Role of battery in Telecom

8/10/2019 Role of battery in Telecom

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BSNL(Bharat Sanchar Nigam Limited)

APresentation

On

“Role of batteries and power plant intelecommunication installations”

Presented by: Animesh SinhaG. GeetaPankaj Nema Aman Kumar SahaJitendra Kumar



Valve-Regulated lead-acid(VLRA) Batteries

Ensures a reliable, effective & user friendly source ofpower.

It is spill proof, leak proof, & explosion resistant.

There is no need to add water or to clean terminals.

It has a low self discharge rate which eliminates theneed for equalizing charges.

The water loss throughout the life due to gassing isroughly 0.1% of the total electrolyte present in thecell.

Introduction




Batteries lose some charge during as well as during theperiod prior to installation.

A battery should be installed and given a fresheningcharge after receipt as soon as possible.

Battery positive (+) terminal should be connected tocharge positive (+) terminal and battery negative (-)

terminal to charger negative (-) terminal. Constant voltage is the only charging method

recommended. Most modern chargers are of the constant voltage type.

Freshening Charge




An equalizing charge is a special charge given to a

battery when non-uniformity in voltage hasdeveloped between cells.

Under normal operating conditions an equalizingcharge is not required.

It is given to restore all cells to a fully chargedcondition.

Equalizing Charge




A pilot cell is selected in the series string to reflectthe general condition of all cells in the battery.

The cell selected should be the lowest cell voltage inthe series string following the initial charge.

Reading and recording pilot cell voltage monthly

serves as an indicator of battery condition betweenscheduled overall individual cell readings.

Pilot Cell




Sealed Maintenance Free Valve Regulated Lead AcidBatteries represent the state of the art in Lead Acidtechnology.

The terminal voltage of the battery is directly related to theconcentration of the electrolyte.

Therefore, if the open circuit voltage of the battery ismeasured then, the state of charge can be determined.

The Open Circuit Voltage (OCV) readings should be taken24 hrs. after charging is discontinued.

The OCV value is co-related to the state of charge of VRLA batteries as per the table.

Determination of State of Charge




Table for determining the state of charge from thecorresponding Open Circuit Voltage

% State of Charge Open Circuit Voltage

100 2.15

90

2.13

80 2.11

70 2.09

60 2.07

50 2.05

40

2.03

30 2.01

20 1.97

0 1.95



SMPS (Switch Mode Power Supply)

What is SMPS?

SMPS means Switch Mode Power Supply.

This is used for D.C-to-D.C conversion. This works on the principle of switching regulation.

The SMPS system is highly reliable, efficient,noiseless and compact because the switching is done

at very high rate in the order of several KHz to MHz.



SMPS (Switch Mode Power Supply)

The SMPS regulators are used in B.S.N.L at variouslocations like CDOT, E 10 B Transmission systemsetc.

Necessity



50V – 2000A Power Plant

The power system is intended primarily to provideuninterrupted DC power Telecom. equipments and currentfor charging the batteries in the presence of AC Mains.

The system works from commercial AC mains which isrectified and regulated to –50V DC and is fed to theequipment (exchange).

The system has provision to connect three sets of VRLA batteries and facility to charge them simultaneously toensure that uninterrupted DC power supply is alwaysavailable to the exchange.

Suitable for VRLA Batteries with 100A SMPS RectifierModules



Functional description of power system

Eight racks – One main, one auxiliary and six extension

racks. AC Distribution module in each rack.

Rectifier modules (A maximum of three modules inextension rack and two each in main rack and auxiliary

rack). DC distribution module in each rack.

Metering in each rack.

Power system controller in main rack.

This Power System is of multi rack type and consists of thefollowing:



Functional Description of Rectifier

The SMPS 50V-5600W rectifier is a state-of-the-art switch-mode power conversion equipment.

The unit consists of two cascaded power convertersperforming power factor correction and DC/DC conversion.

The power stages are synchronized and working with constantswitching frequency of 100 kHz.

The rectified AC mains voltage is processed first in the powerfactor corrector circuit, which is based on a boost topology.

The boost converter has the inherent advantage of continuous

input current waveform, which relaxes the input filterrequirements.

The output of the boost converter is a stabilized 400V DC voltage.



Functional Description of Rectifier

Conversion of the stabilized high voltage output of thepower factor corrector circuit is necessary to generate theisolated low voltage output and to provide the requiredprotection functions for telecommunication application.

These tasks are achieved in the DC/DC converter circuit, which is based on a full-bridge topology.

The full-bridge circuit is operated by phase-shift pulse with modulation with current mode control.

Proper operation of the power converters is managed byindividual controller circuits and supervised by thehousekeeping electronics.



Functional Description of Power System Controller

Power system controller is designed to control the modes ofoperation of rectifiers, acknowledge and displays the status ofrectifiers and system and controls parameters of rectifiers.

The controller accepts signal from individual rectifiersthrough 8-pin telephone jack and controls the operation ofeach individual rectifiers.

The mode of operation of rectifier modules depends on thecoded signal M1 and M2 from the controller.

These signals are decoded to display whether the modules are

in auto float/charge or fail condition. The total battery current can be suitably programmed to limit

the current supplied from the modules through currentprogramming pin in modules.



Earthing Systems

Earthing is a effective measure of protection fromhazardous electric currents which may result either

due to power induction, lightning or short circuits. The charges of electricity could be dissipated by

connecting the charged body to the general mass ofearth through an electrode.

Earthing for sake of protection is used at practicallyevery point of the supply network from generators tothe electrical apparatus used by the consumer.

Introduction



Earthing Systems

Reduction of Crosstalk and Noise:

One pole of the battery (positive pole) is earthed inthe telephone exchange so that cross talk betweenthe various circuits due to the speech currents of onecircuit finding path through the other via common

battery feed points of the transmission bridge andreduced NSN via earthed terminal of the battery.

Purpose of Earthing :



Earthing Systems

Earth is used to afford convenience & reliability, in the operate pathof the circuits involved in the switching apparatus of telecomcircuits.

Used as return path for the conductors in some telegraph and voicecircuits.

Protection of costly apparatus and persons against foreign voltagesand leakage currents from power wirings to the metallic frame ofthe equipment.

Protection of buildings and equipments from lightning strikes. Earthing in power supply systems is used to effect reliability of

power as it helps to provide stability of voltage conditionspreventing excess fluctuations and providing a measure ofprotection against lightning.

Purpose of Earthing :



Classes of Earthing Systems

Service Earthing Systems

Protective Earthing Systems

Earthing systems are provided to serve manydifferent purposes. They may be divided into twomajor categories :



Requirements for Service Earthing Systems

Service-earthing systems should have a low D.C. resistance to thegeneral body of the earth, in order to ensure that the potential dropacross the earth connection is low.

If any current flows through the service earthing system, a potentialdifference will be developed across the earth connection.

This can introduce interference in the form of electrical noise intoany telecommunication circuit connected to that earthing system.

The value of resistance which must be met by a service earthing willdepend on the purpose for which the earth likely to be carried by the

earthing system, and the tolerable voltage drop across the earthconnection.

The value chosen by most administrations is usually not more thanten ohms, although in some isolated cases higher values areacceptable.



Requirements for Protective Earthing Systems

The requirements to be satisfied by a protective earthingsystem are governed by the purpose for which the earthis being provided.

Earths, which protect against excessive current (e.g.

power supply protective earth) must have a lowresistance in order to:1. Carry the anticipated value of over current without overheating

and “burning out”.

2. Enable sufficient current to flow to ground to ensure that any

over current protective devices will operate to disconnect thecurrent after a very short time.

3. Able to withstand indefinitely the corrosive action of soil.



Design Principles for Earthing Systems

Adequate current carrying capability (DC or AC asappropriate).

Adequate mechanical strength to withstand therigorous of service without fracturing.

In the case of lightning protective earths adequate – surge-current carrying ability.

Earthing systems should be designed to achievethe following:



Telephone Exchanges

To provide a low resistance path to ground.

To be able to discharge the maximum anticipatedcurrent, which the earth system is expected to carry,

both under working conditions and under fault

conditions.

The main requirements of the earthing system ata telephone exchange are :



Earth Electrodes

(1) Rod electrodes.

(2) Plate electrodes.

(3) Strip electrodes.

(4) Ring electrodes.

Three types of earth electrodes are commonly used forearthing system:



Conditions determining the type of earth electrodes system to be used

Spike earth electrode system is generally used for allnew auto exchange installations where adequatespace is available and on sub soil suitable for drivingthe pipes to the prescribe depth.

The lead strip electrode system is used whenadequate is available but rock is encountered at adepth less than 375 cm below ground level.

Earth plate electrode system is used when layout ofexchange site is such that adequate space is notavailable.



IMPORTANT POINTS FOR CONSIDERATION INEARTHING

Chemical treatment of earth using salts etc. are notrecommended as the chemical treatment does notlast long and needs to be checked periodically.

Earthing conductors should not pass through anymetallic conduit or pipe, as this will increase surgeimpedance.

There should be no sharp bends along the entire

length of earth conductors. Bending should be done with a radius of one meter.

All the joint of the similar metals should be waterproof

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Role of battery in Telecom