electirc section

7/29/2019 Electirc Section

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ELECTIRC SECTION

The Electric section is mainly classified into two that is

i. High Tension (HT)ii. Low Tension (LT)

In High Tension

i. 11Kv Yardii. VCB Panel

iii. Transformer

In LT sectioniv. ACBv. MCCB

vi. Starters, are includedIn HT section 11Kv feeder line firstly come to a KSEB post. The

feeder line again transmits to a Kochin Cagaz post. The 11Kv supply

voltage from Kochin Cagaz post, which is reaches to a Vacuum Circuit

Breaker (VCB)

1. 11 Kv YARD

Single Line Layout of 11Kv Feeder line


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KSEB POST


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KOCHIN KAGAZ POST


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The generating voltage in India is 11Kv. The voltage is generated by

different power stations i.e., Hydraulic, Thermal, Diesel, Nuclear etc.

Firstly the power stations are generated the voltage, after thegeneration this voltage is step up and then transmit. This transmit

voltage is step down for proper use and at last this voltage is

distributed (The line voltage is 415v and Phase voltage is 230).

Transmission and distribution lines are vital links between

generating (Power) stations and consumers or customers. Transmission

lines carry power at high voltage such as 66Kv, 132Kv, 220Kv or

400Kv over a long distance from the generating stations to the major

load centres or receiving stations. The power is supplied to the variousconsumers, both domestic and industrial, from the secondary

substations by means of distribution lines. The distribution line is also

carried out by means of underground cables.

THE MAIN COMPONENTS IN YARD

InsulatorGang operating switchLighting arrestorDO fuseCT & PTTOD Meter

INSULATOR

Insulators are provided between conductors and cross arms /

structures in order to prevent short circuit between the different phaseconductors of the line and also prevent leakage of current to earth

through cross-arms on the support.

GANG OPERATING SWITCH

Used for ON and OFF of 11Kv line


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LIGHTNING ARRESTOR

To discharge high voltage induced on the line to earth, due to

lightning and to protect the transformer and associated equipment fromlighting strokes.

DO FUSE

The drop out fuses simplest and most effective safety device for small

distribution transformer. The drop out fuse opens the circuit and serves

the mechanical isolation of system in case of flow of fault current. The

drop out fuses is designed for vertical installation. They are practically

maintenance free as they required duly replacement of fuse element.

CT & PT

Current transformer (CT) is used for measurement of electric

currents. Current transformers, together with (potential transformers

(PT)), are known as instrument transformers. When current in a circuit

is too high to directly apply to measuring instruments, a current

transformer produces a reduced current accurately proportional to the

current in the circuit, which can be conveniently connected tomeasuring and recording instruments. A current transformer also

isolates the measuring instruments from what may be very high

voltage in the monitored circuit. Current transformers are commonly

used in metering and protective relays in the electrical power industry.

TOD METER (Trivector Operating Display)

TOD Meter is used to measure Apparent power (KVA), Active

power (KW), Reactive power (KVAR) , Power factor (PF), Current

and Voltage etc.

2.VCB (Vacuum Circuit Breaker)

i. A circuit breaker is an equipment which can make or break acircuit either manually or remote control under normal

condition

ii. Break a circuit automatically under fault condition
http://en.wikipedia.org/wiki/Protective_relayhttp://en.wikipedia.org/wiki/Electrical_power_industryhttp://en.wikipedia.org/wiki/Electrical_power_industryhttp://en.wikipedia.org/wiki/Protective_relay


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iii. Make a circuit either manually or by remote control underfault conditions. Thus a circuit breaker (CB) in operates

manual as well as automatic control for switching functions.

The later control employs relates and operates only under fault

conditions

The Vacuum Circuit Breaker vacuum is the arc quenching medium.

Vacuum offers the highest insulating strength. It has far superior arc

quenching properties than any medium. When contacts of a breaker

are opened in vacuum the interruption occurs at first current zero with

dielectric strength between the contacts building up at a higher rate

than obtained with other circuit breakers.Principle

When the contacts of the breaker are opened in vacuum an arc is

produced between the contacts by the ionisation of metal vapours of

the contacts the arc is quickly extinguish because the metallic vapours,

electrons and ions produced during arc rapidly content on surface of

the breaker contact. Resulting quick recovery of dielectric strength.

Working

When the breaker operates the moving contact separate from the

fixed contact and an arc is struck the production of arc is due to

ionisation metal ions and depends upon the material of the contacts.

The arc is quickly extinguish because the metallic vapours, electrons

and ions produced during arc are diffused and seized by surface of

contact and shield. Vacuum has very fast rate of recovery of dielectric

strength. The arc extinction in vacuum breaker occurs with a shortcontact separation (say .625 cm ).

Advantages and Disadvantages of VCB

Advantages

1. They are compact reliable and have longer life2. There is no fire hazards .3. There is no generation of Gas during and after operation.


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4. They can interrupt any fault current. The outstanding feature of aVCB is that it can break any fault current perfectly just before

the contact reach the definite opening position .

5. They require little maintenance and smooth operation.6. They can successfully with stand lighting surges.7. They have low arc energy.8. They are requiring small power for control mechanism.Disadvantages

1. Requirement of high technology for production of vacuuminterrupters.

2. Vacuum interruption is costlier.3. It needs additional surge suppressors with each phase.4. Loss of vacuum due to transit damage or failure makes the

entire interrupter useless and cannot be require at site.

Application of VCB

1. Because of the short gap and excellent recovery characteristics itcan be used at very high speed making switches in industrial

applications

2. They are used in shunt reactor switching, transformer switching,line dropping capacitor bank switching.

3. They are used at voltages are high and current to be interrupted islow.

4. For low fault interrupting capacitors its cost is low.5. These are used along with static over current relays.

TRANSFORMER( Indoor Delta Star Type)

A transformer is static AC machine which transfers the electricpower from one electric circuit to another electric circuit with same

frequency at different voltage and currents. It works on the

productions of statically induced emf.

Working principle of a Transformer

It mainly consists of two inductive coils which are electrically

separated but magnetically linked through a path of low resistance.

When one coil of the transformer is connected to an AC supply mains,


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an alternating flux is set up in the laminated core, most of this flux

links with the other coil and produces mutually induced emf(according

to Faradays Law of Electromagnetic induction). The coil connected to

the supply mains is called primary winding and the coil connected to

the load circuit is called secondary winding.

When the transformer rises the voltage i.e. when the output

voltage of a transformer is higher than its input voltage it is called step

up transformer and when it lower the voltage i.e. when its output

voltage is less than input voltage it is called step down transformer.

Specifications of Transformer

Tap changing - ON Load Oil temperature - Winding temperature - Neutral CT Rating - 2000KVA 11Kv/433V KVA - 2000 Volts -11000 HV No load Ampere -433 Ampere - HV 105

- LV 2666.8

Phase - HV -3- LV-3

Type of cooling -ONAN Frequency -50Hz Impedance volts in % -5.75 Core & winding kg -2600 Oil kg -1500 Total weight kg -6600 Oil in litre -1750 Year of manufacturing - 2002


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Onload tap changing Transformer

In order to make the tap changing possible with the transformer

on load ( without interrupting the supply ) special arrangements are to

be provided. One way is to divide the coil into two parallel sectionswith identical tapings

Under normal working conditions switches Sa and Sb are closed

with same number of tapings i.e.(1& ) and each winding carry half

of the total current.

When the tapings to be changed. One of the switches say Sa is

open to take the winding A out of the circuit at this instant the

second winding B carries full current (double of its rated current)

now the tapings on the winding A is changed and switch Sa is closed

at this moment only the two windings will have different induce emf

and share the load unequally. The other switch Sb is open to disconnect

winding B the tapings on this winding is changed ( equal to windingA) and switch Sb is closed. Now both of the winding will share the

load equally.

Disadvantages of on load tap changing

During switching the impedance of the transformer is increasedThe no. of tapings required is double the voltage steps

Complication are introduced in the design in order to obtain ahigh reactance between the parallel windings


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The fault occurring in Power Transformer

Open circuit fault Earth fault Phase to phase fault Inter turn fault Overheating from overloading or some internal cause such as

core heating

For power transformers the protection is to be provided

usually against dangerous over loads and excessive

temperature rise. Dangerous over load may be due to

external fault or internal fault hence the protection for

internal fault is to be provided in such transformer.

Differential protection is the most important type of

protection used for protection against internal phase to

phase and phase to earth fault.


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Transformer protection device

o Vss-Voltage selector switcho REF-Restricted earth fault relayo Buchhols relay-it is used to detect internal fault of transformer

LT Section

ACB (Air Blast Circuit Breaker)

The breaker employs a high pressure air blast is quenching

medium. The contacts are opened in a flow of air blast established by

the opening of the blast valve. The air blast cools the arc and sweepsaway the arcing products to the atmosphere. This rapidly increase the

dielectric strength of the medium between the contacts and prevents

from the pre establishing the arc and consequently arc is extinguish

and flow of current interrupted

Advantages

The risk of fire is eliminatedArcing products are completely removed by the blastThe growth of dielectric strength is to rapid that final contact

gap needed for arc extinction is very small. There by reducing

the size of the device

The arcing time is very small due the rapid build-up of thedielectric strength between the contacts.

Disadvantages

The air has relatively inferior arc extinguishing propertyThe air blast circuit breaker are very sensitive to the variation in

the rate of rise of restriking voltage

The air blast CB are used in high voltage installation the majorityof circuit breakers for voltages beyond 110Kv


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MCCB

Molded case circuit breaker is mainly used for over load and short circuit protection .The simplest

C.B, MCBs are mainly used for circuit protection but in the case of MCCBs ,they are used in heavy

circuits

Different range of MCCBs are used in industry mainly to drive a motors

800A,50 KVA

630A,50KVA

11KV

VCB

200KVATRANSFORMER (11/440V)

ACB

3200A, Main MCB

MAIN ISOLATER

IND. ISOLATER S/W

RELAY/CONTACTER

MOTOR

STARTERS


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The DOL starters are mainly used up to 15 hp motors

Circuit diagram of DOL starter

Functions of starters are following

Start and stop the motor

Protect motor from over load under voltage and single phasing

VFD

The full form of VFD is variable frequency motor . This device is used in above 50 hp

motors. It is a newest method for controlling motor

VFD is mainly used for

AC to DC conversion

DC to AC conversion

The VFDs are used in IGBT (Insulated gauge bipolar transistor) to change


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Frequency and voltage . It is used for proper control of motor and also adjust the frequency and

control the speed of motor. The VFD includes the provision for change temperature, voltage and

current. It also provides the provisions for the regulation of voltage. This device is working on the

basis of pre set program

ADVENTAGES

It reduces the starting current as low

Speed can be adjustable so wear and tear is reduced

Increases the efficiency of motor

DISADVENTAGE

Initial cost is high

Voltage surge

APFC Panel

Full form of it is that is AutomaticPower Factors Control. 14 capacitors are used in this

panel. The available range of capacitors are 20KVA, 25KVAR etc. it used to improve power factor.

MOTORS

Induction motors are mainly classified as slip ring induction motors &squirrel cage

induction motors.

An induction motor is a rotating machine which converts the electrical energy into

mechanical energy. It is most commonly used due to following advantages

Simple rugged and unbreakable construction

Its cost is low and is reliable

It has sufficiently high efficiency

It requires less maintenance

It is self starting

Its speed control is easy by using semiconductor devices


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Ofcours the induction motor also has few disadvantages like its speed decrease with increase in

load and the starting torque is some what inferior to that of a DC shunt motor

Squirrel cage induction motor

It is cylindrical (solid) in shape and built up of number of laminations having slots on itsouter surface. Solid copper or aluminium bars short circuited at both ends by copper rings are

inserted in these slots. There is no insulation between the iron core and the conductors. The current

induced in the rotor is contained within the circuit formed by the conductors and end rings. Skewing

the rotor slots helps avoid logging (locking in at sub synchronous speed) and reduces vibration.

Wound rotor (slip ring) induction motor

It consist of laminated cylindrical core having slots on its outer surface. These slots carry

three phase winding similar to the one in the stator. The rotor winding is uniformly distributes in the

slots and is usually star connected.

The rotor is wound for as many poles as the number of stator poles. The rotor winding are

brought out and joined to three insulated slip rings mounted on the rotor shaft with one brush

resting on each slip ring. The three brushes are connected to a three phase star connected rheostat.

At starting the external resistance is included in the rotor circuit to give large starting torque and to

reduce the starting current. As the motor speed up, resistance is gradually reduced up to zero

Working principal of a 3- phase induction motor


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The two essential parts of a 3-pahase induction motor as mentioned earlier are stationary parts

known as stator and rotating parts known as rotor. When 3-phase stator winding is fed from 3-phase

supply, a rotating magnetic field of constant magnitude and rotating at synchronous [Ns=120f/p]

speed is produced. The rotating flux passes through the air gap and cuts the stationary rotor

conductors. Due to relative speed between the rotating flux and stationary rotor conductors, an emf

is induced in the later according to Faradays Laws of Electro Magnetic Induction. The frequency of

induced emf is same as supply frequency. Its magnitude is proportional to the relative speed

between the flux and the rotor conductors and its direction is given by Flemings Right Hand Rule,

since the rotor conductors form a closed circuit and has no external path to the induced current

whose direction as given by Lenzs Law, Such as to oppose the very cause producing it. In this case

the cause which producing it is the relative speed. The rotor starts rotate in the same direction as

that of stator flux and tried to catch it, but it never do so.

MAIN MOTORS

150 Hp VFD

LINE SHAF

After dryer and MG

100Hp VFD

Motor windings in Star and Delta

In star

In delta


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Slip ring motor approach -7.5 Hp &10 Hp

Squirrel cage motor approach 1.75 Hp & 5 Hp

Lighting circuit (82 KVA lighting load)

Hpmv -150

Hpsv 250w & 150w

Halogen 125w

MH lamp 125w

Fuses (HRC)

Ns type -4A control fuse

Hf type 63A

Size 00 fuse 125A

Size 01 fuse 250A

Size 02 fuse 415A

Total Load

6 pm to 10pm Peak time

10pm to 6am Off peak time

6am to 6pm Normal time


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Boiler

Boiler is a device used to heat water by combustion of fuel. The water tube boilers uses in

industry. Water tube boiler, in which water is inside the tube and fire outside. In the presence of fire

water is converted into steam

DM plant :- de mineralization of water to reduce the hardness of water. The use of hard water in

boiler

Boiler efficiency is decreased

Amount of fuel is increased

Working time is increasedLife of boiler is decreased

In this type of boiler 10 ton water is used per hour and the capacity of fuel is 10Kg/cm2

Boiler mountings:- it includes safety valve, pressure gauge, main steam stop valve, godown valve,

tap etc. the saturation point of slum is 100o

c.

Economizer :- it is a device used to heat the feed water

Mabry :- it is a device mainly provided the protection of boiler.

ID fan :- it is help to suck the air for its proper working.

FN fan :- it provide suitable air for rotating sand like hot materials used in boilers.

PA fan :-effluent treatment plant for recycling water

Producer section


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Raw material

Pulpier section

Turbo separator

Vibrator screen

TDR

Fan pump

Pressure screen

Belt

Press roll

Mg dryer

(after dryer)

Roll

Rewinder


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Dispatch

Tinal roll

In pulpier section divide into 3 and in which provides 3 motors 150,100,100 Hp respectively.

Pulp from pulpier section transferred to turbo separator, where 30 Hp motor is used to separate

plastic. Then pulp transferred to vibrator screen where it is grinding again and then it goes to . In

which the presence of agitator pulp rotates and transferred to TDR. In TDR 150 Hp motor is used and

pulp transferred to different steps. At last roll is formed

Production from the plants are that from the first plant is 30 Ton & from second plant is 40 T0n. theproduction rate depends up on the orders to the company


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