ASTM D1169-95

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
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Designation: D 1169 – 95
Standard Test Method for
Specific Resistance (Resistivity) of Electrical Insulating
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Liquids
This standard is issued under the fixed designation D 1169; 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 3.1.1 specific resistance (resistivity), n—the ratio of the dc
potential gradient in volts per centimetre paralleling the current
1.1 This test method covers the determination of specific
flow within the specimen, to the current density in amperes per
resistance (resistivity) applied to new electrical insulating
square centimetre at a given instant of time and under
liquids, as well as to liquids in service, or subsequent to
prescribed conditions. This is numerically equal to the resis-
service, in cables, transformers, circuit breakers, and other
tance between opposite faces of a centimetre cube of the liquid.
electrical apparatus.
The units are ohm-centimetres.
1.2 This test method covers a procedure for making referee
tests with dc potential.
4. Significance and Use
1.3 When it is desired to make routine determinations
4.1 The resistivity of a liquid is a measure of its electrical
requiring less accuracy, certain modifications to this test
insulating properties under conditions comparable to those of
method are permitted as described in Sections 19-26.
the test. High resistivity reflects low content of free ions and
1.4 This standard does not purport to address all of the
ion-forming particles, and normally indicates a low concentra-
safety concerns, if any, associated with its use. It is the
tion of conductive contaminants.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5. General Considerations
bility of regulatory limitations prior to use. See Note 5 for a
5.1 Theory and measuring equipment pertaining to this
specific cautionary statement.
method shall be in accordance with Test Methods D 257.
2. Referenced Documents 5.2 Where both ac loss characteristic (dissipation factor or
power factor) and resistivity measurements are to be made
2.1 ASTM Standards:
consecutively on the same specimen, make the ac measurement
D 150 Test Methods for A-C Loss Characteristics and
before applying the dc potential to the specimen, and short
Permittivity (Dielectric Constant) of Solid Electrical Insu-
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circuit the cell electrodes for 1 min immediately prior to
lating Materials
making the resistivity measurements.
D 257 Test Methods for D-C Resistance or Conductance of
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5.3 Make referee tests for resistivity in an atmosphere of
Insulating Materials
less than 50 % relative humidity. For repeatable results make
D 923 Test Method for Sampling Electrical Insulating
3 these tests under carefully controlled atmospheric conditions.
Liquids
5.4 Aside from the adverse influence of contamination on
D 924 Test Method for Dissipation Factor (or Power Factor)
results of the resistivity test, there are other factors that can
and Relative Permittivity (Dielectric Constant) of Electri-
3 contribute to variations in the test results as follows:
cal Insulating Liquids
5.4.1 The use of an instrument not having an adequate range
E 145 Specification for Gravity-Convection and Forced-
4 for accurately measuring the current flowing in the circuit. (See
Ventilation Ovens
Section 6 for two types of recommended instruments.)
3. Terminology 5.4.2 When the time of electrification is not exactly the
same for every test. Upon the application of voltage the current
3.1 Definitions of Terms Specific to This Standard:
flow through the specimen decreases asymptotically toward a
limiting value. Variation in the time of electrification can result
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This test method is under the jurisdiction of ASTM Committee D-27 on
in appreciable variation in the test results.
Electrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-
5.4.3 Undue length of time required for the test specimen in
mittee D27.05on Electrical Tests.
Current edition approved Sept. 10, 1995. Published November 1995. Originally
the cell to attain the desired test temperature. This is one of the
published as D 1169 – 51 T. Last previous edition D 1169 – 89.
main sources of erroneous results. For optimum results, attain
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Annual Book of ASTM Standards, Vol 10.01.
3 the test temperature within 20 min.
Annual Book of ASTM Standards, Vol 10.03.
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5.4.4 Fluctuations in the test voltage (see 6.1.4).
Annual Book of ASTM Standards, Vol 14.02.
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