Download PV System Commissioning – Operating Current Test

PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ PV System Commissioning – Operating Current Test 1 Purpose
The scope of this work instruction is to set out the procedure for the safe testing of PV String IV curves in photovoltaic (PV) arrays operating at voltages over 120V DC (ELV). This procedure is specific to the SMA Tripower PV inverter. Performing the IV curve test on selected or random PV strings is a suggested commissioning test for PV arrays as set out AS/NZS 5033:2014 ‐ Appendix D Commissioning and the CEC Install and Supervise Guidelines. The purpose of testing the IV curve of PV strings is to verify that the PV modules are performing according to specification. Any circuits which do not pass the test criteria are to be rectified and retested until they pass the test criteria. The procedure for the combined PV string test is based on the Solmetric PV Analyser PVA‐1000S operating instructions. 2 Definition
Terms, abbreviations and acronyms A Amps DC Direct Current ELV Extra‐low voltage (< 50V AC or <120V ripple free DC) Irradiance Radiant solar power incident upon unit area of surface, measured in watts per square meter ISC The short circuit current of a PV module or PV string at STC, as specified by the manufacturer ISC ARRAY The short circuit current of the PV array at STC LV Low Voltage (exceeding ELV but not exceeding 1000V AC or 1500 VDC) PV Photovoltaic PV Array Definition Assembly of electrically interconnected PV modules, PV strings or PV sub‐
arrays comprising all components up to the DC input terminals of the inverter or other power conversion equipment ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 1 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ PV Array maximum voltage The VOC ARRAY value corrected for the lowest expected operating temperature PV Cell The most elementary device that exhibits the photovoltaic effect (i.e. the direct non‐thermal conversion of radiant energy into electrical energy) PV Module The smallest complete environmentally protected assembly of interconnect PV cells PV String A circuit of one or more series connected PV modules DC Combiner Box A junction box where PV strings are connected which also contains overcurrent protection devices or switch‐disconnectors or both STC Standard Test Conditions – a set of reference conditions used for the testing and rating of PV modules (PV cell temp 25°C, 1000W/m2 irradiance in plane of PV module, atmospheric air mass 1.5) V Volts VMP Maximum power voltage of a PV module at STC, as specified by the manufacturer VOC MOD The open circuit voltage of a PV module at STC, as specified by the manufacturer VOC ARRAY The open circuit voltage of the PV array at STC 3 Responsibilities
Role Responsibility Tester Conducting the tests set out in this document Test Engineer Reviewing and assessing results, ensuring documentation is completed ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 2 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ 4 Activities
EquipmentandMaterialsRequired
1.
Insulated tools (1000V DC rating) 2.
Seaward PV150 solar installation tester 3.
Seaward current clamp for PV150 4.
Adapter cables and connectors for use with Sunclix and MC4 connectors 5.
Seaward Solar Survey 200R with ambient / module temperature probes 6.
Laptop with Seaward Solar Datalogger software installed SafetyNotes
All personnel involved in conducting and witnessing tests shall be inducted and briefed on all safety issues and potential hazards involved in conducting tests prior to commencement. The test is to be conducted by a suitably qualified electrical worker licensed to work on LV systems. WARNING: PV Array DC circuits are live during daylight hours and cannot be isolated before performing this test. Pre‐testConditions
Before undertaking this test procedure, please ensure that the following Work Instructions have been satisfactorily completed: 1.
CPS‐WI 09/XX – PV System Commissioning – PV Wiring Inspection 2.
CPS‐WI 09/XX – PV System Commissioning – PV Earthing Inspection 3.
CPS‐WI 09/XX – PV System Commissioning – DC Circuit Protection Inspection 4.
CPS‐WI 09/XX – PV System Commissioning – AC Circuit Protection Inspection 5.
CPS‐WI 09/XX – PV System Commissioning – PV Inverter Inspection 6.
CPS‐WI 09/XX – PV System Commissioning – PV Array Earthing Tests 7.
CPS‐WI‐090 – PV System Commissioning – Combined PV Array Tests 8.
CPS‐WI‐091 – PV System Commissioning – IV Cure Test 9.
CPS‐WI‐09X– PV System Commissioning – Inverter Commissioning ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 3 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ Pre‐test conditions: 
PV System electrical components and inverters have been commissioning and the system is able to be connected to the grid for testing purposes 
All PV string fuses are installed 
All PV inverters are commissioned 
Test equipment is fully charged, in satisfactory condition and calibrated (if applicable) 
Test equipment irradiance sensor is clean 
Latest issue design documentation is available showing PV array cabling schedule and electrical schematics for each test area TestNotes
Test conditions: 
All tests to be conducted with the site irradiance level exceeding 600W/m2 on an unshaded PV array during the four hour spread over solar noon 
The PV inverter associated with the PV strings to be tested is switched on as per the inverter manufacturer start up procedures and is operating correctly with no faults 
Carefully study the PV150 and Survey 200R safety and operating instructions prior to the test SAFETY NOTE: Keep all staff away from metallic parts of the PV array or any surface of any PV module during testing Location of test: 
Testing point is the PV string cabling on the input of the PV string fuses which is located at the respective DC Combined Box TestProcedure
1.
Check that the PV150 tester is paired with the Solar Survey 200R. Pairing the two devices will allow for the automatic recording of the irradiation level, module temperature and ambient temperature at the time of the test. a. Turn on the PV150 and Solar Survey 200R b. Turn the Solar Survey 200R transmit mode on by pressing and holding the temperature key, and then momentarily pressing the OK key c. If the units are paired, the PV150 will show the irradiation value at the top of the screen d. Refer to page 16 of the PV150 operating instructions for details on how to pair the units and to troubleshoot the connection ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 4 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ 2.
Set the date and time on the Solar Survey 200R as shown below or refer to Quick Start guide. 3.
Install the Survey 200R on the PV array frame close to the test location at the same angle as the modules. Make sure the Survey 200R is not shaded. 4.
Attach the module temperature sensor lead to the back of a nearby PV module. 5.
Check that the Survey 200R is reading the irradiation, module and ambient temperatures values. 6.
Disconnect all cables from the PV150 PV test inputs 8 & 9 as shown in figure 2 below ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 5 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ 7.
Connect the current clamp to the red – black 4mm probe inputs. 8.
Move the current clamp switch to the 40A position. 9.
Press the zero button on the current clamp. 10.
Record the DC Combiner Box ID and time of test 11.
Open the DC Combiner Box and remove the escutcheon cover Place the clamp around the positive PV string cable assigned to PV string number 1 on input A of the PV inverter. Refer to the DC interconnection diagram for specific details of the PV array wiring. 12.
Press the Viso button until the clamp icon (figure 3, icon b) appears on the LCD ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 6 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ 13.
The measured current is shown on the LCD next to the clamp icon. 14.
Press Memory Store button (disc symbol) to store all measured values on the display. The User Memory display at the bottom of the display screen indicates the memory location of the results stored or recalled on the LCD. 15.
Remove the clamp meter from the PV string cable and repeat the test sequence for PV string 2 and for the remaining strings in the DC Combiner Box. IMPORTANT: Make sure the PV string testing is done in a sequential order that matches the PV string wiring shown in the DC interconnection diagram e.g. PV string 1 – 2 – 3 ‐4 – 5. 16.
Once all the PV strings have been tested, remove the test clamp and re‐install the escutcheon cover. 17.
Assess the results and confirm that all PV strings tested meet the Pass criteria. 18.
Repeat the test for all PV strings at each DC Combiner Box location. 19.
Should any circuits fail the Pass criteria, test the circuit again to confirm the results and then rectify any PV wiring or PV module faults before retesting the circuit. ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 7 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ TestRecordForm
All test results shall be recorded in the following document/s: 
E.17 – Operating Current Test Record Form PostTestConditions

Test Record sheet fully completed including any rectification notes and signed off by tester 
Reinstate any disconnected equipment 
All mark ups or notes applied to design documentation and drawings for inclusion in As built documentation ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 8 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ OperatingCurrentTestPass/FailCriteria
The measured operating current values should be compared with the expected value (IMP EXPECTED) to determine whether the PV circuit is operating correctly. The expected value is calculated from the IMP MOD values taken from the PV module datasheet which are adjusted according to the irradiance measured at the time of testing. The measured operating current of each PV circuit should be within +/‐ 5% of the expected value. If there is a larger difference, the wiring should be checked and any faults rectified before retesting the circuit. Potential causes of unexpected readings: 
The inverter maximum power point tracking (MPPT) operation can influence the PV string operating current readings as the inverter is continually adjusting the PV array voltage and current to extract the maximum power from the PV array. Any form of power reduction or control by the inverter or the PV system control system can also affect the operating current values. Low measurements could indicate the presence of circulating earth fault currents in the array due to multiple earth faults or shading Defective surge protection can also be a cause of lower than expected readings High readings are usually the result of wiring errors (too many PV strings in parallel) or higher than normal irradiance levels 
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As the current output of a PV module is directly proportional to the level of irradiance, it is possible to calculate the expected operating current under varying irradiance conditions by the using the following formula: Formula for calculating the expected value: IMP EXPECTED = n x IMP MOD x (GI / 1000) x 0.95 Formula values: IMP MOD = maximum power current of the PV module at STC as specified by the manufacturer n = number of parallel connected PV strings in the segment under test GI = plane of array irradiance (W/m2) 0.95 = factor to account for mismatch ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 9 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ Note that the operating current of crystalline silicon based PV modules are relatively insensitive to variations in ambient temperate over a wide operating range (‐10°C to 40°C), increasing only slightly with temperature. OperatingCurrentWorkedExample
Formula: IMP EXPECTED = n x IMP MOD x (GI / 1000) x 0.95 Typical PV module datasheet ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 10 PV SYSTEM COMMISSIONING – OPERATING CURRENT TEST ____________________________________________________________________________________ Worked example formula values are based on the Jinko JKM315‐PP 315W PV module data as per above specifications, using the following assumptions: IMP MOD = 8.48A n = 1 (single PV string) GI = 800W/m2 IMP SEGMENT = IMP MOD x n = 8.48 x 1 = 8.48A IMP EXPECTED = n x IMP MOD x (GI / 1000) x 0.95 = 1 x 8.48 x (800 / 1000) x 0.95 = 8.48 x 0.8 x 0.95 = 6.44A 5 References
Document Ref. Title & Description AS/NZS 5033:2014 Installation and safety requirements for photovoltaic (PV) arrays AS/NZS 3000:2007 Australian Wiring Code ‐ Clean Energy Council Grid‐Connected Solar PV Systems – Install and Supervise Guidelines for Accredited Installers (Issue 10 Sept 2015) 6 RelatedDocuments
Ref. CPS‐FM‐264 Title & Description E.17 – Operating Current Test Record Form ______________________________________________________________________________________ Doc ID CPS‐WI‐090 Hardcopy Uncontrolled Rev 0 Date 01/02/2016 DMS ID: 5709‐1 Page | 11