ASTM D877-02(2007)
(Test Method)Standard Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using Disk Electrodes
Standard Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using Disk Electrodes
SIGNIFICANCE AND USE
The dielectric breakdown voltage is a measure of the ability of an insulating liquid to withstand electrical stress. The power-frequency breakdown voltage of a liquid is reduced by the presence of contaminants such as cellulosic fibers, conducting particles, dirt, and water. A low result in this test method indicates the presence of significant concentrations of one or more of these contaminants in the liquid tested. See Appendix X1.
A high breakdown voltage measured in this test method does not necessarily indicate that the amount of the contaminants present in a liquid from which the sample was taken are sufficiently low for the sampled liquid to be acceptable in all electrical equipment. Test Method D 877 is not sensitive to low levels of these contaminants. Breakdown in this test method is dominated by events occurring at the electrode edges. The voltage stress distribution between the parallel disk electrodes used in this test method are quasi-uniform and there is substantial stress concentration at the sharp edges of the flat disk faces.
This test method may be used for evaluation of insulating liquids in equipment that is designed to be filled with unprocessed liquids as delivered by a vendor.
This test method is not recommended for evaluation of the breakdown voltage of liquids used in equipment that requires the application of vacuum and filtering of the oil before being placed into service. Test Method D 1816 should be used to determine the breakdown voltage of filtered and degassed liquids.
This test method is used in laboratory or field tests. For field breakdown results to be comparable to laboratory results, all criteria including room temperature (20 to 30°C) must be met.
SCOPE
1.1 This test method describes two procedures, A and B, for determining the electrical breakdown voltage of insulating liquid specimens. The breakdown test uses ac voltage in the power-frequency range from 45 to 65 Hz.
1.2 This test method is used to judge if the disk electrode breakdown voltage requirements are met for insulating liquids, as delivered from the manufacturer, that have never been filtered or dried. See Specification D 3487, Specification D 4652, and Guide D 5222 for the minimum specified electrical breakdown. This test method should be used as recommended by professional organization standards such as IEEE C57.106.
1.3 Limitations of the Procedures
1.3.1 The sensitivity of this test method to the general population of contaminants present in a liquid sample decreases as applied test voltages used in this test method become greater than approximately 25 kV rms.
1.3.2 If the concentration of water in the sample at room temperature is less than 60 % of saturation, the sensitivity of this test method to the presence of water is decreased. For further information refer to RR: D27-1006.
1.3.3 The suitability for this test method has not been determined for a liquid's viscosity higher than 900 cSt at 40C.
1.4 Procedure Applications
1.4.1 Procedure A
Procedure A is used to determine the breakdown voltage of liquids in which any insoluble breakdown products easily settle during the interval between the required repeated breakdown tests. These liquids include petroleum oils, hydrocarbons, and askarels (PCB) used as insulating and cooling liquids in transformers, cables, and similar apparatus.
Procedure A may be used to obtain the dielectric breakdown of silicone fluid as specified in Test Methods D 2225, provided the discharge energy into the sample is less than 20 mJ (milli joule) per breakdown for five consecutive breakdowns.
1.4.2 Procedure BThis procedure is used to determine the breakdown voltage of liquids in which any insoluble breakdown products do not completely settle from the space between the disks during the 1-min interval required in Procedure A. Procedure B, modified in accordance with Section 17 of Test Methods D 2225, is acceptable for testing silicone dielectri...
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Designation: D877 − 02(Reapproved 2007)
Standard Test Method for
Dielectric Breakdown Voltage of Insulating Liquids Using
Disk Electrodes
This standard is issued under the fixed designation D877; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 1.4.1.2 Procedure A may be used to obtain the dielectric
breakdown of silicone fluid as specified in Test Methods
1.1 This test method describes two procedures,Aand B, for
D2225, provided the discharge energy into the sample is less
determining the electrical breakdown voltage of insulating
than 20 mJ (milli joule) per breakdown for five consecutive
liquid specimens. The breakdown test uses ac voltage in the
breakdowns.
power-frequency range from 45 to 65 Hz.
1.4.2 Procedure B:
1.2 This test method is used to judge if the disk electrode
1.4.2.1 This procedure is used to determine the breakdown
breakdown voltage requirements are met for insulating liquids,
voltage of liquids in which any insoluble breakdown products
as delivered from the manufacturer, that have never been
do not completely settle from the space between the disks
filtered or dried. See Specification D3487, Specification
during the 1–min interval required in Procedure A. Procedure
D4652, and Guide D5222 for the minimum specified electrical
B, modified in accordance with Section 17 of Test Methods
breakdown. This test method should be used as recommended
D2225,isacceptablefortestingsiliconedielectricliquidsifthe
by professional organization standards such as IEEE C57.106.
requirements of 1.4.1.2 can not be achieved.
1.4.2.2 Procedure B should also be applied for the determi-
1.3 Limitations of the Procedures:
nation of the breakdown voltage of liquid samples containing
1.3.1 The sensitivity of this test method to the general
insolublematerialsthatsettlefromthespecimenduringtesting.
population of contaminants present in a liquid sample de-
These may include samples taken from circuit breakers, load
creasesasappliedtestvoltagesusedinthistestmethodbecome
tap changers, and other liquids heavily contaminated with
greater than approximately 25 kV rms.
insoluble particulate material. These examples represent
1.3.2 If the concentration of water in the sample at room
samples that may have large differences between replicate
temperature is less than 60 % of saturation, the sensitivity of
tests. The use of Procedure B will result in a more accurate
this test method to the presence of water is decreased. For
value of breakdown voltage when testing such liquids.
further information refer to RR:D27-1006.
1.4.2.3 Use Procedure B to establish the breakdown voltage
1.3.3 The suitability for this test method has not been
of an insulating liquid where an ASTM specification does not
determined for a liquid’s viscosity higher than 900 cSt at 40°C.
exist or when developing a value for an ASTM guide or
1.4 Procedure Applications
standard. Procedure A may be used once the single operator
1.4.1 Procedure A:
precision of 13.1 has been demonstrated.
1.4.1.1 Procedure A is used to determine the breakdown
1.5 BoththeSIandinch-poundunitsareequallyacceptable.
voltage of liquids in which any insoluble breakdown products
1.6 This standard does not purport to address all of the
easily settle during the interval between the required repeated
safety concerns, if any, associated with its use. It is the
breakdown tests. These liquids include petroleum oils,
responsibility of the user of this standard to establish appro-
hydrocarbons, and askarels (PCB) used as insulating and
priate safety and health practices and determine the applica-
cooling liquids in transformers, cables, and similar apparatus.
bility of regulatory limitations prior to use.
2. Referenced Documents
1 3
This test method is under the jurisdiction of ASTM Committee D27 on
2.1 ASTM Standards:
Electrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-
D923 Practices for Sampling Electrical Insulating Liquids
mittee D27.05 on Electrical Test.
Current edition approved Oct. 1, 2007. Published October 2007. Originally
´2
approved in 1946. Last previous edition approved in 2002 as D877–02 . DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/D0877-02R07. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
RR:D27-1006, Round-Robin Data Using Modified VDE Electrode Cell for Standards volume information, refer to the standard’s Document Summary page on
Dielectric Strength Tests on Oil, is available from ASTM Headquarters. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D877 − 02 (2007)
D1816 Test Method for Dielectric Breakdown Voltage of 4. Electrical Apparatus
Insulating Oils of Petroleum Origin Using VDE Elec-
4.1 In addition to this section, use IEEE Standard 4 to
trodes
determine other requirements necessary for conducting test
D2225 Test Methods for Silicone Fluids Used for Electrical
methods and making measurements using alternating voltages.
Insulation
Procedures to ensure accuracy should follow the requirements
D2864 Terminology Relating to Electrical Insulating Liq-
of IEEE Standard 4. Calibration(s) shall be traceable to
uids and Gases
national standards and should be conducted annually or more
D3487 Specification for Mineral Insulating Oil Used in
often.
Electrical Apparatus
4.1.1 Test Voltage—The test voltage shall be an alternating
D4652 Specification for Silicone Fluid Used for Electrical
voltage having a frequency in the range from 45 to 65 Hz,
Insulation
normally referred to as power-frequency voltage. The voltage
D5222 Specification for High Fire-Point Mineral Electrical
Insulating Oils waveshapeshouldapproximateasinusoidwithbothhalfcycles
4 closely alike, and it should have a ratio of peak-to-rms values
2.2 IEEE Standards:
equal to the square root of 2 within 65%.
Standard 4, IEEE Standard Techniques for High-Voltage
4.1.2 Generation of the Test Voltage— The test voltage is
Testing
generally supplied by a transformer or resonant circuit. The
C57.106 Guide forAcceptance and Maintenance of Insulat-
ing Oil in Equipment voltage in the test circuit should be stable enough to be
practically unaffected by varying current flowing in the capaci-
3. Significance and Use tive and resistive paths of the test circuit. Nondisruptive
discharges in the test circuit should not reduce the test voltage
3.1 The dielectric breakdown voltage is a measure of the
to such an extent, and for such a time, that the disruptive
ability of an insulating liquid to withstand electrical stress.The
discharge (breakdown) voltage of the test specimen is signifi-
power-frequency breakdown voltage of a liquid is reduced by
cantly affected. In the case of a transformer, the short-circuit
thepresenceofcontaminantssuchascellulosicfibers,conduct-
current delivered by the transformer should be sufficient to
ing particles, dirt, and water. A low result in this test method
maintain the test voltage within 3 % during transient current
indicates the presence of significant concentrations of one or
pulses or discharges, and a short circuit current of 0.1 A may
more of these contaminants in the liquid tested. See Appendix
suffice.
X1.
4.1.3 Disruptive Voltage Measurement— Design the mea-
3.2 Ahigh breakdown voltage measured in this test method
surement circuit so the voltage recorded at the breakdown is
does not necessarily indicate that the amount of the contami-
the maximum voltage across the test specimen immediately
nants present in a liquid from which the sample was taken are
prior to the disruptive breakdown with an error no greater than
sufficiently low for the sampled liquid to be acceptable in all
3%.
electrical equipment. Test Method D877 is not sensitive to low
levels of these contaminants. Breakdown in this test method is
4.2 Circuit-Interrupting Equipment— Design the circuit
dominated by events occurring at the electrode edges. The
used to interrupt the disruptive discharge through the specimen
voltage stress distribution between the parallel disk electrodes
to operate when the voltage across the specimen has collapsed
used in this test method are quasi-uniform and there is
to less than 100 V. It is recommended that the circuit design
substantial stress concentration at the sharp edges of the flat
limit the disruptive current duration and magnitude to low
disk faces.
values that will minimize damage to the disks and limit
3.3 This test method may be used for evaluation of insulat- formation of non-soluble materials resulting from the break-
ing liquids in equipment that is designed to be filled with down, but consistent with the requirements of 4.1.1.
unprocessed liquids as delivered by a vendor.
4.3 Voltage Control Equipment—Use a rate of voltage rise
3.4 This test method is not recommended for evaluation of
of 3 kV/s. The tolerance of the rate of rise should be 5 % for
the breakdown voltage of liquids used in equipment that
any new equipment. Automatic equipment should be used to
requires the application of vacuum and filtering of the oil
control the voltage rate of rise because of the difficulty of
beforebeingplacedintoservice.TestMethodD1816shouldbe
maintaining a uniform voltage rise manually. The equipment
used to determine the breakdown voltage of filtered and
should produce a straight-line voltage-time curve over the
degassed liquids.
operating range of the equipment. Calibrate and label auto-
matic controls in terms of rate-of-rise.
3.5 This test method is used in laboratory or field tests. For
field breakdown results to be comparable to laboratory results,
4.4 Measuring Systems—The voltage shall be measured by
all criteria including room temperature (20 to 30°C) must be
a method that fulfills the requirements of IEEE Standard No. 4,
met.
giving rms values.
4.5 Connect the electrode such that the voltage measured
4 from each electrode with respect to ground during the test is
Available from The Institute of Electrical and Electronics Engineers, Inc., PO
Box 1331, Piscataway, NJ 08855. equal within 5 %.
D877 − 02 (2007)
5. Electrodes samples. If a value lower than expected is obtained, flush or
clean the cup as necessary until test results meet the expected
5.1 The electrodes shall have parallel faces and axes in a
value for the known sample.
coincident horizontal line when mounted in the cup. Construct
the electrodes of polished brass as disks 25.4 mm (1.0 in.) in 7.4 Electrode Edge Verification—Using a 0.010-in.
diameter 62.0 %, and at least 3.18 mm ( ⁄8 in.) thick, and with (0.254-mm equivalent), radius gage or an optical comparator,
sharp edges. The sharp edge shall have a quarter circle radius verify that the radius of the edge of the electrode, on the gap
no greater than 0.254 mm (0.010 in.). Refer to Annex A1 for side, is less than 0.010 in. (0.254 mm), verify the face of the
illustrations of measuring edge radius. electrodesareat90 61°tothesideedgeoftheelectrode.Ifthe
edge radius is no greater than the value specified and the sides
6. Test Cup
are at 90°, the electrodes are satisfactory for continued use.
6.1 Construct the cup of a material having high dielectric
Check the disk in at least four locations for each criteria. If the
strength, that is inert to any of the cleaning or test liquids. The
radius exceeds the tolerance or the edges are not at 90°, the
cup material shall not absorb moisture or the cleaning and test
electrodes shall be resurfaced to the specified values. Refer to
liquids. The vector sum of the resistive and capacitive current
Annex A1 for illustrations of measuring edge radius.
of the cup, when filled with oil meeting the requirements of
7.5 Polishing of Electrodes—When examination of elec-
Specification D3487, shall be less than 200 µA at 20 kV, at
trodes shows minor scratching or pitting, the electrodes should
power frequency. Construct the cup so that no part is less than
be removed from the test cup and polished by buffing with
12.7 mm (0.5 in.) from any part of the electrode disk. The cup
jeweler’s rouge using a soft cloth or soft buffing wheel.
shall be designed to permit easy removal of the electrodes for
(Resurfacing may be necessary in order to remove deep pit
cleaning and polishing, verification that the sharp edge is
marks or edge damage.) Care must be taken in resurfacing or
withinthespecifiedtolerance,andtopermiteasyadjustmentof
in polishing to ensure that the electrode faces remain perpen-
the gap spacing. The top of the cup shall be maintained at least
dicular to the axis and the edges’ radius does not exceed the
25.4 mm (1.0 in.) above the top of the electrodes.
value specified in 7.4. All residue from the buffing must be
removed before the electrodes are reinstalled in the test cup.
7. Adjustment and Care of Electrodes and Test Cup
This can be accomplished by repeated wiping with lint-free
7.1 Daily Use—At the beginning of each day’s testing
tissue paper saturated with a suitable solvent (such as petro-
examine the electrodes for scratches, pitting, and contamina-
leum ether), followed by solvent rinsing or ultrasonic cleaning.
tion. If pitting or scratches of the disk faces are found, examine
After the electrodes have been reinstalled in the test cup, clean
the electrodes in accordance with 7.4 for the proper sharp edge
and adjust spacing in accordance with 7.2 and 7.3.
and then polish in accordance with 7.5. For severe problems
7.6 Storage of Test Cup—When not in use, the cup, if used
resurfacing may be required. The gap shall be reset in
for referee tests, shall be stored filled with a new, dry, filtered
accordance with 7.2. Clean and prepare the cup in accordance
liquid of the type being tested, and tightly covered.
with 7.3.
7.2 Electrode Spacing—The spacing of the electrodes dur-
8. Sampling
ing tests is 2.54 mm (0.100 in.). The adjustment is made with
8.1 Obtain a sample of the liquid to be tested in accordance
a standard round gage of 2.54 mm (0.100 in.) 61.0 % or 0.100
with Test Method D923. Record on the label of the sample
6 0.0005 in., or flat steel “go” and “no-go” gages having a
container identification of the device from which the sample
thickness of 2.53 mm and 2.55 mm or 0.0995 and 0.1005 in.,
was obtained, the date, and temperature of the sample at the
respectively. Recheck the spacing following any disturbance of
timeofcollection(Note1).Priortostartingthetest,thesample
the cup or el
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