ASTM D117-22

Standard Guide for Sampling, Test Methods, and Specifications for Electrical Insulating Liquids

ABSTRACT
This guide describes methods of testing and specifications for electrical insulating oils of petroleum origin intended for use in electrical cables, transformers, oil circuit breakers, and other electrical apparatus where the oils are used as insulating, or heat transfer media, or both. This guide is classified into the following categories: sampling practices, physical tests, electrical tests, chemical tests, and specifications. The test methods shall be as follows: aniline point; coefficient of thermal expansion; color; examination; flash and fire point; interfacial tension; pour point of petroleum products; refractive index; relative density; specific heat; thermal conductivity; turbidity; viscosity; dielectric breakdown voltage; dissipation factor and relative permittivity; gassing tendency; resistivity; stability under electrical discharge; acidity; carbon-type composition; compatibility with construction material; copper content; furanic compounds; gas analysis; gas content; inorganic chlorides and sulfates; neutralization numbers; oxidation inhibitor content; oxidation stability; polychlorinated biphenyl content; sediment and soluble sludge; sulfur; water content; mineral insulating oil for electrical apparatus; and high firepoint electrical insulating oils.
SCOPE
1.1 This guide describes methods of testing and specifications for electrical insulating liquids intended for use in electrical cables, transformers, liquid-filled circuit breakers, and other electrical apparatus where the liquids are used as insulating, or heat transfer media, or both.  
1.2 The purpose of this guide is to outline the applicability of the available test methods. Where more than one is available for measuring a given property, their relative advantages are described, along with an indication of laboratory convenience, precision, (95 % confidence limits), and applicability to specific types of electrical insulating liquids.  
1.3 This guide is classified into the following categories: Sampling Practices, Physical Tests, Electrical Tests, Chemical Tests, and Specifications. Within each test category, the test methods are listed alphabetically by property measured. A list of standards follows:    
Category  
Section  
ASTM Standard  
Sampling:  
3  
D923  
Physical Tests:  
Aniline Point  
4  
D611  
Coefficient of Thermal Ex-
pansion  
5  
D1903  
Color  
6  
D1500  
Examination: Visual Infrared  
7  
D1524, D2144, D2129  
Flash and Fire Point  
8  
D92  
Interfacial Tension  
9  
D971  
Pour Point of Petroleum
Products  
10  
D97, D5949, D5950  
Particle Count in Mineral
Insulating Oil  
11  
D6786  
Refractive Index and Specific
Optical Dispersion  
12  
D1218  
Relative Density (Specific
Gravity)  
13  
D287, D1217, D1298, D1481, D4052  
Specific Heat  
14  
D2766  
Thermal Conductivity  
15  
D2717  
Viscosity  
16  
D445, D2161, D7042  
Electrical Tests:  
Dielectric Breakdown Voltage  
17  
D877, D1816, D3300  
Dissipation Factor and Rela-
tive Permittivity (Dielectric
Constant)  
18  
D924  
Gassing Characteristic
Under Thermal Stress  
19  
D7150  
Gassing Tendency  
20  
D2300  
Resistivity  
21  
D1169  
Chemical Tests:  
Acidity, Approximate  
22  
D1534  
Carbon-Type Composition  
23  
D2140  
Compatibility with Construc-
tion Material  
24  
D3455  
Copper Content  
25  
D3635  
Elements by Inductively
Coupled Plasma (ICP-AES)  
26  
D7151  
Furanic Compounds in
Electrical Insulating Liquids  
27  
D5837  
Dissolved Gas Analysis  
28  
D3612  
Gas Content of Cable and
Capacitor Liquids  
29  
D831, D1827, D2945  
Neutralization (Acid and
Base) Numbers  
30  
D664, D974  
Oxidation Inhibitor Content  
31  
D2668, D4768  
Oxidation Stability  
32  
D1934, D2112, D2440  
P...

General Information

• Status: Published
• Publication Date: 30-Apr-2022
• ICS: 29.040.10 - Insulating oils
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.01 - Mineral

Relations

• Refers: ASTM D445-24 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Apr-2024
• Refers: ASTM D1500-24 - Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
• Effective Date: 01-Mar-2024
• Refers: ASTM D1275-24 - Standard Test Method for Corrosive Sulfur in Electrical Insulating Liquids
• Effective Date: 15-Jan-2024
• Refers: ASTM D2140-23 - Standard Practice for Calculating Carbon-Type Composition of Insulating Oils of Petroleum Origin
• Effective Date: 01-Dec-2023
• Refers: ASTM D924-23 - Standard Test Method for Dissipation Factor (or Power Factor) and Relative Permittivity (Dielectric Constant) of Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Refers: ASTM D2140-23e1 - Standard Practice for Calculating Carbon-Type Composition of Insulating Oils of Petroleum Origin
• Effective Date: 01-Dec-2023
• Refers: ASTM D5837-15(2023) - Standard Test Method for Furanic Compounds in Electrical Insulating Liquids by High-Performance Liquid Chromatography (HPLC)
• Effective Date: 01-Dec-2023
• Refers: ASTM D2112-15(2023) - Standard Test Method for Oxidation Stability of Inhibited Mineral Insulating Oil by Pressure Vessel
• Effective Date: 01-Dec-2023
• Refers: ASTM D6786-15(2023) - Standard Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
• Effective Date: 01-Dec-2023
• Refers: ASTM D7151-15(2023) - Standard Test Method for Determination of Elements in Insulating Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
• Effective Date: 01-Dec-2023
• Refers: ASTM D923-15(2023) - Standard Practices for Sampling Electrical Insulating Liquids
• Effective Date: 01-Dec-2023
• Refers: ASTM D445-23 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Nov-2023
• Refers: ASTM D1217-20 - Standard Test Method for Density and Relative Density (Specific Gravity) of Liquids by Bingham Pycnometer
• Effective Date: 01-May-2020
• Refers: ASTM D971-20 - Standard Test Method for Interfacial Tension of Insulating Liquids Against Water by the Ring Method
• Effective Date: 01-Apr-2020
• Refers: ASTM D4768-11(2019) - Standard Test Method for Analysis of 2,6-Ditertiary-Butyl Para-Cresol and 2,6-Ditertiary-Butyl Phenol in Insulating Liquids by Gas Chromatography
• Effective Date: 01-Dec-2019

Overview

ASTM D117-22 is the ASTM International standard guide for sampling, test methods, and specifications for electrical insulating liquids, primarily of petroleum origin. These insulating liquids are critical in electrical apparatus such as transformers, cables, and circuit breakers, where they function as both dielectric insulation and heat transfer media. The standard covers essential methodologies for sample collection, physical, electrical, and chemical property assessment, and specifications ensuring quality and performance throughout the lifecycle of electrical insulating liquids.

Key Topics

The standard focuses on several key aspects of electrical insulating liquids:

• Sampling Practices: Guidance on representative sampling using ASTM D923 to avoid contamination and ensure accurate analysis.
• Physical Properties: Methods to assess aniline point, thermal expansion, color, flash and fire point, interfacial tension, pour point, particle count, refractive index, relative density, specific heat, thermal conductivity, turbidity, and viscosity. Each property impacts how the insulating oil performs under operational conditions.
• Electrical Properties: Testing includes dielectric breakdown voltage, dissipation factor, relative permittivity, gassing characteristics, resistivity, and stability under electrical discharge, all of which are vital for electrical insulation performance and reliability.
• Chemical Properties: Evaluation of acidity, carbon-type composition, compatibility with materials, copper content, furanic compounds, dissolved gas content, gas content, chlorides and sulfates, neutralization numbers, inhibitor content, oxidation stability, PCB content, sediment and sludge, sulfur content, and water content determines oil purity and service life.
• Specifications: Parameters for different insulating fluids, including mineral, silicone, and natural ester oils, ensuring compatibility and safety in various electrical apparatus.

Applications

ASTM D117-22 is widely used in industries maintaining, designing, or manufacturing high-voltage equipment. Practical applications include:

• Transformer Oil Testing: Routine monitoring for properties such as dielectric strength, moisture, and acidity to ensure transformer reliability and prevent failures.
• Cable Insulating Liquids: Assessment of pour point, viscosity, and interfacial tension to confirm proper flow and insulation over a range of temperatures.
• Oil-Filled Circuit Breakers: Evaluating dielectric breakdown and gassing properties to minimize risk of equipment malfunction or fire.
• Material Compatibility: Ensuring that insulating liquids do not degrade internal materials, such as gaskets and metals, within electrical equipment.

Through prescribed test methods, the standard helps users detect contamination, oxidation, and aging, driving predictive maintenance and extending equipment life. It also assists manufacturers and utilities in certifying that products meet quality benchmarks for performance and regulatory compliance.

Related Standards

ASTM D117-22 is closely linked with numerous other ASTM standards referenced within its text:

• ASTM D923: Practices for sampling electrical insulating liquids
• ASTM D445, D2161, D7042: Viscosity measurement methods
• ASTM D877, D1816: Dielectric breakdown voltage testing
• ASTM D924: Dissipation factor and relative permittivity
• ASTM D1500: Color determination methods
• ASTM D1533: Measurement of water content by Karl Fischer
• ASTM D3487/D4652/D6871: Specifications for mineral oil, silicone, and natural ester insulating liquids

Other international standards, such as those from IEC or IEEE, may provide complementary guidance for insulating liquids in electrical applications.

---

Keywords: ASTM D117-22, transformer oil test methods, electrical insulating liquid standards, insulating oil sampling, dielectric fluid specifications, transformer maintenance, electrical equipment insulation, oil-filled circuit breaker testing.

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: D117 −22
Standard Guide for
Sampling, Test Methods, and Specifications for Electrical
Insulating Liquids
This standard is issued under the fixed designation D117; 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
Category Section ASTM Standard
Dielectric Breakdown Voltage 17 D877, D1816, D3300
1.1 This guide describes methods of testing and specifica-
Dissipation Factor and Rela- 18 D924
tions for electrical insulating liquids intended for use in tive Permittivity (Dielectric
Constant)
electrical cables, transformers, liquid-filled circuit breakers,
Gassing Characteristic 19 D7150
and other electrical apparatus where the liquids are used as
Under Thermal Stress
insulating, or heat transfer media, or both. Gassing Tendency 20 D2300
Resistivity 21 D1169
1.2 The purpose of this guide is to outline the applicability
Chemical Tests:
Acidity, Approximate 22 D1534
oftheavailabletestmethods.Wheremorethanoneisavailable
Carbon-Type Composition 23 D2140
for measuring a given property, their relative advantages are
Compatibility with Construc- 24 D3455
described, along with an indication of laboratory convenience,
tion Material
Copper Content 25 D3635
precision, (95% confidence limits), and applicability to spe-
Elements by Inductively 26 D7151
cific types of electrical insulating liquids.
Coupled Plasma (ICP-AES)
Furanic Compounds in 27 D5837
1.3 This guide is classified into the following categories:
Electrical Insulating Liquids
Sampling Practices, Physical Tests, Electrical Tests, Chemical
Dissolved Gas Analysis 28 D3612
Gas Content of Cable and 29 D831, D1827, D2945
Tests, and Specifications. Within each test category, the test
Capacitor Liquids
methods are listed alphabetically by property measured. A list
Neutralization (Acid and 30 D664, D974
of standards follows:
Base) Numbers
Oxidation Inhibitor Content 31 D2668, D4768
Category Section ASTM Standard
Oxidation Stability 32 D1934, D2112, D2440
Sampling: 3 D923
Polychlorinated Biphenyl 33 D4059
Physical Tests:
Content (PCB)
Aniline Point 4 D611
Sulfur, Corrosive 34 D1275
Coefficient of Thermal Ex- 5 D1903
Water Content 35 D1533
pansion
Specification:
Color 6 D1500
Mineral Insulating Liquid for 36 D3487
Examination: Visual Infrared 7 D1524, D2144, D2129
Electrical Apparatus
Flash and Fire Point 8 D92
Less Flammable Electrical 37 D5222
Interfacial Tension 9 D971
Insulating Liquids
Pour Point of Petroleum 10 D97, D5949, D5950
Silicone Fluid used for Electrical 38 D4652
Products
Insulation
Particle Count in Mineral 11 D6786
Natural (Vegetable Oil) Ester 39 D6871
Insulating Oil
Fluids used in Electrical
Refractive Index and Specific 12 D1218
Apparatus
Optical Dispersion
Relative Density (Specific 13 D287, D1217, D1298, D1481,
1.4 The values stated in SI units are to be regarded as
Gravity) D4052
standard. The values stated in parentheses are provided for
Specific Heat 14 D2766
information only.
Thermal Conductivity 15 D2717
Viscosity 16 D445, D2161, D7042
1.5 This standard does not purport to address all of the
Electrical Tests:
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
This guide is under the jurisdiction of ASTM Committee D27 on Electrical
Insulating Liquids and Gases and is the direct responsibility of Subcommittee
mine the applicability of regulatory limitations prior to use.
D27.01 on Mineral.
1.6 This international standard was developed in accor-
Current edition approved May 1, 2022. Published June 2022. Originally
dance with internationally recognized principles on standard-
published as D117–21T. Last previous edition approved in 2018 as D117–18.
DOI: 10.1520/D0117-22. ization established in the Decision on Principles for the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D117 − 22
Development of International Standards, Guides and Recom- D1534Test Method for Approximate Acidity in Electrical
mendations issued by the World Trade Organization Technical Insulating Liquids by Color-Indicator Titration
Barriers to Trade (TBT) Committee. D1816Test Method for Dielectric Breakdown Voltage of
Insulating Liquids Using VDE Electrodes
2. Referenced Documents
D1827Test Method for Gas Content (Nonacidic) of Insulat-
ing Liquids by Displacement with Carbon Dioxide (With-
2.1 ASTM Standards:
drawn 2009)
D92Test Method for Flash and Fire Points by Cleveland
Open Cup Tester D1903Practice for Determining the Coefficient of Thermal
Expansion of Electrical Insulating Liquids of Petroleum
D97Test Method for Pour Point of Petroleum Products
D287Test Method forAPI Gravity of Crude Petroleum and Origin, and Askarels
D1934Test Method for Oxidative Aging of Electrical Insu-
Petroleum Products (Hydrometer Method)
D445Test Method for Kinematic Viscosity of Transparent lating Liquids by Open-Beaker Method
D2112Test Method for Oxidation Stability of Inhibited
and Opaque Liquids (and Calculation of DynamicViscos-
ity) Mineral Insulating Oil by Pressure Vessel
D2129Test Method for Color of Clear Electrical Insulating
D611Test Methods for Aniline Point and Mixed Aniline
Liquids (Platinum-Cobalt Scale)
Point of Petroleum Products and Hydrocarbon Solvents
D2140Practice for Calculating Carbon-Type Composition
D664Test Method for Acid Number of Petroleum Products
of Insulating Oils of Petroleum Origin
by Potentiometric Titration
D2144Practices for Examination of Electrical Insulating
D831Test Method for Gas Content of Cable and Capacitor
Oils by Infrared Absorption
Oils
D2161Practice for Conversion of Kinematic Viscosity to
D877Test Method for Dielectric Breakdown Voltage of
Saybolt Universal Viscosity or to Saybolt Furol Viscosity
Insulating Liquids Using Disk Electrodes
D2300Test Method for Gassing of Electrical Insulating
D923Practices for Sampling Electrical Insulating Liquids
Liquids Under Electrical Stress and Ionization (Modified
D924Test Method for Dissipation Factor (or Power Factor)
Pirelli Method)
and Relative Permittivity (Dielectric Constant) of Electri-
D2440Test Method for Oxidation Stability of Mineral
cal Insulating Liquids
D971Test Method for Interfacial Tension of Insulating Insulating Oil
D2668Test Method for 2,6-di-tert-Butyl- p-Cresol and 2,6-
Liquids Against Water by the Ring Method
D974Test Method for Acid and Base Number by Color- di-tert-Butyl Phenol in Electrical Insulating Oil by Infra-
red Absorp
Indicator Titration
D1169Test Method for Specific Resistance (Resistivity) of D2717Test Method for Thermal Conductivity of Liquids
(Withdrawn 2018)
Electrical Insulating Liquids
D1217Test Method for Density and Relative Density (Spe- D2766Test Method for Specific Heat of Liquids and Solids
(Withdrawn 2018)
cific Gravity) of Liquids by Bingham Pycnometer
D2864Terminology Relating to Electrical Insulating Liq-
D1218Test Method for Refractive Index and Refractive
uids and Gases
Dispersion of Hydrocarbon Liquids
D2945Test Method for Gas Content of Insulating Oils
D1250Guide for the Use of the Joint API and ASTM
(Withdrawn 2012)
Adjunct for Temperature and Pressure Volume Correction
D3300Test Method for Dielectric Breakdown Voltage of
FactorsforGeneralizedCrudeOils,RefinedProducts,and
Insulating Liquids Under Impulse Conditions
Lubricating Oils: API MPMS Chapter 11.1
D3455Test Methods for Compatibility of Construction Ma-
D1275Test Method for Corrosive Sulfur in Electrical Insu-
terial with Electrical Insulating Oil of Petroleum Origin
lating Liquids
D3487Specification for Mineral Insulating Oil Used in
D1298Test Method for Density, Relative Density, or API
Electrical Apparatus
Gravity of Crude Petroleum and Liquid Petroleum Prod-
D3612Test Method for Analysis of Gases Dissolved in
ucts by Hydrometer Method
D1481Test Method for Density and Relative Density (Spe- Electrical Insulating Oil by Gas Chromatography
D3635Test Method for Dissolved Copper In Electrical
cific Gravity) of Viscous Materials by Lipkin Bicapillary
Pycnometer Insulating Oil By Atomic Absorption Spectrophotometry
D4052Test Method for Density, Relative Density, and API
D1500Test Method forASTM Color of Petroleum Products
(ASTM Color Scale) Gravity of Liquids by Digital Density Meter
D4059Test Method for Analysis of Polychlorinated Biphe-
D1524Test Method for Visual Examination of Used Elec-
trical Insulating Liquids in the Field nyls in Insulating Liquids by Gas Chromatography
D4652Specification for Silicone Liquid Used for Electrical
D1533Test Method for Water in Insulating Liquids by
Insulation
Coulometric Karl Fischer Titration
D4768Test Method for Analysis of 2,6-Ditertiary-Butyl
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 last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
D117 − 22
Para-Cresol and 2,6-Ditertiary-Butyl Phenol in Insulating placedinatubeandmixedmechanically.Themixtureisheated
Liquids by Gas Chromatography at a controlled rate until the two phases become miscible. The
D5185Test Method for Multielement Determination of mixture is then cooled at a controlled rate, and the temperature
Used and Unused Lubricating Oils and Base Oils by at which the two phases separate is recorded as the aniline
Inductively Coupled Plasma Atomic Emission Spectrom- point.
etry (ICP-AES)
4.3 Significance and Use—Theanilinepointofaninsulating
D5222Specification for High Fire-Point Mineral Electrical
liquid indicates the solvency of the liquid for some materials
Insulating Oils
that are in contact with the liquid. A higher aniline point
D5837Test Method for Furanic Compounds in Electrical
implies a lower aromaticity and a lower degree of solvency for
Insulating Liquids by High-Performance Liquid Chroma-
some materials.
tography (HPLC)
D5949Test Method for Pour Point of Petroleum Products
5. Coefficient of Thermal Expansion
(Automatic Pressure Pulsing Method)
5.1 Scope—Practice D1903 covers the determination of the
D5950Test Method for Pour Point of Petroleum Products
coefficient of thermal expansion of electrical insulating liquids
(Automatic Tilt Method)
of petroleum origin.
D6786Test Method for Particle Count in Mineral Insulating
5.2 Definition:
Oil Using Automatic Optical Particle Counters
D6871SpecificationforNatural(VegetableOil)EsterFluids 5.2.1 coeffıcient of thermal expansion—the change in vol-
ume per unit volume per degree change in temperature. It is
Used in Electrical Apparatus
D7042Test Method for Dynamic Viscosity and Density of commonly stated as the average coefficient over a given
temperature range.
Liquids by Stabinger Viscometer (and the Calculation of
Kinematic Viscosity)
5.3 Summary of Practice—Thespecificgravityofinsulating
D7150Test Method for the Determination of Gassing Char-
liquids is determined at two temperatures below 90°C and
acteristics of Insulating Liquids Under Thermal Stress
separated by not less than 5°C nor more than 14°C. Test
D7151Test Method for Determination of Elements in Insu-
methods used may be D287, D1217, D1298,or D1481. The
lating Oils by Inductively Coupled Plasma Atomic Emis-
calculation of average coefficient of thermal expansion over
sion Spectrometry (ICP-AES)
this temperature range is given in Practice D1903.
2.2 ASTM Adjunct:
5.4 Significance and Use—Aknowledgeofthecoefficientof
Adjunct to D1250Guide for Petroleum MeasurementTables
expansion of a liquid is essential to compute the required size
(API MPMS Chapter 11.1)
of a container to accommodate a volume of liquid over the full
temperature range to which it will be subjected. It is also used
SAMPLING
to compute the volume of void space that would exist in an
3. Sampling
inelasticdevicefilledwiththeliquidaftertheliquidhascooled
to a lower temperature.
3.1 Accurate sampling, whether of the complete contents or
only parts thereof, is extremely important from the standpoint
6. Color
of evaluation of the quality of the product sampled. Obviously,
careless sampling procedure or contamination in the sampling 6.1 Scope—Test Method D1500 covers the visual determi-
equipment will result in a sample that is not truly representa- nation of color of a wide variety of liquid petroleum products,
tive. This generally leads to erroneous conclusions concerning including mineral insulating liquids.
qualityandincurslossofthetime,effort,andexpenseinvolved
6.2 Summary of Test Method:
in securing, transporting, and testing the sample.
6.2.1 Test Method D1500—The test specimen is placed in a
3.2 Sample the insulating liquid in accordance with Prac- glass sample jar (an ordinary 125-mL test specimen bottle is
tices D923 as appropriate. satisfactory for routine tests). The color of the sample by
transmitted light is compared with a series of tinted glass
PHYSICAL PROPERTIES
standards. The glass standard matching the sample is selected,
or if an exact match is not possible, the next darker glass is
4. Aniline Point
selected. The results are reported numerically on a scale of 0.5
4.1 Scope—Test Method D611 covers the determination of
to 8.0.
the aniline point of petroleum products, provided that the
6.3 Significance—A low color number is an essential re-
aniline point is below the bubble point and above the solidifi-
quirement for inspection of assembled apparatus in a tank.An
cation point of the aniline-sample mixture.
increase in the color number during service is an indicator of
4.2 Summary of Test Method:
deterioration or contamination of the insulating liquid.
4.2.1 Test Method D611—Equal volumes of aniline and test
specimen or aniline and test specimen plus n-heptane are
7. Examination: Visual/Infrared
7.1 Scope:
7.1.1 Both visual examination and qualitative infrared ab-
Available from ASTM International Headquarters. Order Adjunct No. ADJ-
ADJD1250. Original adjunct produced in 1983. sorption are described in this section. The test methods are:
D117 − 22
7.1.2 Test Method D1524—This is a visual examination of (9°F⁄minto11°F⁄min)andapplythetestflameevery2°C(or
mineral insulating liquids that have been used in transformers, 5°F) until a flash occurs. Continue heating and testing every
liquid-filled circuit breakers, or other electrical apparatus as 2°C (or 5°F) until the liquid continues to burn for at least 5 s.
insulating or cooling media, or both. The procedure is described in Test Method D92.
7.1.3 Practices D2144—Theinfraredabsorptionfrom2.5to
8.4 Significance and Use—The flash point and fire point
−1
25 µm (4000 to 400 cm ) is recorded as a means of (a)
tests give an indication of the flammability of a liquid. They
establishing continuity by comparison with the spectra of
may also be used to provide a qualitative indication of
previous shipments by the same supplier, (b) for the detection
contamination with more flammable materials. In the latter
of some types of contaminants, (c) for the identification of
context, the flash point test is more sensitive.
liquids in storage or service. This practice is not intended for
the determination of the various constituents of a liquid.
9. Interfacial Tension
7.2 Summary of Test Methods:
9.1 Scope—These test methods cover the measurement,
7.2.1 Test Method D1524—The condition of the test speci-
under nonequilibrium conditions, of the interfacial tension of
men is estimated by observation of cloudiness, foreign
insulating liquids against water. These test methods have been
particles, or suspended matter in the sample by reflected light.
shown by experience to give a reliable indication of the
By use of this test method andTest Methods D1500 or D2129,
presence of hydrophilic compounds.
the color and condition of a test specimen of electrical
9.2 Definition:
insulating liquid may be estimated during a field inspection,
9.2.1 interfacial tension—the molecular attractive force be-
thus assisting in the decision as to whether or not the sample
tween unlike molecules at an interface. It is usually expressed
should be sent to a central laboratory for full evaluation.
in millinewtons per meter.
7.2.2 Practices D2144—The infrared spectrum is recorded
−1
from 2.5 to 25 µm (4000 to 400 cm ) either as the absorption
9.3 Summary of Test Methods:
spectrum itself, or as the differential between the test specimen
9.3.1 Test Method D971—Interfacial tension is determined
and reference liquid. The spectra are compared with reference
by measuring the force necessary to detach a platinum wire
spectra to establish the identity of the liquid. upwardfromtheoilwaterinterface.Tocalculatetheinterfacial
tension, the force so measured is corrected by an empirically
7.3 Significance and Use:
determined factor which depends upon the force applied, the
7.3.1 Practices D2144—The infrared spectrum of an elec-
densities of both oil and water, and the dimensions of the ring.
trical insulating liquid indicates the general chemical compo-
The measurement is completed within 1 min of the formation
sition of the sample. Because of the complex mixture of
of the interface.
compounds present in insulating liquids, the spectrum is not
sharply defined and may not be suitable for quantitative 9.4 Significance and Use—Interfacialtensionmeasurements
estimation of components. The identity of the liquid can be
on electrical insulating liquids provide a sensitive means of
quickly established as being the same or different from detecting small amounts of soluble polar contaminants and
previous samples by comparison with the reference spectra.
products of oxidation.Ahigh value for new mineral insulating
liquidindicatestheabsenceofmostundesirablepolarcontami-
8. Flash and Fire Point
nants. The test is frequently applied to service-aged liquids as
an indication of the degree of deterioration.
8.1 Scope:
8.1.1 Test Method D92 covers the determination of flash
10. Pour Point of Petroleum Products
and fire points of all petroleum products except fuel oil and
those having an open cup flash below 79 °C (175 °F).
10.1 Scope—The pour point is applicable to any petroleum
8.1.2 Thistestmethodshouldbeusedsolelytomeasureand liquid.
describe the properties of materials in response to heat and
10.2 Definition:
flame under controlled laboratory conditions and should not be
10.2.1 pour point—the lowest temperature, expressed as a
used for the description, appraisal, or regulation of the fire
multiple of 3 °C at which the liquid is observed to flow when
hazard of materials under actual fire conditions.
cooled and examined under prescribed conditions.
8.2 Definitions:
10.3 Summary of Test Methods:
8.2.1 flash point—the temperature at which vapors above
10.3.1 After preliminary heating, the test specimen is
the liquid surface first ignite when a small test flame is passed
cooled at a specified rate and examined at intervals of 3 °C for
across the surface under specified conditions.
flow characteristics. The lowest temperature at which move-
8.2.2 fire point—the temperature at which liquid first ignites
mentoftheliquidisobservedwithin5sisreportedasthepour
and burns for at least 5 s when a small test flame is passed
point. The procedure is described in Test Method D97.
across the surface under specified conditions.
10.3.2 TestMethodD5949coversthedeterminationofpour
8.3 Summary of Test Method—Fill the test cup to the point of petroleum products by an automatic instrument that
specifiedlevelwiththetestspecimen.Heatthesampleinitially applies a controlled burst of nitrogen gas onto the specimen
at 14°C⁄min to 17°C⁄min (25°F⁄min to 30°F⁄min) until the surface while the specimen is being cooled and detects
temperature is 56°C (100°F) below the expected flash point. movement of the surface of the test specimen with an optical
Reducetherateoftemperaturechangeto5°C⁄minto6°C⁄min eye.
D117 − 22
10.3.3 Test method D5950 covers the determination of pour 12.1.1 Test Method D1218—Describes a precise method for
point of petroleum products by an automatic instrument that determiningrefractiveindexaccurateto0.00006andrefractive
tilts the test jar during cooling and detects movement of the dispersionaccurateto0.00012.Theliquidmustbetransparent,
surface of the test specimen with an optical eye. no darker thanASTM 4.0 color (see Test Method D1500) and
have a refractive index between 1.33 and 1.50. The specific
10.4 Significance and Use:
optical dispersion is calculated by dividing the refractive
10.4.1 The pour point of an insulating liquid gives an
dispersion value by the specific gravity of the liquid.
indication of the temperature below which it may not be
possible to pour or remove the liquid from its container. 12.2 Definitions:
10.4.2 In connection with liquid for use in cable systems,
12.2.1 refractive index—the ratio of the velocity of light in
the pour point may be useful to indicate the point at which no air to its velocity in the substance under test.
free movement will take place in the cable or to indicate the
12.2.2 specific optical dispersion —the difference between
temperature at which partial separation of wax may occur. the refractive indexes of light of two different wave lengths,
10.4.3 The pour point of an electrical insulating liquid is
both indexes measured at the same temperature, the difference
important as an index of the lowest temperature to which the being divided by the specific gravity also measured at the test
materialmaybecooledwithoutseriouslylimitingthedegreeof
temperature. For convenience, the specific dispersion value is
circulation of the liquid. Some materials are sensitive to
multiplied by 10 .
temperature cycling or prolonged storage at low temperatures,
12.3 Summary of Test Method:
and their pour points may not adequately predict their low
12.3.1 The two methods differ in the accuracy of the
temperature flow properties.
refractometer used.After adjusting the instrument temperature
to 25°C, apply the test specimen to the refracting prism, read
11. Particle Count in Mineral Insulating Oil Using
the refractive index, and read the compensator dial reading.
Automatic Optical Particle Counters
Fromthecorrelationtablessuppliedwiththeinstrumentobtain
11.1 Scope—Test Method D6786 covers the determination
the refractive dispersion. Calculate the specific optical disper-
of particle concentration and particle size distribution in
sion by dividing refractive dispersion by the specific gravity of
mineral insulating liquid. It is suitable for testing liquids
the liquid.
having a viscosity of 6 to 20 mm /s at 40 °C. The test method
12.4 Significance and Use:
is specific to liquid automatic particle analyzers that use the
light extinction principle. 12.4.1 Refractive Index of an insulating liquid varies with
its composition and with the nature and amount of contami-
11.2 Summary of Test Method:
nants held in solution. Where the refractive index of an
11.2.1 Samples are taken in particle-clean bottles that are
insulating liquid when new is known, determinations made on
suitable for particle analysis. The sample bottle is agitated to
the same liquid after periods of service may form a basis for
redistribute particles in the liquid, then the liquid is placed in
estimating any change in composition or the degree of con-
an automatic particle counter, where the number of particles
tamination acquired through service.
andtheirsizedistributionaredeterminedbythelightextinction
12.4.2 Specific Optical Dispersion serves as a quick index
principle.
totheamountofunsaturatedcompoundspresentinaliquid.As
11.2.2 As particles pass through the sensing zone of the
the dispersion values for paraffinic and naphthenic compounds
instrument, the quantity of light reaching the detector is
are nearly the same and are essentially independent of molecu-
obscured. This signal is translated to an equivalent projected
lar weight and structural differences, values above a minimum
areadiameterbasedoncalibrationwithaNIST-traceableliquid
ofabout97bearadirectrelationshiptotheamountofaromatic
(ISO Medium Test Dust suspension).
compounds present in insulating liquid.
11.3 Significance and Use:
11.3.1 Particles in insulating liquid can have a detrimental
13. Relative Density (Specific Gravity)
effect on the dielectric properties of the liquid, depending on
13.1 Scope:
the size, concentration, and nature of the particles. The source
13.1.1 The methods used to measure relative density (spe-
of these particles can be external contaminants, liquid degra-
cific gravity) may use a hydrometer, pycnometer, or an
dationbyproducts,orinternalmaterialssuchasmetals,carbon,
oscillating tube.
or cellulose fibers.
13.1.1.1 Test Method D287—UsesanAPIhydrometerandis
11.3.2 Particle counts provide a general degree of contami-
limited to liquids having a Reid vapor pressure of 180 kPa (26
nation level and may be useful in assessing the condition of
psi) or less.
specific types of electrical equipment. Particle counts can also
13.1.1.2 Test Method D1217—Covers the use of a pycnom-
be used to determine filtering effectiveness when processing
eter to measure the relative density (specific gravity) of
liquid.
petroleum fractions.
11.3.3 If more specific knowledge of the nature of the
13.1.1.3 Test Method D1298—Covers the use of a hydrom-
particles is needed, other tests such as metals analysis or fiber
etertomeasurerelativedensity(specificgravity)directlyorthe
identification and counting must be performed.
measurementofAPIgravityfollowedbyconversiontorelative
12. Refractive Index and Specific Optical Dispersion
density (specific gravity).This test method is limited to liquids
12.1 Scope: having a Reid vapor pressure of 179 kPa (26 psi) or less. This
D117 − 22
test method is most suitable for use with mobile transparent neous single body of liquid. Such conditions have caused
liquids, although it can also be used with viscous liquids if serious overheating of self-cooled apparatus. Suitable precau-
sufficient care is taken in the measurement. tions should be taken to ensure mixing.
13.1.1.4 Test Method D1481—Covers the determination of
the densities of liquids more viscous than 15 mm /s at 20 °C. 14. Specific Heat
Theliquidshouldnothaveavaporpressuregreaterthan13kPa
14.1 Scope—Test Method D2766 covers determination of
(100mmHg)atthetesttemperature.Tomeasurethedensityof
the specific heat of electrical insulating liquids of petroleum
less viscous liquids more accurately than permitted by the
origin.
hydrometer method, Test Method D1217 is available.
14.2 Definition:
13.1.1.5 Test Method D4052—Covers the measurement of
14.2.1 specific heat (or heat capacity) of a substance—a
relative density (specific gravity) by the measurement of
thermodynamic property that is a measure of the amount of
change in oscillation frequency of a vibrating glass tube filled
energy required to produce a given temperature change within
with test liquid.
a unit quantity of that substance. The standard unit of heat
13.2 Definition:
capacity is J/(kg·°C) at some defined temperature.
13.2.1 relative density (specific gravity)—the ratio of the
14.3 Summary of Test Method—The specific heat is deter-
mass(weighedinvacuum)ofagivenvolumeofliquidat15°C
mined by Test Method D2766. The measurement is made by
(60 °F) to the mass of an equal volume of pure water at the
heating a test specimen at a known and fixed rate. Once
same temperature. When reporting results, explicitly state the
dynamic heating equilibrium is obtained, the heat flow is
reference temperature, for example, specific gravity 15/15 °C.
recorded as a function of temperature. The heat flow normal-
13.3 Summary of Test Method:
ized to specimen mass and heating rate is directly proportional
13.3.1 API gravity may be measured at the liquid tempera-
to the specimen’s specific heat capacity.
ture using a hydrometer (Test Methods D287 or D1298)or
14.4 Significance and Use—A knowledge of the specific
Digital Density Meter (Test Method D4052) and converting to
heat is helpful in designing adequate heat transfer properties
15 °C or 60 °F using adjunct to Guide D1250.
forelectricalapparatus.Ahigherspecificheatvalueindicatesa
13.3.2 Relative density (specific gravity) may be measured
more efficient heat transfer medium.
at the liquid temperature using a hydrometer (Test Method
D1298) or by Digital Density Meter (Test Method D4052) and
15. Thermal Conductivity
converted to 15 °C or 60 °F using adjunct to Guide D1250.
15.1 Scope—Test Method D2717 covers the determination
13.3.3 Test Method D1481—The liquid is drawn into the
of the thermal conductivity of electrical insulating liquids of
bicapillary pycnometer through the removable siphon arm and
petroleum origin.
adjusted to volume at the temperature of test. After equilibra-
tion at the test temperature, liquid levels are read; and the
15.2 Definition:
pycnometer is removed from the thermostated bath, cooled to
15.2.1 thermal conductivity—the ability of a substance to
room temperature, and weighed. Density or relative density
transfer energy as heat in the absence of mass transport
(specific gravity), as desired, is then calculated from the
phenomena. The standard unit of thermal conductivity is as
volume at the test temperature, and the weight of the sample.
follows:
The effect of air buoyancy is included in the calculation.
W/ ~m·°C!
13.4 Significance and Use:
15.3 Summary of Test Method—The thermal conductivity is
13.4.1 Electrical insulating liquids are usually sold on the
determined byTest Method D2717.This test method measures
basis of volume delivered at 15 °C (60 °F). Delivery is often
thetemperaturegradientproducedacrosstheliquidbyaknown
made on the basis of net weight of product in drums, and the
amountofenergyintroducedintothetestcellbyanelectrically
specificgravitiesoftenaremeasuredattemperaturesotherthan
heated platinum element.
15°C.Thevaluesofrelativedensity(specificgravity)at15°C
15.4 Significance and Use—A knowledge of thermal con-
must be known to calculate the volume at 15 °C of the liquid
ductivity is helpful in designing adequate heat transfer prop-
delivered.
erties for electrical apparatus. A high value indicates a good
13.4.2 The relative density (specific gravity) of a mineral
heat transfer efficiency property for the liquid.
insulating liquid influences the heat transfer rates and may be
pertinent in determining suitability for use in specific applica-
16. Viscosity
tions. In certain cold climates, ice may form in de-energized
electrical equipment exposed to temperatures below 0 °C, and 16.1 Scope:
the maximum specific gravity of the liquid used in such
16.1.1 Test Method D445—This test method specifies a
equipmentshouldbeatavaluethatwillensurethaticewillnot
procedure for the determination of the kinematic viscosity of
float in the liquid at any temperature the liquid might attain.
liquid petroleum products, both transparent and opaque, by
13.4.3 When making additions of insulating liquid to appa- measuringthetimeforavolumeofliquidtoflowundergravity
ratus in service, a difference in relative density (specific through a calibrated glass capillary viscometer. The dynamic
gravity) may indicate a tendency of the two bodies of liquid to viscosity can be obtained by multiplying the kinematic viscos-
remain in separate layers rather than mixing into a homoge- ity by the density of the liquid.
D117 − 22
16.1.2 Practice D2161—Providestablesorequationsforthe 17.1.3 Test Method D1816—This test method covers the
conversion of centistokes into Saybolt Universal Seconds or determinationofthedielectricbreakdownvoltageofinsulating
Saybolt Furol Seconds at the same temperatures. liquids (liquids of petroleum origin, silicone liquids, high
fire-point mineral electrical insulating liquids, synthetic ester
16.2 Summary of Test Methods:
liquidsandnaturalesterliquids).Thistestmethodisapplicable
16.2.1 Test Method D445—Thetimeismeasuredinseconds
to insulating liquids commonly used in cables, transformers,
for a fixed volume of liquid to flow under gravity through the
liquid-filled circuit breakers, and similar apparatus as an
capillary of a calibrated viscometer under a reproducible
insulating and cooling medium. Refer to Terminology D2864
driving head and at a closely controlled temperature. The
for definitions used in this test method.
kinematic viscosity is the product of the measured flow time
17.1.4 Test Method D3300—Applicable to any liquid com-
and the calibration constant of the viscometer.
monly used as an insulating and cooling medium in high-
16.2.2 Practice D2161—The Saybolt Universal viscosity
voltage apparatus subjected to impulse conditions, such as
equivalent to a given kinematic viscosity varies with the
transient voltage stresses arising from such causes as nearby
temperature at which the determination is made. The basic
lightning strikes and high-voltage switching operations.
conversion values are given in Table 1 of this practice for
17.2 Definition:
37.8°C (100°F). Factors are given for converting units at
17.2.1 dielectric breakdown voltage—the potential differ-
othertemperatures.TheSayboltFurolviscosityequivalentsare
enceatwhichelectricalfailureoccursinanelectricalinsulating
given in Table 3 of this practice for 50.0°C and 98.9°C
material or insulation structure, under prescribed test condi-
(122°F and 210°F) only.
tions.
16.2.3 Test Method D7042—This test method covers and
17.3 Summary of Test Methods:
specifies a procedure for the concurrent measurement of both
17.3.1 Test Method D877—The insulating liquid is tested in
thedynamicviscosity, η,andthedensity, ρ,ofliquidpetroleum
a test cup between two 25.4-mm (1-in.) diameter disk elec-
products and crude oils, both transparent and opaque. The
trodes spaced 2.54 mm (0.100 in.) apart. A 60-Hz voltage is
kinematicviscosity, ν,canbeobtainedbydividingthedynamic
applied between the electrodes and raised from zero at a
viscosity, η, by the density, ρ, obtained at the same test
uniform rate of 3 kV/s. The dielectric breakdown voltage is
temperature.
recorded, prior to the occurrence of disruptive discharge, when
16.3 Significance and Use:
thevoltageacrossthespecimenhasdroppedtolessthan100V.
16.3.1 The fundamental and preferred method for measur-
In the referee procedure, one breakdown test is made on each
ing kinematic viscosity is by use of Test Method D445.
of five fillings of the test cup, and the average and individual
16.3.2 Viscosity of electrical insulating liquids influences
values of breakdown voltage are reported.
theirheattransferproperties,andconsequentlythetemperature
17.3.2 Test Method D1816—Theliquidistestedinatestcell
rise of energized electrical apparatus containing the liquid. At
between spherically capped (VDE) electrodes spaced either 1
low temperatures, the resulting higher viscosity influences the
mm (0.040 in.) or 2 mm (0.080 in.) apart. The liquid is stirred
speed of moving parts, such as those in power circuit breakers,
before and during application of voltage by means of a
switchgear, load tapchanger mechanisms, pumps, and regula-
motor-driven stirrer. A 60-Hz voltage is applied between the
tors.Viscosity controls insulating liquid processing conditions,
electrodes and raised from zero at a uniform rate of 0.5 kV/s.
such as dehydration, degassification and filtration, and liquid
Thevoltageatwhichthecurrentproducedbybreakdownofthe
impregnation rates. High viscosity may adversely affect the
liquid reaches the range of 2 to 20 mA, tripping a circuit
starting up of apparatus in cold climates (for example, spare
breaker, is considered to be the dielectric breakdown voltage.
transformers and replacements). Viscosity affects pressure
In the procedure, five breakdown tests are made on one filling
drop, liquid flow, and cooling rates in circulating liquid
of the test cell. If the five breakdowns fall within the statistical
systems, such as in pipe-type cables and transformers.
requirements, the average value is reported. If not, five
additional breakdowns are required with the average of the ten
ELECTRICAL PROPERTIES
values reported.
17.3.3 Test Method D3300—The electrode system consists
17. Dielectric Breakdown Voltage
of either: (1) two 12.7-mm (0.5-in.) diameter spheres spaced
17.1 Scope: 3.8 mm (0.15 in.) apart or (2) a 12.7-mm (0.5-in.) diameter
sphere and a steel phonograph needle of 0.06-mm radius of
17.1.1 There are two standard test methods for determining
curvatureofpoint,spaced25.4mm(1.0in.)apart.Thepolarity
thedielectricbreakdownvoltageofelectricalinsulatingliquids
of the needle with respect to the sphere can be either positive
at commercial power frequencies, D877 and D1816, and one
or negative. The electrodes are immersed in the liquid in a test
standard test method for determining the dielectric breakdown
cell. An impulse wave of 1.2 by 50 µs wave shape (times to
voltage of insulating liquids under impulse conditions, D3300.
reach crest value and to decay to half of crest value, respec-
17.1.2 Test Method D877—Applicable to petroleum liquids,
tively) is applied at progressively higher voltages until break-
hydrocarbons, and askarels commonly used as insulating and
down occurs.
cooling media in cables, transformers, liquid-filled circuit
breakers, and similar apparatus.The suitability ofTest Method 17.4 Significance and Use:
D877 for testing liquids having viscosities exceeding 900 17.4.1 Power Frequencies (Test Methods D877 and
mm /s at 40 °C (104 °F) has not been determined. D1816)—The dielectric breakdown voltage of an insulating
D117 − 22
liquid at commercial power frequencies is of importance as a 18.1.1 Test Method D924 covers new electrical insulating
measure of the liquid’s ability to withstand electric stress. It is liquids as well as liquids in service or subsequent to service in
thevoltageatwhichbreakdownoccursbetweentwoelectrodes cables, transformers, liquid-filled circuit breakers, and other
under prescribed test conditions. It also serves to indicate the electrical apparatus.
presence of contaminating agents, such as water, dirt, moist 18.1.2 This test method provides a procedure for making
cellulosic fibers, or conducting particles in the liquid, one or refereeandroutinetestsatacommercialfrequencyofapproxi-
more of which may be present when low dielectric breakdown mately 60 Hz.
valuesarefoundbytest.However,ahighdielectricbreakdown
18.2 Summary of Test Method:
voltage does not indicate the absence of all contaminants. See
18.2.1 The loss characteristic is commonly measured in
Appendix X1 of either test method for other influences that
terms of dissipation factor (tangent of the loss angle) or of
affect the dielectric breakdown voltage of a liquid.
power factor (sine of the loss angle). For values up to 0.05,
17.4.1.1 The ability of an insulating liquid to resist break-
dissipation factor and power factor values are equal to each
down under the test conditions is an indication of the ability of
other within about one part in one thousand and the two terms
the insulating liquid to perform its insulating function in
may be considered interchangeable.
electrical apparatus. The average breakdown voltage is com-
18.2.2 Test Method D924—The liquid test specimens are
monly used in specifications for the qualification and accep-
tested in a three-terminal or guarded electrode test cell main-
tance of insulating liquids. It is also used as a control test for
tained at the desired test temperature. Using a bridge circuit,
the refining of new or reclaiming of used insulating liquids.
measure the loss characteristics and capacitance following the
Because of the complex interactions of the factors affecting
instructions appropriate to the bridge being used. For routine
dielectric breakdown voltage the values obtained cannot be
tests, a two-electrode cell may be used.
used for design purposes.
18.3 Significance and Use:
17.4.1.2 The square-edged disk electrodes of Test Method
18.3.1 Dissipation Factor (or Power Factor)—This prop-
D877 are relatively insensitive to dissolved water in concen-
erty is a measure of the dielectric losses in a liquid, and hence,
trations below 60% of the saturation level. This method is
of the amount of energy dissipated as heat. A low value of
recommended for acceptance tests on unprocessed insulating
dissipation factor (or power factor) indicates low dielectric
liquids received from vendors in tank cars, tank trucks, and
losses and a low level of soluble polar ionic or colloidal
drums. It also may be used for the routine testing of liquids
contaminants. This characteristic may be useful as a means of
from selected power systems apparatus.
qualitycontrolandasanindicationofliquidchangesinservice
17.4.1.3 The more uniform electric field associated with
resulting from contamination and liquid deterioration.
VDE electrodes employed in Test Method D1816 is more
18.3.2 Relative Permittivity (Dielectric Constant)—
sensitive to the deleterious effects of moisture in solution,
Insulating liquids are used in general either to insulate com-
especially when cellulosic fibers are present in the liquid, than
ponents of an electrical network from each other and from
is the field in Test Method D877. Test Method D1816 can be
ground,aloneorincombinationwithsolidinsulatingmaterials,
used for processed or as received liquids. Filtering and dehy-
or to function as the dielectric of a capacitor. For the first use,
drating the liquid may increase Test Method D1816 dielectric
a low value of relative permittivity is often desirable in order
breakdown voltages substantially.
to have the capacitance be as small as possible, consistent with
17.4.2 Impulse Conditions (Test Method D3300):
acceptable chemical and heat transfer properties. However, an
17.4.2.1 This test method is most commonly performed
intermediate value of relative permittivity may sometimes be
using a negative polarity point opposing a grounded sphere
advantageous in achieving a better voltage distribution be-
(NPS). The NPS breakdown voltage of fresh unused liquids
tween the liquid and solid insulating materials with which the
measured in the highly divergent field in this configuration
liquid may be in series. When used as the dielectric in a
depends on liquid composition; decreasing with increasing
capacitor, it is desirable to have a higher value of relative
concentrationofaromatic,particularlypolyaromatic,hydrocar-
permittivity so the physical size of the capacitor may be as
bon molecules.
small as possible.
17.4.2.2 This test method may be used to evaluate the
continuity of composition of a liquid from shipment to ship-
19. Gassing Characteristics of Insulating Liquids Under
ment.TheNPSimpulsebreakdownvoltageofaliquidcanalso
Thermal Stress at Low Temperature
be substantially lowered by contact with materials of
19.1 Scope:
construction, by service aging, and by other impurities. Test
19.1.1 Test Method D7150 describes the procedures to
results lower than those expected for a given fresh liquid may
determine the low temperature (120°C) gassing characteristics
also indicate use or contamination of that liquid.
of insulating liquids specifically and without the influence of
17.4.2.3 Although polarity of the voltage wave has little or
other electrical apparatus materials or electrical stresses. This
no effect on the breakdown strength of an liquid in uniform
test method was primarily designed for insulating mineral
fields, polarity does have a marked effect on the breakdown
liquid. It can be applied to other insulating liquids in which
voltage of an liquid in nonuniform electric fields.
dissolved gas-in-liquid analysis (Test Method D3612) is com-
18. Dissipation Factor and Relative Permittivity
monly performed.
(Dielectric Constant)
19.1.2 This test method is particularly suited for detection
18.1 Scope: ofthephenomenonsometimesknownas“straygassing”andis
D117 − 22
also referred to in CIGRE TF11 B39. 1.3 This test method is onethatissealedfromtheoutsideatmosphere.Liquidssparged
performed on electrical insulating liquids to determine the with air generally produce much more hydrogen as a percent-
propensity of the liquid to produce certain gases
...

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: D117 − 18 D117 − 22
Standard Guide for
Sampling, Test Methods, and Specifications for Electrical
Insulating Liquids
This standard is issued under the fixed designation D117; 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 guide describes methods of testing and specifications for electrical insulating liquids intended for use in electrical cables,
transformers, liquidliquid-filled circuit breakers, and other electrical apparatus where the liquids are used as insulating, or heat
transfer media, or both.
1.2 The purpose of this guide is to outline the applicability of the available test methods. Where more than one is available for
measuring a given property, their relative advantages are described, along with an indication of laboratory convenience, precision,
(95 % confidence limits), and applicability to specific types of electrical insulating oils.liquids.
1.3 This guide is classified into the following categories: Sampling Practices, Physical Tests, Electrical Tests, Chemical Tests, and
Specifications. Within each test category, the test methods are listed alphabetically by property measured. A list of standards
follows:
Category Section ASTM Standard
Sampling: 3 D923
Physical Tests:
Aniline Point 4 D611
Coefficient of Thermal Ex- 5 D1903
pansion
Color 6 D1500
Examination: Visual Infrared 7 D1524, D2144, D2129
Flash and Fire Point 8 D92
Interfacial Tension 9 D971, D2285
Interfacial Tension 9 D971
Pour Point of Petroleum 10 D97, D5949, D5950
Products
Particle Count in Mineral 11 D6786
Insulating Oil
Particle Count in Mineral 11 D6786
Insulating Oil
Refractive Index and Specific 12 D1218, D1807
Optical Dispersion
Refractive Index and Specific 12 D1218
Optical Dispersion
Relative Density (Specific 13 D287, D1217, D1298, D1481,
Gravity) D4052
Specific Heat 14 D2766
Thermal Conductivity 15 D2717
This guide is under the jurisdiction of ASTM Committee D27 on Electrical Insulating Liquids and Gases and is the direct responsibility of Subcommittee D27.01 on
Mineral.
Current edition approved Nov. 1, 2018May 1, 2022. Published December 2018June 2022. Originally published as D117 – 21 T. Last previous edition approved in 20102018
as D117 – 10.D117 – 18. DOI: 10.1520/D0117-18.10.1520/D0117-22.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D117 − 22
Category Section ASTM Standard
Turbidity 16 D6181
Viscosity 17 D445, D2161
Viscosity 16 D445, D2161, D7042
Electrical Tests:
Dielectric Breakdown Voltage 18 D877, D1816, D3300
Dielectric Breakdown Voltage 17 D877, D1816, D3300
Dissipation Factor and Rela- 19 D924
tive Permittivity (Dielectric
Constant)
Dissipation Factor and Rela- 18 D924
tive Permittivity (Dielectric
Constant)
Gassing Characteristic 20 D7150
Under Thermal Stress
Gassing Characteristic 19 D7150
Under Thermal Stress
Gassing Tendency 21 D2300
Gassing Tendency 20 D2300
Resistivity 22 D1169
Resistivity 21 D1169
Stability Under Electrical 23 D6180
Discharge
Chemical Tests:
Acidity, Approximate 24 D1534
Acidity, Approximate 22 D1534
Carbon-Type Composition 25 D2140
Carbon-Type Composition 23 D2140
Compatibility with Construc- 26 D3455
tion Material
Compatibility with Construc- 24 D3455
tion Material
Copper Content 27 D3635
Copper Content 25 D3635
Elements by Inductively 28 D7151
Coupled Plasma (ICP-AES)
Elements by Inductively 26 D7151
Coupled Plasma (ICP-AES)
Furanic Compounds in 29 D5837
Electrical Insulating Liquids
Furanic Compounds in 27 D5837
Electrical Insulating Liquids
Dissolved Gas Analysis 30 D3612
Dissolved Gas Analysis 28 D3612
Gas Content of Cable and 31 D831, D1827, D2945
Capacitor Oils
Gas Content of Cable and 29 D831, D1827, D2945
Capacitor Liquids
Inorganic Chlorides and 32 D878
Sulfates
Neutralization (Acid and 33 D664, D974
Base) Numbers
Neutralization (Acid and 30 D664, D974
Base) Numbers
Oxidation Inhibitor Content 34 D2668, D4768
Oxidation Inhibitor Content 31 D2668, D4768
Oxidation Stability 35 D1934, D2112, D2440
Oxidation Stability 32 D1934, D2112, D2440
Polychlorinated Biphenyl 36 D4059
Content (PCB)
Polychlorinated Biphenyl 33 D4059
Content (PCB)
Relative Content of 37 D6802
Dissolved Decay
Sediment and Soluble Sludge 38 D1698
Sulfur, Corrosive 39 D1275
Sulfur, Corrosive 34 D1275
Water Content 40 D1533
Water Content 35 D1533
Specification:
Mineral Insulating Oil for 41 D3487
Electrical Apparatus
Mineral Insulating Liquid for 36 D3487
Electrical Apparatus
High Firepoint Electrical 42 D5222
Insulating Oils
Less Flammable Electrical 37 D5222
Insulating Liquids
D117 − 22
Category Section ASTM Standard
Silicone Fluid used for Electrical 43 D4652
Insulation
Silicone Fluid used for Electrical 38 D4652
Insulation
Natural (Vegetable Oil) Ester 44 D6871
Fluids used in Electrical
Apparatus
Natural (Vegetable Oil) Ester 39 D6871
Fluids used in Electrical
Apparatus
1.4 The values stated in SI units are to be regarded as standard. The values stated in parentheses are provided for information only.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.6 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:
D92 Test Method for Flash and Fire Points by Cleveland Open Cup Tester
D97 Test Method for Pour Point of Petroleum Products
D287 Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer Method)
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D611 Test Methods for Aniline Point and Mixed Aniline Point of Petroleum Products and Hydrocarbon Solvents
D664 Test Method for Acid Number of Petroleum Products by Potentiometric Titration
D831 Test Method for Gas Content of Cable and Capacitor Oils
D877 Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using Disk Electrodes
D878 Test Methods for Inorganic Chlorides and Sulfates in Insulating Oils (Withdrawn 2015)
D923 Practices for Sampling Electrical Insulating Liquids
D924 Test Method for Dissipation Factor (or Power Factor) and Relative Permittivity (Dielectric Constant) of Electrical
Insulating Liquids
D971 Test Method for Interfacial Tension of Insulating Liquids Against Water by the Ring Method
D974 Test Method for Acid and Base Number by Color-Indicator Titration
D1169 Test Method for Specific Resistance (Resistivity) of Electrical Insulating Liquids
D1217 Test Method for Density and Relative Density (Specific Gravity) of Liquids by Bingham Pycnometer
D1218 Test Method for Refractive Index and Refractive Dispersion of Hydrocarbon Liquids
D1250 Guide for the Use of the Joint API and ASTM Adjunct for Temperature and Pressure Volume Correction Factors for
Generalized Crude Oils, Refined Products, and Lubricating Oils: API MPMS Chapter 11.1
D1275 Test Method for Corrosive Sulfur in Electrical Insulating Liquids
D1298 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by
Hydrometer Method
D1481 Test Method for Density and Relative Density (Specific Gravity) of Viscous Materials by Lipkin Bicapillary Pycnometer
D1500 Test Method for ASTM Color of Petroleum Products (ASTM Color Scale)
D1524 Test Method for Visual Examination of Used Electrical Insulating Liquids in the Field
D1533 Test Method for Water in Insulating Liquids by Coulometric Karl Fischer Titration
D1534 Test Method for Approximate Acidity in Electrical Insulating Liquids by Color-Indicator Titration
D1698 Test Method for Sediments and Soluble Sludge in Service-Aged Insulating Oils (Withdrawn 2014)
D1807 Test Methods for Refractive Index and Specific Optical Dispersion of Electrical Insulating Liquids (Withdrawn 2014)
D1816 Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using VDE Electrodes
D1827 Test Method for Gas Content (Nonacidic) of Insulating Liquids by Displacement with Carbon Dioxide (Withdrawn
2009)
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.
The last approved version of this historical standard is referenced on www.astm.org.
D117 − 22
D1903 Practice for Determining the Coefficient of Thermal Expansion of Electrical Insulating Liquids of Petroleum Origin, and
Askarels
D1934 Test Method for Oxidative Aging of Electrical Insulating Liquids by Open-Beaker Method
D2112 Test Method for Oxidation Stability of Inhibited Mineral Insulating Oil by Pressure Vessel
D2129 Test Method for Color of Clear Electrical Insulating Liquids (Platinum-Cobalt Scale)
D2140 Practice for Calculating Carbon-Type Composition of Insulating Oils of Petroleum Origin
D2144 Practices for Examination of Electrical Insulating Oils by Infrared Absorption
D2161 Practice for Conversion of Kinematic Viscosity to Saybolt Universal Viscosity or to Saybolt Furol Viscosity
D2285 Test Method for Interfacial Tension of Electrical Insulating Oils of Petroleum Origin Against Water by the Drop-Weight
Method (Withdrawn 2008)
D2300 Test Method for Gassing of Electrical Insulating Liquids Under Electrical Stress and Ionization (Modified Pirelli Method)
D2440 Test Method for Oxidation Stability of Mineral Insulating Oil
D2668 Test Method for 2,6-di-tert-Butyl- p-Cresol and 2,6-di-tert-Butyl Phenol in Electrical Insulating Oil by Infrared Absorp
D2717 Test Method for Thermal Conductivity of Liquids (Withdrawn 2018)
D2766 Test Method for Specific Heat of Liquids and Solids (Withdrawn 2018)
D2864 Terminology Relating to Electrical Insulating Liquids and Gases
D2945 Test Method for Gas Content of Insulating Oils (Withdrawn 2012)
D3300 Test Method for Dielectric Breakdown Voltage of Insulating Liquids Under Impulse Conditions
D3455 Test Methods for Compatibility of Construction Material with Electrical Insulating Oil of Petroleum Origin
D3487 Specification for Mineral Insulating Oil Used in Electrical Apparatus
D3612 Test Method for Analysis of Gases Dissolved in Electrical Insulating Oil by Gas Chromatography
D3635 Test Method for Dissolved Copper In Electrical Insulating Oil By Atomic Absorption Spectrophotometry
D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter
D4059 Test Method for Analysis of Polychlorinated Biphenyls in Insulating Liquids by Gas Chromatography
D4652 Specification for Silicone Liquid Used for Electrical Insulation
D4768 Test Method for Analysis of 2,6-Ditertiary-Butyl Para-Cresol and 2,6-Ditertiary-Butyl Phenol in Insulating Liquids by
Gas Chromatography
D5185 Test Method for Multielement Determination of Used and Unused Lubricating Oils and Base Oils by Inductively
Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
D5222 Specification for High Fire-Point Mineral Electrical Insulating Oils
D5837 Test Method for Furanic Compounds in Electrical Insulating Liquids by High-Performance Liquid Chromatography
(HPLC)
D5949 Test Method for Pour Point of Petroleum Products (Automatic Pressure Pulsing Method)
D5950 Test Method for Pour Point of Petroleum Products (Automatic Tilt Method)
D6180 Test Method for Stability of Insulating Oils of Petroleum Origin Under Electrical Discharge (Withdrawn 2014)
D6181 Test Method for Measurement of Turbidity in Mineral Insulating Oil of Petroleum Origin (Withdrawn 2012)
D6786 Test Method for Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
D6802 Test Method for Determination of the Relative Content of Dissolved Decay Products in Mineral Insulating Oils by
Spectrophotometry (Withdrawn 2019)
D6871 Specification for Natural (Vegetable Oil) Ester Fluids Used in Electrical Apparatus
D7042 Test Method for Dynamic Viscosity and Density of Liquids by Stabinger Viscometer (and the Calculation of Kinematic
Viscosity)
D7150 Test Method for the Determination of Gassing Characteristics of Insulating Liquids Under Thermal Stress
D7151 Test Method for Determination of Elements in Insulating Oils by Inductively Coupled Plasma Atomic Emission
Spectrometry (ICP-AES)
2.2 ASTM Adjunct:
Adjunct to D1250 Guide for Petroleum Measurement Tables (API MPMS Chapter 11.1)
SAMPLING
3. Sampling
3.1 Accurate sampling, whether of the complete contents or only parts thereof, is extremely important from the standpoint of
evaluation of the quality of the product sampled. Obviously, careless sampling procedure or contamination in the sampling
equipment will result in a sample that is not truly representative. This generally leads to erroneous conclusions concerning quality
and incurs loss of the time, effort, and expense involved in securing, transporting, and testing the sample.
Available from ASTM International Headquarters. Order Adjunct No. ADJADJD1250. Original adjunct produced in 1983.
D117 − 22
3.2 Sample the insulating oilliquid in accordance with Practices D923 as appropriate.
PHYSICAL PROPERTIES
4. Aniline Point
4.1 Scope—Test Method D611 covers the determination of the aniline point of petroleum products, provided that the aniline point
is below the bubble point and above the solidification point of the aniline-sample mixture.
4.2 Summary of Test Method:
4.2.1 Test Method D611—Equal volumes of aniline and test specimen or aniline and test specimen plus n-heptane are placed in
a tube and mixed mechanically. The mixture is heated at a controlled rate until the two phases become miscible. The mixture is
then cooled at a controlled rate, and the temperature at which the two phases separate is recorded as the aniline point.
4.3 Significance and Use—The aniline point of an insulating oilliquid indicates the solvency of the oilliquid for some materials
that are in contact with the oil.liquid. A higher aniline point implies a lower aromaticity and a lower degree of solvency for some
materials.
5. Coefficient of Thermal Expansion
5.1 Scope—Practice D1903 covers the determination of the coefficient of thermal expansion of electrical insulating liquids of
petroleum origin.
5.2 Definition:
5.2.1 coeffıcient of thermal expansion—the change in volume per unit volume per degree change in temperature. It is commonly
stated as the average coefficient over a given temperature range.
5.3 Summary of Test Method—Practice—The specific gravity of insulating oilsliquids is determined at two temperatures below
90°C90 °C and separated by not less than 5°C5 °C nor more than 14°C.14 °C. Test methods used may be D287, D1217, D1298,
or D1481. The calculation of average coefficient of thermal expansion over this temperature range is given in Practice D1903.
5.4 Significance and Use—A knowledge of the coefficient of expansion of a liquid is essential to compute the required size of a
container to accommodate a volume of liquid over the full temperature range to which it will be subjected. It is also used to
compute the volume of void space that would exist in an inelastic device filled with the liquid after the liquid has cooled to a lower
temperature.
6. Color
6.1 Scope—Test Method D1500 covers the visual determination of color of a wide variety of liquid petroleum products, including
mineral insulating oils.liquids.
6.2 Summary of Test Method:
6.2.1 Test Method D1500—The test specimen is placed in a glass sample jar (an ordinary 125-mL test specimen bottle is
satisfactory for routine tests). The color of the sample by transmitted light is compared with a series of tinted glass standards. The
glass standard matching the sample is selected, or if an exact match is not possible, the next darker glass is selected. The results
are reported numerically on a scale of 0.5 to 8.0.
6.3 Significance—A low color number is an essential requirement for inspection of assembled apparatus in a tank. An increase in
the color number during service is an indicator of deterioration or contamination of the insulating oil.liquid.
D117 − 22
7. Examination: Visual/Infrared
7.1 Scope:
7.1.1 Both visual examination and qualitative infrared absorption are described in this section. The test methods are:
7.1.2 Test Method D1524—This is a visual examination of mineral insulating oilsliquids that have been used in transformers,
oilliquid-filled circuit breakers, or other electrical apparatus as insulating or cooling media, or both.
−1
7.1.3 Practices D2144—The infrared absorption from 2.5 to 25 μm (4000 to 400 cm ) is recorded as a means of (a) establishing
continuity by comparison with the spectra of previous shipments by the same supplier, (b) for the detection of some types of
contaminants, (c) for the identification of oilsliquids in storage or service. This test method practice is not intended for the
determination of the various constituents of an oil.a liquid.
7.2 Summary of Test Methods:
7.2.1 Test Method D1524—The condition of the test specimen is estimated by observation of cloudiness, foreign particles, or
suspended matter in the sample by reflected light. By use of this test method and Test Methods D1500 or D2129, the color and
condition of a test specimen of electrical insulating liquid may be estimated during a field inspection, thus assisting in the decision
as to whether or not the sample should be sent to a central laboratory for full evaluation.
−1
7.2.2 Practices D2144—The infrared spectrum is recorded from 2.5 to 25 μm (4000 to 400 cm ) either as the absorption spectrum
itself, or as the differential between the test specimen and reference oil.liquid. The spectra are compared with reference spectra to
establish the identity of the oil.liquid.
7.3 Significance and Use:
7.3.1 Practices D2144—The infrared spectrum of an electrical insulating oilliquid indicates the general chemical composition of
the sample. Because of the complex mixture of compounds present in insulating oils,liquids, the spectrum is not sharply defined
and may not be suitable for quantitative estimation of components. The identity of the oilliquid can be quickly established as being
the same or different from previous samples by comparison with the reference spectra.
8. Flash and Fire Point
8.1 Scope:
8.1.1 Test Method D92 covers the determination of flash and fire points of all petroleum products except fuel oilsoil and those
having an open cup flash below 79°C (175°F).79 °C (175 °F).
8.1.2 This test method should be used solely to measure and describe the properties of materials in response to heat and flame
under controlled laboratory conditions and should not be used for the description, appraisal, or regulation of the fire hazard of
materials under actual fire conditions.
8.2 Definitions:
8.2.1 flash point—the temperature at which vapors above the oilliquid surface first ignite when a small test flame is passed across
the surface under specified conditions.
8.2.2 fire point—the temperature at which oilliquid first ignites and burns for at least 5 s when a small test flame is passed across
the surface under specified conditions.
8.3 Summary of Test Method—Fill the test cup to the specified level with the test specimen. Heat the sample initially at
1414 °C ⁄min to 17°C/min17 °C (25⁄min (25 °F ⁄min to 30°F/min)30 °F ⁄min) until the temperature is 56°C (100°F)56 °C (100 °F)
below the expected flash point. Reduce the rate of temperature change to 55 °C ⁄min to 6°C/min6 °C (9⁄min (9 °F ⁄min to
11°F/min)11 °F ⁄min) and apply the test flame every 2°C2 °C (or 5°F)5 °F) until a flash occurs. Continue heating and testing every
2°C2 °C (or 5°F)5 °F) until the oilliquid continues to burn for at least 5 s. The procedure is described in Test Method D92.
D117 − 22
8.4 Significance and Use—The flash point and fire point tests give an indication of the flammability of an oil.a liquid. They may
also be used to provide a qualitative indication of contamination with more flammable materials. In the latter context, the flash
point test is more sensitive.
9. Interfacial Tension
9.1 Scope—These test methods cover the measurement, under nonequilibrium conditions, of the interfacial tension of insulating
oilsliquids against water. These test methods have been shown by experience to give a reliable indication of the presence of
hydrophilic compounds.
9.2 Definition:
9.2.1 interfacial tension—the molecular attractive force between unlike molecules at an interface. It is usually expressed in
millinewtons per meter.
9.3 Summary of Test Methods:
9.3.1 Test Method D971—Interfacial tension is determined by measuring the force necessary to detach a platinum wire upward
from the oil-water oil water interface. To calculate the interfacial tension, the force so measured is corrected by an empirically
determined factor which depends upon the force applied, the densities of both oil and water, and the dimensions of the ring. The
measurement is completed within 1 min of the formation of the interface.
9.3.2 Test Method D2285—Interfacial tension is determined by measuring the volume of a drop of water that the oil will support.
The larger the drop of water, the higher the interfacial tension of the oil. The instrument used to measure the volume of the drops
of water is calibrated to read approximately in millimewtons per meter interfacial tension. For better accuracy, the reading can be
corrected by a factor that depends on the density of the oil. The drop is allowed to age for 30 s and to fall between 45 and 60 s
after formation.
9.4 Significance and Use—Interfacial tension measurements on electrical insulating oilsliquids provide a sensitive means of
detecting small amounts of soluble polar contaminants and products of oxidation. A high value for new mineral insulating oilliquid
indicates the absence of most undesirable polar contaminants. The test is frequently applied to service-aged oilsliquids as an
indication of the degree of deterioration.
10. Pour Point of Petroleum Products
10.1 Scope—The pour point is applicable to any petroleum oil.liquid.
10.2 Definition:
10.2.1 pour point—the lowest temperature, expressed as a multiple of 3°C 3 °C at which the oilliquid is observed to flow when
cooled and examined under prescribed conditions.
10.3 Summary of Test Methods:
10.3.1 After preliminary heating, the test specimen is cooled at a specified rate and examined at intervals of 3°C 3 °C for flow
characteristics. The lowest temperature at which movement of the oilliquid is observed within 5 s is reported as the pour point.
The procedure is described in Test Method D97.
10.3.2 Test Method D5949 covers the determination of pour point of petroleum products by an automatic instrument that applies
a controlled burst of nitrogen gas onto the specimen surface while the specimen is being cooled and detects movement of the
surface of the test specimen with an optical eye.
10.3.3 Test method D5950 covers the determination of pour point of petroleum products by an automatic instrument that tilts the
test jar during cooling and detects movement of the surface of the test specimen with an optical eye.
D117 − 22
10.4 Significance and Use:
10.4.1 The pour point of an insulating oilliquid gives an indication of the temperature below which it may not be possible to pour
or remove the oilliquid from its container.
10.4.2 In connection with oilliquid for use in cable systems, the pour point may be useful to indicate the point at which no free
movement will take place in the cable or to indicate the temperature at which partial separation of wax may occur.
10.4.3 The pour point of a transformer oil an electrical insulating liquid is important as an index of the lowest temperature to which
the material may be cooled without seriously limiting the degree of circulation of the oil.liquid. Some materials are sensitive to
temperature cycling or prolonged storage at low temperatures, and their pour points may not adequately predict their low
temperature flow properties.
11. Particle Count in Mineral Insulating Oil Using Automatic Optical Particle Counters
11.1 Scope—Test Method D6786 covers the determination of particle concentration and particle size distribution in mineral
insulating oil.liquid. It is suitable for testing oilsliquids having a viscosity of 6 to 20 mm /s at 40°C. 40 °C. The test method is
specific to liquid automatic particle analyzers that use the light extinction principle.
11.2 Summary of Test Method:
11.2.1 Samples are taken in particle-clean bottles that are suitable for particle analysis. The sample bottle is agitated to redistribute
particles in the oil,liquid, then the oilliquid is placed in an automatic particle counter, where the number of particles and their size
distribution are determined by the light extinction principle.
11.2.2 As particles pass through the sensing zone of the instrument, the quantity of light reaching the detector is obscured. This
signal is translated to an equivalent projected area diameter based on calibration with a NIST-traceable liquid (ISO Medium Test
Dust suspension).
11.3 Significance and Use:
11.3.1 Particles in insulating oilliquid can have a detrimental effect on the dielectric properties of the oil,liquid, depending on the
size, concentration, and nature of the particles. The source of these particles can be external contaminants, oilliquid degradation
byproducts, or internal materials such as metals, carbon, or cellulose fibers.
11.3.2 Particle counts provide a general degree of contamination level and may be useful in assessing the condition of specific
types of electrical equipment. Particle counts can also be used to determine filtering effectiveness when processing oil.liquid.
11.3.3 If more specific knowledge of the nature of the particles is needed, other tests such as metals analysis or fiber identification
and counting must be performed.
12. Refractive Index and Specific Optical Dispersion
12.1 Scope:
12.1.1 Test Method D1218—Describes a precise method for determining refractive index accurate to 0.00006 and refractive
dispersion accurate to 0.00012. The liquid must be transparent, no darker than ASTM 4.0 color (see Test Method D1500) and have
a refractive index between 1.33 and 1.50. The specific optical dispersion is calculated by dividing the refractive dispersion value
by the specific gravity of the liquid.
12.1.2 Test Method D1807—Describes a routine method for measuring refractive index accurate to three units in the fourth
decimal place, measuring refractive dispersion, and calculating specific optical dispersion accurate to three units in the fourth
decimal place. The oils must be transparent and light colored.
12.2 Definitions:
D117 − 22
12.2.1 refractive index—the ratio of the velocity of light in air to its velocity in the substance under test.
12.2.2 specific optical dispersion —the difference between the refractive indexes of light of two different wave lengths, both
indexes measured at the same temperature, the difference being divided by the specific gravity also measured at the test
temperature. For convenience, the specific dispersion value is multiplied by 10 .
12.3 Summary of Test Method:
12.3.1 The two methods differ in the accuracy of the refractometer used. After adjusting the instrument temperature to 25°C, apply
the test specimen to the refracting prism, read the refractive index, and read the compensator dial reading. From the correlation
tables supplied with the instrument obtain the refractive dispersion. Calculate the specific optical dispersion by dividing refractive
dispersion by the specific gravity of the oil.liquid.
12.4 Significance and Use:
12.4.1 Refractive Index of an insulating liquid varies with its composition and with the nature and amount of contaminants held
in solution. Where the refractive index of an insulating liquid when new is known, determinations made on the same liquid after
periods of service may form a basis for estimating any change in composition or the degree of contamination acquired through
solution.service.
12.4.2 Specific Optical Dispersion serves as a quick index to the amount of unsaturated compounds present in an oil.a liquid. As
the dispersion values for paraffinic and naphthenic compounds are nearly the same and are essentially independent of molecular
weight and structural differences, values above a minimum of about 97 bear a direct relationship to the amount of aromatic
compounds present in insulating oil.liquid.
13. Relative Density (Specific Gravity)
13.1 Scope:
13.1.1 The methods used to measure relative density (specific gravity) may use a hydrometer, pycnometer, or an oscillating tube.
13.1.1.1 Test Method D287—Uses an API hydrometer and is limited to liquids having a Reid vapor pressure of 180 kPa (26 psi)
or less.
13.1.1.2 Test Method D1217—Covers the use of a pycnometer to measure the relative density (specific gravity) of petroleum
fractions.
13.1.1.3 Test Method D1298—Covers the use of a hydrometer to measure relative density (specific gravity) directly or the
measurement of API gravity followed by conversion to relative density (specific gravity). This test method is limited to liquids
having a Reid vapor pressure of 179 kPa (26 psi) or less. This test method is most suitable for use with mobile transparent liquids,
although it can also be used with viscous oilsliquids if sufficient care is taken in the measurement.
13.1.1.4 Test Method D1481—Covers the determination of the densities of oilsliquids more viscous than 15 mm /s at 20°C. 20
°C. The liquid should not have a vapor pressure greater than 13 kPa (100 mm Hg) at the test temperature. To measure the density
of less viscous liquids more accurately than permitted by the hydrometer method, Test Method D1217 is available.
13.1.1.5 Test Method D4052—Covers the measurement of relative density (specific gravity) by the measurement of change in
oscillation frequency of a vibrating glass tube filled with test liquid.
13.2 Definition:
13.2.1 relative density (specific gravity)—the ratio of the mass (weighed in vacuum) of a given volume of liquid at 15.6°C (60°F)
15 °C (60 °F) to the mass of an equal volume of pure water at the same temperature. When reporting results, explicitly state the
reference temperature, for example, specific gravity 15.6/15.6°C.15/15 °C.
13.3 Summary of Test Method:
D117 − 22
13.3.1 API gravity may be measured at the oilliquid temperature using a hydrometer (Test Methods D287 or D1298) or Digital
Density Meter (Test Method D4052) and converting to 15.6°C 15 °C or 60 °F using adjunct to Guide D1250.
13.3.2 Relative density (specific gravity) may be measured at the oilliquid temperature using a hydrometer (Test Method D1298)
or by Digital Density Meter (Test Method D4052) and converted to 15.6°C 15 °C or 60 °F using adjunct to Guide D1250.
13.3.3 Test Method D1481—The liquid is drawn into the bicapillary pycnometer through the removable siphon arm and adjusted
to volume at the temperature of test. After equilibration at the test temperature, liquid levels are read; and the pycnometer is
removed from the thermostated bath, cooled to room temperature, and weighed. Density or relative density (specific gravity), as
desired, is then calculated from the volume at the test temperature, and the weight of the sample. The effect of air buoyancy is
included in the calculation.
13.4 Significance and Use:
13.4.1 Electrical insulating oilsliquids are usually sold on the basis of volume delivered at 15.6°C (60°F). 15 °C (60 °F). Delivery
is often made on the basis of net weight of product in drums, and the specific gravities often are measured at temperatures other
than 15.6°C. 15 °C. The values of relative density (specific gravity) at 15.6°C 15 °C must be known to calculate the volume at
15.6°C 15 °C of the oilliquid delivered.
13.4.2 The relative density (specific gravity) of a mineral insulating oilliquid influences the heat transfer rates and may be pertinent
in determining suitability for use in specific applications. In certain cold climates, ice may form in de-energized transformers
electrical equipment exposed to temperatures below 0°C, 0 °C, and the maximum specific gravity of the oilliquid used in such
equipment should be at a value that will ensure that ice will not float in the oilliquid at any temperature the oilliquid might attain.
13.4.3 When making additions of insulating liquid to apparatus in service, a difference in relative density (specific gravity) may
indicate a tendency of the two bodies of liquid to remain in separate layers rather than mixing into a homogeneous single body
of liquid. Such conditions have caused serious overheating of self-cooled apparatus. Suitable precautions should be taken to ensure
mixing.
14. Specific Heat
14.1 Scope—Test Method D2766 covers determination of the specific heat of electrical insulating liquids of petroleum origin.
14.2 Definition:
14.2.1 specific heat (or heat capacity) of a substance—a thermodynamic property that is a measure of the amount of energy
required to produce a given temperature change within a unit quantity of that substance. The standard unit of heat capacity is
J/(kg·°C) at some defined temperature.
14.3 Summary of Test Method—The specific heat is determined by Test Method D2766. The measurement is made by heating a
test specimen at a known and fixed rate. Once dynamic heating equilibrium is obtained, the heat flow is recorded as a function
of temperature. The heat flow normalized to specimen mass and heating rate is directly proportional to the specimen’s specific heat
capacity.
14.4 Significance and Use—A knowledge of the specific heat is helpful in designing adequate heat transfer properties for electrical
apparatus. A higher specific heat value indicates a more efficient heat transfer medium.
15. Thermal Conductivity
15.1 Scope—Test Method D2717 covers the determination of the thermal conductivity of electrical insulating liquids of petroleum
origin.
15.2 Definition:
15.2.1 thermal conductivity—the ability of a substance to transfer energy as heat in the absence of mass transport phenomena. The
standard unit of thermal conductivity is as follows:
D117 − 22
W/ m·°C
~ !
15.3 Summary of Test Method—The thermal conductivity is determined by Test Method D2717. This test method measures the
temperature gradient produced across the liquid by a known amount of energy introduced into the test cell by an electrically heated
platinum element.
15.4 Significance and Use—A knowledge of thermal conductivity is helpful in designing adequate heat transfer properties for
electrical apparatus. A high value indicates a good heat transfer efficiency property for the liquid.
16. Turbidity
16.1 Scope—Test Method D6181 determines the amount of suspended particulate matter in electrical insulating oil of petroleum
origin.
16.2 Definition:
16.2.1 turbidity, n—the reduction of transparency due to presence of particulate matter. The standard unit of turbidity is the
nephelometric turbidity unit (NTU), which is defined as the intensity of light scattered by a known aqueous suspension of
formazine.
16.3 Summary of Test Method—The turbidity is determined by Test Method D6181. This test method measures the scattered light
at 0.5 π rad (90°) or 0.5 and 1.5 π rad (90° and 270°) angles to the incident beam using a nephelometer that has been calibrated
with a standard aqueous suspension of formazine.
16.4 Significance and Use—Turbidity measures particulate contamination in electrical insulating oil that may not be apparent to
the unaided human eye and could affect the performance of the dielectric liquid.
16. Viscosity
16.1 Scope:
16.1.1 Test Method D445—This test method specifies a procedure for the determination of the kinematic viscosity of liquid
petroleum products, both transparent and opaque, by measuring the time for a volume of liquid to flow under gravity through a
calibrated glass capillary viscometer. The dynamic viscosity can be obtained by multiplying the kinematic viscosity by the density
of the liquid.
16.1.2 Practice D2161—Provides tables or equations for the conversion of centistokes into Saybolt Universal Seconds or Saybolt
Furol Seconds at the same temperatures.
16.2 Summary of Test Methods:
16.2.1 Test Method D445—The time is measured in seconds for a fixed volume of liquid to flow under gravity through the capillary
of a calibrated viscometer under a reproducible driving head and at a closely controlled temperature. The kinematic viscosity is
the product of the measured flow time and the calibration constant of the viscometer.
16.2.2 Practice D2161—The Saybolt Universal viscosity equivalent to a given kinematic viscosity varies with the temperature at
which the determination is made. The basic conversion values are given in Table 1 of this practice for 37.8°C (100°F).37.8 °C
(100 °F). Factors are given for converting units at other temperatures. The Saybolt Furol viscosity equivalents are given in Table
3 of this practice for 50.050.0 °C and 98.9°C (12298.9 °C (122 °F and 210°F)210 °F) only.
16.2.3 Test Method D7042—This test method covers and specifies a procedure for the concurrent measurement of both the
dynamic viscosity, η, and the density, ρ, of liquid petroleum products and crude oils, both transparent and opaque. The kinematic
viscosity, ν, can be obtained by dividing the dynamic viscosity, η, by the density, ρ, obtained at the same test temperature.
16.3 Significance and Use:
D117 − 22
16.3.1 The fundamental and preferred method for measuring kinematic viscosity is by use of Test Method D445.
16.3.2 Viscosity of electrical insulating oilsliquids influences their heat transfer properties, and consequently the temperature rise
of energized electrical apparatus containing the liquid. At low temperatures, the resulting higher viscosity influences the speed of
moving parts, such as those in power circuit breakers, switchgear, load tapchanger mechanisms, pumps, and regulators. Viscosity
controls insulating oilliquid processing conditions, such as dehydration, degassification and filtration, and oilliquid impregnation
rates. High viscosity may adversely affect the starting up of apparatus in cold climates (for example, spare transformers and
replacements). Viscosity affects pressure drop, oilliquid flow, and cooling rates in circulating oilliquid systems, such as in pipe-type
cables and transformers.
ELECTRICAL PROPERTIES
17. Dielectric Breakdown Voltage
17.1 Scope:
17.1.1 There are two standard test methods for determining the dielectric breakdown voltage of electrical insulating liquids at
commercial power frequencies, D877 and D1816, and one standard test method for determining the dielectric breakdown voltage
of insulating oilsliquids under impulse conditions, D3300.
17.1.2 Test Method D877—Applicable to liquid petroleum oils,liquids, hydrocarbons, and askarels commonly used as insulating
and cooling media in cables, transformers, oilliquid-filled circuit breakers, and similar apparatus. The suitability of Test Method
D877 for testing liquids having viscosities exceeding 900 mm /s (5000 SUS) at 40°C (104°F)at 40 °C (104 °F) has not been
determined.
17.1.3 Test Method D1816—This test method covers the determination of the dielectric breakdown voltage of insulating liquids
(oils(liquids of petroleum origin, silicone fluids,liquids, high fire-point mineral electrical insulating oils,liquids, synthetic ester
fluidsliquids and natural ester fluids).liquids). This test method is applicable to insulating liquids commonly used in cables,
transformers, oilliquid-filled circuit breakers, and similar apparatus as an insulating and cooling medium. Refer to Terminology
D2864 for definitions used in this test method.
17.1.4 Test Method D3300—Applicable to any liquid commonly used as an insulating and cooling medium in high-voltage
apparatus subjected to impulse conditions, such as transient voltage stresses arising from such causes as nearby lightning strikes
and high-voltage switching operations.
17.2 Definition:
17.2.1 dielectric breakdown voltage—the potential difference at which electrical failure occurs in an electrical insulating material
or insulation structure, under prescribed test conditions.
17.3 Summary of Test Methods:
17.3.1 Test Method D877—The insulating liquid is tested in a test cup between two 25.4-mm (1-in.) diameter disk electrodes
spaced 2.54 mm (0.100 in.) apart. A 60-Hz voltage is applied between the electrodes and raised from zero at a uniform rate of 3
kV/s. The dielectric breakdown voltage is recorded, prior to the occurrence of disruptive discharge, when the voltage across the
specimen has dropped to less than 100 V. In the referee procedure, one breakdown test is made on each of five fillings of the test
cup, and the average and individual values of breakdown voltage are reported.
17.3.2 Test Method D1816—The oilliquid is tested in a test cell between spherically capped (VDE) electrodes spaced either 1 mm
(0.040 in.) or 2 mm (0.080 in.) apart. The oilliquid is stirred before and during application of voltage by means of a motor-driven
stirrer. A 60-Hz voltage is applied between the electrodes and raised from zero at a uniform rate of 0.5 kV/s. The voltage at which
the current produced by breakdown of the oilliquid reaches the range of 2 to 20 mA, tripping a circuit breaker, is considered to
be the dielectric breakdown voltage. In the procedure, five breakdown tests are made on one filling of the test cell. If the five
breakdowns fall within the statistical requirements, the average value is reported. If not, five additional breakdowns are required
with the average of the ten values reported.
D117 − 22
17.3.3 Test Method D3300—The electrode system consists of either: (1) two 12.7-mm (0.5-in.) diameter spheres spaced 3.8 mm
(0.15 in.) apart or (2) a 12.7-mm (0.5-in.) diameter sphere and a steel phonograph needle of 0.06-mm radius of curvature of point,
spaced 25.4 mm (1.0 in.) apart. The polarity of the needle with respect to the sphere can be either positive or negative. The
electrodes are immersed in the oilliquid in a test cell. An impulse wave of 1.2 by 50 μs wave shape (times to reach crest value and
to decay to half of crest value, respectively) is applied at progressively higher voltages until breakdown occurs.
17.4 Significance and Use:
17.4.1 Power Frequencies (Test Methods D877 and D1816)—The dielectric breakdown voltage of an insulating liquid at
commercial power frequencies is of importance as a measure of the liquid’s ability to withstand electric stress. It is the voltage
at which breakdown occurs between two electrodes under prescribed test conditions. It also serves to indicate the presence of
contaminating agents, such as water, dirt, moist cellulosic fibers, or conducting particles in the liquid, one or more of which may
be present when low dielectric breakdown values are found by test. However, a high dielectric breakdown voltage does not indicate
the absence of all contaminants. See Appendix X1 of either test method for other influences that affect the dielectric breakdown
voltage of a liquid.
17.4.1.1 The ability of an insulating liquid to resist breakdown under the test conditions is an indication of the ability of the
insulating liquid to perform its insulating function in electrical apparatus. The average breakdown voltage is commonly used in
specifications for t
...