ASTM E2047-2005 Standard Test Method for Wet Insulation Integrity Testing of Photovoltaic Arrays《光电阵列湿绝缘完整性试验的标准试验方法》.pdf

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1、Designation: E 2047 05Standard Test Method forWet Insulation Integrity Testing of Photovoltaic Arrays1This standard is issued under the fixed designation E 2047; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi

2、sion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure to determine theinsulation resistance of a photovoltaic (PV) array (or itscomponent string

3、s), that is, the electrical resistance betweenthe arrays internal electrical components and is exposed,electrically conductive, non-current carrying parts and surfacesof the array.1.2 This test method does not establish pass or fail levels.The determination of acceptable or unacceptable results isbe

4、yond the scope of this test method.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limit

5、ations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 772 Terminology Relating to Solar Energy ConversionE 1328 Terminology Relating to Photovoltaic Solar EnergyConversionE 1462 Standard Test Methods for Insulation Integrity andGround Path Continuity of Photovoltaic Modules3. Terminology3

6、.1 DefinitionsDefinitions of terms used in this testmethod may be found in Terminologies E 772 and E 1328.3.2 Definitions of Terms Specific to This Standard:3.2.1 insulation resistance, nthe electrical resistance of aphotovoltaic arrays insulation, measured between the photo-voltaic circuit and expo

7、sed, electrically conductive non-current-carrying parts and surfaces of the array.3.2.2 metal oxide varistor MOV, na surge protectiondevice.3.2.3 photovoltaic circuitthe active electrical circuit thatconducts the photovoltaic generated power.4. Summary of Test Method4.1 A procedure is provided for t

8、esting the electrical isola-tion between the arrays internal electrical components and itsexposed, electrically conductive, non-current carrying partsand surfaces of the array.4.2 The procedure offers two ways to connect the arrayduring the test, either open-circuited or short-circuited. Eachoption

9、has advantages and disadvantages (see 5.5).4.3 A wetting solution is applied to the array, then a voltageis applied between the PV circuit and the exposed, electricallyconductive, non-current carrying parts and surfaces of thearray, while monitoring the current or resistance, to findlocalized region

10、s where the insulation resistance is signifi-cantly reduced by the wetting solution. The array is theninspected for evidence of possible arcing.5. Significance and Use5.1 The design of a PV module or system intended toprovide safe conversion of the suns radiant energy into usefulelectricity must tak

11、e into consideration the possibility of hazardshould the user come into contact with the electrical potentialof the array. In addition, the insulation system provides abarrier to electrochemical corrosion, and insulation flaws canresult in increased corrosion and reliability problems. This testmetho

12、d describes a procedure for verifying that the design andconstruction of the array provides adequate electrical isolationthrough normal installation and use.At no location on the arrayshould the PV-generated electrical potential be accessible, withthe obvious exception of the output leads. The isola

13、tion isnecessary to provide for safe and reliable installation, use, andservice of the PV system.5.2 This test method describes a procedure for determiningthe ability of the array to provide protection from electricalhazards. Its primary use is to find insulation flaws that could bedangerous to pers

14、ons who may come into contact with thearray. Corrective action taken to address such flaws is beyondthe scope of this test method.5.3 This procedure may be specified as part of a series ofacceptance tests involving performance measurements anddemonstration of functional requirements. Large arrays ca

15、n betested in smaller segments. The size of the array segment to be1This test method is under the jurisdiction of ASTM Committee E44 on Solar,Geothermal and Other Alternative Energy Sources , and is the direct responsibilityof Subcommittee E44.09 on Photovoltaic Electrical Power Conversion.Current e

16、dition approved April 1, 2005. Published May 2005. Originallyapproved in 1999. Last previous edition approved in 1999 as E 204799.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informat

17、ion, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.tested (called “circuit under test” in this test method) is usuallyselected at a convenient break point and sized su

18、ch that theexpected resistance or current reading is within the middlethird of the meters range.5.4 Insulation leakage resistance and insulation leakagecurrent leakage are strong functions of array dimensions,ambient relative humidity, absorbed water vapor, and otherfactors. For this reason, it is t

19、he responsibility of the user of thistest method to specify the minimum acceptable leakage resis-tance for this test.5.4.1 Even though a numerical quantity is specified, actualresults are often pass-fail in that when a flaw is found, theleakage current changes from almost nothing to the full scaleva

20、lue on the meter.5.5 The user of this test method must specify the optionused for connection to the array during the test. The short-circuited option requires a shorting device with leads toconnect the positive and negative legs of the circuit under test.For larger systems, where the shorting device

21、 may have to berated for high current and voltage levels, the open-circuitedoption may be preferred. The open-circuited option requiresthe user to correct readings to account for the PV-generatedvoltage, and the procedure for making such corrections isbeyond the scope of this test method. The short-

22、circuitedoption may be easier for small systems where the voltage andcurrent levels are low and the distance between the plus andminus leads of the circuit under test are small. The short-circuited option minimizes the chance of exposing arraycomponents to voltage levels above those for which they a

23、rerated.6. Apparatus6.1 Choose one of the following, depending on the optionselected (see 4.2 and 5.5):6.1.1 Variable dc Voltage Power SupplyA dc voltagepower supply capable of providing a nominal test voltage of500 V, as specified in Test Method E 1462. A common term forthis apparatus is insulation

24、 tester.6.1.2 MegohmmeterA high-impedance ohmmeter, orsimilar device, capable of adequately measuring leakage resis-tance in the range of anticipated readings, and that can providea nominal test voltage of 500 V.6.2 Wetting SolutionA solution of tap water and a wettingagent3, with a surface tension

25、of 0.03 N/m or less at 23C.6.3 Spray ApparatusA system for applying the wettingsolution to the array, capable of providing a water pressure of35 kPa.4The force and flow rate of the wetting solution mustbe sufficient to reach all of the test segment surfaces andmaintain wetted surfaces, front and bac

26、k.NOTE 1The spray pressure is only enough to completely wet theexposed surfaces; it is not intended to penetrate enclosed spaces such asthe interiors of junction boxes. It is not necessary to use a forceful streambecause the wetting agent helps to penetrate small crevices.6.4 Array ShorterA dc-rated

27、 switch, circuit beaker orother device capable of interrupting the maximum short circuitcurrent of the circuit under test. The array shorter is onlyrequired if the short-circuited option is used.6.4.1 The array shorter must be rated for the maximumopen-circuit voltage of the circuit under test plus

28、the insulationtester or ohmmeter.6.4.2 The wiring between the array shorter and the positiveand negative terminals of the circuit under test must also berated for the continuous maximum short-circuit current of thecircuit under test.7. Hazards7.1 Touching the modules or array during the testing may

29、behazardous because of the high voltage applied.7.2 Use caution whenever short circuiting any high voltagePV array. It may be advisable to reduce the risk involved byshort-circuiting the array at night, when the current and voltageare minimized.7.3 The megohmmeter or insulation tester should be turn

30、edoff while wetting the array. This may not always be desirable,such as when trying to pinpoint the location of an insulationflaw. In these cases, appropriate personnel protection (electricalgloves with keepers, safety glasses, etc.) should be worn andcare should be taken to keep the wetting solutio

31、n from enteringthe gloves, boots, etc.8. Procedure8.1 Assemble the requisite equipment and personnel at thearray to be tested.8.2 Prepare the wetting solution.8.3 Measure and record the site meteorological conditions(irradiance, ambient temperature, wind speed) or arrange forthe data to be measured

32、by the site data acquisition system.NOTE 2It is recommended that this test not be performed underconditions where the ambient temperature is greater than 40C or the windspeed is greater than 7.5 m/s, since high values of either make it difficultto keep the array wet long enough to make the necessary

33、 measurements.If the short-circuited option is used, it may be necessary to conduct the testat a reduced irradiance to ensure that the currents produced in theshort-circuited PV components are within manufacturers requirements.Refer to the manufacturers recommendations concerning shorting ofmodules

34、and other array components at high irradiance.8.4 Isolate the circuit(s) to be tested prior to the start ofspraying. Depending on the design of the PV system, this mayinvolve opening source circuit switches, taking out removablelinks, or disconnecting bolted connections or connectors. Allpoles of th

35、e circuit to be tested (positive, negative and neutral)must be isolated. Disconnect positive and negative monopolesfrom each other. Ground connections among module frames,panels, array structures and system/earth ground must be left inplace.NOTE 3The size of the array segment to be tested (circuit u

36、nder test)may be limited to the area that can be kept wet at any given time. In certainsituations for example, attempting to locate specific fault locations, it maybe desirable to apply the test voltage first, and then apply the wettingsolution.3An acceptable wetting solution that has been found to

37、produce adequatesheeting action is 1 part Liqui-nox detergent in 500 parts water. Liqui-Nox isavailable from Alconox, Inc., 9T East 40th St., New York, NY 10016, as partnumber C63082.4Molded nylon Rain-Test spray heads are available from Underwriters Labo-ratories, Inc., 333 Pfingsten Rd., Northbroo

38、k, IL 60062, as part number SA0820B.E20470528.5 Verify that MOVs or similar voltage surge protectiondevices are disconnected and are not part of the isolatedcircuits. If such devices are connected between the active arraycircuit and ground, they must be disconnected as they mayinvalidate the tests o

39、r be damaged by the test voltage.8.6 Set the insulation tester or megohmmeter on an appro-priate scale for the size of the circuit under test. Ensure that theinsulation tester or megohmmeter is turned off before anyelectrical connections are made.8.7 There are two acceptable options for performing t

40、histest: with the output leads of the circuit under test eithershort-circuited or open-circuited. Specify the option accordingto the criteria described in 4.2.8.7.1 Short-CircuitedShort the output leads of the arraytogether, using the array shorter (unless already done, see 7.2).Connect the shorted

41、output terminals of the string(s) to thehigh-potential (positive) terminal of the insulation tester.8.7.2 Open-CircuitedConnect the positive lead of theinsulation tester to the negative terminal of the circuit undertest. The positive terminal of the circuit under test is leftunconnected and protecte

42、d so that it will not become wet andinterfere with the test.NOTE 4Depending on the circuit under test, it is acceptable and maybe more convenient to connect the negative lead of the megohmmeter tothe positive terminal of the circuit under test, leave the circuits negativeterminal unconnected, and co

43、nnect the positive lead of the megohmmeterto earth ground.8.8 Connect the grounded (negative) terminal of the insula-tion tester or megohmmeter to the grounding point of the array,or subarray string, being tested.8.8.1 If there is no common array ground, the proceduremay need to be repeated to measu

44、re the insulation resistancebetween the circuit under test and each separate and uncon-nected electrically conductive component.8.8.2 Any connections to electrically conductive compo-nents must be made to uninsulated points for the test results tobe valid. For example, an anodized aluminum frame wou

45、ld notqualify unless the anodization was removed at the test point.8.9 Apply the test voltage. Measure and record the dryinsulation resistance in megohms after the capacitive chargingeffect has subsided and the reading has established (perhaps 30s or more). For insulation testers that indicate leaka

46、ge current,divide the voltage applied by the tester, in volts, by the testerreading, in microamperes. Also note any instability in thereading which may indicate shorting or arcing.NOTE 5The capacitance of the circuit under test may be large enoughto cause large currents to flow while the insulation

47、capacitance is charging.When using the open-circuited option, the wetting of the circuit under testcan cause changes in system voltage as the array temperature changes. Theoperator must be aware of such possibilities and allow time for theconditions to stabilize.8.10 Thoroughly wet the back (away fr

48、om the sun) side ofthe circuit under test. Take care not to get water into the interiorof the interface junction boxes, the power-conditioning unit,the insulation tester or megohmmeter, or similar items that arenot under test. Also, try to avoid wetting adjacent modules andpanels in segments not yet

49、 tested, as this would interfere withsubsequent dry resistance measurements (see 8.9).8.11 While the entire test segment is wet, measure andrecord the wet leakage current or resistance reading after thecapacitive charging effect has subsided (perhaps 30 s or more).Also, note any instability in the reading and the areas beingsprayed at that time to provide an indication of the location ofdefects. Especially note any large changes in resistance, whichindicate regions where the insulation integrity is compromised.NOTE 6Defects can be located more precisely by