ASTM E2047-99
(Test Method)Standard Test Method for Wet Insulation Integrity Testing of Photovoltaic Arrays
Standard Test Method for Wet Insulation Integrity Testing of Photovoltaic Arrays
SCOPE
1.1 This test method covers a procedure to determine the insulation resistance of a photovoltaic (PV) array (or its component strings), that is, the electrical resistance between the array's internal electrical components and is exposed, electrically conductive, non-current carrying parts and surfaces of the array.
1.2 This test method does not establish pass or fail levels. The determination of acceptable or unacceptable results is beyond the scope of this test method.
1.3 There is no similar or equivalent ISO standard.
1.4 Units-The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.
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Designation:E2047–99
Test Method for
Wet Insulation Integrity Testing of Photovoltaic Arrays
This standard is issued under the fixed designation E 2047; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope voltaic circuit and exposed, electrically conductive non-
current-carrying parts and surfaces of the array.
1.1 This test method covers a procedure to determine the
3.2.2 metal oxide varistor MOV, n—a surge protection
insulation resistance of a photovoltaic (PV) array (or its
device.
component strings), that is, the electrical resistance between
3.2.3 photovoltaic circuit—the active electrical circuit that
the array’s internal electrical components and is exposed,
conducts the photovoltaic generated power.
electrically conductive, non-current carrying parts and surfaces
of the array.
4. Summary of Test Method
1.2 This test method does not establish pass or fail levels.
4.1 A procedure is provided for testing the electrical isola-
The determination of acceptable or unacceptable results is
tion between the array’s internal electrical components and its
beyond the scope of this test method.
exposed, electrically conductive, non-current carrying parts
1.3 There is no similar or equivalent ISO standard.
and surfaces of the array.
1.4 Units—The values stated in either SI units or inch-
4.2 The procedure offers two ways to connect the array
pound units are to be regarded separately as standard. The
during the test, either open-circuited or short-circuited. Each
values stated in each system may not be exact equivalents;
option has advantages and disadvantages (see 5.5).
therefore, each system shall be used independently of the other.
4.3 Awetting solution is applied to the array, then a voltage
Combining values from the two systems may result in non-
is applied between the PV circuit and the exposed, electrically
conformance with the standard.
conductive, non-current carrying parts and surfaces of the
1.5 This standard does not purport to address all of the
array, while monitoring the current or resistance, to find
safety concerns, if any, associated with its use. It is the
localized regions where the insulation resistance is signifi-
responsibility of the user of this standard to establish appro-
cantly reduced by the wetting solution. The array is then
priate safety and health practices and determine the applica-
inspected for evidence of possible arcing.
bility of regulatory limitations prior to use.
5. Significance and Use
2. Referenced Documents
5.1 The design of a PV module or system intended to
2.1 ASTM Standards:
2 provide safe conversion of the sun’s radiant energy into useful
E 772 Terminology Relating to Solar Energy Conversion
electricitymusttakeintoconsiderationthepossibilityofhazard
E 1328 Terminology Relating to Photovoltaic Solar Energy
2 should the user come into contact with the electrical potential
Conversion
of the array. In addition, the insulation system provides a
E 1462 Standard Test Methods for Insulation Integrity and
2 barrier to electrochemical corrosion, and insulation flaws can
Ground Path Continuity of Photovoltaic Modules
result in increased corrosion and reliability problems. This test
3. Terminology method describes a procedure for verifying that the design and
construction of the array provides adequate electrical isolation
3.1 Definitions—Definitions of terms used in this test
through normal installation and use.At no location on the array
method may be found in Terminologies E 772 and E 1328.
should the PV-generated electrical potential be accessible, with
3.2 Definitions of Terms Specific to This Standard:
the obvious exception of the output leads. The isolation is
3.2.1 insulation resistance, n—the electrical resistance of a
necessary to provide for safe and reliable installation, use, and
photovoltaic array’s insulation, measured between the photo-
service of the PV system.
5.2 This test method describes a procedure for determining
the ability of the array to provide protection from electrical
This test method is under the jurisdiction of ASTM Committee E-44 on Solar,
hazards. Its primary use is to find insulation flaws that could be
GeothermalandOtherAlternativeEnergySources,andisthedirectresponsibilityof
dangerous to persons who may come into contact with the
Subcommittee E44.09 on Photovoltaic Electrical Power Conversion.
array. Corrective action taken to address such flaws is beyond
Current edition approved October 10, 1999. Published December 1999.
Annual Book of ASTM Standards, Vol 12.02. the scope of this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2047
5.3 This procedure may be specified as part of a series of must be sufficient to reach all of the test segment surfaces and
acceptance tests involving performance measurements and maintain wetted surfaces, front and back.
demonstration of functional requirements. Large arrays can be
NOTE 1—The spray pressure is only enough to completely wet the
tested in smaller segments. The size of the array segment to be
exposed surfaces; it is not intended to penetrate enclosed spaces such as
tested (called “circuit under test” in this test method) is usually
the interiors of junction boxes. It is not necessary to use a forceful stream
selected at a convenient break point and sized such that the because the wetting agent helps to penetrate small crevices.
expected resistance or current reading is within the middle
6.4 Array Shorter—A dc-rated switch, circuit beaker or
third of the meter’s range.
other device capable of interrupting the maximum short circuit
5.4 Insulation leakage resistance and insulation leakage
current of the circuit under test. The array shorter is only
current leakage are strong functions of array dimensions,
required if the short-circuited option is used.
ambient relative humidity, absorbed water vapor, and other
6.4.1 The array shorter must be rated for the maximum
factors.Forthisreason,itistheresponsibilityoftheuserofthis
open-circuit voltage of the circuit under test plus the insulation
test method to specify the minimum acceptable leakage resis-
tester or ohmmeter.
tance for this test.
6.4.2 The wiring between the array shorter and the positive
5.4.1 Even though a numerical quantity is specified, actual
and negative terminals of the circuit under test must also be
results are often pass-fail in that when a flaw is found, the
rated for the continuous maximum short-circuit current of the
leakage current changes from almost nothing to the full scale
circuit under test.
value on the meter.
5.5 The user of this test method must specify the option
7. Hazards
used for connection to the array during the test. The short-
7.1 Touchingthemodulesorarrayduringthetestingmaybe
circuited option requires a shorting device with leads to
hazardous because of the high voltage applied.
connect the positive and negative legs of the circuit under test.
7.2 Use caution whenever short circuiting any high voltage
For larger systems, where the shorting device may have to be
PV array. It may be advisable to reduce the risk involved by
rated for high current and voltage levels, the open-circuited
short-circuiting the array at night, when the current and voltage
option may be preferred. The open-circuited option requires
are minimized.
the user to correct readings to account for the PV-generated
7.3 The megohmmeter or insulation tester should be turned
voltage, and the procedure for making such corrections is
off while wetting the array. This may not always be desirable,
beyond the scope of this test method. The short-circuited
such as when trying to pinpoint the location of an insulation
option may be easier for small systems where the voltage and
flaw.Inthesecases,appropriatepersonnelprotection(electrical
current levels are low and the distance between the plus and
gloves with keepers, safety glasses, etc.) should be worn and
minus leads of the circuit under test are small. The short-
care should be taken to keep the wetting solution from entering
circuited option minimizes the chance of exposing array
the gloves, boots, etc.
components to voltage levels above those for which they are
rated.
8. Procedure
6. Apparatus
8.1 Assemble the requisite equipment and personnel at the
6.1 Choose one of the following, depending on the option array to be tested.
selected (see 4.2 and 5.5): 8.2 Prepare the wetting solution.
6.1.1 Variable dc Voltage Power Supply—A dc voltage 8.3 Measure and record the site meteorological conditions
power supply capable of providing a nominal test voltage of (irradiance, ambient temperature, wind speed) or arrange for
500V, as specified inTest Method E 1462.Acommon term for the data to be measured by the site data acquisition system.
this apparatus is insulation tester.
NOTE 2—It is recommended that this test not be performed under
6.1.2 Megohmmeter—A high-impedance ohmmeter, or
conditions where the ambient temperature is greater than 100°F (40°C) or
similar device, capable of adequately measuring leakage resis-
thewindspeedisgreaterthan17mph(7.5m/s),sincehighvaluesofeither
tance in the range of anticipated readings, and that can provide make it difficult to keep the array wet long enough to make the necessary
measurements. If the short-circuited option is used, it may be necessary to
a nominal test voltage of 500 V.
conduct the test at a reduced i
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