the normal operating condition. The leakage current must not be exceeded then 10mA.

The higher voltage DC set contains following equipments

(1) Control set

(2) Step up transformer

(3) Rectifier

Control set

It is control panel, which is used for controlling and measuring supply voltage provided for testing the cable. It has 1 voltmeter and two millimeter for measuring the leakage current. Through this set single-phase 220V supply is provided to the transformer. At this one controlling switch is also provided for controlling the input of the transformer.

Step up transformer

A single-phase step up transformer is used for providing higher voltage.

Rectifier

It is used for converting high voltage AC supply to DC supply. it contains two terminal for input and one for out put the out put return is provided earth.

Checks during commissioning of transformer

(1) Check the foundation for cracking and setting.

(2) Check oil level in conservator.

(3) Check oil-circulating pump is working or not.

(4) Relay panel is working or not.

(5) The entire indicator is working or not.

(6) Check the insulation level of winding per phase to earth.

(7) Test of buchholtz relay, there is no in protector, angle of injection.

(8) Oil and winding temperature alarm is working.

(9) Out put voltage on output side in all the tap position.

(10) Ratio of the transformer. Low voltages are applied at the primary get the output at secondary.

(11) Transformer sec. Short circuit test.

(12) Oil insulation test.

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