Designation D117 − 10 Standard Guide for Sampling, Test Methods, and Specifications for Electrical Insulating Oils of Petroleum Origin1 This standard is issued under the fixed designation D117; the nu[.]
Trang 1Designation: D117−10
Standard Guide for
Sampling, Test Methods, and Specifications for Electrical
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
specifica-tions 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
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
spe-cific types of electrical insulating oils
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 Method
Physical Tests:
Aniline Point 4 D611
Coefficient of Thermal
Ex-pansion
5 D1903
Examination: Visual Infrared 7 D1524, D2144
Flash and Fire Point 8 D92
Interfacial Tension 9 D971, D2285
Pour Point of Petroleum
Products
10 D97 Particle Count in Mineral
Insulating Oil
11 D6786 Refractive Index 12 D1218, D1807
Relative Density (Specific
Gravity)
13 D287, D1217, D1298, D1481 Specific Heat 14 D2766
Category Section ASTM Method Thermal Conductivity 15 D2717
Viscosity 17 D88, D445, D2161
Electrical Tests:
Dielectric Breakdown Voltage 18 D877, D1816, D3300 Dissipation Factor and
Rela-tive Permittivity (Dielectric Constant)
19 D924
Gassing Characteristic Under Thermal Stress
20 D7150 Gassing Tendency 21 D2300 Resistivity 22 D1169 Stability Under Electrical
Discharge
23 D6180
Chemical Tests:
Acidity, Approximate 24 D1534 Carbon-Type Composition 25 D2140 Compatibility with
Construc-tion Material
26 D3455 Copper Content 27 D3635 Elements by Inductively
Coupled Plasma (ICP-AES)
28 D7151 Furanic Compounds in
Electrical Insulating Liquids
29 D5837 Gas Analysis 30 D3612 Gas Content 31 D831, D1827, D2945 Inorganic Chlorides and
Sulfates
32 D878 Neutralization (Acid and
Base) Numbers
33 D664, D974 Oxidation Inhibitor Content 34 D2668, D4768 Oxidation Stability 35 D1934, D2112, D2440 Polychlorinated Biphenyl
Content
36 D4059 Relative Content of
Dissolved Decay
37 D6802 Sediment and Soluble Sludge 38 D1698 Sulfur, Corrosive 39 D1275 Water Content 40 D1533
Specification:
Mineral Insulating Oil for Electrical Apparatus
41 D3487 High Firepoint Electrical
Insulating Oils
42 D5222
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 This guide is under the jurisdiction of ASTM Committee D27 on Electrical
Insulating Liquids and Gasesand is the direct responsibility of Subcommittee
D27.01 on Mineral.
Current edition approved Sept 15, 2010 Published October 2010 Originally
published as D117 – 21 T Last previous edition approved in 2002 as D117 – 02.
DOI: 10.1520/D0117-10.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 United States
Trang 21.5 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
appro-priate safety and health practices and determine the
applica-bility of regulatory limitations prior to use.
2 Referenced Documents
2.1 ASTM Standards:2
D88Test Method for Saybolt Viscosity
D92Test Method for Flash and Fire Points by Cleveland
Open Cup Tester
D97Test Method for Pour Point of Petroleum Products
D287Test Method for API Gravity of Crude Petroleum and
Petroleum Products (Hydrometer Method)
D445Test Method for Kinematic Viscosity of Transparent
and Opaque Liquids (and Calculation of Dynamic
Viscos-ity)
D611Test Methods for Aniline Point and Mixed Aniline
Point of Petroleum Products and Hydrocarbon Solvents
D664Test Method for Acid Number of Petroleum Products
by Potentiometric Titration
D831Test Method for Gas Content of Cable and Capacitor
Oils
D877Test Method for Dielectric Breakdown Voltage of
Insulating Liquids Using Disk Electrodes
D878Test Method for Inorganic Chlorides and Sulfates in
Insulating Oils
D923Practices for Sampling Electrical Insulating Liquids
D924Test Method for Dissipation Factor (or Power Factor)
and Relative Permittivity (Dielectric Constant) of
Electri-cal Insulating Liquids
D971Test Method for Interfacial Tension of Oil Against
Water by the Ring Method
D974Test Method for Acid and Base Number by
Color-Indicator Titration
D1169Test Method for Specific Resistance (Resistivity) of
Electrical Insulating Liquids
D1217Test Method for Density and Relative Density
(Spe-cific Gravity) of Liquids by Bingham Pycnometer
D1218Test Method for Refractive Index and Refractive
Dispersion of Hydrocarbon Liquids
D1250Guide for Use of the Petroleum Measurement Tables
D1275Test Method for Corrosive Sulfur in Electrical
Insu-lating Oils
D1298Test Method for Density, Relative Density, or API
Gravity of Crude Petroleum and Liquid Petroleum
Prod-ucts by Hydrometer Method
D1481Test Method for Density and Relative Density
(Spe-cific Gravity) of Viscous Materials by Lipkin Bicapillary
Pycnometer
D1500Test Method for ASTM Color of Petroleum Products
(ASTM Color Scale)
D1524Test Method for Visual Examination of Used
Elec-trical Insulating Oils of Petroleum Origin in the Field
D1533Test Method for Water in Insulating Liquids by Coulometric Karl Fischer Titration
D1534Test Method for Approximate Acidity in Electrical Insulating Liquids by Color-Indicator Titration
D1698Test Method for Sediments and Soluble Sludge in Service-Aged Insulating Oils
D1807Test Methods for Refractive Index and Specific Optical Dispersion of Electrical Insulating Liquids
D1816Test Method for Dielectric Breakdown Voltage of Insulating Liquids Using VDE Electrodes
D1827Test Method for Gas Content (Nonacidic) of Insulat-ing Liquids by Displacement with Carbon Dioxide (With-drawn 2009)3
D1903Practice for Determining the Coefficient of Thermal Expansion of Electrical Insulating Liquids of Petroleum Origin, and Askarels
D1934Test Method for Oxidative Aging of Electrical Insu-lating Petroleum Oils by Open-Beaker Method
D2112Test Method for Oxidation Stability of Inhibited Mineral Insulating Oil by Pressure Vessel
D2140Practice for Calculating Carbon-Type Composition
of Insulating Oils of Petroleum Origin
D2144Practices for Examination of Electrical Insulating Oils by Infrared Absorption
D2161Practice for Conversion of Kinematic Viscosity to Saybolt Universal Viscosity or to Saybolt Furol Viscosity
D2285Test Method for Interfacial Tension of Electrical Insulating Oils of Petroleum Origin Against Water by the Drop-Weight Method(Withdrawn 2008)3
D2300Test Method for Gassing of Electrical Insulating Liquids Under Electrical Stress and Ionization (Modified Pirelli Method)
D2440Test Method for Oxidation Stability of Mineral Insulating Oil
D2668Test Method for di-tert-Butyl- p-Cresol and 2,6-di-tert-Butyl Phenol in Electrical Insulating Oil by
Infra-red Absorption
D2717Test Method for Thermal Conductivity of Liquids
D2759Practice for Sampling Gas from a Transformer Under Positive Pressure
D2766Test Method for Specific Heat of Liquids and Solids
D2945Test Method for Gas Content of Insulating Oils (Withdrawn 2012)3
D3300Test Method for Dielectric Breakdown Voltage of Insulating Oils of Petroleum Origin Under Impulse Con-ditions
D3305Practice for Sampling Small Gas Volume in a Trans-former
D3455Test Methods for Compatibility of Construction Ma-terial with Electrical Insulating Oil of Petroleum Origin
D3487Specification for Mineral Insulating Oil Used in Electrical Apparatus
D3612Test Method for Analysis of Gases Dissolved in Electrical Insulating Oil by Gas Chromatography
D3635Test Method for Dissolved Copper In Electrical
2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3 The last approved version of this historical standard is referenced on www.astm.org.
Trang 3Insulating Oil By Atomic Absorption Spectrophotometry
D4052Test Method for Density, Relative Density, and API
Gravity of Liquids by Digital Density Meter
D4059Test Method for Analysis of Polychlorinated
Biphe-nyls in Insulating Liquids by Gas Chromatography
D4768Test Method for Analysis of 2,6-Ditertiary-Butyl
Para-Cresol and 2,6-Ditertiary-Butyl Phenol in Insulating
Liquids by Gas Chromatography
D5185Test Method for Multielement Determination of
Used and Unused Lubricating Oils and Base Oils by
Inductively Coupled Plasma Atomic Emission
Spectrom-etry (ICP-AES)
D5222Specification for High Fire-Point Mineral Electrical
Insulating Oils
D5837Test Method for Furanic Compounds in Electrical
Insulating Liquids by High-Performance Liquid
Chroma-tography (HPLC)
D6180Test Method for Stability of Insulating Oils of
Petroleum Origin Under Electrical Discharge
D6181Test Method for Measurement of Turbidity in
Min-eral Insulating Oil of Petroleum Origin (Withdrawn
2012)3
D6786Test Method for Particle Count in Mineral Insulating
Oil Using Automatic Optical Particle Counters
D6802Test Method for Determination of the Relative
Con-tent Of Dissolved Decay Products in Mineral Insulating
Oils by Spectrophotometry
D7150Test Method for the Determination of Gassing
Char-acteristics of Insulating Liquids Under Thermal Stress at
Low Temperature
D7151Test Method for Determination of Elements in
Insu-lating Oils by Inductively Coupled Plasma Atomic
Emis-sion Spectrometry (ICP-AES)
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
representa-tive 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
3.2 Sample the insulating oil in accordance with Practices
D923,D2759andD3305as appropriate
PHYSICAL PROPERTIES
4 Aniline Point
4.1 Scope—This test method 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
oil indicates the solvency of the oil for some materials that are
in contact with the oil 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—This test method 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
vol-ume per unit volvol-ume per degree change in temperature It is commonly stated as the average coefficient over a given temperature range
5.3 Summary of Test Method—The specific gravity of
insu-lating oils is determined at two temperatures below 90°C and separated by not less than 5°C nor more than 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 Test Method 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—This test method covers the visual
determina-tion of color of a wide variety of liquid petroleum products, including mineral insulating oils
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
re-quirement 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
7 Examination
7.1 Scope:
7.1.1 Both visual examination and qualitative infrared ab-sorption are described in this section The test methods are:
7.1.2 Test Method D1524 —This is a visual examination of
mineral insulating oils that have been used in transformers, oil
Trang 4circuit breakers, or other electrical apparatus as insulating or
cooling media, or both This test is intended for use in the field
7.1.3 Test Method D2144 —The infrared absorption from 2.5
to 25 µm (4000 to 667 cm−1) 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 oils
in storage or service This test method is not intended for the
determination of the various constituents of an oil
7.2 Summary of Test Methods:
7.2.1 Test Method D1524 —Estimate the color of the oil by
use of an oil comparator, matching the oil test specimen with
tinted glass color standards Note the presence of cloudiness,
particles of insulation, metal corrosion products, or other
undesirable suspended materials in the oil
7.2.2 Test Methods D2144 —The infrared spectrum is
re-corded from 2.5 to 25 µm (4000 to 667 cm−1) either as the
absorption spectrum itself, or as the differential between the
test specimen and reference oil The spectra are compared with
reference spectra to establish the identity of the oil
7.3 Significance and Use:
7.3.1 Test Method D1524 —The observation of the color and
condition of the oil in a field inspection permits a determination
of whether the sample should be sent to a central laboratory for
full evaluation
7.3.2 Test Methods D2144 —The infrared spectrum of an
electrical insulating oil indicates the general chemical
compo-sition of the sample Because of the complex mixture of
compounds present in insulating oils, the spectrum is not
sharply defined and may not be suitable for quantitative
estimation of components The identity of the oil 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 This test method covers the determination of flash and
fire points of all petroleum products except fuel oils and those
having an open cup flash below 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 oil 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 oil 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 14 to 17°C/min (25 to 30°F/min) until the temperature is
56°C (100°F) below the expected flash point Reduce the rate
of temperature change to 5 to 6°C/min (9 to 11°F/min) and
apply the test flame every 2°C (or 5°F) until a flash occurs
Continue heating and testing every 2°C (or 5°F) until the oil continues to burn for at least 5 s The procedure is described in Test Method D92
8.4 Significance and Use—The flash point and fire point
tests give an indication of the flammability of an oil They may also be used to provide a qualitative indication of contamina-tion 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 oils 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
be-tween unlike molecules at an interface It is usually expressed
in dynes per centimetre or millinewtons per metre
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 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 dynes per centimeter 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 oils provide a sensitive means of detecting small amounts of soluble polar contaminants and products of oxidation A high value for new mineral insulating oil indicates the absence of undesirable polar contaminants The test is frequently applied to service-aged oils as an indication of the degree of deterioration
10 Pour Point
10.1 Scope—The pour point is applicable to any petroleum
oil
10.2 Definition:
10.2.1 pour point—the lowest temperature, expressed as a
multiple of 3°C at which the oil is observed to flow when cooled and examined under prescribed conditions
10.3 Summary of Test Method—After preliminary heating,
the test specimen is cooled at a specified rate and examined at
Trang 5intervals of 3°C for flow characteristics The lowest
tempera-ture at which movement of the oil is observed within 5 s is
reported as the pour point The procedure is described in Test
MethodD97
10.4 Significance and Use:
10.4.1 The pour point of an insulating oil gives an
indica-tion of the temperature below which it may not be possible to
pour or remove the oil from its container
10.4.2 In connection with oil 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 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 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
prop-erties
11 Particle Count in Mineral Insulating Oil Using
Automatic Opticle Particle Counters
11.1 Scope—This test method covers the determination of
particle concentration and particle size distribution in mineral
insulating oil It is suitable for testing oils having a viscosity of
6 to 20 cSt at 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, then the oil 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 fluid
(ISO Medium Test Dust suspension)
11.3 Significance and Use:
11.3.1 Particles in insulating oil can have a detrimental
effect on the dielectric properties of the fluid, depending on the
size, concentration, and nature of the particles The source of
these particles can be external contaminants, oil degradation
byproducts, or internal materials such as metals, carbon, or
cellulose fibers
11.3.2 Particle counts provide a general degree of
contami-nation 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
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 precision 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 refrac-tive 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:
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 104
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 disper-sion by dividing refractive disperdisper-sion by the specific gravity of the oil
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 contami-nants 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 con-tamination acquired through solution
12.4.2 Specific Optical Dispersion serves as a quick index
to the amount of unsaturated compounds present in an oil As the dispersion values for paraffinic and naphthenic compounds are nearly the same and are essentially independent of molecu-lar 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
13 Relative Density (Specific Gravity)
13.1 Scope:
13.1.1 The methods used to measure relative density (spe-cific 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
pycnom-eter to measure the relative density (specific gravity) of petroleum fractions
Trang 613.1.1.3 Test Method D1298 —Covers the use of a
hydrom-eter 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 oils if
sufficient care is taken in the measurement
13.1.1.4 Test Method D1481 —Covers the determination of
the densities of oils more viscous than 15 cSt at 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 MethodD1217is 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) 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
13.3 Summary of Test Method:
13.3.1 API gravity may be measured at the oil temperature
using a hydrometer (Test Methods D287 or D1298) and
converting to 15.6°C using GuideD1250
13.3.2 Relative density (specific gravity) may be measured
at the oil temperature using a hydrometer (Test MethodD1298)
and converted to 15.6°C using 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
equilibra-tion 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 oils are usually sold on the basis
of volume delivered at 15.6°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
The values of relative density (specific gravity) at 15.6°C must
be known to calculate the volume at 15.6°C of the oil
delivered
13.4.2 The relative density (specific gravity) of a mineral
insulating oil influences the heat transfer rates and may be
pertinent in determining suitability for use in specific
applica-tions In certain cold climates, ice may form in de-energized
transformers exposed to temperatures below 0°C, and the
maximum specific gravity of the oil used in such equipment
should be at a value that will ensure that ice will not float in the
oil at any temperature the oil might attain
13.4.3 When making additions of insulating liquid to appa-ratus 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 homoge-neous single body of liquid Such conditions have caused serious overheating of self-cooled apparatus Suitable precau-tions should be taken to ensure mixing
14 Specific Heat
14.1 Scope—This test method 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 Joules/Kg°C at some defined temperature; specific heat is dimensionless as it is the ratio of the substance’s heat capacity relative to that of water
14.3 Summary of Test Method—The specific heat is
deter-mined 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 normal-ized 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—This test method 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:
W/~mK! ~Cal/cm s °C!
15.3 Summary of Test Method—The thermal conductivity is
determined by Test MethodD2717 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
con-ductivity is helpful in designing adequate heat transfer prop-erties for electrical apparatus A high value indicates a good heat transfer efficiency property for the liquid
16 Turbidity
16.1 Scope—This test method determines the amount of
suspended particulate matter in electrical insulating oil of petroleum origin
16.2 Definition:
Trang 716.2.1 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
scat-tered 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 fluid
17 Viscosity
17.1 Scope:
17.1.1 Test Method D88 —Covers the empirical
measure-ment of Saybolt viscosity of petroleum products using the
Saybolt viscometer at temperatures between 25.1and 98.9°C
(70 and 210°F)
17.1.2 Test Method D445 —Covers the determination of the
kinematic viscosity of liquid petroleum products by measuring
the time for a volume of liquid to flow under gravity through
a calibrated glass capillary viscometer
17.1.3 Practice D2161 —Provides tables or equations for the
conversion of centistokes into Saybolt Universal Seconds or
Saybolt Furol Seconds at the same temperatures
17.2 Summary of Test Methods:
17.2.1 Test Method D88 —The efflux time in seconds for 60
mL of test specimen to flow through a calibrated orifice in the
Saybolt viscometer is measured under carefully controlled
conditions, particularly temperature and liquid head The time
is converted by an orifice factor and reported as the viscosity of
the sample at that temperature
17.2.2 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
17.2.3 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) Factors are given for converting units at other
temperatures The Saybolt Furol viscosity equivalents are
given in Table 3 of this practice for 50.0 and 98.9°C (122 and
210°F) only
17.3 Significance and Use:
17.3.1 The fundamental and preferred method for
measur-ing kinematic viscosity is by use of Test Method D445 The
Saybolt instrument in Test Method D88, being of all-metal
construction, may be more rugged for field use, but values
obtained are significantly less accurate than those obtained by
the use of the capillary viscometers in Test Method D445
17.3.2 Viscosity of electrical insulating oils 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 regula-tors Viscosity controls insulating oil processing conditions, such as dehydration, degassification and filtration, and oil 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, oil flow, and cooling rates in circulating oil systems, such
as in pipe-type cables and transformers
ELECTRICAL PROPERTIES
18 Dielectric Breakdown Voltage
18.1 Scope:
18.1.1 There are two standard test methods for determining the dielectric breakdown voltage of electrical insulating fluids
at commercial power frequencies, D877andD1816, and one standard test method for determining the dielectric breakdown voltage of insulating oils under impulse conditions,D3300
18.1.2 Test Method D877 —Applicable to liquid petroleum
oils, hydrocarbons, and askarels commonly used as insulating and cooling media in cables, transformers, oil circuit breakers, and similar apparatus The suitability of Test MethodD877for testing liquids having viscosities exceeding 900 cSt (5000 SUS) at 40°C (104°F) has not been determined
18.1.3 Test Method D1816 —Applicable to liquid petroleum
oils commonly used as an insulating and cooling medium in cables, transformers, oil circuit breakers, and similar apparatus The suitability of Test Method D1816for testing oils having viscosities of more than 19 cSt (100 SUS) at 40°C (104°F) has not been determined
18.1.4 Test Method D3300 —Applicable to any liquid
com-monly 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
18.2 Definition:
18.2.1 dielectric breakdown voltage—the potential
differ-ence at which electrical failure occurs in an electrical insulating material or insulation structure, under prescribed test condi-tions
18.3 Summary of Test Methods:
18.3.1 Test Method D877 —The insulating liquid is tested in
a test cup between two 25.4-mm (1-in.) diameter disk elec-trodes 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
18.3.2 Test Method D1816 —The oil is tested in a test cell
between spherically capped (VDE) electrodes spaced either 1
Trang 8mm (0.040 in.) or 2 mm (0.080 in.) apart The oil 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 of1⁄2 kV/s
The voltage at which the current produced by breakdown of the
oil 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
18.3.3 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 oil in a test
cell An impulse wave of 1.2by 50 µs wave shape (times to
reach crest value and to decay to half of crest value,
respec-tively) is applied at progressively higher voltages until
break-down occurs
18.4 Significance and Use:
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
18.4.1.1 The ability of a fluid to resist breakdown under the
test conditions is an indication of the ability of the fluid to
perform its insulating function in electrical apparatus The
average breakdown voltage is commonly used in specifications
for the qualification and acceptance of insulating fluids It is
also used as a control test for the refining of new or reclaiming
of used insulating fluids Because of the complex interactions
of the factors affecting dielectric breakdown voltage the values
obtained cannot be used for design purposes
18.4.1.2 The square-edged disk electrodes of Test Method
D877 are relatively insensitive to dissolved water in
concen-trations below 60 % of the saturation level This method is
recommended for acceptance tests on unprocessed insulating
liquids received from vendors in tank cars, tank trucks, and
drums It also may be used for the routine testing of liquids
from selected power systems apparatus
18.4.1.3 The more uniform electric field associated with
VDE electrodes employed in Test Method D1816 is more
sensitive to the deleterious effects of moisture in solution,
especially when cellulosic fibers are present in the oil, than is
the field in Test MethodD877 Test MethodD1816can be used
for processed or as received oils Filtering and dehydrating the oil may increase Test Method D1816 dielectric breakdown voltages substantially
18.4.2 Impulse Conditions (Test Method D3300 ):
18.4.2.1 This test method is most commonly performed using a negative polarity point opposing a grounded sphere (NPS) The NPS breakdown voltage of fresh unused oils measured in the highly divergent field in this configuration depends on oil composition; decreasing with increasing con-centration of aromatic, particularly polyaromatic, hydrocarbon molecules
18.4.2.2 This test method may be used to evaluate the continuity of composition of an oil from shipment to shipment The NPS impulse breakdown voltage of an oil can also be substantially lowered by contact with materials of construction,
by service aging, and by other impurities Test results lower than those expected for a given fresh oil may also indicate use
or contamination of that oil
18.4.2.3 Although polarity of the voltage wave has little or
no effect on the breakdown strength of an oil in uniform fields, polarity does have a marked effect on the breakdown voltage of
an oil in nonuniform electric fields
19 Dissipation Factor and Relative Permittivity (Dielectric Constant)
19.1 Scope:
19.1.1 This test method covers new electrical insulating liquids as well as liquids in service or subsequent to service in cables, transformers, oil circuit breakers, and other electrical apparatus
19.1.2 This test method provides a procedure for making referee and routine tests at a commercial frequency of approxi-mately 60 Hz
19.2 Summary of Test Method:
19.2.1 The loss characteristic is commonly measured in terms of dissipation factor (tangent of the loss angle) or of power factor (sine of the loss angle) For values up to 0.05, dissipation factor and power factor values are equal to each other within about one part in one thousand and the two terms may be considered interchangeable
19.2.2 Test Method D924 —The oil test specimens are tested
in a three-terminal or guarded electrode test cell maintained at the desired test temperature Using a bridge circuit, measure the loss characteristics and capacitance following the instruc-tions appropriate to the bridge being used For routine tests, a two-electrode cell may be used
19.3 Significance and Use:
19.3.1 Dissipation Factor (or Power Factor)—This
prop-erty is a measure of the dielectric losses in an oil, and hence,
of the amount of energy dissipated as heat A low value of dissipation factor (or power factor) indicates low dielectric losses and a low level of soluble polar ionic or colloidal contaminants This characteristic may be useful as a means of quality control and as an indication of oil changes in service resulting from contamination and oil deterioration
19.3.2 Relative Permittivity (Dielectric Constant)—
Insulating liquids are used in general either to insulate com-ponents of an electrical network from each other and from
Trang 9ground, alone or in combination with solid insulating materials,
or to function as the dielectric of a capacitor For the first use,
a low value of relative permittivity is often desirable in order
to have the capacitance be as small as possible, consistent with
acceptable chemical and heat transfer properties However, an
intermediate value of relative permittivity may sometimes be
advantageous in achieving a better voltage distribution
be-tween the liquid and solid insulating materials with which the
liquid may be in series When used as the dielectric in a
capacitor, it is desirable to have a higher value of relative
permittivity so the physical size of the capacitor may be as
small as possible
20 Gassing Characteristics of Insulating Liquids Under
Thermal Stress at Low Temperature
20.1 Scope:
20.1.1 This test method describes the procedures to
deter-mine the low temperature (120°C) gassing characteristics of
insulating liquids specifically and without the influence of
other electrical apparatus materials or electrical stresses This
test method was primarily designed for insulating mineral oil
It can be applied to other insulating liquids in which dissolved
gas-in-oil analysis (Test Method D3612) is commonly
per-formed
20.1.2 This test method is particularly suited for detection
of the phenomenon sometimes known as “stray gassing” and is
also referred to in CIGRE TF11 B39 1.3 This test method is
performed on transformer insulating liquids to determine the
propensity of the oil to produce certain gases such as hydrogen
and hydrocarbons at low temperatures
20.1.3 This test method details two procedures:
20.1.3.1 Method A describes the procedure for determining
the gassing characteristics of a new, unused insulating liquid,
as received, at 120°C for 164 h
20.1.3.2 Method B describes the procedure for processing
the insulating liquid through an attapulgite clay column to
remove organic contaminants and other reactive groups that
may influence the gassing behavior of an insulating liquid,
which is suspected of being contaminated This procedure
applies to both new and used insulating liquids
20.2 Summary of Test Method:
20.2.1 Method A—Insulating liquid is filtered through a
mixed cellulose ester filter A portion of the test specimen is
sparged for 30 min with dry air A test specimen is then placed
into a glass syringe, capped and aged at 120 6 2°C for 164 h
The test is run in duplicate The other portion of the test
specimen is sparged for 30 min with dry nitrogen A test
specimen is then placed into a glass syringe, capped and aged
at 120°C 6 2°C for 164 h The test is run in duplicate After,
the test specimens have cooled, dissolved gas-in-oil analysis is
then performed according to Test MethodD3612
20.2.2 Method B—Insulating oil is passed through a heated
(60 to 70°C) attapulgite clay column at a rate of 3 to 5 mL per
minute The insulating liquid is contacted with the attapulgite
clay at a ratio of 1 g clay to 33 mL (range: 30 to 35 mL) of
insulating liquid (0.25 lb clay: 1 gal of insulating liquid) The
insulating liquid is collected and subjected to the testing as
outlined in4.1
20.3 Significance and Use:
20.3.1 Generation of combustible gases is used to determine the condition of oil-filled electrical apparatus Many years of empirical evidence has yielded guidelines such as those given
in IEEE C 57.104, IEC 60599 and IEC 61464 Industry experience has shown that electric and thermal faulted in oil-filled electrical apparatus are the usual sources that generate gases Experience has shown that some of the gases could form
in the oil at low temperatures or as a result of contamination, without any other influences
20.3.2 Some severely hydro-treated transformer oils sub-jected to thermal stress and oils that contain certain types of contamination may produce specific gases at lower tempera-tures than normally expected for their generation and hence, falsely indicate abnormal operation of the electrical apparatus Some new oils have produced large amounts of gases, espe-cially hydrogen, without the influence of other electrical apparatus materials or electrical stresses This renders interpre-tation of the dissolved gas analysis more complicated 20.3.3 Heating for 164 h has been found to be a sufficient amount of time to reach a stable and characteristic gassing pattern
20.3.4 This method uses both dry air and dry nitrogen as the sparging gas This is to reflect either a electrical apparatus preservation system that allows oxygen to contact the oil or one that is sealed from the outside atmosphere Oils sparged with air generally produce much more hydrogen as a percentage of the total combustible gas content as compared to oils sparged with nitrogen as these produce more hydrocarbons in relation
to hydrogen
21 Gassing Tendency
21.1 Scope—Test MethodD2300 describes a procedure to measure the rate at which gas is evolved or absorbed by insulating oils when subjected to electrical stress of sufficient intensity to cause ionization The oil test specimen is initially saturated with a selected gas (usually hydrogen) at atmospheric pressure
21.2 Summary of Test Method:
21.2.1 Test Method D2300 —After being saturated with a
gas (usually hydrogen) the oil is subjected to a radial electrical stress at a controlled temperature The gas space above the oil
is ionized due to the electrical stresses; and therefore, the oil surface at the oil-gas interface is subjected to ion bombard-ment The evolution or absorption of gas is measured with a gas burette and reported in µL/min
21.3 Significance and Use—This test method indicates
whether insulating oils are gas absorbing or gas evolving under the test conditions Numerical results obtained in different laboratories may differ significantly in magnitude, and the results of this test method should be considered as qualitative
in nature
21.3.1 For certain applications when insulating oil is stressed at high voltage gradients, it is desirable to be able to determine the rate of gas evolution or gas absorption under specified test conditions At the present time, correlation of such test results with equipment performance is limited
Trang 1022 Resistivity
22.1 Scope:
22.1.1 This test method covers the determination of specific
resistance (resistivity) applied to new electrical insulating
liquids, as well as to liquids in service, or subsequent to
service, in cables, transformers, circuit breakers, and other
electrical apparatus
22.1.2 This test method covers a procedure for making
referee and routine tests with dc potential
22.2 Definition:
22.2.1 specific resistance (resistivity)—of a liquid, the ratio
of the dc potential gradient in volts per centimetre paralleling
the current flow within the test specimen, to the current density
in amperes per square centimetre at a given instant of time and
under prescribed conditions This is numerically equal to the
resistance between opposite faces of a centimetre cube of a
liquid It is measured in ohm centimetres
22.3 Summary of Test Method:
22.3.1 Test Method D1169 —The oil test specimen is tested
in three-terminal, or guarded-electrode test cell maintained at
the desired test temperature A dc voltage is applied of such
magnitude that the electric stress in the liquid is between 200
and 1200 V/mm (5 to 30 V/mL) The current flowing between
the high-voltage and guarded measuring electrode is measured
at the end of 1 min of electrification and the resistivity
calculated using specified equations appropriate to the method
of measurement used A two-electrode cell may be used for
routine tests
22.4 Significance and Use—The resistivity of a liquid is a
measure of its electrical insulating properties under conditions
comparable to those of the test High resistivity reflects low
content of free ions and ion-forming particles and normally
indicates a low concentration of conductive contaminants
23 Stability Under Electric Discharge
23.1 Scope—Test Method D6180 measures the relative
stability of new, used, or reclaimed insulating oils of petroleum
origin in the presence of a controlled electric discharge by
monitoring the pressure increase in the evacuated discharge
chamber
23.2 Summary of Test Method—A test specimen is
intro-duced into a discharge cell and degassed under vacuum at room
temperature An ac potential of 10 KV is applied for 300 min
The gradual rise of pressure inside the discharge cell is
measured as a function of time The dissipation factor of the oil
at 100°C is determined before and after the stability test using
Test Method D924
23.3 Significance and Use—The changes observed in the
generation of gases as noted by pressure change and the
composition modification as reflected in dissipation factor
increases may provide a relative assessment of the stability of
the oil for high voltage application
CHEMICAL PROPERTIES
24 Acidity, Approximate
24.1 Scope—Test MethodD1534covers the determination
of the approximate total acid value of used electrical insulating
liquids, in general, those having viscosities less than 24 cSt at 40°C It is a simple procedure that can be applied in the field Where a quantitative neutralization value is required, use Test MethodD664orD974 These test methods should be applied
in the laboratory
24.2 Summary of Test Method:
24.2.1 Test Method D1534 —To determine whether the
acid-ity is greater or less than a fixed arbitrary value, a fixed volume
of liquid to be tested is added to the test bottle or graduated cylinder, together with a small amount of indicator (phenol-phthalein) and the appropriate quantity of standard potassium hydroxide solution The mixture is shaken and allowed to separate The color of the aqueous layer at the bottom of the container when testing mineral oils, or at the top when testing askarels, determines whether the acidity is less than or greater than the arbitrary value chosen
24.3 Significance and Use:
24.3.1 The approximate acidity of used electrical insulating oils is an estimate of the total acid value of the oil As acid values increase, usually due to oxidation of the oil in service, the impairment of those oil qualities, important to proper functioning of specific apparatus, increases In general, acidic by-products produce increased dielectric loss, increased corrosivity, and may cause thermal difficulties attributable to insoluble components called “sludge.” This test method is adapted to a specific volume of oil; total acid values of 0.05 to 0.5 mg of potassium hydroxide per gram of oil is a range which
is functionally significant
25 Carbon-Type Composition
25.1 Scope—This test method covers the determination of
carbon-type composition of insulating oils by correlation with basic physical properties Carbon-type composition is ex-pressed as percentage of aromatic carbons, percentage of naphthenic carbons, and percentage of paraffinic carbons Viscosity, relative density (or specific gravity), and refractive index are the only measurements required for use of this test method
25.2 Summary of Test Method:
25.2.1 Test Method D2140 —The viscosity, density and
spe-cific gravity, and refractive index of the oil are measured From these values, the viscosity-gravity constant and refractivity intercept are calculated Using these two computed values, percentage of aromatic carbons, naphthenic carbons, and paraffinic carbons are estimated from a correlation chart
25.3 Significance and Use—The primary purpose of this test
method is to characterize the carbon-type composition of an oil It is also applicable in observing the effect on oil consti-tution of various refining processes, such as solvent extraction, acid treatment, and so forth It has secondary application in relating the chemical nature of an oil to other phenomena that have been demonstrated to be related to oil composition
26 Compatibility with Construction Material
26.1 Scope—This test method covers screening for the
compatibility of materials of construction with electrical insu-lating oil for use in electrical equipment Solid materials that