Solar System For Railway Signaling

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SOLAR PANEL Introduction Environmental pollution like deposition of carbon dioxide in the atmosphere is increasing day-by-day due to use of conventional energy sources such as coal, petrol, diesel, etc. Also sources of such conventional and non-renewable energy are diminishing continuously on Earth, the formation of which is a long process. Hence a need for alternative energy sources was felt such as Wind energy, Bioenergy, Solar energy. These are called as nonconventional or renewable energy sources. Of which Solar energy, which is abundant in nature and free of cost, is considered to be the best and most popular one. Solar energy is obtained through the use of Solar cells. The Solar cells convert sunlight into electrical energy, based on the principle of photovoltaic effect.. Therefore, solar cells are replacing other conventional energy devices and finding way in wide range of applications. Indian Railways is one of the biggest Central Government organizations working under a single management, which has biggest network all over the country. It requires lot of energy to run the equipments and engines, which are mainly operated through diesel and electricity. As we know that electricity is the best form of energy, which is used widely in the operation of rolling stock as well as Signalling gears such as Signals, Point machines, Relays, Block instruments, Axle Counters etc. But at Solar Panel

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many places it poses problems due to nonavailability of electricity for long period or erratic power. It is well established that solar power is the best-known conventional source of energy, which can immediately be converted into electricity by solar photovoltaic modules. The electricity so obtained can directly be used to charge the batteries used for equipments associated with the abovementioned gears. These batteries can be charged even at the remote places where grid supply is not available round the clock or not available at all. Thus solar photovoltaic power may prove a boon for the Railways in future. Therefore it is considered to switch over to non-conventional sources of energy. For this purpose, it is well thought to train the manpower for using the system of non-conventional energy. 1.1

Advantages and Disadvantages of Solar Panel : Advantages        

Fuel source for Solar Panel is direct and endless so no external fuels required. Sunlight - free of cost. Unlimited life of Solar Modules , fast response and high reliability. Can operate under high temperature and in open. Inherently short circuit protected and safe under any load condition. Pollution free. Minimum Maintenance Independent working

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        



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Operation is simple and no electrochemical reaction and no liquid medium. Noise-free as there are no moving parts. No AC to DC conversion losses as DC is produced directly. No transmission losses as installed in the vicinity of the load. Suitable for remote, isolated and hilly places. Suitable for moving loads/objects Since it is in modular form, provision of future expansion of capacity is available. It can generate powers from MilliWatts to several MegaWatts. It can be used almost everywhere from small electronic device to large scale MW power generation station. It can be installed and mounted easily with minimum cost. Disadvantages

   

  

Initial cost is high Dependent on sunlight Additional cost for storage battery. Climatic condition, location, latitude, longitude, altitude, tilt angle, ageing, dent, bird dropping, etc. affect the output. It has no self-storage capacity. Manufacturing is very complicated process. To install solar panel large area is required.

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1. Photo Voltaic effect Electricity can be generated directly from sunlight, by a process called photovoltaic effect, which is defined as the generation of an electromotive force as a result of the absorption of ionizing radiation. The photo voltaic effect can be observed in almost any junction of material that have different electrical characteristics, but the best performance to date has been from solar cells made of Silicon.

DC Electricity Fig 1:Photo Voltaic Effect

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2. Solar Cell: Construction & Working The basic building block of a photovoltaic system is the Solar Cell, a semiconductor device having a simple p-n junction and which when exposed to sunlight produces DC electricity. The solar cell is made up of “Semi-Conductor” materials that are processed to make the device photovoltaic. The solar cell is made of single crystal silicon, polycrystalline and amorphous Silicon with an area of a few sq. centimeters to 200 sq. centimeters and even more. A thin p type silicon wafer is taken through phosphorus diffusion process and by screen-printing technology electrodes are made. The P-N junction of the solar cell gives rise to diode characteristics. Hence a solar cell is a PN junction device on which front and back electrical contacts are screen-printed. A sketch of typical psuedo-square solar cell is shown in Fig.2 (a) & (b). The side, which has negative polarity, is taken as front side and that which has positive polarity is taken as backside. The front or Negative side is exposed to sunlight for conduction to take place. Two Tinned copper strips work as terminal leads for interconnection to other cells. For collection of charge from the cell and conduction to terminal leads on negative side, Silver Oxide lines are screen printed horizontally and these are joined to terminal leads at close spacing (refer Fig 2 a). These lines cover only 5% of the total area of the cell, so that these do not pose any hindrance to the exposure of Solar Panel

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Sunrays. The back or Positive side is not exposed to sunlight; hence Aluminium is coated on whole surface for better conductivity (refer Fig 2 b). Aluminium is coated instead of Silver Oxide as latter is expensive hence not economical. The operation of solar cells involves these major processes: i) Absorption of sunlight into semiconductor materials ii) Generation of charge carriers. iii) Separation of +ve & -ve charges to different regions of the cell to produce e.m.f.

Tinned Copp er Strips Silver Oxide lines

Fig 2 (a) Sketch showing front view of typical pseudo square solar cell Solar Panel

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Tinned Copper Strips

Aluminium coating

Fig 2 (b) Sketch showing rear view of typical pseudo square solar cell

Fig. 2 (c): Solar Cell: Actual view (CEL make)

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Solar Photo Voltaic (SPV) Module The power generated by a single cell is small and therefore several cells are interconnected in series/parallel combination to get the required voltage and current. When a number of solar cells are connected in series to get a specific voltage the unit so formed is called as Solar Module. Charging batteries is the primary use of SPV module. Therefore normally 36 cells are joined in series to form a standard module, which is capable of charging 12 volts battery. A terminal box is provided on the backside of the module for external connections. A Bypass diode is connected across +ve and –ve in the terminal box. Cathode of the diode will be at +ve terminal and Anode will be at –ve terminal of the module. This diode protects the module cells from overheating due to shadowing of the module or any cell breakage. Generally rating of bypass diode is 1.52 times of the maximum current of module. The Repetitive Reverse Peak Voltage Vrrm of the diode should be double the string open voltage. For Indian Railways Solar Photovoltaic Module is manufactured as per RDSO Specification No. IRS:S 84/92. A typical solar module is shown in Fig 3.

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9 Bypass Diode

-ve

+ve

Blocking Diode

Fig 3: Solar Module Solar Panel

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Solar Panel A Solar panel consists of a number of solar modules, which are connected in series and parallel configuration to provide specific voltage and current to charge a battery. A diode is connected on the +ve terminal of such string in forward bias. This is called Blocking diode. This diode is provided so that in daytime current can flow from module to battery, but at night or in cloudy day current should not flow back from battery to module or from one string to another string Drawing shown in Fig 4 below illustrates a Solar panel:

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+ Bypass Diode

-

-

-

-

Fig 4: Solar Panel Solar Panel

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Battery set

+

Charge Controller

Blocking Diode

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Fabrication of Module In a Solar module cells are joined by tinned copper strips. 36 cells are connected in series to charge 12 Volts battery. Now this string is sandwitched between Ethyl Vinyle Acetate (EVA) sheets, a kind of thermo-plastic material. It serves as an encapsulant and it is provided to protect the cells from weather conditions. After this a Polyester Tedelar Polyester sheet (built in three layers) is kept at the bottom and a toughened glass at the top. Toughened glass of high transmittance is used which has less iron content. Also its refractive index matches with that of EVA hence deviation of sunlight is less. This whole unit is laminated in special equipment at 140 deg. C by which all the moisture and air is drawn out and the EVA sheets are coated uniformly all over the cells and become transparent. To prevent damage to the glass the laminate is further fitted inside an anodized Aluminium channel frame. Terminals are provided inside a junction box for external connections at the backside of this frame. This completes the fabrication of solar panel. The solar modules supplied to Railways are of the rating 70 Watts, 35 Watts, 20 Watts and 10 Watts. 80-Watt module is under certification of Railways. The module crosssection comprising of glass and encapsulating material such as EVA, Toughened glass and Tedlar are shown in Fig No.5.

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Toughened Glass EVA sheet Solar cell string EVA sheet Polyester Tedlar Polyester Aluminum Frame

Fig 5: Cross section of a Solar Module 5.2 Types of Solar Panels : Solar panels are classified on the basis of the following points : 1) Crystalline Silicon (Mono/Poly/Amorphous) 2) Different Size or Area of cells 3) Type of cells & nos. (Rectangular/Circular/ Square/ Pseudo-square/Semi-circular etc.) 4) Power (High/Mid/Low range) 5) Connection of cells (Series/Parallel) 6) Specified use 6.

Testing before installation: Before installation the solar panels are tested at the manufacturing unit to check for the following parameters: • • • •

Solar Panel

Voc-Open circuit voltage Isc-Short circuit current Vmax- Maximum Voltage Imax- Maximum Current March 2006

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• Pmax- Maximum power at Standard Test Conditions or Peak Power Output The following table shows typical specifications of different modules: TABLE A Peak Power Output (Pmax) 4W 4W 8W 10W 12W 18W 35W 40W 50W 65W 70W 75W 90W

Nom inal Volt age 6V 12V 12V 12V 12V 12V 12V 12V 12V 12V 12V 12V 12V

Open Circuit Voltage (Voc) >11.5V >21V >21V >21V >21V >21V >21V >21V >21V >21V >21V >21V >21V

Short Circuit Current (Isc) >0.63A >0.3A >0.56A >0.70A >0.84A >1.26A >2.4A >2.7A >3.3A >4.0A >4.5A >5.0A >6.0A

Max. Voltage (Vmax) at Pmax 8.5 V 16.7 V 16.7 V 16.7 V 16.7 V 16.7 V 16.7 V 16.7 V 16.7 V 16.7 V 16.7 V 16.7 V 16.7 V

user’s

Max. Current (Imax) at Pmax 0.47 A 0.23 A 0.47 A 0.59 A 0.71 A 1.07 A 2.09 A 2.39 A 2.99 A 3.89 A 4.19A 4.49 A 5.38 A

The above values are at standard testing conditions such as 25-degree cell temperature and 100-mW/Sq. cm solar radiation. The output will be reduced as temperature rises and intensity of sunlight reduces. Although accurate power is measured with the help of Module Tester at supplier’s end, however to check working of module Voc and Isc can be measured at site as shown in Fig.7 (a) & (b) by simple multimeter Solar Panel

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in two different modes i.e. Current mode and Voltage mode when module is placed in sunlight.

V

A +

_

Solar M odule

Measurement of: (a) Isc

+

_

Solar M odule

(b)Voc

Fig 7:Testing before installation The solar panel is kept in such a position that it receives maximum sunlight. The typical I-V curve of a 35-Watt module with 36 series connected cells is illustrated in Fig 8.

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MODULE PERFORMANCE AT 25 DEG. C & 100 MW/Sq cm. 3000.0

2400.0

1800.0 Amps. 1200.0

600.0

Isc Voc FF I load V load P load

: : : : : :

2.44 Amp. 21.38 volts 70.31% 2.21 Amp. 16.00 volts 35.43 watts

0.0000 0.0000

6.0000

12.0000

18.0000

24.0000

30.0000

Volts

Fig 8 : IV curve of a 35 watt Solar module 7.

Installation Solar modules are to be installed firmly and permanently on metallic structures. The structures depend on the application and size of the system. For smaller systems like solar home systems, simple module mounting structures are used. For systems like solar streetlights, solar powered signal lighting, solar pumps etc. pole mounting module frames are used. For bigger systems like solar power plants and Solar powered Railway signalling installations, bigger array mounting structures are used.

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The installation of Solar Power System involves the following major steps:  Civil Foundation Job  Assembly and fixing of support structure.  Mounting of Solar Modules on the Support Structure.  Installation of Battery Bank.  Interconnection of SPV panel, Charge Control Unit, Battery Bank and Load (explained in para 9 of page 22).  Earthing of Lightning Protection Unit. The Solar panels are generally installed in such a way that they can receive maximum direct sunlight without shade from any building/trees nearby falling on them at any part of the day. As we know that the Sun rises in the East and sets in the West as a result of Earth’s rotation around its own axis. Also the Earth revolves around the Sun. Due to these two movements there is variation in the angle at which the Sun’s rays fall on Earth’s surface over a year. At any particular place on Earth this variation in angle in one year may be upto 45 degrees. Considering these facts the following guidelines are to be kept in mind while installing solar panels: a. Solar panels should be installed at an angle of ‘(LATITUDE of the place + 10) degree’ from horizontal. For example, New Delhi has a Latitude of 26 degree, hence any solar panel in New Delhi is to Solar Panel

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be installed at an angle of 26 + 10=36 degree inclined to horizontal. b. Solar panels should be installed South facing in the Northern hemisphere and North facing in the Southern hemisphere. Since India is in the Northern hemisphere, Solar panels will be installed alwaysSouth facing in our country. The directions NorthSouth may be found with the help of Magnetic Compass. The photograph given in Fig .9 illustrates this.

Fig. 9 : A Solar Panel installation c. Any obstruction (such as tree or building) should be avoided in East, West or South of the place of installation. The following is the criteria: i. East or West: The distance between solar panel and obstruction should be more than double the height of obstruction. Solar Panel

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ii.

South: The distance should be more than half the height of obstruction.

d. The support for the Solar panel need to be a robust one and should not be accessible to general public. It should be so installed that rainwater, bird dropping, leaves etc. do not accumulate and the top surface can be cleaned easily. 8.

Main Components of Solar Photo Voltaic System: The solar power system consists of the following components: 8.1. 8.2. 8.3. 8.4. 8.5. 8.6. 8.7.

Solar Panel

Solar array. Battery Bank Solar Charge Controller Inverter (DC to AC) Converter (DC to DC) Solar Module Mounting Structure Cables.

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DC Loads (Relays, Blocks Points etc.)

Solar Charge Controller Inverter (DC to AC)

AC Loads (Signals, Tracks Panel indications)

Battery

Fig.10: Block diagram of Solar Photo Voltaic System

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8.1

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Solar Array: Consists of series/parallel combination of modules, which are mounted on the metallic structure in sunny and shadow free area at a fixed angle as recommended by designer. All the modules will face the South in Northern hemisphere. Cables from the array area will come to the control and battery room through junction boxes from panels of modules.

8.2

Battery Bank: The Sun is not always available and it is not regular. However, loads are to be fed any time of the day. Therefore power should be stored in a battery bank. Stationary Lead acid battery as per IRS: S 88/93 or latest of specified capacity will be provided. The capacity of this battery bank is given in AmpereHour (AH) and bus bar voltage. The bus-bar voltage is decided by the voltage requirement of the load.

8.3

Solar Charge Controller Charge controller is the interface between Array and battery bank. It protects the battery from overcharging and moderate charging at finishing end of charge of battery bank. Therefore it enhances the life of the battery bank. Also, it indicates the charging status of batteries like battery undercharged, overcharged or deep discharged by using LEDs. Some switches and MCBs are also provided for manual or accidental cut-off of charging. In some charge controllers load terminals are also provided through a low battery charge cut-off device so that it

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can protect the battery bank from deep discharge. Solar Charge Controller units for Indian Railways are manufactured as per RDSO Specification No.RDSO/SPN/187/2004. The front view of a typical CEL make Charge Controller is shown in Fig.11

Fig 11: Front view of a Charge Controller 8.4

Inverter (DC to AC) Sometimes, some of the equipments require AC power supply, and then we have to use an Inverter, which can give AC output of the required voltage, current and frequency. For this purpose Railways specify the input/output specification of the inverter to the manufacturer. Inverter may be a separate unit as per IRS: S 82/92 with amendment 2 or latest or it may be integrated with IPS system as per RDSO/SPN/165/2004 with amendment 4 or latest.

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22

Converter (DC to DC) Sometimes, if different DC voltage levels are required to operate some equipment, then a DC-to-DC Converter is required. For this purpose railway will specify the voltage of the battery bank and output voltage of the converter so that equipment of different voltage may be operated. This is applicable for signalling loads where different DC supplies are required such as 12 Volts, 24 Volts, 60 Volts etc.

8.6

Solar Module Mounting Structure This is made up of galvanized iron frames and angles. In this structure flexibility is provided to change the module-mounting angle seasonally. This structure is grouted by small civil work and modules are mounted subsequently. Also, this mounting structure should be earthed suitably at several places if voltage of the array is more than 50 Volts. Provision of earthing shall be done as follows: The installation shall have proper earth terminals and shall be properly earthed. Zonal Railways shall provide earthing arrangement as per IS:S 3043 and directions issued by RDSO for Lighting and Surge protection for signalling equipment vide letter No. STS/E/SPD dated 22.06.2004. The earth resistance shall not be more than 2 ohm. Earth provided shall preferably be maintenance free using earth resistance improvement material.

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Cables: We require different types of cables to connect module to module, modules to charge controller, charge controller to battery, battery bank to inverter and inverter to load or connect battery to load as required. The cable size used for interconnection of SPV module, Charge Controller and battery shall be minimum 2 X 25 sq. mm Cu. Cable. As far as some hardware is concerned the screws and bolts/nuts are of Chrome plated, stainless steel and brass so that rusting should not be take place.

9.

Electrical Interconnections The connections to the charge control unit are to be made in the FOLLOWING SEQUENCE ONLY: Connect at FIRST one end of the 2 core cable supplied with the unit, to the charge controller at the terminal marked ‘B’ +ve with ‘Red Wire’ and the terminal marked ‘B’ –ve with ‘Black Wire’ then connect the other end of the cable to the respective terminal of the Battery Bank. Check the glow of LED marked ‘BATT REV’, if it is glowing reverse the connection. Connect the SPV array output to the terminals at ‘SPV-IN’ position marked on Charge controller unit. LED marked ‘CHG ON’ should glow. Switch off the MCB provided in front face. Connect the load to the terminals at ‘LOAD’ position marked on the unit. Then switch ON the MCB.

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While disconnecting the Charge Controller, the reverse sequence is to be followed. The SPV array and battery bank are to be connected to the Charge Control Unit using minimum 2 X 25 sq. mm. size Cu. cable. The thimbles, required for crimping at the cable ends after cutting the required lengths are being supplied separately. A typical diagram showing interconnections among SPV array, Lightening protection unit, SPV Charge Controller, Battery and Load is given in Fig. 12 below: PU 360 SPV in + -

SPV out Gnd + -

SC-351 CI A +

L +

B +

B -

L -

A -

+

SPV Panel

Battery

To load

LIGHTNING PROTECTION UNIT Fig 12: Interconnection diagram 10. Operation Operation of the Solar power source is very simple. Once the system is installed, CHG. ON (Green) LED will glow during daytime and will indicate that the power is available for charging Battery Bank from SPV panel. Connect the equipment to be operated on Solar Panel

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solar power to the SPV Charge Control Unit at terminals marked ‘LOAD’ position. 11. Maintenance 



12.

Solar panels require virtually no maintenance. However once a fortnight the surface of the panels should be wiped clean with wet rag to remove dust, fallen leaves, bird dropping etc. Only water to be used and no other cleaning agent. With Solar Panel Secondary battery maintenance becomes minimum. Still general periodical maintenance of battery should be carried out in usual manner and as per maintenance manual. Solar Panel Requirement for IPS System at PI Station in Non-RE Area RDSO has standardized the Solar Panel requirements for IPS System at Panel Interlocked Station in NonRE area based on the assumption that all three sources of supply i.e. solar power, AC commercial supply and DG set supply will be utilized everyday for running signalling system at a station. Battery capacity has already been specified as 300 AH for IPS system in non-RE area. These requirements are separately worked out for up to 3 line station, 4 line station, 6 line station and 4 line station with DC LED Signals, and are tabulated in Table B below:

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TABLE B Sr

Description

Up to 3 line station

Up to 4 line station

Up to 6 line station

1.

Approximate Signalling load (AC + DC) except track circuit at 110 V

13A

22A

28A

2. a.

Required from solar power (in AH) for 12 hrs. load 12x13= 12x22= 12x28= per day 156 AH 264 AH 336 AH for 10 hrs. load 10x13= 10x22= 10x28= per day 130 AH 220 AH 280 AH for 08 hrs. load 08x13= 08x22= 08x28= per day 104 AH 176 AH 224 AH for 06 hrs. load 06x13= 78 06x22= 06x28= per day AH 132 AH 168 AH SPV requirement for 110 V system Derating factor 10% (0.9) 10% 10% of Solar Panel (0.9) (0.9) Derating factor 10% (0.9) 10% 10% of Battery (0.9) (0.9) efficiency Sun availability 5 Hrs. 5 Hrs. 5 Hrs. assumed Charging current 4.2 A 4.2 A 4.2 A of Solar panel No. of 12 V, 70 W Solar Panels required in parallel for 12 hrs. load 156/ 264/ 336/ per day (0.9X0.9X (0.9X0. (0.9X0.9 5X4.2)=1 9X5X4. X5X4.2) 0 Nos. 2)=16 =20 Nos Nos

b. c. d. 3. i) ii)

iii) iv) v) a.

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Up to 4 line station with DC LED signal 16A

12x16= 192 AH 10x16= 160 AH 08x16= 128 AH 06x16= 96 AH 10% (0.9) 10% (0.9)

5 Hrs. 4.2 A

192/ (0.9X0.9 X5X4.2) =12 Nos

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Sr

Description

Up to 3 line station

Up to 4 line station

Up to 6 line station

b.

for 10 hrs. load per day

130/ (0.9X0.9X 5X4.2)=0 8 Nos.

280/ (0.9X0.9 X5X4.2) =17 Nos

c.

for 08 hrs. load per day

104/ (0.9X0.9X 5X4.2)=0 7 Nos.

224/ (0.9X0.9 X5X4.2) =14 Nos

128/ (0.9X0.9 X5X4.2) =08 Nos

d.

for 06 hrs. load per day

78/ (0.9X0.9X 5X4.2)=0 5 Nos.

168/ (0.9X0.9 X5X4.2) =10 Nos

96/ (0.9X0.9 X5X4.2) =06 Nos

vi)

220/ (0.9X0. 9X5X4. 2)=13 Nos 176/ (0.9X0. 9X5X4. 2)=11 Nos 132/ (0.9X0. 9X5X4. 2)=08 Nos 9

Up to 4 line station with DC LED signal 160/ (0.9X0.9 X5X4.2) =10 Nos

No. of 12V, 70W 9 9 9 Solar panel required Total solar panel required (nos.) for 12 hrs. load 90 144 180 108 per day for 10 hrs. load 72 117 153 90 per day for 08 hrs. load 63 99 126 72 per day for 06 hrs. load 45 72 90 54 per day Area requirement for fixing solar panels (size approx. 1.2 mx0.55m per panel) in square meter for 12 hrs. load 60 95 119 72 per day for 10 hrs. load 48 78 101 60 per day

vii) a. b. c. d. 4. a. b.

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Sr

Description

Up to 3 line station

Up to 4 line station

Up to 6 line station

c.

for 08 hrs. load per day for 06 hrs. load per day

42

66

84

Up to 4 line station with DC LED signal 48

30

48

60

36

d.

5. a. b. c. d.

Approximate cost of solar panels (@ Rs. 15400/-) for 12 hrs. load 14 lakhs 23 lakhs 28 lakhs per day for 10 hrs. load 11 lakhs 18 lakhs 24 lakhs per day for 08 hrs. load 10 lakhs 16 lakhs 20 lakhs per day for 06 hrs. load 07 lakhs 11 lakhs 14 lakhs per day

17 lakhs 14 lakhs 11 lakhs 9 lakhs

Note: Actual solar panel requirement shall be carried out by the Railway as per the guidelines given above in the table B based on actual signalling load at a station with IPS system. 13. Troubleshooting The SPV Power Source is reliable Source of Electrical energy. However, there may be rare instances, when the SPV Power Source is not able to drive the connected equipment.

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SPV Panel

Inverter

29

Battery

Charge Controller

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Load

Fig. No. 13 - SPV Power Source

The diagnosis of the problem in such situations starts with the battery. Check the voltage of the battery bank. If the voltage of the battery bank is correct as indicated in Charge controller, there may be problem in the inverter or switch between load and inverter i.e. either inverter is tripped or switch/load MCB is tripped or load fuse is blown off. If none of the above fault is observed then check the specific gravity of the electrolyte in the secondary cells of the battery. There may be two cases: a.If the specific gravity is above the level 1.2 (Hydrometer reading 1200) value or as specified in the maintenance manual, it implies that the battery is in order and the problem would be either with the Charge Controller or Load. Disconnect the load (S & T Equipment) from Charge Controller and connect it directly to Battery Bank. If the equipment operates, the defect may be with the Charge Controller. Disconnect the Charge Controller and check as per troubleshooting instructions given in the manual supplied with it or inform the manufacturer/supplier. b. If the specific gravity of the electrolyte is below the specified level and BATT/LOW (Red)) LED is Solar Panel

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glowing, the problem may be with any of the following: i. Load: This may be drawing more current from the battery than required. In such case, battery is bound to get discharged, even if SPV Panel is functioning properly. This would result in frequent tripping of the load. To avoid this, get the load equipment checked and replace any defective components. ii. SPV Panel: The SPV Panel may not be producing required power for which the Power Source has been designed. In that case, check the SPV Panel as given below:  Check for any loose connection/breakage of wire in SPV module interconnections.  If there is no such loose connection, clean the SPV Modules with soft cloth. Whenever there is bright sunshine, measure the voltage and current of each module after disconnecting the wire. Open circuit voltage of each module should be around 21 volts and short circuit current should be as per table given under Para 6 depending upon the wattage of the module, at 100 mW/Sq.cm AM 1.5 Solar radiation.  If any of the SPV modules gives low voltage/current output during bright sunlight (Sun intensity 90 mW/Sq. cm) inform the manufacturer/Supplier with module serial number along with the Solar Panel

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measurement investigations. iii.

31

taken,

for

necessary

Failure of blocking diode: Blocking diode fails in short circuit and open circuit mode. If it is failed in short circuit mode, voltage across its terminal will be zero in place of 0.7 V while charging current flows through it. When it fails in open circuit mode, the current will not flow through the diode. The diode may be checked as per standard method of checking of diode by removing from the circuit.

Apart from these some possible complaints and trouble shooting methods for Solar modules are listed below : S. No. 1.

Symptom No output

Failure Cable Connector

Junction box

Cause Conductor break Defective connector Corrosion Mechanical damage

Connection problem None of the Internal above problem 2.

Output voltage Solar Panel

Cell/interco nnections

Internal damage

Action Replace cable Replace connector Replace connector Return to factory for servicing Connect properly Return to factory, if within warranty Return to factory, if March 2006

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3. 4.

5.

Symptom OK, but no output current Front glass broken No voltage across blocking diode Voltage high across blocking diode

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Failure

32

Cause

Breakage

Action within warranty

Mishandling/ transportatio n Diode Random failed in failure short circuit mode

Unserviceable , Replace Replace diode

the

Diode Random failed in failure open circuit mode

Replace diode

the

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33 SPV power source not driving the load

Check SPV Panel Disconnect C/C Connect load directly to battery

Is battery voltage OK? Any loose Connection/ Breakage?

Yes Check inverter and switch between load & C/C

No

Is load working?

Clean SPV Module

Yes Is inverter or switch OK?

Check Voc & Isc

No

Problem in charge controller

Rectify

Yes Check or inform supplier

Check Specific Gravity of each cell

Is Voc and Isc OK?

No Inform supplier/ manufacturer

No

Is Sp. Gravity OK?

Yes

No Check load Replace defective components

Fig. No. 14 - Troubleshooting flowchart for SPV Panel

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14. Precautions and Preventive Steps Please ensure that: a.SPV Modules are connected in parallel and SPV Panel output voltage is less than 25 Volts under normal sunshine condition (for 12 V System/Module) b. All connections are properly made tight and neat using the crimped Red (for +ve) and Black (for –ve) wires supplied by the manufacturer in order to avoid reverse connection. c.The rating of the fuse in the charge controller is not changed. d. The SPV Panel is installed facing SOUTH and with the correct ‘Angle of tilt’. e.There is no shadow on any part of the SPV Panel at any time of the day, to get maximum power. f. SPV Modules are protected against any act of vandalism and accidental strike or hit by heavy objects, like stone, hammer etc. If the SPV Panel is installed on ground, it must be fenced properly to protect it from cattle and to prevent from any damage/theft. Fencing should be made in such a way that no shadow should fall on SPV Panel at any time of the day. g. Battery Bank is placed on a rack or platform insulated from ground and located in a well-ventilated room and also sufficient clearance is there over the battery. Solar Panel

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h. FIRST the Battery Bank, then SPV Panel and then Load is connected to SPV Charge Control Unit and for disconnection reverse sequence is adopted. i. Battery terminals are never shorted even momentarily as shorting will result in HEAVY SPARK AND FIRE. (To avoid the same connect the cable at Charge Controller end ‘First’ and then Battery end.) j. Never connect the Load directly to the SPV Panel as SPV Panel may give higher/lower voltage than required by the Load Equipment and hence the equipment may be DAMAGED permanently. k. Blocking diode is provided at the array output for protection against reverse polarity. 15.

Utilization of Solar Power Supply System in the Indian Railways: The efficient running and control of Railway traffic in the country is some times seriously hampered by the irregular grid supply (by State Electricity Board) resulting in traffic congestion and other operational equipment failures also. The alternate D.G. sets pose considerable problem as it has a high maintenance cost and necessitates the use of additional D.G. sets as stand by. Again diesel oil is prone to pilferage, and moreover transportation and storage costs are involved. It also causes atmospheric pollution. Hence by harnessing the abundantly available and non-polluting by nature solar energy source for power requirements came into action after decades of research and field experience.

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15.1 Advantages of Solar Powered System for Signalling Along with the advantages mentioned earlier the following are the additional advantages w.r.t. Signalling: 1. Totally Solid State design and highly desirable. 2. Eliminates need for kerosene lamps or other out dated light sources. 3. Does not use Soda cells or other primary cells, which need frequent replacement. 4. Power supply cabling from station building to the signal unit or cabin not needed, since the unit is a self contained power sources. This saves cabling cost. 5. Minimum maintenance, which can be easily done by low skilled worker. 6. Long life of whole system and the system gives trouble free performance. 7. System design suited to monsoon and low light condition thus ensuring failure free operation of the signalling gears throughout the year. 15.2 Application of Solar Powered System for Signalling & Telecommunications: Almost all signalling and Telecommunication gears can be run by solar power. In Indian Railway Signalling system is Solar powered in phased manner. Priorities are given to those locations where there is no conventional power or power transmission Solar Panel

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through cables is cost effective. Some example of application of solar power for signalling and telecommunication gears are given below: 1. Semaphore signal lighting at night. 2. Charging battery to power Signal lighting and Point Machines. 3. Charging battery for Optic Fibre Cable hut. 4. Solar powered Radio warning system/Gate Signal/HKT/TC. 5. Solar powered RRI/PI/relay operation (internal and external circuits)/ALR. 6. Charging secondary cells for Tokenless/Token block instruments. 7. Lighting Outer/Warner Signals and Distant Signal with motor operation. 8. Solar distillation plants.

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March 2006