types of communication used in pspcl

8/7/2019 Types of Communication Used in Pspcl

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TYPES OF COMMUNICATION USED IN PSPCL

There are 4 types of communication used in PSPCL. Each type of

communication has different area of usage & application .The most commonly

used communication is power line communicaton .This communicationconnects each station of PSPCL with other by power lines & the four types of

communication used are:

MICRO WAVE COMMUNICATIONVERY SMALL APERTURE TERMINAL COMMUNICATIONWIRE LESS COMMUNICATIONLAND LINE COMMUNICATION

DETAILS OF COMMUNICATION

MICROWAVE COMMUNICATION:This type of communication is much advanced & used preferably in whole of

PSPCL . This type of communication not only connects the whole state but also

the whole of north india with the offices of the board . The communication

dependent upon anteena , receievers & transmitters . the microwave

communication is very much faster than others & provide more facilities like no.

of channels etc.

VSAT ( VERY SMALL APERTURE TERMINAL ) :This communication is not used so much in the organization because this type

of communication is not so efficient as like microwave communication . In this

type of communication there are small dish anteenas used to transmit thesignals .


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WIRELESS COMMUNICATION :This communication is used to connect those places where land linecommunication is not possible . The area where land line communication can

not reach & also at those places which are far from sub stations , then wireless

communication is used .

LAND LINE COMMUNICATION :This communication is very versatile in PSPCL . In this stations are connected

using power lines . The speech signal is sent in power lines therefore , it is called

POWER LINE COMMUNICATION.

o GENERAL:The power system of an organization like PSPCL comprising of power

houses, high tension lins & su ststion is so complex & extensive thet to control

the same an equal large & complex telecommunication system of high rliability

is required . The telecommunication system should provide the following

facilities :

TELEPHONETELEPHONE SWITCHINGTELE PROTECTIONREMOTE CONTROL & INDICATION OF LOADPOWER FREQUENCY SYSTEMREMOTE ALARM INDICATIONSTELE METERINGTELE PRINTINGDATA TRANSMISSION

For PSPCL , its own power line carrier (PLC) channels provide the tele

communication syatem , about 300 houses & 220kva , 132 kv ,66 kv sub stations


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rae served bythe PLC system . A PLC channel consist of two PLC terminal at two

stations A & B connected together with the help of high tension transmission

lines & coupling devices like coupling capacitor , coupling devices , wave trape &

high freq cable .

Information for the above listed facilities is accepted by the PLCterminal & passed on to its counter part at remote station in the form of high

frequency signals . The remote PLC terminal delievers the same in original

form to local users or passes on the same to adjoining PLC

Terminal to next station over the next line selector.

Thus two PLC terminal at two station communicate with each

other . PLC terminal use amplitude modulation with single side band (SSB)

transmission . If F1/F2 are the frequencies of high frequency carrier used by the

one PLC terminal for transmitting / receiver carrier signal then F2/F1 are usedby opposite end PLC terminal for transmitting /receiving the same. In a PLC

system F2 or F2 has to lie between the range from 30khz to 500 khz , the hiogh

frequency of the station B . If F2 is the transmitting frequency of the station B

then F2 the receiving frequency of the station & vice versa .


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BASIC SIGNALS :

TELEPHONE SIGNALS :The telephone transmitter (mouth piece ) of a telephone get convert the spoken

audio speech into corresponding electric speech signals .These are random

changing signals , characteristics of each individual signal changing electric

signal can be said to be alternating current signals. Telephony signals in PLC

channels cover a speech frequency band of 300 hz ti 2400 hz .This mouth piece

of PLC ckt design to handle sine wave ac signals of frequencies between 300 hz

to 2400 hz , will give equally good response to human speech signals . In other

words the electronic ckt to handle speech signal are designed & tested with the

help of signal generator of sine wave ac outputs of frequencies 300 hz to 2400hz . This is speech fixed in PLC terminals . All speech characteristics are covered

with in this band & person heard on PLC telephones is equally recognised .

TELEPHONE SIGNALING :This is the information available from switching equipments for the purpose of

establishment interconnections between telephone sets in the PLC systems . a

telephone subscriber or a station has to contact remote subscriber or ststions .This is done by dialing the no. of desired stations .The no. of information from

the dial is converted in the form of earth & no earth pulses by the switching

equipment.

This earth & no earth information is fed to PLC terminals A

digit dialed form the telephone set causes earth pulses of the same no. on the s

wire connecting equipment & the PLC terminal.

The earth & :no earth conditiuon go to a signal oscillatpor ckt

in the PLC terminal . The earth condition forces the signal oscillator to give asine wave signal of frequency in our PLC terminal are 2700hz & 2580hz .The

two frequencies produced differ by 60hz to give uf signal representing earth &

no earth dial pulse from switching equipments.

The response of PLC receiver & the dial pulse is just the opposite .

each PLC terminal is equipped with a dial receiver ckt .


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The UF signals from remote station of this relay gives the earth

&no earth pulses to local switching equipment. From the dial signal oscillator

to the dial signal receiver is formed what is known as the dial channel between

the two stations .Telephony signaling information received from switching

equipment by the PLC terminal at station A as passed on to theswitchingequipment by the PLC terminal at station B & vice versa.


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TELEGRAPHY (TELEPRINTER ) SIGNAL :

Our teleprinter machine receives signal in the form of DC pulses . For each

character of type writer , a unique set (or train) of DC pulses is generated . A DC

pulse has two states i.e high or low.


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BAND WIDTH OF PLC SIGNAL :

We have seen that a PLC terminal is required to transmit & receive signal which

lie in the UF band as follows :

TELEPHONY : 300HZ TO 2400 HZ TELEPHONE SWITCHING : 2580 + 30 HZVFT CHANNELS : 2880 + 60HZ TO 3600 + 60HZ

As per ISO 9482-1980 adopted in india for ssb PLC terminals , a nominal carrier

frequency of 4 khz is provided in the PLC terminals whenever PLC terminals

are required to transmit a telephony speech only (i.e no UFT signal the nominalcarrier frequency band of 2.5khz)

The idea about band width will become more clear in the following discussion

on amplitude modulation.

AMPLITUDE MODULATION

The modern system of transmitting basic signal is with the help of a carrier

signal of much higher frequency. The necessity of using a carrier signal can be

easily understood I case of PLC .The UF freq of basic signal discussed above are

very close topower freq 50hz exsisting on high terminal lines . It is not possible

design filter ( combination of wave traps , coupling capacitor , tunning

componenets etc) which will withstand high terminal power voltage & current&

at the same time separate power current 50hz to4000hz . Basic signal must betransmitted to a much higher freq quite away from 50hz . I n communication ,

microwave , radar etc make use of carrier freq of hundered 7 thousand of mhz.

In communication theory vital reason are also explained for the necessity of

acrrier freq to transmit basic signal.


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For eg radio communication , tv communication ,

microwave , radar , etc, make use of of freq of thousands& hundreds of mhz .At

carrier fe=req the requirement of send power , size of anteena . Power lines

associated with many types of noises are not designed or ideal for

communication purpose . However fully satisfactory PLC channels , usingcarrier freq in the range of 30 khz to 500 khz are now used.

Basic signals are translated with carrier freq signals to

obtain efficient & satisfactory transmission over the power line . The problem is

how to add the basic audio (UF)signalto the carrier freq saignal or wave . Some

characteristics of carrier wave is to be changed in accordance with the basic

signal.

BANDWIDTH OF A.M WAVE

The carrier freq Fe is many time greater than the signal freq Fs. Hence the side

band freq are close to the carrier freq.


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It is known that the bandwidth of amplitude modulated wave is twice the signal

freq . The basic contained in the side band freq or rather fully in each of the side

band .Therefore the PLC terminal design now is such that one side band & the

carrier freq signalare suppressed & only the remaining side band is transmitted .

This reduces the band with each requirement of each plc terminal & at the sametime enable the entire transit power to be allotted to useful side band. This

means more of carrier channels can be put on the adjoining line sections with in

the allocated carrier band (30 -500 khz).Without expecting interference

between any two carrier freq.


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Diagram shows the basic arrangement to produce amplitude & the

resultant side band. A high pass filter will eliminate the carrier &lower side band

freq signals from composite AM freq.

TWO STAGE MODULATION

Supposing an audio tone of 1 khz is to modulate a carrier wave of freq 300khz.

Then the resultant AM wave will contain high freq tone of freq 299 khz ,300 khz

&301 khz . the resultant freq are so close to each other that it is impossible to

design cheap filter to eliminate a pure sideband freq (299 or 301 khz)from the

composite wave. Unwanted carrier & the other sideband will unnecessarily leak

through the load to send the signal power available . Then there will be problem

to the 1 khz audio signal from the side band in the process of demodulationwhich will have to provide a 100% original freq for demodulation .To overcome

these difficulties . the modern PLC terminal design make use of two stage

modulation (& of course demodulation )

In two stage modulation , the audio tone first modulation & intermodulation

carrier freq signal of freq 12khz,16.45khz,20khz etc depending on the

modulation .

From this AM signal , one side band is selected for modulation ,

which is final HF carrier wave , the two side band in the HF stage only one sideband of transmission.


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POWER SUPPLY TO PLC TERMINALSIt is now standard sized that all PLC terminals should be suitable for connection

to 48v dc supply .Each PLC station is provided with a 48 v dc battery& the

battery charger of required capacity . The battery & PLC load are connected to

the charger .On the failure of ac mains , the load comes over to battery , whichhas capacituy to bear rated load for atleast 10 hours .

But some of the transistorized ITI/SIEMENS & BPL/SIEMENS PLC

terminal received in 1970-1972 where suitable for connection to 220 volt ac

mains. These PLC were used at stations , where emergency power supply

equipment comprising rotary converters were available . The rotary convertors

are suitable for supplying 220 v ac from sub station 220v dc batteries .Thus in

the event of ac mains failure , rotary convertors take over.

INPUT / OUTPUT TERMINALS OF PLC

PLC terminals are required to be connected to power supply . HF cable ,

switching equipments , telephone sets etc. For these purpose suitable terminal

connections are provided in each PLC terminals.

For connection to HF cable , HF connector terminal are provided

at the base of terminals . For connections of ac or dc supply separate connector

block is provided at the base .For all other connections a terminal block isprovided with easy access . In modern PLC terminals (IC version ) the earth is

available immediately on initiating a call at the valling station & on the maturity

of a call at the called station.

STUDY OF BATTERY & BATTERY CHARGERBatteries are used to provide alternate power supply in the absence of ac supply

for atleast 10 hours & the batteries ad=re charged with the help of batterycharger . . The batteries are connected to rectifier (dc power supply). The

batteries are placed in a dry , ventilated room in a lead case.

Depending on the type of battery , their level is checked in

terms of specific gravity.B \atteries are maintained by the input of distilled

water regularly .


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BATTERY CHARGER

MANUFACTURERS NAME :STATIC POWER &CONTROL

RATED CHARGE OUTPUT : 40 AMPRATED BATTERY LOAD :0 TO 45 AMPRATED LOAD ACROSS LOAD TERMINALS :0 TO 22.5AMPLOAD CURRENT LIMIT :22.5AMP MAIN INPUT :SINGLE PHASEMAXIMUM EFFICIENCY :70%MAXIMUM POWER DRAWN :4.8KVA AT .88PFQUICK CHARGEVOLTAGE :57.6VTYPE OF PRIMARY PROTECTION :BY USING HRC FUSE ,

AC CONTRACTOR

INSTALLATION & CHARGE INSTRUCTIONS

UNPACKING : Care should be taken in the unpacking & subsequenthandling of cells & other componenets of the battery as rhey can be damageddue torough handling . Store the cells with the vent plugs .Power & vent cum

float guide screwed on firmly & other acvessiories in a dry & dut free covered

area.

BATTERY ROOM :The battery room should be well ventilated , clean &dry .A damp room is dangerous due to possible earth leakage from the battery.

The battery will give the best results when working at room temperatures of20 degree celcius to 35 degree celcius . I t will function satisfactory when

operating at temp between 20 deg cel to 50 deg cel . High temp inc the capacity

but dec the life of the cells . Low temp reduce the capacity available but do no

injury to the battery.


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STANDS & SUPPORTS:Suitable stands should be provided for the support of the cell should be

rranged so that each cell should be arranged so that each cell will be easily

accessible for inspection .

When special drawings have been made available showing the layout ofthe battery , they should be followed very carefully to ensure that connections fit

properly.

POWER REQUIREMENTS:A DC source capable of delivering the current as specified on the

inside front cover will be required . The voltage neede will be 2 times the no. of

cells in the battery. The initial charging of the battery will take approximately 55

of 90 hours.

POLARITY OF CHARGINGHEADS:It is of atmost important that the +ve terminal of the battery is

connected to the +ve lead of the charging source.

ACID

The acid to be used in the battery for initial filling in battery garde sulphuricacid of specific gravity (290+.05) at 27 deg cel.

If the acid is obtained in concentrated form , it is necessary

to dilute it to 190 specific grade . The acid as well as the distilled water to be

used for diluting the acid should confirm to standard institution specification IS

266-1977 & is 1069 -1964 respectively .


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CAUTIONS :

VESSELS:When vessels of hard rubber, plastic , porecelain or lead lined MS tanks

/wooden boxes should be used. Donot use metal vessels other than lead.

PROTECTIVE WEAR:When working with acid or electrolyte always use protective goggles ,

rubber gloves & rubber apron.

ACID SPLASHES:1. ON GARMENTS :Remove garment immediately , neutralize,spot with 5 to 10 %

ammonia or soda solution & wash in water.

2. On skin / eyes : Flush with large quantities of water.A 5 to 10 %solution of ammonia or soda should always be kept ready

prior to operations .

NEVER ADD WATER TO ACID:Add the acid in the thin stream , slowly , stirring the acid solution with a

long glass rod or tube.

TEMPERATURE CORRECTION :

The specific gravity of the electrolyte varies with temp .Any reading

observed on the hydrometer should therefore be corrected to27 deg cel as all the

specific gravity value indicated by us are at 27 deg cel.

The correction should therefore be made as follows . For every 1

deg cel above 27 deg cel add 0 .00007 to the specific gravity as read on the


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hydrometer . Similarly, for every1 deg cel below 27 deg cel . Subtract 0.0007

from specific gravity as read from the hydrometer.

INSTALLATION :

The cell should stand on porecelain / plastic insulator which willbe supplied with the cells of these insulators each with a lead disc on top should

be inserted between the feet of the container & the satnd level the cell , if

necessary by placing one or more of the lead disc between the insulators & the

satnd.

Arrange the cells to the +ve terminal of one cell adjoins the ve terminal plug

of the next throughout the battery. Use a wooden spacer to ensure even spacing

ot of cell.

CONNECT CELLS TOGETHER

When the cells are in position on the stands connect them together smear a little

petroleum jelly on the threads , bolting faces & the bolt holes before bolting up.After bolting up the cells smear petroleum jelly over the nut bolt head &

washers.

INITIAL FILLING OF ELECTROLYTE

Sufficient quantity of of battery grade sulphuric acid & a littly to spare must be

availableat the site for the initial filling of each cells . The sulphuric acid shouldbe 1.190+.005 specific grade at 27 deg cel.

The approximate quantity of the acid required per cell is given in the data

sheet . The total quantity of acid required is obtained by multiplying the

quantity per cell by the number of cells adding 10% to compensate for spillings.


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The cool pure sulphuric acid of 1.190specific grade should be carefully

poured into the cells till the level of indicator in each cell rises to the maximum

recommended level as indicator by lower white band of the float indicator ,

being just visible above the black fload guide . Replace the vent plugs on the cell

but do not tighten level them loose.

PORTION OF CHARGING

FIRST PORTION : The first portion of the charge should be given at any ratebetweenthe starting / finishing currents given on the depending upon the output

of the charge .

SECOND PORTION: The second portion of the charge must be given at thefinishing rate for a period of not less than 300 hours , till the sign of completion

of charge are observed.

PILOT CELLS: As pilot cells select vany one cell ( except the end cell orregulated cell if any ) out of every 60 cells or part of them .

Voltage & specific gravity readings from the pilot cells will indicate

the state of charge of the whole readings.

DURING CHARGE TAKE HOURLY READING

SPECIFICGRAVITY: For some hours after filling in the cells the specificgravity will fall in spite of the fact that cells have already been on charge forsome time . After the charging has been in progress for some time the specificgravity of the electrolyte will cease to fall & will commence rising slowly , finally

reaching a steady value . It doesnot matter what the final specific gravity

reading of the electrolyte is what is important in that it should reach the


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maximum value & reading must remain constant for 3 hours before the battery

can be deemed fully charged.

VOLTAGE:As the charging continues the voltage like the specific gravity ofthe elaectrolyte will steadily increase to a final value of approx 2.75v per cell .

The voltage must remain constant over 3 hours before the charging of the

battery.

TEMPERATURE: During charging of the electrolyte temp of the cellsshould not exceed 50 deg cel . Suspend charging if it exceeds & commence

charging after battery has colled to about 45 deg cel . If necessary , slightly lower

the recommended charging rate . Where ambient temp are normally high , it is

recommended that charging be carried at during thenight & suspend during theday . If necessary use thefinishing rate for first portion of the charge.

OPERATION OF BATTERY CHARGER

1. It is important that the battery should be operated in accordance with theinstruction given on the instruction card supplied .

Make sure that the instruction card is hanged in a prominent &

accessible location in the battery room.

2. It is strongly recommended that the batteries which are to be operated on thetrikle . Charge be subjected to 2-3 cycles of charge & discharge the battery

should that be put on trikle charge when in a fully charged condition .


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Adjust trikle charge to the required value indicated in the data on

page next . After several years the trikly charge current may have to be raised ti

the higher value to compensate the effect of ageing.

The trikle value charge should be adjusted to give an

optimum battery voltageof 2.25 -2.30v per cells.

COMPLITION OF CHARGEWhen all the cells have been gassing freely & when the voltage & specific

gravity of the pilot cell has been constant over 3 siccessive hourly readings , the

cells can be deemed fully charged & the charging terminated.

ADJUST SPECIFICGRAVITY OF EACH CELL

If at the end of the first charge the specific gravity of the

electrolyte exceeds 1.205 withdraws some electrolyte & add pure water ,

continue the charge so that the water & acid mix thoroughly.

If at the end of the of first charge the specific gravity of

electrolyte below 1.195 after both vaoltage & specific gravity have remainedconstant over 3 consecutive hours withdraws some electrolyte & add acid of

1.350 to 1.400 specific gravity continuing the charge in the meantime.

FINAL READING/ RECORD BOOK

After correcting specific gravity & electrolyte levels , start a record book for the

whole life of the battery . The first page should record the specific gravity

readings of each cell & note thet levels & temperature of the pilot cells & not that

levels were correct in each cell . Records details of periodical charges &discharges etc.

A record book is supplied with each battery of 60 v & above , for

smaller batteries than can be obtained at nominal charge . If one copy of the

record sheet is sent periodically to the nearest office of the company free


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technical advice will be given so that the battery is maintained in optimum

condition.

The first charge sheet supplied with the battery should be filled up with

the reading during initial charge & returned tpo the company for comments.

INSTRUCTIONS FOR INSTALLATIUON

INITIAL INSPECTIONInspect the package for external evidence of damage & inform company

handling to transit . Notify the damage & inform company immediately if any.

Donot destroy or remove any of packing material used in damaged shipment.After unpacking unit inspect through visual check to detect any transit damage

to any componenet on the front panel or inside the cubicle . If any lose or

broken connection are noticed set them right.

MECHANICAL INSTALLATION:

The panels are free standing steel structure & should be installed in dust free

well ventilated place.

Clean the equipment properly to remove dust particles settled on the

components & equipment.

ELECTRICAL INSTALLATION:

1. Connect single phase ac input supply through terminal / strip .2. Connect the firm earth to the panel .3. Push all the fuses , they might have become loose in transit.


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4. Check that all the PCB connections are properly connected in their correctposition.

TECHNICAL SPECIFICATIONS

1.NOMINAL INPUT SUPPLYVOLTAGE 230V

2. PHASE : SINGLE

3. FREQUENCY :50H-2 HZ

4. INPUT SUPPLYVOLTAGE RANGE :170-270VAC

5. OUTP[UT VOLTAGE :48 VDC

6.FLOAT MODE : 52.8VDC7. BOOST MODE : 57.6VDC

8. OUTPUT CURRENT LIMIT :20 A

9. BATTERY CURRENT LIMIT :10% OF AHCAPACITY BATTERY

10 . RIPPLE : LESS THAN 5 MV

11. POWER FACTOR : 0.7 LAG

12 EFFICIENCY :BETTER THAN 75 %


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OPERATING INSTRUCTIONS

1. Connect incoming supply on incoming terminal provided at the near of the unitaccessible after opening the near door.

2. Connect battery on battery terminals . Connect +ve on red marked terminal bus&-ve on black terminal bus accessible after opening the near door.

3. Connect load in correct polarity at load feeder terminals .4. Switch on the incoming switch provided on the front of the unit.5. The initially charge the batteries keep mode selector switch to extend position.6. To adjust voltage in float mode open the front door adjust voltage by

potentiometer marked FLOATby rotating .7. To adjust voltage in boost mode use pot marked BOOST.8.To limit the current drawn by the batteriesfrom the charger , the potentiometere

marked battery current can be adjusted.

ACKNOWLEDGE

Engineering is an ocean & an engineer dives in the ocean in search of the

pleasure.

I avail this opportunity of expressing my sincere thanks & personal

gratitude to all those who helped me successful completion of my training. I also


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take this opportunity to express my deep sence of gratitude to the staff of PSPCL

as without teir co operation & able grateful training of this standard & expertise

would not have possible for me. I am also grateful for the ever willing

cooperation & help from the incharge S.VIRSA SINGH (J.E).

PREFACE

The industrial training is mainly aimed at enabling students to their theoretical

knowledge to practice as THEORY IS TO KNOW HOW & PRACTICAL IS TO

DO HOW & to appreciate the limitations of knowledge gained in the class

roomto practical situations & to appreciate the importance of discipline ,

punctuality with the sence of responsibility ,money , value of time & dignity of

labour.

In order to develop awareness of industrial approaches to

problem solving based on broad understanding tools & machinery process ,

models of operations of industrial organization training enable us to various

material process , products & their application s along with the relevant quality

control.

My training was undertaken at PSPCL PATIALA. It is pioneer

organization supplying electricity to almost whole of the state having ultra


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modern facilities & great scope for learning .Many types pof communication are

used here & the trainee is exposed to vast experience of teaching learning

process.

BRIEF ABOUT THE ORGANIZATION

The PSPCL is well known private organization . The organization is providing

electricity to whole of the state from last 43 years . Each substation has a

connection with each power line communication . So they by PLC i.e can

transfer their signals to each stations ,

The organization is regulating & maintaining electric power produced at

major power stations. Daily thousands of megawatt electricity is produced at

these power stations & then supplied to sub stations from where it is supplied to

customers .In sub station this power is stepped up or down as per userrequirements . The main power stations running in the state are as follows:

1. BHAKRA NANGAL2. LEHRA MOHABBAT THERMAL PLANT3. GURU NANAK DEVTHERMAL PLANT4. ROPAR THERMAL PLANT5. RANJIT SAGAR DAM

The power generated at these power stations is supplied to the whole of the

state . The main flow of power is controlled at Patiala sub station . The flow of

electric power is through POWER LINE COMMUNICATION.

PSPCL AT AGLANCE

YEAR OF COMMENCEMENT :1967

COMMENCEMENT OF COMMERCIAL :1967

PRODUCTION RANGE :TELECOM THERMAL EQUIPMENT

LOCATION OF SUBSTATION : 220KVABLOWAL PATIALA

LAND AREA : 40ACRES


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CAPITAL INVESTMENT (IN MILLIONS)

LAND & BUILDING : RS 15.73PLANT MACHINERY : RS 86.46

MAN POWER : RS 200

PILOT SIGNALS

In order to monitor healthiness of PLC channels each terminals seeds a pilot

signal to the opposite end of terminal . Failure of pilot signal is visually

indicated as an alarm signal for the staff .

In F-F terminals , pilot signal is transmitted at all times .

PLC terminals is transmitted during telephony conversation only.

In ITI / SIEMENS transistorized terminals 12khz IF signal is also sent

along with the VF signals . This signal is act as a pilot signal . In other PLC

terminals the telephony switching signal act as the pilot signal.

Each PLC terminal contain a pilot fail alarm ckt containing relay. Under

healthy working condition the presence of pilot signal is indicated by the

operated condition of the relay . Failure of pilot signal will charge the state of the

relay whose contacts are used to give the audio / video indicators.

Therefore before the healthiness of speech signaling channels etc. is checked the

healthiness of the pilot signal has to be checked first . The strength of pilotsignal is receipt also indicate the transmission loss. The level of all other signal

is measured relative to level of pilot signal.

This automatic compresation is done by introducing variable gain . The

metering unit onh PLC terminal measures dc voltage in volts & ac signal In db.

This serves very good purpose in absence of standard level meter.


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A daily or weekly record of built in meter reading is kept in the PLC rooms for

monitoring the healthiness of PLC terminal.

types of communication used in pspcl

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