ASTM D3300-20

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Designation: D3300 − 12 D3300 − 20
Standard Test Method for
Dielectric Breakdown Voltage of Insulating Oils of
Petroleum Origin Liquids Under Impulse Conditions
This standard is issued under the fixed designation D3300; 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 covers the determination of the dielectric breakdown voltage of insulating oilsliquids in a highly divergent
field under impulse conditions.conditions and has been found applicable to liquids of petroleum origin, natural and synthetic esters.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI 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.
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:
D923 Practices for Sampling Electrical Insulating Liquids
D2864 Terminology Relating to Electrical Insulating Liquids and Gases
2.2 IEEE Documents:
IEEE Standard 4-1995 Techniques for High-Voltage Testing
3. Significance and Use
3.1 This test method is most commonly performed using a negative polarity point opposing a needle or a sharp defined point to
an opposing grounded sphere (NPS). The NPS breakdown voltage of fresh unused oilsliquids measured in the highly divergent
field in this configuration depends on oil the insulating liquid composition, decreasing with increasing concentration of aromatic,
particularly polyaromatic, hydrocarbon molecules.molecules in liquids of petroleum origin and decreasing with ester molecular
structure, either natural or synthetic.
This test method is under the jurisdiction of ASTM Committee D27 on Electrical Insulating Liquids and Gases and is the direct responsibility of Subcommittee D27.05
on Electrical Test.
Current edition approved Jan. 1, 2012Nov. 1, 2020. Published January 2012November 2020. Originally approved in 1974. Last previous edition approved in 20062012
as D3300 – 00D3300 – 12.(2006). DOI: 10.1520/D3300-12.10.1520/D3300-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
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D3300 − 20
3.2 This test method may be used to evaluate the continuity of composition of an oil insulating liquid from shipment to shipment.
The NPS impulse breakdown voltage of an oil insulating liquid can also be substantially lowered by contact with materials of
construction, by service aging, particulate matter, and by other impurities. Test results lower than those expected for a given fresh
oilliquid may also indicate use or contamination of that oil.contamination.
3.3 Although polarity of the voltage wave has little or no effect on the breakdown strength of an oil insulating liquid in uniform
fields, polarity does have a marked effect on the breakdown voltage of an oil in nonuniform electric fields.
3.4 Transient voltages may also vary over a wide range in both the time to reach crest value and the time to decay to half crest
or to zero magnitude. The IEEE standard lightning impulse test (see 2.2) specifies a 1.2 by 50-μs negative polarity wave.
4. Apparatus
4.1 Impulse Generator, capable of producing a standard 1.2 by 50-μs full wave adjustable to positive or negative polarity. The
generator shall have a nominal voltage rating of at least 300 kV adjustable in 10-kV steps. Generators having a capability of 1000
W·s (1000 J) at 300 kV have been found satisfactory.
4.2 Voltage-Control Equipment—The controls shall include a suitable measuring device for predetermining the crest voltage to
within 65 %. A voltage stabilizer is desirable at the input to the d-c power supply used for charging the impulse-generator
capacitors.
4.3 Electrodes:
4.3.1 The electrodes shall consist of a polished steel or brass sphere of 0.5 in. (12.7 mm) diameter and a steel point. The point
may be an ordinary steel phonograph needle with a 0.06 mm 6 20 % radius of curvature of point. Needles with drawn tips are
not recommended.
4.3.2 The effect of variation in the radius of curvature of point is subject to further investigation. Both electrodes shall be easily
replaceable.
4.4 Test Cell:
4.4.1 The test cell shall be made of a material of high dielectric strength and of such dimensions that the electrical breakdown is
restricted to the electrode gap. Test cell materials shall resist attack by, and be insoluble in, any of the cleaning or test liquids used.
Test cells such as those shown in Fig. 1 and Fig. 2 have been found satisfactory.
4.4.2 The sphere electrode shall be rigidly fixed and the point electrode mounted such that the gap may be adjusted from zero to
the required value.
5. Sampling
5.1 Obtain a sample of the insulating liquid to be tested using appropriate ASTM sampling apparatus in accordance with Practices
D923.
6. Adjustments and Care of Electrodes and Test Cell
6.1 Electrode Spacing:
6.1.1 For the cell shown in Fig. 1, reduce the electrode gap to zero spacing. Proceed very carefully to avoid damaging the point.
The point of contact shall be established electrically with an ohmmeter. Open the gap to the specified spacing using a dial
micrometer or other suitable method.
The following steel needle has been found satisfactory for this method: Type L Nickel Plated Steel Phonograph Needle.
The sole source of supply of the apparatus known to the committee at this time is Victrola Repair Service, 206 Cliff St., St. Johnsbury, VT, 05819. If you are aware of
alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible
technical committee, which you may attend.
D3300 − 20
FIG. 1 Test Cell
6.1.2 For the cell shown in Fig. 2, the gap may be set with a go-no-go gage.
6.1.3 The gap spacings shall be 1.0 in. (25.4 mm) for point-to-sphere and 0.15 in. (3.8 mm) for sphere-to-sphere electrode
configuration.
6.2 Cleaning—Degrease the cell and electrodes by rinsing them with reagent grade petroleum ether, washing with detergent and
hot water, rinsing thoroughly in hot tap water, and then rinsing them with distilled water. Dry the cell and hardware in an oven
for 2 h at approximately 105 to 110°C, remove, and store in a desiccator until needed.needed or clean with acceptable hydrocarbon
solvent such as heptane, hexane or pentane. Allow solvent to evaporate or place into oven to dry. Keep cell protected from outside
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