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The TopicsThe Topics1.1. Power Plant @ TelephonePower Plant @ Telephone

ExchangeExchange2.2. BatteryBattery3.3. EarthingEarthing

Power Plant @ TelephonePower Plant @ TelephoneExcgExcg..

What is it?What is it?

‘‘heartheart’’ of the Telecomof the Telecominstallationinstallation

Power supply =>>Successfulcommunicationsystem

Telecom Networks needTelecom Networks needDirect CurrentDirect Current

Why??Why??

1.1. A.C. Harmonics.A.C. Harmonics.

2. Arranging Stand2. Arranging Stand--by source of DCby source of DCis easier.is easier.

3. Transistors ICs are3. Transistors ICs areunidirectional so DC is must.unidirectional so DC is must.

5. Less hazardous to human life5. Less hazardous to human life

The Power SchemeThe Power Schemein ain a

Telephone ExchangeTelephone Exchange..

TheThe powerpower system in BSNL consists ofsystem in BSNL consists of …………..

1. SMPS Rectifier/Power plant1. SMPS Rectifier/Power plant::

2. Battery system2. Battery system::

Engine AlternatorEngine Alternator

The Rectifier SetThe Rectifier Set

The OptionsThe Options

Conventional Power Plant(SCR based)

SMPS Power Plant(MOSFET based)

Advantages of SMPS rectifierAdvantages of SMPS rectifier CompactCompact

ModularModular

High ReliabilityHigh Reliability

High Power EfficiencyHigh Power Efficiency

Temp.Compensation Logic for batteriesTemp.Compensation Logic for batteries

The Specifications.The Specifications.

a)a) MultiMulti--rack configurationrack configuration

b)b) Facility to parallel a maximumFacility to parallel a maximumof 21of 21 nosnos of modulesof modules

c)c) Termination for 3 sets of VRLATermination for 3 sets of VRLAbatteries & exchange.batteries & exchange.

System Input : Three phase , 4System Input : Three phase , 4--wire , 50wire , 50Hz supplyHz supply

System Output:System Output: --54V D.C.54V D.C.

SpecificationSpecification

1) Input Voltage 320 V to 480 V1) Input Voltage 320 V to 480 V Frequency 45 Hz TO 65 HzFrequency 45 Hz TO 65 Hz 2) Output Voltage2) Output Voltage in Float Modein Float Mode --54.054.0 ±± 0.5 V.0.5 V. adjadj

rangerange --48 V to48 V to --56V56V in charge mode :in charge mode : --55.2 V55.2 V ±± 0.5V0.5V 3) Input power factor >0.95 Lag with3) Input power factor >0.95 Lag with

25% to 100% load at nominal input.25% to 100% load at nominal input.

The modular block diagramThe modular block diagram

FLOAT RECTIFIERFLOAT RECTIFIER STEPSSTEPS ::1. Input Stages1. Input Stages------a)EMI Filter b)Inrusha)EMI Filter b)Inrush

Current LimiterCurrent Limiter

2. Active Power Factor Correction Stages2. Active Power Factor Correction Stages--------------------------------------------a)a)fwfw Bridge rectifier b) pfBridge rectifier b) pfcorrector(boost converter)corrector(boost converter)

3. DC/DC Converter Stages3. DC/DC Converter Stages——a) Full Bridgea) Full Bridgepower converter b)High frequency steppower converter b)High frequency stepdown transformer c)full bridgedown transformer c)full bridgerectifier(LVDC)rectifier(LVDC)

4. Output Stages4. Output Stages------a) filter b) shunt toa) filter b) shunt tomonitor output currentmonitor output current

FLOAT RECTIFIERFLOAT RECTIFIERCOMPONENTS OF ACOMPONENTS OF A Power Plant(ITI)Power Plant(ITI) ::1.1. AC Terminal BlockAC Terminal Block : AC Cables are terminated in a: AC Cables are terminated in a

block.HRC fuses of proper rating are provided.block.HRC fuses of proper rating are provided.2 The Lightening Protection Unit(LPU)2 The Lightening Protection Unit(LPU)3 The surge Protection Unit(SPU).3 The surge Protection Unit(SPU).4 One main & two Extension racks.4 One main & two Extension racks.5 AC distribution arrangement in main rack.5 AC distribution arrangement in main rack.6 Rectifier modules.6 Rectifier modules.7 DC distribution arrangement in main rack.7 DC distribution arrangement in main rack.8 Metering on the front panel in main rack.8 Metering on the front panel in main rack.9 Power System controller card in main rack.9 Power System controller card in main rack.10 Display & Alarm card in main rack.10 Display & Alarm card in main rack.1111 TemcoTemco card in main rack.card in main rack.

The Protection Units for theThe Protection Units for therectifiersrectifiers

Lightning protection UnitLightning protection Unit Surge protection UnitSurge protection Unit

MaintenanceMaintenance

PowerPower--Plant room neat and clean.Plant room neat and clean.

The room rodent free.The room rodent free.

Ensure ProperEnsure Proper EarthingEarthing otherwise LPUotherwise LPU&SPU will not function.&SPU will not function.

Ensure proper connection of LPU & SPU.Ensure proper connection of LPU & SPU.

Maintain Load Sharing.Maintain Load Sharing.

Avoid prolonged overloading ofAvoid prolonged overloading ofmodules.modules.

Check Battery regularly.Check Battery regularly.

Avoid discharging of batteries.Avoid discharging of batteries.

Check for phase fail.Check for phase fail.

MaintenanceMaintenance

SMPS Power Plants of various makeSMPS Power Plants of various makein BSNLin BSNL

1.1. ITI, RaeITI, Rae BareliBareli (UP)(UP)2.2. HimachalHimachal ExicomExicom, New Delhi, New Delhi3.3. AdorAdor PowertronPowertron,,PunePune4.4. HBLHBL SabnifeSabnife, Hyderabad, Hyderabad5.5. XLXL--Telecom, HyderabadTelecom, Hyderabad6.6. AmararajaAmararaja,, TirupatiTirupati

SHUNTSHUNT

Manganin resistor (500A/75mv)

Tong TesterTong Tester

AnalogueAnalogue MultimeterMultimeter

DigitalDigital MultimetersMultimeters

PowerPower--Plant module of HECLPlant module of HECLmakemake

ITI makeITI make

AdorAdor powertronpowertron

XL TelecomXL Telecom

TEC Testing procedures of SMPS power PlantTEC Testing procedures of SMPS power Plant1)1) LAR(Location Alignment & Rigidity)LAR(Location Alignment & Rigidity)--

According to plan check PhysicalAccording to plan check Physicalmounting securely.mounting securely.

2)2) Earth Testing <= 0.5Earth Testing <= 0.5ΩΩ3)3) Insulation Resistance testInsulation Resistance test

a) Shorted Input to Earth >2Ma) Shorted Input to Earth >2MΩΩb) Shorted Output to Earth >1Mb) Shorted Output to Earth >1MΩΩc) Shorted Input to Output > 5Mc) Shorted Input to Output > 5MΩΩ

4) Power factor4) Power factor –– Take reading using p.fTake reading using p.fmeter at nominal input , maximummeter at nominal input , maximumoutput load of 25% to 100 %output load of 25% to 100 %

Should be better than 0.95 laggingShould be better than 0.95 lagging

The Battery Set @ ExchangeThe Battery Set @ Exchange

Parallel with theParallel with the RectifierRectifier and theand theLoad.Load.

StandbyStandby to the Rectifier.to the Rectifier. Two to three sets.Two to three sets.

FLOATRECTIFIER

BTYSET-1 BTY

SET -2

DC toLOAD

The building unitThe building unit-- CellCell A cell is a device in which anA cell is a device in which an

electric difference of potentialelectric difference of potentialis established between the twois established between the twoelectrodes as a result ofelectrodes as a result ofchemical reaction between thechemical reaction between theelectrodes and the electrolyteelectrodes and the electrolyte..

PrimarySecondary

chemicals such that chemical reaction can be made reversible.* BSNL Telephone exchanges employ Secondary cells.

A CellA Cell

(Positive Plate)

(Negative Plate)

(Electrolyte)

The reaction during dischargeThe reaction during discharge

The reaction during ChargingThe reaction during Charging

BSNL employs theBSNL employs theMFMF--VRLA BatteryVRLA Battery……..

Maintenance FreeMaintenance Free-- Valve RegulatedValve RegulatedLead Acid Battery.Lead Acid Battery.

QuesQues : Why Maintenance free????: Why Maintenance free????Ans:Ans: Battery with a valve regulator, whichBattery with a valve regulator, which

does not allow thedoes not allow the gases to escape thegases to escape thebattery container and there is no needbattery container and there is no needof topping up of theof topping up of the battery.battery.

In flooded cells, the oxygen gasIn flooded cells, the oxygen gasevolved at the positive plateevolved at the positive platebubblesbubbles upwards through theupwards through theelectrolyte and is released through theelectrolyte and is released through thevents.vents.

In MFIn MF--VRLAVRLA batteries the oxygenbatteries the oxygenevolved, at the positive plate, instead ofevolved, at the positive plate, instead ofbubbling upwards isbubbling upwards is transported in thetransported in thegas phase through the separator mediumgas phase through the separator mediumto the negative plate.to the negative plate.

The separator is a highly absorbent glassThe separator is a highly absorbent glassmatrix type with very high porosity,matrix type with very high porosity,designed to have pore volume in excessdesigned to have pore volume in excessof the electrolyte volume (starvedof the electrolyte volume (starvedelectrolyteelectrolyte design), due to which thedesign), due to which theoxygen finds an unimpeded path to theoxygen finds an unimpeded path to thenegative plate.negative plate.

TheThe oxygen gets reduced by reactionoxygen gets reduced by reactionwith the spongy lead at the negativewith the spongy lead at the negativeplate, turning aplate, turning a part of it into apart of it into apartially discharged condition, therepartially discharged condition, thereby effectively suppressing theby effectively suppressing thehydrogen gas evolution at thehydrogen gas evolution at thenegative plate. This is what is knownnegative plate. This is what is knownas theas the oxygenoxygen recombinationrecombinationprinciple.principle.

The reaction : oxygen recombination principleThe reaction : oxygen recombination principle

1) At +ve plate :1) At +ve plate :--HH22O =O = ½½ OO22 + 2 e+ 2 e-- ……………………..(1)..(1)2)2) AtAt ––ve plate:ve plate:--PbPb ++ ½½ OO22 == PbOPbO……………………………….(2).(2)PbOPbO+ H+ H22SOSO44=PbSO=PbSO44 + H+ H22OO…………(3)(3)

(this H(this H22OO ……..to (1))..to (1))PbSOPbSO44+2H+2H++ + 2e+ 2e-- ==PbPb + H+ H22SOSO44……..(4)..(4)

(H(H22SOSO44…………to (3))to (3))((PbPb ………………………………..to (2))..to (2))

3) The total reaction at3) The total reaction at ––ve plate:ve plate:--½½ OO22 + 2H+ 2H++ = H= H22OO

Thus the recombination technology makes theThus the recombination technology makes thebattery virtuallybattery virtually maintenance free.maintenance free.

What makes VRLAWhat makes VRLAmaintenance free???maintenance free??? The Oxygen RecombinationThe Oxygen Recombination

principleprinciple

Highly Absorbent micro porous separator

The Unit for Battery CapacityThe Unit for Battery Capacity TheThe ““AmphereAmphere HourHour””--An ampere hour(AH) is the amount ofAn ampere hour(AH) is the amount of

energy charge in a battery that will allowenergy charge in a battery that will allowone ampere of current to flow for oneone ampere of current to flow for onehour.hour.

Typical technical Spec. :Typical technical Spec. :Capacity of the Battery@10Hr. RateCapacity of the Battery@10Hr. Ratedischarge to1.75 ECV =1000AHdischarge to1.75 ECV =1000AH

Typical Capacities:Typical Capacities:600 AH, 1000AH, 1500 AH,2000 AH, 2500600 AH, 1000AH, 1500 AH,2000 AH, 2500AH, 3000 AH, 4000 AH & 5000 AHAH, 3000 AH, 4000 AH & 5000 AH..

The Battery SetThe Battery Set

Two to three per SMPS rectifier set.Two to three per SMPS rectifier set. Consists of 24 cells connected inConsists of 24 cells connected in

series.series. Float Voltage per cell= 2.25 VoltsFloat Voltage per cell= 2.25 Volts Total Float Voltage = 2.25 x 24 =Total Float Voltage = 2.25 x 24 =

54 volts54 volts Charge Voltage per cell = 2.30 VoltsCharge Voltage per cell = 2.30 Volts Total Charge Voltage = 2.30 x 24=Total Charge Voltage = 2.30 x 24=

55.2 volts55.2 volts

Maintenance Schedule of VRLA batteriesMaintenance Schedule of VRLA batteries

DailyDaily :: MeasureMeasure Pilot CellPilot Cell ..

MonthlyMonthly :: MeasureMeasure all theall the cells.cells. Physical verificationPhysical verification

QuarterlyQuarterly :: Ensure the tightness of terminal bolts .Ensure the tightness of terminal bolts . Apply boost charge for 24Hrs.Apply boost charge for 24Hrs.

The TelThe Tel ExcgExcg.. EarthingEarthing The protection ofThe protection of

equipments and theequipments and thepersonnel frompersonnel from

Foreign Voltages.Foreign Voltages. Lightning.Lightning. Serve as commonServe as common

return path.return path. Reduces Noise &Reduces Noise &

Cross talkCross talk

Tel.Tel. ExcgExcg.. EarthingEarthing (contd.)(contd.) EarthEarth ResistanceofResistanceof teltel excgexcg.. ≤≤ 0.50.5 .. Earth Resistance is measured usingEarth Resistance is measured using

““Earth TesterEarth Tester””

Types ofTypes of EarthingEarthing 1)1) Rod(Spike) electrodesRod(Spike) electrodes:: space is not a problem.space is not a problem.

375 CM375 CM 375 CM 375 CM

375 CM

375 CM

375 CM20 EARTH

SPIKES(375CM)

TO EARTHCOLLECTIOR

SPIKE EARTHFIGURE =1

38.0mm dia

EEAARRTTHHIINNGG PROCEDUREPROCEDURE

Spike earths:The present arrangement of earth electrode system consists oftwenty numbers of 25.0 mm or 38.0 mm dia. GI pipes, each of275 cm or 375 cm length. Each pipe is used a earth spike and isso driven into the ground that its top remains at some depthbelow the ground surface. The spacing between any twospikes should not be less than 375 cm or ordinarily. In no case,it should be less than 250 cm. A typical layout is shown inFigure

2) Plate Earthing:there is not muchspace but digging is not a problem.

Types of Earthing

PIPE FOR WATERINGTHE EARTH

TO POWER ROOM EARTHDISTRIBUTION PLATS

GI STRIP (50X3mm)

GI . PLATES (4NOS)DISTRIBUTION 600 X 600 X 6.5mm(1,2,3 &4)

GI INTERCONNECTION STRIPS (4NOS)DIMENSION, (50X 3mm(a,b,c & d)

GI STRIP (5

0X3mm)

GI STRIP (5

0X3mm)

TO TOWER EARTH

2M

2M

3M

a

b

c

d

EarthingEarthing ProcedureProcedure

Plate Electrode SystemPlate Electrode System This consists of fourThis consists of four galvanisedgalvanised iron plates ofiron plates of

1414 swgswg 76 cms(276 cms(2’’66””) square plates. These) square plates. Thesefour plates are placed vertically and atfour plates are placed vertically and atdiagonally opposite ends in an excavation ofdiagonally opposite ends in an excavation of185 square and of a depth sufficient to reach185 square and of a depth sufficient to reachdamp soil.The depth should never be lessdamp soil.The depth should never be lessthan 250than 250 cmscms and need not be greater thanand need not be greater than500500 cmscms. The lead pipe carrying the main. The lead pipe carrying the mainearth lead should be as close to the tails ofearth lead should be as close to the tails ofplates as possible.plates as possible.

3)3) Strip electrodesStrip electrodes:: In hilly areas where digging beyond 2In hilly areas where digging beyond 2--3ft depth3ft depth

is not possibleis not possible and space is available.and space is available.

Types ofTypes of EarthingEarthing

Dimensioning of BusDimensioning of Bus--bar/cables,bar/cables,PowerPower--plant and battery.(As per TEC)plant and battery.(As per TEC)

The basicsThe basics-- The ultimate loadThe ultimate load: x: x RedundancyRedundancy : 10% of ultimate load(0.1x): 10% of ultimate load(0.1x) Battery backupBattery backup : 6 Hours: 6 Hours Battery capacityBattery capacity: 6 hours backup up to 80%: 6 hours backup up to 80%

DODDOD Battery effective capacity @ C/6 = 0.83% Safety factor for bus bar cable & cableSafety factor for bus bar cable & cable: 1.5: 1.5

PowerPower--plant ultimate capacityplant ultimate capacity : C: C

Calculations:Calculations:

Load: xLoad: xBattery Backup=6 hoursBattery Backup=6 hours Battery capacity: 6x/0.8*0.83 =Battery capacity: 6x/0.8*0.83 = 9x9x( At 80% DOD)( At 80% DOD)

Calculations(contd.)Calculations(contd.) Battery charging current@ CBattery charging current@ C1010==

99x/10 =0.9xx/10 =0.9xPowerPower--plant ultimate capacity=plant ultimate capacity=(x + 0.1x + 0.9x) = 2(x + 0.1x + 0.9x) = 2xx

Safety factor for busSafety factor for bus--bar or cable :bar or cable :1.251.25

The busThe bus--bar/cable rating=bar/cable rating= 1.5x1.5x

Calculations(contd.)Calculations(contd.)

Therefore the summarized resultsTherefore the summarized results::

Battery capacity:Battery capacity: 9x9x PowerPower--plant:plant: 2x2x BusbarBusbar/cable:/cable: 1.5x1.5x

1) Modern day SMPS used in BSNLutilizes the switching technology of………..

a) SCR b) Diode c) MOSFET d) Triac.

2) Which of the following is not amanufacturer of SMPS , used in BSNL? a) ITI b) Amararaja c) Godrej d) Himachal Exicom

3) The positive cable in exchange is ofcolor ……………..

a) black b) Blue c) red d) yellow

4) The device needed to regulateunbalanced 3 phase voltage is

a) SMPS b)Rectifier c)AVR d) Inverter

5) The negative plate of secondary cells inBSNL exchanges is chemically-

a) PbO2

b) Pb c) PbO d) H2SO4

6) The positive plate of secondary cells inBSNL exchanges is chemically-

a) PbO2

b)Pb c)Fe d)H2SO4

7) The electrolyte in the secondarycells is ………

a) HCl b)H2SO4

c) PbSO4

d)Na2SO4

8) The technology that makes theVRLA battery maintenance free-

a) Hydrogen recombination b) Oxygen recombination c) Acidic recombination d) Sulphuric recombination

9) The capacity of a storage cell isexpressed in terms of

a) Amphere b) VoltsHour c) AmphereHour d) Henry

10) The following type of earthing ispreferred where space is not a problem

a) rod b) plate c) strip d) none of the above

11) The following type of earthing is preferredwhere there is not much space but digging is not aproblem.

a) rod b) plate c) strip d) none of the above

12) The following type of earthing ispreferred in hilly areas.

a) rod b) plate c) strip d) none of the above

13) If the load of an exchange is “x”, then theinstalled battery capacity should be

(as per TEC)

a) 9xb) 2xc) 1.5xd) 2.5x

14) If the load of an exchange is “x”, then the installedPower-plant capacity should be (as per TEC)

a) 9xb) 2xc) 1.5xd) 2.5x

15) If the load of an exchange is “x”, then theinstalled Busbar/cable capacity should be (asper TEC)

a) 9xb) 2xc) 1.5xd) 2.5x