BSNL (Bharat Sanchar Nigam Limited) A Presentation On “Role of power plant in telecommunication installations” Presented by: Ria Ghosh P.Gowtami Harshita Jaisawal Jagruti Thakker Isha Choubey

FLOAT WORKING OF PLANT BATTE RY EXCHAN GE INVERT OR POWER PLANT E/ A C.G. POWER GENERA TOR 51.8V DC 3 PHASE 230 V 2 SET 50 V 230 V AC

V ALVE -R EGULATED LEAD - ACID (VLRA) B ATTERIES Ensures a reliable, effective & user friendly source of power. 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 the need for equalizing charges. The water loss throughout the life due to gassing is roughly 0.1% of the total electrolyte present in the cell. Introduction

V ALVE -R EGULATED LEAD - ACID (VLRA) B ATTERIE S Batteries lose some charge during as well as during the period prior to installation. A battery should be installed and given a freshening charge after receipt as soon as possible. Freshening Charge Equalizing Charge  An equalizing charge is a special charge given to a battery when non-uniformity in voltage has developed between cells.  It is given to restore all cells to a fully charged condition.

V ALVE -R EGULATED LEAD - ACID (VLRA) B ATTERIES A pilot cell is selected in the series string to reflect the general condition of all cells in the battery. The cell selected should be the lowest cell voltage in the series string following the initial charge. Reading and recording pilot cell voltage monthly serves as an indicator of battery condition between scheduled overall individual cell readings. Pilot Cell

SMPS (S WITCH M ODE P OWER S UPPLY ) 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. What is SMPS?

SMPS (S WITCH M ODE P OWER S UPPLY ) The SMPS regulators are used in B.S.N.L at various locations like CDOT, E 10 B Transmission systems etc. Necessity

50V – 2000A P OWER P LANT  The power system is intended primarily to provide uninterrupted DC power Telecom. equipments and current for charging the batteries in the presence of AC Mains.  The system works from commercial AC mains which is rectified and regulated to –50V DC and is fed to the equipment (exchange).  The system has provision to connect three sets of VRLA batteries and facility to charge them simultaneously to ensure that uninterrupted DC power supply is always available to the exchange. Suitable for VRLA Batteries with 100A SMPS Rectifier Modules

A LTERNATOR An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. electrical generatoralternating current Based on a modular design, the POWER alternator is sure to respond perfectly to any type of need. These are used in case of power supply failure as a substitute of continuous power supply.

OPERATION OF E/A The rotating magnetic field induces an AC voltage in the stator windings. Since the currents in the stator windings vary in step with the position of the rotor, an alternator is a synchronous generator. [1]rotating magnetic fieldAC voltage [1] Alternators used in central power stations also control the field current to regulate reactive power and to help stabilize the power system against the effects of momentary faults.power stationsreactive powerfaults Often there are three sets of stator windings, physically offset so that the rotating magnetic field produces a three phase current, displaced by one-third of a period with respect to each other.three phase

F UNCTIONAL 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 in extension 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 the following:

F UNCTIONAL D ESCRIPTION OF R ECTIFIER The SMPS 50V-5600W rectifier is a state-of-the-art switch-mode power conversion equipment. The unit consists of two cascaded power converters performing power factor correction and DC/DC conversion. The power stages are synchronized and working with constant switching frequency of 100 kHz. The rectified AC mains voltage is processed first in the power factor 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 filter requirements. The output of the boost converter is a stabilized 400V DC voltage.

F UNCTIONAL D ESCRIPTION OF R ECTIFIER Conversion of the stabilized high voltage output of the power factor corrector circuit is necessary to generate the isolated low voltage output and to provide the required protection 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 by individual controller circuits and supervised by the housekeeping electronics.

F UNCTIONAL D ESCRIPTION OF P OWER S YSTEM C ONTROLLER Power system controller is designed to control the modes of operation of rectifiers, acknowledge and displays the status of rectifiers and system and controls parameters of rectifiers. The controller accepts signal from individual rectifiers through 8-pin telephone jack and controls the operation of each individual rectifiers. The mode of operation of rectifier modules depends on the coded 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 current programming pin in modules.

E ARTHING S YSTEMS Earthing is a effective measure of protection from hazardous 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 of earth through an electrode. Earthing for sake of protection is used at practically every point of the supply network from generators to the electrical apparatus used by the consumer. Introduction

E ARTHING S YSTEMS Earth is used to afford convenience & reliability, in the operate path of the circuits involved in the switching apparatus of telecom circuits. Used as return path for the conductors in some telegraph and voice circuits. Protection of costly apparatus and persons against foreign voltages and leakage currents from power wirings to the metallic frame of the 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 conditions preventing excess fluctuations and providing a measure of protection against lightning. Reduction of Crosstalk and Noise Purpose of Earthing :

E ARTH E LECTRODES Three types of earth electrodes are commonly used for earthing system: (1) Rod electrodes. (2) Plate electrodes. (3) Strip electrodes. (4) Ring electrodes.

D ESIGN P RINCIPLES FOR E ARTHING S YSTEMS Adequate current carrying capability (DC or AC as appropriate). Adequate mechanical strength to withstand the rigorous of service without fracturing. In the case of lightning protective earths adequate – surge-current carrying ability. Earthing systems should be designed to achieve the following:

T ELEPHONE E XCHANGES To provide a low resistance path to ground. To be able to discharge the maximum anticipated current, which the earth system is expected to carry, both under working conditions and under fault conditions. The main requirements of the earthing system at a telephone exchange are :