ASTM E2047-2010 Standard Test Method for Wet Insulation Integrity Testing of Photovoltaic Arrays《光电阵列湿绝缘完整性测试的标准试验方法》.pdf

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1、Designation: E2047 10Standard Test Method forWet Insulation Integrity Testing of Photovoltaic Arrays1This standard is issued under the fixed designation E2047; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi

2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 strings),

3、 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 isbeyon

4、d the scope of this test method.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of

5、 this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E772 Terminology Relating to Solar Energy ConversionE1328 Terminology Relating to Photovoltaic Solar EnergyConversio

6、nE1462 Test Methods for Insulation Integrity and GroundPath Continuity of Photovoltaic Modules3. Terminology3.1 DefinitionsDefinitions of terms used in this testmethod may be found in Terminologies E772 and E1328.3.2 Definitions of Terms Specific to This Standard:3.2.1 insulation resistance, nthe el

7、ectrical resistance of aphotovoltaic arrays insulation, measured between the photo-voltaic circuit and exposed, 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 circu

8、it thatconducts the photovoltaic generated power.4. Summary of Test Method4.1 A procedure is provided for testing 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

9、 offers two ways to connect the arrayduring the test, either open-circuited or short-circuited. Eachoption 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 c

10、arrying parts and surfaces of thearray, while monitoring the current or resistance, to findlocalized regions 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 mod

11、ule or system intended toprovide safe conversion of the suns radiant energy into usefulelectricity must take 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 electrochemica

12、l corrosion, and insulation flaws canresult in increased corrosion and reliability problems. This testmethod 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 th

13、e PV-generated electrical potential be accessible, withthe obvious exception of the output leads. The isolation 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 pr

14、otection from electricalhazards. Its primary use is to find insulation flaws that could bedangerous to persons who may come into contact with the1This test method is under the jurisdiction of ASTM Committee E44 on Solar,Geothermal and Other Alternative Energy Sources , and is the direct responsibili

15、tyof Subcommittee E44.09 on Photovoltaic Electric Power Conversion.Current edition approved June 1, 2010. Published July 2010. Originally approvedin 1999. Last previous edition approved in 2005 as E204705. DOI: 10.1520/E2047-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or

16、contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, 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.array. Corrective

17、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 can betested in smaller segments. The size of the array se

18、gment to betested (called “circuit under test” in this test method) is usuallyselected at a convenient break point and sized such that theexpected resistance or current reading is within the middlethird of the meters range.5.4 Insulation leakage resistance and insulation leakagecurrent leakage are s

19、trong functions of array dimensions,ambient relative humidity, absorbed water vapor, and otherfactors. For this reason, it is the 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, act

20、ualresults are often pass-fail in that when a flaw is found, theleakage current changes from almost nothing to the full scalevalue 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 dev

21、ice with leads toconnect the positive and negative legs of the circuit under test.For larger systems, where the shorting device 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 accoun

22、t for the PV-generatedvoltage, and the procedure for making such corrections isbeyond the scope of this test method. The short-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 sm

23、all. The short-circuited option minimizes the chance of exposing arraycomponents to voltage levels above those for which they arerated.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

24、 of providing a nominal test voltage of500 V, as specified in Test Method E1462. A common term forthis apparatus is insulation 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 p

25、rovidea nominal test voltage of 500 V.6.2 Wetting SolutionA solution of tap water and a wettingagent3, with a surface tension 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

26、of the wetting solution mustbe sufficient to reach all of the test segment surfaces andmaintain wetted surfaces, front and back.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

27、 not necessary to use a forceful streambecause the wetting agent helps to penetrate small crevices.6.4 Array ShorterA dc-rated 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-circ

28、uited option is used.6.4.1 The array shorter must be rated for the maximumopen-circuit voltage of the circuit under test plus 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 continu

29、ous maximum short-circuit current of thecircuit under test.7. Hazards7.1 Touching the modules or array during the testing may 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-ci

30、rcuiting the array at night, when the current and voltageare minimized.7.3 The megohmmeter or insulation tester should be turnedoff 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 prote

31、ction (electricalgloves with keepers, safety glasses, etc.) should be worn andcare should be taken to keep the wetting solution 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

32、 record the site meteorological conditions(irradiance, ambient temperature, wind speed) or arrange forthe data to be measured 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

33、 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 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

34、 PV components are within manufacturers requirements.Refer to the manufacturers recommendations concerning shorting ofmodules 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

35、 opening source circuit switches, taking out removablelinks, or disconnecting bolted connections or connectors. Allpoles of the circuit to be tested (positive, negative and neutral)3An acceptable wetting solution that has been found to produce adequatesheeting action is 1 part Liqui-nox detergent in

36、 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., Northbrook, IL 60062, as part number SA0820B.E2047 102must be isolated. D

37、isconnect 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 under test)may be limited to the area that can be kept wet at any given tim

38、e. In certainsituations for example, attempting to locate specific fault locations, it maybe desirable to apply the test voltage first, and then apply the wettingsolution.8.5 Verify that MOVs or similar voltage surge protectiondevices are disconnected and are not part of the isolatedcircuits. If suc

39、h devices are connected between the active arraycircuit and ground, they must be disconnected as they mayinvalidate the tests or 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 test

40、er or megohmmeter is turned off before anyelectrical connections are made.8.7 There are two acceptable options for performing thistest: 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-Ci

41、rcuitedShort the output leads of the arraytogether, using the array shorter (unless already done, see 7.2).Connect the shorted 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

42、the negative terminal of the circuit undertest. The positive terminal of the circuit under test is leftunconnected and protected 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 lea

43、d of the megohmmeter tothe positive terminal of the circuit under test, leave the circuits negativeterminal unconnected, and connect 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

44、 array,or subarray string, being tested.8.8.1 If there is no common array ground, the proceduremay need to be repeated to measure the insulation resistancebetween the circuit under test and each separate and uncon-nected electrically conductive component.8.8.2 Any connections to electrically conduct

45、ive compo-nents must be made to uninsulated points for the test results tobe valid. For example, an anodized aluminum frame would 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 capacitiv

46、e chargingeffect has subsided and the reading has established (perhaps 30s or more). For insulation testers that indicate leakage 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

47、arcing.NOTE 5The capacitance of the circuit under test may be large enoughto cause large currents to flow while the insulation 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. Theo

48、perator must be aware of such possibilities and allow time for theconditions to stabilize.8.10 Thoroughly wet the back (away from 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

49、megohmmeter, or similar items that arenot under test. Also, try to avoid wetting adjacent modules andpanels in segments not yet 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