F0RM2
THE PATENTS ACT, 1970
(39 of 1970)
&
Patent Rules 2003
PROVISIONAL SPECIFICATION
(See section 10; rule 13)


1. Title - AN INTEGRATED AC POWER SYSTEM FOR
TELECOMMUNICATION APPLICATION
2. Applicant - MAHINDRA & MAHINDRA LTD.
1, GATEWAY BUILDING, APOLLO BUNDER, MUMBAI - 400001, AN INDIAN COMPANY
The following specification describes the invention.


FIELD OF THE INVENTION
This Invention relates to an electrical AC power system for telecommunication application. The invention further relates to system and method of controlling engine driven generator AC power and power from external power distribution network for telecommunication facility.
BACKGROUND OF THE INVENTION
Telecommunication tower, commonly known as Base Transceiver Station (BTS) functions to transmit and receive data and voice over, monitor quality of speech and interconnect the terminal and a base station controller. In view of this, uninterrupted, reliable and dependable electrical power supply is of paramount importance to the BTS. To cater to this need, typically, AC power system is used to supply power to the BTS for lighting, Air Conditioners and more importantly to charge the battery bank through the battery charger which converts the AC supply to DC supply. The shelter room of the BTS houses the communication equipment and the said battery bank to support the DC power requirements of the said communication equipment and a battery charger unit to charge the batteries. Normally, the AC power supply available from the commercial electric supply system of the area, hereinafter referred to as electricity board supply or EB power supply is used to meet the AC power requirement of the BTS. To overcome the erratic condition of EB supply, a healthy phase selection device also known as auto phase selector to select healthy phase of the three phase power supply and a voltage conditioning unit (VCU) to condition the supply voltage between the set upper and lower limit are employed along with a controller which together are also located inside the said shelter. The VCU has its own battery for its DC power supply needs and a battery charger unit to charge the battery. It also has a
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user interface panel having switches, display, alarm units and fault annunciators.
A genset AC power plant is provided outside the shelter for use when EB power supply is unavailable, that is, fails or fluctuates beyond use. A voltage sensor senses the fluctuations in EB supp|y and sends signal to the controller which starts the genset and Controls the change over system also located in the shelter to disconnect the EB supply and connect the genset supply to shelter. The genset AC power plant typically has a control panel for user interface and controls are usually handled in manual mode. The genset AC power plant also has its own battery for starting engine of the genset and a battery charger unit for charging it.
It is always desirable co provide singl'e point user interface integrating key components avoiding duplication of the Same so as to save space and facilitate better heat dissipation from the Components, avoiding use of air conditioning means to make the power supply system compact, techno-economically viable, easily maintainable and energy efficient.
Several efforts have been made in the past to provide power system for telecommunication. They are as follows:
US Patent 6693810 discloses power supply any battery back-up system for telecommunications systems. It includes an AC/DC power supply and a battery for supplying operating power to a telecommunications system. The battery is connected to the telecommunications system and is designed to supply the telecommunications system with operating power if the power supply fails for some reason. The power supply is designed to output the peak operating power required by the telecommunications system, supplying the telecommunications system with whatever operating power it needs and supplying the difference between the operating power supplied to the telecommunications
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system and the peak operating power output by the power supply to the battery for charging. However, this system suffers from the shortcomings that does not provide single point user interface.
US Patent 5332927 discloses power supply system for a telecommunication system. It includes an internal combustion engine driving an alternator the output of which is rectified and supplied to DC bus lines across which a storage battery is connected. The voltage across the bus lines is sensed and when the voltage drops below a selected value, indicating that the consuming devices is drawing power from the battery beyond a desired limit, the engine is turned on for a period of time to warm it up, during which the power from the generator is not supplied to the DC bus lines. Thereafter, the generator supplies power- to the DC bus lines to supply the consuming device and partially recharge the battery until the consuming device is no longer drawing power, after which the engine is shut off. However, this invention is focused on the AC generator output and problems with the distortion of the same. It does not teach integration of the key components in the power supply system so as to have single point user interface.
US Patent 70§1687 discloses power system for a telecommunication facility. It includes hydrogen fuel supply system. However, this invention is focused on the generator rather than the entire system.
Review of the; prior art and current systems reveal several short
comings like
lack of integration of key system elements and single point user interface, resulting in higher cost of material and installation and inconvenience to user;
duplication and proliferation of system elements and multiple user interfaces located at more than one location;
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increased shelter temperature due to heat dissipation of the
power supply system elements requiring higher capacities of air
conditioners leading to higher energy consumption;
presence of the power Conditioning Unit and the change over
system inside shelter causes electromagnetic interference with
the sensitive telecommunication equipments;
need for longer cabling and interconnection between system
components.
Thus there is a need for an modular power supply system for telecommunication facility provided with single point / location user interface integrating key components avoiding the duplication of the same so as to save space, cost and facilitate better heat dissipation from the components avoiding use of higher capacity air conditioning means to make the power supply system compact, techno-economically viable, easily maintainable and energy efficient.
SUMMARY OF THE INVENTION
The main object of the present invention is to integrate various components of the engine driven generator AC power system and EB power supply, to provide a compact power system with single point / location user interface and enhanced heat dissipation capability obviating the problems of duplication of the components and air conditioning means.
Another object of the invention is to provide robust control system that works in extended temperatures, immune to noise, vibrations and facilitates alteration of control program on site and future up gradation.
Yet another object of the present invention is to obviate problems associated with cabling and interconnection between system elements.
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Another object of the invention is to provide a modular and compact system.
Yet another object of the present invention is to provide energy efficient power supply system.
Yet another object of the invention is to provide thermally isolated modules which are usable independent of the rest of the system.
Yet another object of the invention is to provide uninterrupted reliable and dependable constantly available DC power supply to the battery bank inside the shelter.
Thus in accordance with the present invention one aspect of the integrated AC power system comprises of:
a controller for the integrated AC power supply system, a user interface control panel, a local battery, a battery charger for the local battery, a voltage regulator or voltage conditioning unit, an auto phase selector, a change over system for changeover between EB power supply and genset power supply, engine driven genset and its auto start device; wherein
the said controller includes
a PLC control unit configured with various system components, input means and the out put means;
Optional digitizer operatively connected to the AC power system for the
control signals of the BTS;
optional lightening arrester for protection from lightening strikes
traveling over the incoming EB AC power supply;
surge protection device to arrest local surge and transients;
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optional aviation lamp to give warning signal to any aircraft in the
vicinity controlled by the controller by the input from a light sensor &
real time sensor;
optional mode selector switch for selection of automode or the manual
mode.
In further aspect of the invention the battery charger of the battery bank disposed in the BTS shelter, is integrated with the AC power supply system obviating the problems of voltage drop and power loss due to length of DC cables between battery bank and telecommunication equipment. One of the aspects of the invention provides a means to keep the AC power supply system in operation even if genset power supply system is required to be shut down or removed for major overhaul or replacement of for upgradation, the battery bank located inside the shelter can maintain an uninterrupted DC power supply to the telecom equipment.
In another aspect of the invention auto phase sensor, voltage sensor, battery charge level sensor, overload sensor, temperatures sensors, engine fuel level sensors, fire sensor and intruder sensor are configured with the said controller.
DETAILED DESCRIPTION OF THE INVENTION
Features and advantages of this invention will become apparent in the following detailed description and the preferred embodiments with reference to the accompanying drawings.
Figure 1 Block diagram of the integrated AC power system (Sheet 1) Figure 2 Disposition of the voltage conditioner module on a trolley (Sheet 2)
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Figure 3 Disposition the voltage conditioner module next to the Power plant (Sheet 2)
Figure1 illustrates the integrated AC power system. It comprises of engine driven genset 1, its auto start unit 2, local battery 3 wherein single battery is used for DC power supply for both genset self starter and for the controller, single battery charger 4 for the said battery, AC to DC converter 5, PLC based controller 6 that is configured with the said components of the system for the control of the entire power system. The said controller 6 is configured with the control panel 7 that forms the single user interface provided on the front of the power plant enclosure reduces inconvenience caused to user having to deal with multiple user interfaces of the currently available systems; further it eliminates the duplication of control switches, buttons, displays, audio/visual alarm signals, bulbs, indicators, fault annunciators and the control panel items.
The genset safety unit 8, single surge protection device 9 are provided for protection against external lightening voltage surges and internal voltage surges within the system, auto phase selector unit 10, the voltage or power conditioning unit 11, the change over unit 12 and the distribution board 13 inside shelter. The digitizer unit (not shown) is housed inside the said distribution board 13 collects all the control input signals, both digital & analog, and digitizes them. The digitized output signals are then transmitted to the controller 6 through a pair of twisted control cables. This not only facilitates sending of plurality of input signals through a single pair of cables but also allows the signals to be transmitted over a considerably longer distance without problems of deterioration or loss of signal. This is particularly important if there is no space for AC power system to be located close to BTS shelter. The output AC supply is shown connected to the distribution board 13 inside the BTS 14 shown in dotted lines. The aviation lamp unit 15 at the top of the BTS also is controlled by the controller of the AC power
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plant. The controller employs a digitizer unit located inside the shelter to which is connected all the signal inputs of BTS for digitization and onward transmission to the AC power plant.
The controller 6 functions to control the operation of the AC power system and to ensure safety of the BTS including that of the AC power supply system by means of appropriate sensors, probes or transducers. PLC based system has advantages of open architecture facilitating alteration of control program on site and future up gradation, as against micro controllers that having closed architecture. The said controller 6 is adapted for multiple inputs and output arrangements, extended temperature ranges. Further it is immune to electrical noise, and resistant to vibration and impact thus is robust and just appropriate for this application. The input means of the controller includes a host of sensors for genset related inputs, electricity board (EB) supply lines related inputs and BTS related inputs like auto phase sensor, voltage sensor, battery charge level sensor, overload sensor, temperatures sensors, engine fuel level sensors, fire sensor and intruder sensor. The output means of the controller include a host of control output devices to control operations of the system elements already described like contactors solid state switching devices, start-stop devices, output devices for alarm signals, displays fault annunciators, LED display for critical alarms and status, data record, data entry devices. Separate controllers are provided for the autophase selector unit and power conditioning unit so that they can operate independent of the main controller.
The main controller is based on Programmable logic controller (PLC). The PLC has a program memory of 7000 instruction capable of programming all features related to power system. The data memory of this PLC is around 10KB and this is used to store 500 events related to the power system. The PLC consists of 12 Digital inputs and 8 Digital outputs. The genset signals are wired to this digital input module also
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the light sensor, intruder sensor are also wired to the same module. The digital output module in the PLC gives command to start the genset, stop the genset, switch on the EB contactor /genset contactor etc. The PLC outputs are wired to relay module which produces potential free output used to directly connect to the genset start & stop wiring. The PLC also is configured with 4 channel analog input module where the local battery voltage, BTS battery voltage and Shelter temperature signal are connected . These signals are conditioned through analog conditioning board and then given to this analog module.
The PLC possesses two communication ports, one for the interfacing the user interface display unit and the other for interfacing the GSM modem & 3nos power transducers.
To extract the events stored in the PLC, a laptop with the software is connected to port used for user interface and upload the events to the laptop. During this small gap of uploading the events, the display will be blank.
Figure 2 and Figure 3 depicts disposition of the power conditioning unit. The said unit is of modular construction having its own enclosure and located above the enclosure of the rest of the power plant to facilitate the heat dissipation directly to atmosphere instead of into the enclosure of the power plant. Figure 2 shows one form of arrangement as above, wherein the modular enclosed power conditioning unit B is located above the enclosure A of the rest of the power plant on a trolley Cf with negligible increase in the foot print area of the power plant. Alternatively, it can be located next to the enclosure of the power plant as shown in Figure 3.The power conditioning unit has its own controller. This arrangement has the further advantage that the power conditioning unit can remain in service for short periods to supply EB
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AC power to shelter even while the rest of the power plant is shut down for maintenance, up gradation or for replacement. The other devices excluding the Power Conditioning Unit (PCU) and the digitizer of the system are provided inside the power plant enclosure and are provided modular construction and being located in a compact enclosure, the power cabling and control cabling is reduced in length considerably saving both material cost and installation time and labors.
In another embodiment of the invention wherein AC power system is located close to the BTS shelter, the battery charger unit of the battery bank inside shelter is integrated with the said integrated AC power system as above, the battery charger being another heat dissipating device which step will not only reduce the space requirement inside shelter further, but also save power by further reducing the requirement of air conditioner capacity. The said battery charger is provided with a suitable enclosure to facilitate dissipation of heat directly to atmosphere and can be conveniently placed over or next to the AC power system, if the AC power system is close to the shelter or placed close or next to the enclosure of the telecom equipment if the AC power plant is away from shelter.
Thus it is evident from the present invention that the judicious configuration of the said PLC based controller with system elements has been achieved that facilitates single point / location user interface avoiding the duplication of the same so as to save space and facilitate better heat dissipation from the components avoiding use of air conditioning means to make the power supply system energy efficient, compact, techno-economically viable, easily maintainable that facilitates alteration of control program on site and future up gradation.

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