DETAILED TECHNICAL SPECIFICATIONS
(Grid Connected Solar Rooftop Photo Voltaic (SPV) power plant-with/without battery bank)
The projects shall be installed and commissioned as per the technical specifications given below.
A Grid Connected Solar Rooftop Photo Voltaic (SPV) power plant consists of SPV array, Module Mounting Structure, Inverter/Power Conditioning Unit (PCU) consisting of Maximum Power Point Tracker (MPPT), and Controls & Protections, interconnect cables and switches. PV Array is mounted on a suitable structure. Grid connected SPV power plant may be with or without battery and should be designed with necessary features to supplement the grid power during day time. Components and parts used in the SPV power plants including the PV modules, metallic structures, cables, junction box, switches, inverters/PCUs, battery etc., should conform to the BIS or IEC or international specifications, wherever such specifications are available and applicable.
Module mounting structure (MMS) should be of anodised aluminium or Hot Dipped Galvanised Iron (HDGI), of prescribed Specifications given below, for mounting of SPV modules at site. The panel frame structure should be capable of withstanding a minimum wind speed load of 150 KM per hour, after grouting and installation. MMS should be sturdy & designed to assist SPV Modules to render maximum output. The hardware (fasteners) used for installation of SPV Modules & MMS should be of suitable Stainless Steel (SS 304). Each MMS should be with minimum four legs grouted on pedestals of minimum 300X300X250 mm with anchoring/ chipping & chemical sealing of foundation based on RCC roof. Foundation bolts of stainless /GI steel should be at least 300 mm long.
Its size should be with reference to the specifications of the selected make SPV modules. Anti Theft Nut Bolts of SS (with washers) should be used for mounting modules for better theft proofing.
1. Purlin/Rafter (Design is indicative)
Cleat:
2. Leg & Base Plate
Rafter : 60mmX60mmX3.2mm
Purlin : 90mmX45mmX15mmX2.6mm
Vertical Post : 60mmX60mmX3.2mm
Base Plate : 200mmX200mmX8mm
Top Plate : 176mmX176mmX8mm
The CC foundation shall have to be designed on the basis of the weight of the structure with module and minimum wind speed of the site, i.e. 150 Km/hour. Normally, each MMS should be with minimum four legs grouted on pedestals of proper size. However, for sheds CC work will not be required.Thestructure shall be grouted with fasteners with chemical sealing to withstand the required wind velocity. Angle of inclination shall be between 150 to 300,however,maybe changed as per site requirement.
Sufficient numbers of vertical post shall be provided so that the structure may not bent.
As SPV array produce direct current electricity, it is necessary to convert this direct current into alternating current and adjust the voltage levels to match the grid voltage. Conversion shall be achieved using an electronic Inverter and the associated control and protection devices. All these components of the system are termed the “Inverter”. In addition, the inverter shall also house MPPT (Maximum Power Point Tracker), an interface between Solar PV array & the Inverter, to the power conditioning unit/inverter should also be DG set interactive, if necessary. Inverter output should be compatible with the grid frequency. Typical technical features of the inverter shall be as follows:
SpecificationsofInverter |
|
Parameters |
DetailedSpecifications |
Switching devices |
IGBT |
Capacity |
The Rated Capacity of the Inverter shall not be less than the solar PV array capacity. |
Control |
Microprocessor /DSP |
Nominal Voltage |
230V/415V as the case may be |
Voltage range |
Single Phase: Shall work from 180 Volts to 270 Volts; Three Phase: Shall work from 180 Volts to 270 Volts per phase |
Operating frequency/ range |
50 Hz(47to52 Hz) |
Grid Frequency Synchronization range |
± 3 Hz or more (shall also compatible for Synchronization with DG Set) |
Waveform |
SineWave |
Harmonics |
ACsidetotalharmoniccurrentdistortion<5% |
Ripple |
DCvoltageripplecontentshallnotbe morethan1%. |
Efficiency |
|
Losses |
Maximumlossesinsleepmode:2Wper5kW Maximumlossesinstand-bymode:10W |
Casing protection levels |
Degreeofprotection: MinimumIP-21 and 22for indoor useandIP65 certification for outdooruse |
Temperature |
Shouldwithstandfrom-10to+50 degCelsius |
Humidity |
Shouldwithstandupto95%(relativehumidity) |
Operation |
Completely automatic including wake up, synchronization (phase-locking)andshutdown |
MPPT |
Maximum power point tracker shall be integrated in the inverter to maximize energy drawn from the array. MPPT range must be suitable to individual array voltages in power packs |
Protections
|
Mains Under / Over Voltage |
Overcurrent |
|
Over/Undergridfrequency |
|
Over temperature |
|
Short circuit |
|
Lightening |
|
Surge voltage induced at output due to external source |
|
Anti Islanding (for grid synch. mode)
|
|
Battery Under Voltage and Over Voltage
|
|
System Monitoring Parameters |
Inverter/PCU voltage & current Mains Voltage, Current & Frequency PV Voltage, Amps & KWH System Mimic & Faults |
Recommended LCDDisplayonFrontPanel |
Accurate displays on the front panel: |
DC input voltage |
|
DC current |
|
AC Voltage ( all 3 phases, in case of 3 phase) |
|
AC current ( all 3 phases in case of 3 phase) |
|
Ambient temperature |
|
Instantaneous & cumulative output power |
|
Daily DC energy produced |
|
Battery Voltage (in case of Hybrid PCU) |
|
Communication interface |
RS 485 / RS 232 PCU shall also house MPPT (Maximum Power Point Tracker), an interface between Solar PV array to the power conditioning unit/inverter should also be DG set interactive. |
Power Factor |
> 0.9 |
THD |
<3% |
Test Certificates |
The inverter should be tested from the MNRE approved test centres / NABL /BIS /IEC accredited/authorised testing- calibration laboratories. In case of imported power conditioning units, these should be approved by international test houses. |
The battery should be Lithium Ferro Phosphate (LiFePO4) having given capacity. The other feature of battery should be:-
S.No. |
Description |
Specification |
1. |
Battery Type |
LiFePO4 |
2. |
Working temperature range ( both for charging & discharging) |
20-60 Deg. C |
3. |
Minimum capacity of individual Cells |
3.2V 40Ah |
4. |
Type of Cell |
Prismatic or Cylindrical |
The Cell and Battery should be got tested as per IEC 62133-2012 or BIS specifications with MNRE/ NABL/IEC accredited test centre/ laboratory as per IEC/ BIS standard IEC 62133, IEC 61960 & UL1642: Safety of LiFePo4 battery
The Lithium Ferro Phosphate battery needs a very good “Battery Management System (BMS)” to ensure the proper charging and discharging of each cell of battery with proper protection of battery when temperature is reaching beyond battery permissible limits.
S.No. |
Parameters |
Requirements |
Reference |
1. |
Overall Conditions of Service |
Reference to regulations |
Conditions for Supply of Electricity of Distribution Licensees |
2. |
OverallGrid Standards |
Reference to regulations |
Central Electricity Authority (Grid Standards) Regulations 2010 |
3. |
Equipment |
Applicable industry standards |
IEC standards/IS |
4. |
Safetyand Supply |
Reference to regulations, Chapter III (General Safety Requirements) |
Central Electricity Authority (Measures of Safety and Electricity Supply) Regulations, 2010 and subsequent amendments |
5. |
Meters |
Reference to regulations and additional conditions issued by the Commission. |
Central Electricity Authority (Installation & Operation of Meters) regulations 2006 and subsequent amendments |
6. |
Harmonic Current |
Harmonic current injections from a generating station shall not exceed the limits specified in IEEE 519 |
IEEE 519 relevant CEA (Technical Standards for Connectivity of the distributed generation resource) regulations 2013 and subsequent amendments |
7. |
Synchronization |
Photovoltaic system must be equipped with a grid frequency synchronization device, if the system is using synchronizer inherently built into the inverter than no separate synchronizer is required. |
Relevant CEA (Technical Standards for Connectivity of the distributed generation resources) regulations 2013 and subsequent amendments. |
8. |
Voltage |
The voltage-operating window should minimize nuisance tripping and should be under operating range of 80% to 110% of the nominal connected voltage. beyond a clearing time of 2 seconds, the Photovoltaic system must isolate itself from the grid. |
|
9. |
Flicker |
Operation of Photovoltaic system shouldn’t cause voltage flicker in excess of the limits stated in IEC 61000 or other equivalent Indian standards, if any |
Relevant CEA regulations 2013 and subsequent if any, (Technical Standards for Connectivity of the distributed generation resource) |
10. |
Frequency |
When the Distribution system frequency deviates outside the specified conditions (52 Hz on upper side and 47 Hz on lower side up to 0.2 sec), the Photovoltaic system shouldn’t energize the grid and should shift to island mode. |
|
11. |
DCInjection |
Photovoltaic system should not inject DC power more than 0.5% of full rated output at the interconnection point. or 1% of rated inverter output current into distribution system under any operating conditions |
|
12. |
PowerFactor |
While the output of the inverter is greater than 50%, a lagging power factor of greater than 0.9 shall be maintained |
|
13. |
Islandingand Disconnection |
The Photovoltaic system in the event of voltage or frequency variations must island/ disconnect itself within IEC standard on stipulated period |
|
14. |
Overloadand Overheat |
The invertershouldhavethefacilityto automaticallyswitchoff in case of overload or overheating and should restart when normal conditionsarerestored |
|
15 |
Cable |
For interconnecting Modules, Connecting modules and junction Boxes and junction boxes to inverter, DC copper cable of proper sizes shall be used. To connect inverter with AC panel aluminium cable of proper size shall be used. All the internal cables to be used in the systems shall be included in the cost while 100mtr. AC aluminium cable of proper size to be used to connect inverter/PCU to AC panel shall be included in the cost of the system. |
Relevant CEA regulations 2013 and subsequent if any, (Technical Standards for Connectivity of the distributed generation resource) |
The junction boxes shall be made up of FRP (Hensel or equivalent make)/PP/ABS with dust, water and vermin proof. It should be provided with proper locking arrangements.
Series / Array Junction Box (SJB/AJB) (whichever is required): All the arrays of the modules shall be connected to DCCB. AJB shall have terminals of bus-bar arrangement of appropriate size Junction boxes shall have suitable cable entry with suitable glanding arrangement for both input and output cables. Suitable markings on the bus bars shall have to be provided to identify the bus bars etc. Suitable ferrules shall also have to be provided to identify interconnections. Every AJB should have suitable arrangement Reverse Blocking diode of suitable rating. Suitable SPD, suitable Isolation switches to isolate the DC input to Inverter has to be installed in AJB for protection purpose. Thus AJB should have DC isolator for disconnecting the arrays from inverter input. If in any case diodes, HRC Fuses, SPDs and isolators are installed in the string inverters, then there is need to install these again in AJB. If some of these safety gadgets are not installed in String Inverter it should be installed in AJB. Cable interconnection arrangement shall be within conduit pipe on saddles installed properly. Cable connection should be done in such a manner that fault findings if any, can be identified easily. The cables should be connected in such a manner that clamp meter can be comfortably inserted around the individual cables to measure the data like current, voltage etc. AJB should also be marked as A1, A2, & so on.
However, if the inverter/PCU is equipped with Junction Box, the cables may be connected directly to the ports provided in the inverter/PCU and no separate Junction Box is required.
Both AC & DC lines have suitable MCB/MCCB, Contractors, SPD, HRC Fuse etc to allow safe start up and shut down before & after string inverter installed in the system. String inverters should have protections for overload, surge current, high Temperature, over/ under voltage and over/ under frequency & reverse polarity. The complete operation process & safety instructions should printed on the sticker & suitably pasted on the near inverters.
Inverter should have safety measures to protect inverter from reverse short circuit current due to lightening or line faults of distribution network.
Inverter should be suitably placed in covered area on a suitable platform or wall mounted or concrete platform (on rubber mat) with complete safety measure as per norms.
This shall consist of box shall consists of grid interphase panel of good quality FRP/ suitable powder coated metal casing. One Electronic Energy Meter (0.2S Class), ISI make, Single/Three Phase duly tested by DISCOMs (Meter testing Division) with appropriate CT (if required), of good quality shall have to be installed at suitable placed to measure the power generated from SPV Power Plant, as per HERC Net Metering Regulations. Proper rating MCCB & HRC fuse and AC SPDs shall be installed to protect feeders from the short circuit current and surges as per the requirement of the site. Operation AC Isolator Switch of Grid Connectivity should be such that it can be switched ON or OFF without opening the ACCB.
All cables should be of copper as per IS and should be of 650V/1.1 KV grade as per requirement. All connections should be properly made through suitable lug/terminal crimped with use of suitable proper cable glands. The size of cables/wires should be designed considering the line loses, maximum load on line, keeping voltage drop within permissible limit and other related factors. The cable/wire should be of ISI/ISO mark for overhead distribution. For normal configuration the minimum suggested sizes of cables are:
Module to module/AJB |
: 4 sq mm (single core) DC Cable |
AJBs to MJB/DCCB/Inverter/PCU |
|
Inverter to ACCB/Distribution board |
AC Cable as per design & rating |
The size & rating of the cables may vary depending on the design & capacity of SPV Power Plant.
All the cables should be laid in appropriate GI cable tray as per the requirement of the site, No cable should be laid directly on ground or wall cable tray should be laid such that there is gap of at least two inches above ground/roof/wall.
The bidder has to display a board at the project site mentioning the following:
It should be provided to isolate the system from Grid which should be outside of ACCB.
Variation in supply voltage |
+/- 10 % |
Variation in supply frequency |
+/- 3 Hz |
Regarding the generated power consumption, in case of string inverter, priority need to given for internal consumption first and thereafter any excess power can be exported to grid.
The system should be provided with all necessary protections like earthing, Lightning, and grid anti- islanding as follows:
The SPV Power Plant shall be provided with lightening and over voltage protection. The principal aim in this protection is to reduce the over voltage to a tolerable value before it reaches the PV or other sub-systems components. The source of over voltage can be lightening or any other atmospheric disturbance. The Lighting Arrestor (LA) is to be made of 1¼" diameter (minimum) and 12 feet long GI spike on the basis of the necessary meteorological data of the location of the projects. Necessary foundation for holding the LA is to be arranged keeping in view the wind speed of the site and flexibility in maintenance in future. Each LA shall have to be earthed through suitable size earth bus with earth pits. The earthing pit shall have to be made as per IS 3043. LA shall be installed to protect the array field, all machines and control panels installed in the control rooms. Number of LA shall vary with the capacity of SPV Power Plant & location. Number of LA should be in such a manner that total layout of solar modules should the effective coverage of LA’s.
For systems up to 10 kWp the lightening arrester shall of conventional type and for above 10 kWp systems it should be of Early Streamer Emission (ESE) type.
Each array structure of the PV yard shall be grounded properly. In each array every module should be connected to each other with copper wires, lug teethed washers addition the lightening arrestor/masts shall also be provided inside the array field. Provision shall be kept for shorting and grounding of the PV array at the time of maintenance work. All metal casing/shielding of the plant shall be thoroughly grounded in accordance with Indian Electricity Act/IE rules as amended up to date. The earthing pit shall be made as per IS: 3043. All the array structures and equipments/control systems shall be compulsorily connected to the earth, separately. Number of earthling shall vary with the capacity of SPV Power Plant & location. G.I. /Copper strips should be used for earthling instead of G.I. wires. Adedoteyld&isidnel.NrfAlywiheiyfPVPwrt &. Earth resistance shall not be more than 5 ohms.
Internal surge protection shall consist of three MOV type surge-arrestors connected +ve and –ve terminals to earth (via Y arrangement)
Powered islands present a risk to workers who may expect the area to be unpowered, and they may also damage grid-tied equipment. The RooftopPV system shall be equipped with islanding protection. In addition to disconnection from the grid (due to islanding protection) disconnection due to under and over voltage conditions shall also be provided.
The user have to take approval/NOC from the Concerned DISCOM for the connectivity, technical feasibility, and synchronization of SPV plant with distribution network and submit the same to HAREDA before commissioning of SPV plant, however the supplier have to extend all technical help to the user for preparing the documents required for getting the above clearance from DISCOMs.
Reverse power relay shall be provided by bidder (if necessary), as per the local DISCOM requirement.
The maximum capacity for interconnection with the grid at a specific voltage level shall be as specified in the Distribution Code/Supply Code and amended from time to time. Following criteria have been suggested for selection of voltage level in the distribution system for ready reference of the solar suppliers.
Plant Capacity |
Connecting voltage |
Up to 10 kWp |
240V-single phase or 415V-three phase as per requirement of electric connection of the consumer |
Above 10kWp and up to 100 kWp |
415V – three phase |
Above 100kWp |
415V – three phase or as per site requirement based on the availability of grid level and as per DISCOM rules |
Utilities may have voltage levels other than above, DISCOMS may be consulted before finalization of the voltage level and system shall be designed accordingly.
The bidder shall take entire responsibility for electrical safety of the installation(s) including connectivity with the grid and follow all the safety rules & regulations applicable as per Electricity Act, 2003 and CEA guidelines etc. All work shall be carried out in accordance with the latest edition of the Indian Electricity Act and rules formed there under and as amended from time to time.
The quality of equipment supplied shall be controlled to meet the guidelines for engineering design included in the standards and codes listed in the relevant ISI and other standards, such as :