ASTM D2275-22

Standard Test Method for Voltage Endurance of Solid Electrical Insulating Materials Subjected to Partial Discharges (Corona) on the Surface

SIGNIFICANCE AND USE
5.1 This test method is useful in research and quality control for evaluating insulating materials and systems since they provide for the measurement of the endurance used to compare different materials to the action of corona on the external surfaces. A poor result on this test does not indicate that the material is a poor selection for use at high voltage or at high voltage stress in the absence of surface corona; surface corona is not the same as corona that occurs in internal cavities. (See Test Methods D3382.)  
5.2 This test method is also useful for comparison between materials of the same relative thickness. When agreed upon between the buyer and the seller, it is acceptable to express any differences in terms of relative time to failure or the magnitude of voltage stress (kV/mm or kV/in.) required to produce failure in a specified number of hours.  
5.3 It is possible for this test method to also be used to examine the effects of different processing parameters on the same insulating material, such as residual strains produced by quenching, high levels of crystallinity or molding processes that control the concentration and sizes of gas-filled cavities.  
5.4 The data are generated in the form of a set of values of lifetimes at a voltage. The dispersion of failure times is analyzed using one of the methods below:  
5.4.1 Weibull Probability Plot.  
5.4.2 Statistically (see IEEE/IEC 62539-2007 for additional information), to yield an estimate of the central value of the distribution and its standard deviation.  
5.4.3 Truncating a test at the time of the fifth failure of a set of nine and using that time as the measure of the central tendency. Two such techniques are described in 10.2.  
5.5 This test method intensifies some of the more commonly met conditions of corona attack so that materials are able to be evaluated in a time that is relatively short compared to the life of the equipment. As with most accelerated life tests, caution is necessary in...
SCOPE
1.1 This test method determines the voltage endurance of solid electrical insulating materials for use at commercial power frequencies under the action of corona (see Note 1). This test method is more meaningful for rating materials with respect to their resistance to prolonged ac stress under corona conditions for comparative evaluation between materials.
Note 1: The term “corona” is used almost exclusively in this test method instead of “partial discharge,” because it is a visible glow at the edge of the electrode interface that is the result of partial discharge. Corona, as defined in Terminology D1711, is “visible partial discharges in gases adjacent to a conductor.”  
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.  
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 7.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Mar-2022
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.12 - Electrical Tests

Relations

• Refers: ASTM D1711-24 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Mar-2024
• Refers: ASTM D1868-20 - Standard Test Method for Detection and Measurement of Partial Discharge (Corona) Pulses in Evaluation of Insulation Systems
• Effective Date: 01-Mar-2020
• Refers: ASTM D149-20 - Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies
• Effective Date: 01-Jan-2020
• Refers: ASTM D1711-15 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2015
• Refers: ASTM D1711-14a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2014
• Refers: ASTM D1711-14 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2014
• Refers: ASTM D1711-13 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2013
• Refers: ASTM D1868-13 - Standard Test Method for Detection and Measurement of Partial Discharge (Corona) Pulses in Evaluation of Insulation Systems
• Effective Date: 01-Nov-2013
• Refers: ASTM D1711-11a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Aug-2011
• Refers: ASTM D618-08 - Standard Practice for Conditioning Plastics for Testing
• Effective Date: 01-Nov-2008
• Refers: ASTM D1711-08 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2008
• Refers: ASTM D1868-07 - Standard Test Method for Detection and Measurement of Partial Discharge (Corona) Pulses in Evaluation of Insulation Systems
• Effective Date: 01-May-2007
• Refers: ASTM D3382-07 - Standard Test Methods for Measurement of Energy and Integrated Charge Transfer Due to Partial Discharges (Corona) Using Bridge Techniques
• Effective Date: 01-May-2007
• Refers: ASTM D618-05 - Standard Practice for Conditioning Plastics for Testing
• Effective Date: 01-Nov-2005
• Refers: ASTM D149-97a(2004) - Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies
• Effective Date: 01-Mar-2004

Overview

ASTM D2275-22 is the internationally recognized standard test method developed by ASTM International for assessing the voltage endurance of solid electrical insulating materials when subjected to partial discharges, commonly referred to as surface corona. This standard is essential for comparing the resistance of different insulating materials or systems exposed to prolonged AC voltage stress and corona effects at commercial power frequencies.

The significance of ASTM D2275-22 lies in its ability to provide a comparative evaluation between various materials based on their endurance under corona conditions, supporting research, quality control, and material selection for electrical insulation applications.

Key Topics

• Voltage Endurance Testing: The standard outlines procedures to determine how long insulating materials can withstand high-voltage stress accompanied by corona discharges on their surface, using nine test specimens at voltages above inception but below those causing rapid failure.
• Surface Corona vs. Internal Partial Discharge: ASTM D2275-22 distinguishes between surface corona, a visible discharge at the insulation/electrode interface, and internal partial discharges in cavities-important for correct material evaluation.
• Data Analysis: Results are processed to show time to failure, typically visualized through Weibull Probability Plots, and may be statistically analyzed for mean, median, and distribution variability.
• Accelerated Life Testing: The test method allows for frequency-accelerated aging, observing how increased voltage frequency can shorten the time required to assess material endurance, while cautioning against over-interpretation of results for actual service life.
• Influencing Factors: The standard notes that corona-induced failure can result from erosion, carbonization, chemical byproduct formation, gas release, “treeing” effects, and embrittlement.

Applications

ASTM D2275-22 is used in several practical scenarios in electrical insulation technology:

• Research & Development: Laboratories utilize the standard for investigating the durability and failure mechanisms of new insulating materials or formulations.
• Quality Control: Manufacturers of electrical components apply ASTM D2275-22 for batch-to-batch comparison of insulating material performance, ensuring consistency and reliability under high-voltage conditions.
• Material Selection: Electrical engineers and system designers rely on test data from this standard to select materials best suited for applications where surface corona exposure is expected, such as in transformers, switchgear, or high-voltage cable systems.
• Process Evaluation: The method assists in examining the effects of manufacturing processes (e.g., quenching, crystallinity changes, or molding-induced cavities) on insulation performance.
• Specification Compliance: Buyers and sellers can agree on acceptance criteria based on voltage endurance, defining performance expectations for supplied insulation materials.

Related Standards

• ASTM D149 - Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies.
• ASTM D1868 - Test Method for Detection and Measurement of Partial Discharge (Corona) Pulses.
• ASTM D3382 - Test Methods for Measurement of Energy and Charge Transfer Due to Partial Discharges (Corona).
• ASTM D1711 - Terminology Relating to Electrical Insulation.
• IEC 60343 - Recommended Test Methods for Determining the Relative Resistance of Insulating Materials to Breakdown by Surface Discharges.
• IEEE/IEC 62539-2007 (IEEE 930) - Guide for the Statistical Analysis of Electrical Insulation Breakdown Data.

Summary

ASTM D2275-22 is a key standard for evaluating solid electrical insulating materials under surface corona stress, supporting comparative analysis, quality assurance, and improved product reliability in high-voltage electrical applications. Adhering to this test method helps manufacturers, laboratories, and design engineers ensure the durability and performance of electrical insulation systems. For comprehensive material assessment and international consistency, use ASTM D2275-22 alongside other related standards in insulation testing and specification.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D2275 − 22
Standard Test Method for
Voltage Endurance of Solid Electrical Insulating Materials
Subjected to Partial Discharges (Corona) on the Surface
This standard is issued under the fixed designation D2275; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope DielectricStrengthofSolidElectricalInsulatingMaterials
at Commercial Power Frequencies
1.1 This test method determines the voltage endurance of
D618Practice for Conditioning Plastics for Testing
solid electrical insulating materials for use at commercial
D1711Terminology Relating to Electrical Insulation
powerfrequenciesundertheactionofcorona(seeNote1).This
D1868Test Method for Detection and Measurement of
test method is more meaningful for rating materials with
Partial Discharge (Corona) Pulses in Evaluation of Insu-
respect to their resistance to prolonged ac stress under corona
lation Systems
conditions for comparative evaluation between materials.
D3382Test Methods for Measurement of Energy and Inte-
NOTE 1—The term “corona” is used almost exclusively in this test
grated Charge Transfer Due to Partial Discharges (Co-
method instead of “partial discharge,” because it is a visible glow at the
rona) Using Bridge Techniques
edge of the electrode interface that is the result of partial discharge.
Corona,asdefinedinTerminologyD1711,is“visiblepartialdischargesin 2.2 Special Technical Publications:
gases adjacent to a conductor.”
Symposium on Corona, STP 198,ASTM, 1956
Corona Measurement and Interpretation, Engineering
1.2 The values stated in SI units are to be regarded as
Dielectrics, Vol 1, STP 669, ASTM, 1979
standard. The values given in parentheses are mathematical
conversions to inch-pound units that are provided for informa-
2.3 International Electrotechnical Commission (IEC)
tion only and are not considered standard.
Documents:
IECPublication60343RecommendedTestMethodsforDe-
1.3 This standard does not purport to address all of the
termining the Relative Resistance of Insulating Materials
safety concerns, if any, associated with its use. It is the
to Breakdown by Surface Discharges
responsibility of the user of this standard to establish appro-
IEEE/IEC 62539-2007–IEC 62539 Ed.1 (IEEE Std 930™-
priate safety, health, and environmental practices and deter-
2004) Guide for the Statistical Analysis of Electrical
mine the applicability of regulatory limitations prior to use.
Insulation Breakdown Data
For specific hazard statements, see Section 7.
1.4 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3.1 Definitions—For definitions of other terms used in this
Development of International Standards, Guides and Recom-
standard,refertoTerminologyD1711andTestMethodD1868.
mendations issued by the World Trade Organization Technical
3.2 Definitions of Terms Specific to This Standard:
Barriers to Trade (TBT) Committee.
3.2.1 surface corona, n—corona that exists in the electri-
callystressedgaswhereelectrodesarenearinsulationsurfaces.
2. Referenced Documents
3.2.2 threshold voltage—that voltage below which failure
2.1 ASTM Standards:
will not occur under the test conditions irrespective of the
D149Test Method for Dielectric Breakdown Voltage and
duration of the test.
3.2.3 voltage endurance, n—the time that an insulating
1 material can withstand a prolonged alternating voltage stress
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of under the action of surface corona.
Subcommittee D09.12 on Electrical Tests.
Current edition approved March 15, 2022. Published March 2022. Originally
approved in 1964. Last previous edition approved in 2014 as D2275–14. DOI:
10.1520/D2275-22. Available from International Electrotechnical Commission (IEC), 3, rue de
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Varembé, 1st floor, P.O. Box 131, CH-1211, Geneva 20, Switzerland, https://
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM www.iec.ch.
Standards volume information, refer to the standard’s Document Summary page on Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE),
the ASTM website. 445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http://www.ieee.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2275 − 22
3.2.4 voltage stress-time curve, n—aplotofthelogarithmof ofvoltagestress(kV/mmorkV/in.)requiredtoproducefailure
themeanormediantimetofailureofamaterialagainstvoltage in a specified number of hours.
stress (or the logarithm of voltage stress) for a particular set of
5.3 It is possible for this test method to also be used to
test conditions.
examine the effects of different processing parameters on the
3.2.4.1 Discussion—Theplotisthequantitativedepictionof
same insulating material, such as residual strains produced by
the voltage stress endurance over a range of voltage stress for
quenching, high levels of crystallinity or molding processes
the conditions of test, and for the thickness tested. The curves
that control the concentration and sizes of gas-filled cavities.
of a material obtained at two thicknesses are different.
5.4 The data are generated in the form of a set of values of
3.2.5 volt-time curve, n—aplotofthelogarithmofthemean
lifetimes at a voltage. The dispersion of failure times is
or median time to failure of a material against voltage (or the
analyzed using one of the methods below:
logarithm of voltage) for a particular set of test conditions.
5.4.1 Weibull Probability Plot.
3.2.5.1 Discussion—Theplotisthequantitativedepictionof
5.4.2 Statistically (see IEEE/IEC 62539-2007 for additional
the voltage endurance over a range of voltage for the condi-
information), to yield an estimate of the central value of the
tions of the test, which includes the particular thickness tested.
distribution and its standard deviation.
5.4.3 Truncatingatestatthetimeofthefifthfailureofaset
4. Summary of Test Method
of nine and using that time as the measure of the central
4.1 In this test method, voltage sufficient to produce surface
tendency. Two such techniques are described in 10.2.
coronaisappliedtoninesamplesfromthesamespecimenuntil
failure occurs. The voltage endurance is the relative time to 5.5 Thistestmethodintensifiessomeofthemorecommonly
met conditions of corona attack so that materials are able to be
failure, determined by the voltage-time curve or Weibull
Probability Plot. evaluated in a time that is relatively short compared to the life
oftheequipment.Aswithmostacceleratedlifetests,cautionis
4.2 When there is a large dispersion of times to failure for a
necessary in extrapolation from the indicated life to actual life
given sample, it is acceptable to use the median time of nine
under various operating conditions in the field.
specimens (time of fifth failure) as the failure time for the
sample. This removes the necessity of waiting for the last few 5.6 The possible factors related to failures produced by
to fail. The mean can also be determined statistically (see
corona are:
IEEE/IEC 62539-2007 for additional information).
5.6.1 Corona eroding the insulation until the remaining
insulation can no longer withstand the applied voltage.
4.3 Under the conditions outlined in Appendix X2 it is
5.6.2 Corona causing the insulation surface to become
permissible for the test to be accelerated by increasing the
conductingduetocarbonization,sothatfailureoccursquickly.
frequencyoftheappliedvoltage.Incasesagreeduponbetween
5.6.3 Forming of compounds such as oxalic acid crystals
thebuyerandtheseller,orrequiredinrelevantspecificationsto
causing the surface conductance to vary with ambient humid-
perform testing on specific specimens where a service condi-
ity. It is possible conductance will be at a sufficient level to
tionisthoughttoalterthecoronaendurance,thisfactorshallbe
reduce the potential gradient at the electrode edge at moderate
introduced as part of the test and reported.
humidities, and thus cause either a reduction in the amount of
4.4 It is possible to obtain additional information from the
corona, or its cessation, thus retarding failure.
test if corona-voltage levels and corona intensity are measured
5.6.4 Corona causing “treeing” within the insulation and
at the start of the test and monitored at various stages of
consequently accelerating the time to failure.
deterioration of the insulation. The voltage levels include
5.6.5 Gases released within the insulation that change its
corona-inception voltage, corona-extinction voltage, and co-
physical dimensions.
rona intensity using Test Method D1868.
5.6.6 Changes in the physical properties of an insulating
NOTE 2—Comparative measurements of corona power or energy by
material; embrittlement or cracking, for instance, causing the
bridge and oscilloscope techniques can also be informative.
material to lose flexibility or crack, or both, and thus make it
useless.
5. Significance and Use
5.7 Tests are often made in open air, at 50 % relative
5.1 Thistestmethodisusefulinresearchandqualitycontrol
humidity. In cases agreed upon between the buyer and the
for evaluating insulating materials and systems since they
seller, additional information can be obtained for some mate-
provideforthemeasurementoftheenduranceusedtocompare
rials with tests in circulating air at 20 % relative humidity or
different materials to the action of corona on the external
less (see Appendix X1).
surfaces. A poor result on this test does not indicate that the
5.7.1 If tests are made in an enclosure, the restriction in the
material is a poor selection for use at high voltage or at high
flow of air can trap ozone and influence the results (see
voltage stress in the absence of surface corona; surface corona
Appendix X2).
is not the same as corona that occurs in internal cavities. (See
Test Methods D3382.) 5.7.2 When tests are done outside the standard conditions,
the report shall note the deviation and the alternative condi-
5.2 This test method is also useful for comparison between
tions.
materials of the same relative thickness. When agreed upon
betweenthebuyerandtheseller,itisacceptabletoexpressany 5.8 The variability of the time to failure is a function of the
differencesintermsofrelativetimetofailureorthemagnitude consistency of the test parameters, such as voltage levels,
D2275 − 22
which shall be monitored. The Weibull slope factor, β,is the specimen when it fails (see Fig. X3.2). This allows the
recommended as a measure of variability. β is the slope other specimens to continue on test. The failure current
obtained when percent failure is plotted against failure time on simultaneously operates a relay which provides a pulse of
Weibull probability paper. Such a plot is called a Weibull current to operate a recorder such as a recording ammeter, an
Probability Plot (see Fig. 1). event recorder, or a running time meter to indicate the time to
failure. (See Fig. X3.1, for instance.)
5.9 The shape of the Weibull Probability Plot can provide
6.1.2.3 An alternative technique has advantages for lower
additional information. It is possible that a non-straight-line
voltages associated with thin films and with materials of
plot will indicate more than one mechanism of failure. For
relatively low dielectric strength. In such cases, the possibility
instance, a few unaccountably short time failures in the set
exists that the failure current will not be high enough to melt
indicating a small portion of defective specimens with a
fuse wire. It also works better than the fuse wire at higher
different failure mechanism from the rest of the lot.
voltages where intense discharge currents flow sporadically,
6. Apparatus making the fuse wire scheme unreliable. Fig. X3.3 shows a
relay-latch mechanism that has been successfully used. Speci-
6.1 Electrical Circuit:
men failure current energizes the coil of relay LM5, closes the
6.1.1 High-Voltage Supply—A high-voltage source with
contacts, energizes the coil of the latching relay, and releases
controls and voltage-measuring means in accordance with
thelatch,whichopensthecontactsinthespecimencircuit.The
requirementsofTestMethodD149;whichinadditionprovides
latch contacts are designed to open with sufficient clearance to
a test voltage stable within 61% during the test period. If
interrupt the high-voltage arc.Auxiliary contacts of relay LM5
necessary use a voltage stabilizer, or other suitable equipment,
cause the event recorder to indicate the time of failure. The
for this purpose.
remaining specimens remain under continuous test automati-
6.1.2 It is essential to provide for safe, continuous, and
cally with no time lost and no need for extra attention by
reliable operation, with automatic detection of failure times
personnel.
andautomaticremovalofspecimensfromthetestcircuitwhen
6.1.2.4 Circuit Protection—An automatic circuit breaking
they fail. Two suitable circuits are described in detail in
device protects the entire circuit by opening when 0.05 A of
Appendix X3. Particular features are described as follows:
secondary current is drawn for more than 15 s. (See Fig. X3.1,
6.1.2.1 Current Limiting Resistors—A series of resistors in
for instance.)
thehighvoltagelinebetweenthetransformerandthespecimen
limit the current to approximately 0.05 A when a specimen
6.2 Itisimperativetoelectricallyinterlockthetestchamber,
fails. These resistors must have adequate voltage rating. The
and:
current limitation prevents pitting of the electrodes and mini-
6.2.1 Agroundedmetalbaseisrecommendedtobeinstalled
mizes surges. Since accidental grounding of the high voltage
under the specimens and under any high voltage bus structure,
electrodewillcausetheresistorstobecomeextremelyhot,itis
so that any free lead will contact ground and operate the
important to assure that the current goes through the interrup-
breaker (see 7.2).
tion circuit.
6.2.2 An isolation transformer with a grounded shield to
6.1.2.2 Specimen Circuit Opening—An additional resistor
provide power to relay circuits, and event recorders (see 7.2).
of 50kΩ (610%) in series with each specimen develops a
6.2.3 Asmoke detector in the roof of the chamber (see 7.1).
sufficient voltage across it, when a specimen fails, to operate a
specialhigh-voltagefusesystemthatopensagapinserieswith 6.2.4 Ameans of test chamber ventilation (see 7.3 and 7.4).
NOTE 1—Plotting percentage are 100 times the average of (n− ⁄2)/N and n/(N+1).Artificial data were placed on a line (dashed) drawn to illustrate
a Weibull line with a β of 4. A second line (not dashed) illustrates the distribution of failure times which are characteristic of materials with very flat
volt-time curves, such as mica composites. This line has a β value of 0.7.
FIG. 1 Representative Weibull Plot Showing the First Five Failures of a Group Specimen of Nine.
D2275 − 22
6.2.5 Equipment for control of ambient conditions (see 7.3 Warning—The tests of this test method generate ozone
Appendix X1). andotherpotentiallyhazardousgasses.Thisisnotaproblemif
thetestsaremadeinchambersventedtotheoutside.Ifthetests
6.3 Electrodes:
are not safely vented, it is important to note that:
6.3.1 The upper electrodes shall be:
7.3.1 Ozone is a physiologically hazardous gas at elevated
6.3.1.1 Cylinders, 12.7 mm ( ⁄2in.) in diameter, 13 mm
concentrations. The exposure limits are set by governmental
high, with edges rounded to a radius of 1.6 mm (0.0625 in.),
agencies and are usually based upon recommendations made
loaded to give a total weight of at least 90 g, and made
by the American Conference of Governmental Industrial Hy-
self-aligning to conform to the surface of the specimen, or
gienists. Ozone is likely to be present whenever voltages exist
6.3.1.2 Steel Spheres, 12.7 mm ( ⁄2 in.) in diameter, loaded
which are suffıcient to cause partial, or complete, discharges in
to give a total weight of at least 50 g. The steel balls used in
air or other atmospheres that contain oxygen. Ozone has a
ball bearings make satisfactory electrodes, or
distinctive odor which is initially discernible at low concen-
6.3.1.3 Cylinders, 6.0mm 6 0.3mm ( ⁄4 in.) in diameter,
trations but sustained inhalation of ozone can cause temporary
with edges rounded to a radius of 1 mm (0.04 in.) and weight
loss of sensitivity to the scent of ozone. Because of this it is
of approximately 30 g, and made self-aligning to conform to
important to measure the concentration of ozone in the
thesurfaceofthespecimen.ThisistheIECstandardelectrode.
atmosphere, using commercially available monitoring devices,
6.3.2 The lower electrodes shall extend beyond the upper
whenever the odor of ozone is persistently present or when
electrodes by a minimum 12.7mm ( ⁄2in.) and so that the
ozone generating conditions continue. Use appropriate
lower electrode centers are separated by at least 51mm
means, such as exhaust vents, to reduce ozone concentrations
(2.0in.). The simplest design is to make the lower electrode
to acceptable levels in working areas.
one common plate, if that meets the needs of the electrical
7.4 Warning—Oxides of Nitrogen are also hazardous and
circuit.
are generated by this test.
6.3.3 The standard electrode material is stainless steel Type
309 or 310. The surface finish shall be 0.4 µm (16 µin.).
8. Test Specimens
6.4 The test chamber provides for control of the ambient
8.1 Thick Materials (1.4 mm (0.062 in.) and Over)—Nine
conditions by supplying a constant flow of a chosen
specimens with a thickness of 1.4mm 6 0.1 mm (0.06in. 6
atmosphere,orbypreventingflowifthatisdesired.Whenflow
0.004 in.) are required for each test voltage. For thicker
is desired, there are two acceptable methods to introduce the
specimens, reduce the thickness to this value and place the
atmosphere: by controlled draft (as in a hood in a controlled
small electrode against the original surface. The size of the
atmosphere laboratory), or by means of a manifold directing
specimens shall be sufficient to prevent flashover.
the flow to nozzles which terminate at a distance of 13mm 6
1 mm from the edge of the top electrode of the specimen. The 8.2 Thin Materials (Under 1.4 mm (0.062 in.))—Use sheets
chamber must be connected to a vent to remove ozone and of sufficient size to extend under all nine electrodes with an
other gasses (see also 9.1 and Appendix
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D2275 − 14 D2275 − 22
Standard Test Method for
Voltage Endurance of Solid Electrical Insulating Materials
Subjected to Partial Discharges (Corona) on the Surface
This standard is issued under the fixed designation D2275; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method determines the voltage endurance of solid electrical insulating materials for use at commercial power
frequencies under the action of corona (see Note 1). This test method is more meaningful for rating materials with respect to their
resistance to prolonged ac stress under corona conditions for comparative evaluation between materials.
NOTE 1—The term “corona” is used almost exclusively in this test method instead of “partial discharge,” because it is a visible glow at the edge of the
electrode interface that is the result of partial discharge. Corona, as defined in Terminology D1711, is “visible partial discharges in gases adjacent to a
conductor.”
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to
inch-pound units that are provided for information only and are not considered standard.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. For specific hazard statements, see Section 7.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at
Commercial Power Frequencies
D618 Practice for Conditioning Plastics for Testing
D1711 Terminology Relating to Electrical Insulation
D1868 Test Method for Detection and Measurement of Partial Discharge (Corona) Pulses in Evaluation of Insulation Systems
D3382 Test Methods for Measurement of Energy and Integrated Charge Transfer Due to Partial Discharges (Corona) Using
Bridge Techniques
2.2 Special Technical Publications:
Symposium on Corona, STP 198, ASTM, 1956
Corona Measurement and Interpretation,Engineering Dielectrics, Vol 1, STP 669, ASTM, 1979
This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.12 on Electrical Tests.
Current edition approved Nov. 1, 2014March 15, 2022. Published December 2014March 2022. Originally approved in 1964. Last previous edition approved in 20082014
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as D2275 – 01 (2008)D2275 – 14. . DOI: 10.1520/D2275-14.10.1520/D2275-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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2.3 International Electrotechnical Commission (IEC) Documents:
Documents:
IEC Publication 60343 Recommended Test Methods for Determining the Relative Resistance of Insulating Materials to
Breakdown by Surface Discharges
IEEE/IEC 62539-2007 – IEC 62539 Ed.1 (IEEE Std 930™-2004) Guide for the Statistical Analysis of Electrical Insulation
Breakdown Data
2.4 Institute of Electrical and Electronic Engineers (IEEE) Document:
IEEE 930-1987 Guide for the Statistical Analysis of Electrical Insulation Voltage Endurance Data
3. Terminology
3.1 Definitions—For definitions of other terms used in this standard, refer to Terminology D1711 and Test Method D1868.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 surface corona, n—corona that exists in the electrically stressed gas where electrodes are near insulation surfaces.
3.2.2 threshold voltage—that voltage below which failure will not occur under the test conditions irrespective of the duration of
the test.
3.2.3 voltage endurance, n—the time that an insulating material can withstand a prolonged alternating voltage stress under the
action of surface corona.
3.2.4 voltage stress-time curve, n—a plot of the logarithm of the mean or median time to failure of a material against voltage stress
(or the logarithm of voltage stress) for a particular set of test conditions.
3.2.4.1 Discussion—
The plot is the quantitative depiction of the voltage stress endurance over a range of voltage stress for the conditions of test, and
for the thickness tested. The curves of a material obtained at two thicknesses are different.
3.2.5 volt-time curve, n—a plot of the logarithm of the mean or median time to failure of a material against voltage (or the
logarithm of voltage) for a particular set of test conditions.
3.2.5.1 Discussion—
The plot is the quantitative depiction of the voltage endurance over a range of voltage for the conditions of the test, which includes
the particular thickness tested.
4. Summary of Test Method
4.1 In this test method, voltage sufficient to produce surface corona is applied to nine samples from the same specimen until failure
occurs. The voltage endurance is the relative time to failure, determined by the voltage-time curve or Weibull Probability Plot.
4.2 When there is a large dispersion of times to failure for a given sample, it is acceptable to use the median time of nine specimens
(time of fifth failure) as the failure time for the sample. This removes the necessity of waiting for the last few to fail. The mean
can also be determined statistically (see IEEE 930-1987IEEE/IEC 62539-2007 for additional information).
4.3 Under the conditions outlined in Appendix X2 it is permissible for the test to be accelerated by increasing the frequency of
the applied voltage. In cases agreed upon between the buyer and the seller, or required in relevant specifications to perform testing
on specific specimens where a service condition is thought to alter the corona endurance, this factor shall be introduced as part
of the test and reported.
4.4 It is possible to obtain additional information from the test if corona-voltage levels and corona intensity are measured at the
start of the test and monitored at various stages of deterioration of the insulation. The voltage levels include corona-inception
voltage, corona-extinction voltage, and corona intensity using Test Method D1868.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.International Electrotechnical
Commission (IEC), 3, rue de Varembé, 1st floor, P.O. Box 131, CH-1211, Geneva 20, Switzerland, https://www.iec.ch.
Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE), 445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http://www.ieee.org.
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NOTE 2—Comparative measurements of corona power or energy by bridge and oscilloscope techniques can also be informative.
5. Significance and Use
5.1 This test method is useful in research and quality control for evaluating insulating materials and systems since they provide
for the measurement of the endurance used to compare different materials to the action of corona on the external surfaces. A poor
result on this test does not indicate that the material is a poor selection for use at high voltage or at high voltage stress in the absence
of surface corona; surface corona is not the same as corona that occurs in internal cavities. (See Test Methods D3382.)
5.2 This test method is also useful for comparison between materials of the same relative thickness. When agreed upon between
the buyer and the seller, it is acceptable to express any differences in terms of relative time to failure or the magnitude of voltage
stress (kV/mm or kV/in.) required to produce failure in a specified number of hours.
5.3 It is possible for this test method to also be used to examine the effects of different processing parameters on the same
insulating material, such as residual strains produced by quenching, high levels of crystallinity or molding processes that control
the concentration and sizes of gas-filled cavities.
5.4 The data are generated in the form of a set of values of lifetimes at a voltage. The dispersion of failure times is analyzed using
one of the methods below:
5.4.1 Weibull Probability Plot.
5.4.2 Statistically (see IEEE 930-1987IEEE/IEC 62539-2007 for additional information), to yield an estimate of the central value
of the distribution and its standard deviation.
5.4.3 Truncating a test at the time of the fifth failure of a set of nine and using that time as the measure of the central tendency.
Two such techniques are described in 10.2.
5.5 This test method intensifies some of the more commonly met conditions of corona attack so that materials are able to be
evaluated in a time that is relatively short compared to the life of the equipment. As with most accelerated life tests, caution is
necessary in extrapolation from the indicated life to actual life under various operating conditions in the field.
5.6 The possible factors related to failures produced by corona are:
5.6.1 Corona eroding the insulation until the remaining insulation can no longer withstand the applied voltage.
5.6.2 Corona causing the insulation surface to become conducting due to carbonization, so that failure occurs quickly.
5.6.3 Forming of compounds such as oxalic acid crystals causing the surface conductance to vary with ambient humidity. It is
possible conductance will be at a sufficient level to reduce the potential gradient at the electrode edge at moderate humidities, and
thus cause either a reduction in the amount of corona, or its cessation, thus retarding failure.
5.6.4 Corona causing “treeing” within the insulation and consequently accelerating the time to failure.
5.6.5 Gases released within the insulation that change its physical dimensions.
5.6.6 Changes in the physical properties of an insulating material; embrittlement or cracking, for instance, causing the material
to lose flexibility or crack, or both, and thus make it useless.
5.7 Tests are often made in open air, at 50 % relative humidity. In cases agreed upon between the buyer and the seller, additional
information can be obtained for some materials with tests in circulating air at 20 % relative humidity or less (see Appendix X1).
5.7.1 If tests are made in an enclosure, the restriction in the flow of air can trap ozone and influence the results (see Appendix
X2).
5.7.2 When tests are done outside the standard conditions, the report shall note the deviation and the alternative conditions.
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5.8 The variability of the time to failure is a function of the consistency of the test parameters, such as voltage levels, which shall
be monitored. The Weibull slope factor, β, is recommended as a measure of variability. β is the slope obtained when percent failure
is plotted against failure time on Weibull probability paper. Such a plot is called a Weibull Probability Plot (see Fig. 1).
5.9 The shape of the Weibull Probability Plot can provide additional information. It is possible that a non-straight-line plot will
indicate more than one mechanism of failure. For instance, a few unaccountably short time failures in the set indicating a small
portion of defective specimens with a different failure mechanism from the rest of the lot.
6. Apparatus
6.1 Electrical Circuit:
6.1.1 High-Voltage Supply—A high-voltage source with controls and voltage-measuring means in accordance with requirements
of Test Method D149; which in addition provides a test voltage stable within 61 % during the test period. If necessary use a
voltage stabilizer, or other suitable equipment, for this purpose.
6.1.2 It is essential to provide for safe, continuous, and reliable operation, with automatic detection of failure times and automatic
removal of specimens from the test circuit when they fail. Two suitable circuits are described in detail in Appendix X3. Particular
features are described as follows:
6.1.2.1 Current Limiting Resistors—A series of resistors in the high voltage line between the transformer and the specimen limit
the current to approximately 0.05 A when a specimen fails. These resistors must have adequate voltage rating. The current
limitation prevents pitting of the electrodes and minimizes surges. Since accidental grounding of the high voltage electrode will
cause the resistors to become extremely hot, it is important to assure that the current goes through the interruption circuit.
6.1.2.2 Specimen Circuit Opening—An additional resistor of 50 kΩ (610 %) in series with each specimen develops a sufficient
voltage across it, when a specimen fails, to operate a special high-voltage fuse system that opens a gap in series with the specimen
when it fails (see Fig. X3.2). This allows the other specimens to continue on test. The failure current simultaneously operates a
relay which provides a pulse of current to operate a recorder such as a recording ammeter, an event recorder, or a running time
meter to indicate the time to failure. (See Fig. X3.1, for instance.)
6.1.2.3 An alternative technique has advantages for lower voltages associated with thin films and with materials of relatively low
dielectric strength. In such cases, the possibility exists that the failure current will not be high enough to melt fuse wire. It also
works better than the fuse wire at higher voltages where intense discharge currents flow sporadically, making the fuse wire scheme
unreliable. Fig. X3.3 shows a relay-latch mechanism that has been successfully used. Specimen failure current energizes the coil
of relay LM5, closes the contacts, energizes the coil of the latching relay, and releases the latch, which opens the contacts in the
specimen circuit. The latch contacts are designed to open with sufficient clearance to interrupt the high-voltage arc. Auxiliary
NOTE 1—Plotting percentage are 100 times the average of (n − ⁄2)/N and n/(N + 1). Artificial data were placed on a line (dashed) drawn to illustrate
a Weibull line with a β of 4. A second line (not dashed) illustrates the distribution of failure times which are characteristic of materials with very flat
volt-time curves, such as mica composites. This line has a β value of 0.7.
FIG. 1 Representative Weibull Plot Showing the First Five Failures of a Group Specimen of Nine.
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contacts of relay LM5 cause the event recorder to indicate the time of failure. The remaining specimens remain under continuous
test automatically with no time lost and no need for extra attention by personnel.
6.1.2.4 Circuit Protection—An automatic circuit breaking device protects the entire circuit by opening when 0.05 A of secondary
current is drawn for more than 15 s. (See Fig. X3.1, for instance.)
6.2 It is imperative to electrically interlock the test chamber, and:
6.2.1 A grounded metal base is recommended to be installed under the specimens and under any high voltage bus structure, so
that any free lead will contact ground and operate the breaker (see 7.2).
6.2.2 An isolation transformer with a grounded shield to provide power to relay circuits, and event recorders (see 7.2).
6.2.3 A smoke detector in the roof of the chamber (see 7.1).
6.2.4 A means of test chamber ventilation (see 7.3 and 7.4).
6.2.5 Equipment for control of ambient conditions (see Appendix X1).
6.3 Electrodes:
6.3.1 The upper electrodes shall be:
6.3.1.1 Cylinders, 12.7 mm ( ⁄2 in.) in diameter, 13 mm high, with edges rounded to a radius of 1.6 mm (0.0625 in.), loaded to
give a total weight of at least 90 g, and made self-aligning to conform to the surface of the specimen, or
6.3.1.2 Steel Spheres, 12.7 mm ( ⁄2 in.) in diameter, loaded to give a total weight of at least 50 g. The steel balls used in ball
bearings make satisfactory electrodes, or
6.3.1.3 Cylinders, 6.06.0 mm 6 0.3 mm 0.3 mm ( ⁄4 in.) in diameter, with edges rounded to a radius of 1 mm (0.04 in.) and weight
of approximately 30 g, and made self-aligning to conform to the surface of the specimen. This is the IEC standard electrode.
6.3.2 The lower electrodes shall extend beyond the upper electrodes by a minimum 12.7 mm 12.7 mm ( ⁄2 in.) and so that the lower
electrode centers are separated by at least 51 mm 51 mm (2.0 in.). The simplest design is to make the lower electrode one common
plate, if that meets the needs of the electrical circuit.
6.3.3 The standard electrode material is stainless steel Type 309 or 310. The surface finish shall be 0.4 μm (16 μin.).
6.4 The test chamber provides for control of the ambient conditions by supplying a constant flow of a chosen atmosphere, or by
preventing flow if that is desired. When flow is desired, there are two acceptable methods to introduce the atmosphere: by
controlled draft (as in a hood in a controlled atmosphere laboratory), or by means of a manifold directing the flow to nozzles which
terminate at a distance of 1313 mm 6 1 mm from the edge of the top electrode of the specimen. The chamber must be connected
to a vent to remove ozone and other gasses (see also 9.1 and Appendix X1).
7. Hazards
7.1 Warning—Provide adequate protection against fire. Avoid the use of panels and enclosures made of flammable materials such
as transparent plastics. Electrical design features related to this risk are given in 6.2.1 and 6.4.
7.2 Warning—Lethal voltages are present during this test. It is essential that the test apparatus, and all associated equipment
electrically connected to it, be properly designed and installed for safe operation.
7.2.1 Solidly ground all electrically conductive parts that any person might come in contact with during the test.
7.2.2 At the completion of any test, provide means to ground any parts which possibly acquired an induced charge during the test
and retained even after disconnection of the voltage source.
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7.2.3 Thoroughly instruct all operators in the proper way to conduct the test safely. When making high voltage tests, particularly
in compressed gas or in oil, the energy released at breakdown has the potential to be suffıcient enough to result in fire, explosion,
or rupture of the test chamber. Design test equipment, test chambers, and test specimens so as to minimize the possibility of such
occurrences and to eliminate the possibility of personal injury.
7.3 Warning—The tests of this test method generate ozone and other potentially hazardous gasses. This is not a problem if the
tests are made in chambers vented to the outside. If the tests are not safely vented, it is important to note that:
7.3.1 Ozone is a ph
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