3-1982- IEEE Recommended Practice in the Selection of Reference Ambient Conditions for Test...

ANSIIIEEE Std 3-1987

IEEE Recommended Practice in the Selection of Reference Ambient Conditions for Test Measurements of Electrical Apparatus

Published by The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017, USA

SH08425 June 8 , 1 9 8 2

IEEE Std 3-1982 (Revision of IEEE Std 3-1962)


Sponsor

Power System Instrumentation and Measurements Committee of the

IEEE Power Engineering Society

@Copyright 1982 by

The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017

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Foreword

(This Foreword is not a part of IEEE Std 3-1982, IEEE Recommended Practice in the Selection of Reference

As originally prepared by the AIEE Standards Coordinating Committee No 1, this standard tab- ulated the reference values of ambient parameters for electrical measurements which had been adopted by various groups. The current revision, while recognizing the need for certain exceptions, recommends a single set of specified reference ambient parameters.

The Temperature and Environmental Measurements of Electrical Apparatus Subcommittee of the Power System Instrumentation and Measurements Committee of the IEEE Power Engineering Soci- ety had the following members at the time it approved this standard:

Ambient Conditions for Test Measurements of Electrical Apparatus. )

F. R. Kotter, Chairman

H. C. Dunbar S. D. Ebneter J. J. Mikos

P. J. Mobus W. E. Rich R. L. Richardson

I. N. Howell, Jr, Chairman

G. Y. R. Allen J. J. Archambault J. H. Beall J. T. Boettger Edward Chelotti Edward J. Cohen Len S. Corey

Approved May 21,1981

IEEE Standards Board

Sava I. Sherr, Secretary

Jay Forster Kurt Greene Loering M. Johnson Joseph L. Koepfinger J. E. May Donald T. Michael* J. P. Riganati

Irving Kolodny, Vice Chairman

F. Rosa R. W. Seelbach J. S. Stewart W. E. Vannah Virginius N. Vaughan, Jr Art Wall Robert E. Weiler

*Member emeritus

Contents

SECTION PAGE

1 . PurposeandScope ........................................................... 7

2 . References ................................................................. 7

3 . Temperature ................................................................ 7 3.1 Definitions ............................................................. 7 3.2 Preferred Values ......................................................... 7

4 . BarometricPressure .......................................................... 8

4.2 Preferred Values ......................................................... 8 4.3 Special Considerations ..................................................... 8

5 . Altitude ................................................................... 8

5.2 Preferred Values ......................................................... 9

6.2 Corrections for Relative Air Density .......................................... 9

7 . Humidity .................................................................. 9

7.3 Preferred Values ........................................................ 10

8 . Standard Laboratory Atmosphere .............................................. 10

Appendix A The Underground Thermal Environment ................................ 12

A1 . General Considerations .................................................. 1 2 A2 . Ambient Earth Temperature .............................................. 1 2 A3 . Earth Thermal Resistivity ................................................ 1 2

Appendix B Related Standards .................................................. 1 5

4.1 Definitions ............................................................. 8

5.1 Definitions ............................................................. 8

9 6.1 Definitions ............................................................. 9

.......................................................... 6 . Relative Air Density

7.1 General ................................................................ 9 7.2 Definitions ............................................................ 1 0

APPENDIXES

A4 . Bibliography ........................................................... 14

APPENDIX FIGURES Fig A1 Ambient Earth Temperatures Near Detroit, MI ............................... 13 Fig A2 Ambient Earth Temperatures at an Unspecified Location ....................... 13


1. Purpose and Scope

In general test results and the performance of electrical apparatus are significantly influenced by variations in such parameters as temperature, barometric pressure, and humidity. A meaning- ful comparison of the results of two tests made under different ambient conditions is possible when the result of one of the tests is corrected or adjusted to indicate the results that would have been obtained if the ambient conditions for that test had been identical with those for the other.

Especially in the situation where several tests performed under different conditions are to be compared, it is advantageous to select standard reference values for all pertinent parameters and then to correct or adjust the results of each test to indicate the results that would have been obtained if all tests had been performed under identical conditions, that is, under the reference ambient conditions.

It is the purpose of this document to identify and recommended a set of standard reference values for certain ambient parameters which are significant in electrical test measurements.

Even though agreed-upon correction factors may not be available, the ambient temperature, the barometric pressure, and the relative humidity should always be recorded and reported. In this way retesting will not be necessary when agreed-upon correction factors become available.

2. References

[ 11 ANSI/ASTM E171-63(R1972),I American National Standard Specification for Standard Atmospheres for Conditioning and Materials

ANSI documents are available from the partment of American National Standards 1430 Broadway, New York, NY 10018.

Testing

Sales de- Insti tu te.

[2] ANSI/ASTM D618-61(R1977), American National Standard Methods of Conditioning Plastics and Electrical Insulating Materials for Testing [3] ANSI/IEEE Std 4-1978, IEEE Standard High Voltage Testing Techniques

[4] US Standard Atmosphere, 1962.2 [ 51 US Standard Atmosphere Supplements, 1966.

3. Temperature

3.1 Definitions 3.1.1 standard reference temperature. A suit-

ably selected temperature value for which test records or performance data are given in records and standards of various kinds and to which the results of tests made at different temperatures are corrected for purposes of comparison and standardization.

3.1.2 range of ambient temperature for test. The range over which most correction factors are known with sufficient accuracy to permit adjustment of measured values to the values that would have been obtained at the standard reference temperature.

"C degrees Celsius "F degrees Fahrenheit

3.2 Preferred Values 3.2.1 Standard Reference Temperature. In

view of its long history of acceptance and use in international comparisons of mechanical and electrical standards, the temperature 20 "C is recommended as the standard reference temperature.

It is recognized that since temperature cor-

3.1.3 Letter Symbols for Units

These documents are available from US Govern- ment Printing Office, Washington, DC 20401.

7

IEEE Std 3-1982 IEEE RECOMMENDED PRACTICE IN THE SELECTION OF REFERENCE AMBIENT

rection factors for some electrical parameters may not be known with the required precision, a "standard reference temperature" may not be a useful concept in measurements related to them. Comparisons of the results of two measurements of one of those parameters may be valid only if the two measurements were made at the same temperature. Since in the United States most measurements of the dielectric properties of materials are made in accord with standards produced by the American Society for Testing and Materials, it is perhaps necessary that such measurements continue to be made and reported at 23 "C, the temperature specified as one characteristic of the ASTM standard laboratory atmosphere (see Section 8). 3.2.2 Ranges of Ambient Temperature for

Tests. Following are the preferred ranges for use :

20 "C to 30 "C (68 "F to 86 O F )

NOTE : Permits work in normally temperature-controlled indoor spaces.

0 "C to 40 "C (32 "F to 104 O F )

NOTE: Permits outdoor testing.

4. Barometric Pressure

4.1 Definitions 4.1.1 Standard reference pressure. A suitably

selected value for which test and performance data are given in standards and to which the results of tests made at different barometric read- ings are corrected for purposes of comparison and standardization. 4.1.2 range of testing pressure. The range of

barometric conditions considered suitable for acceptance and check tests. 4.1.3 Letter Symbols for Units

mm Hg millimeters of mercury Pa pascal 1 Pa = 1 N/m2

recognized and established as the standard reference in the United States and in international practice. 4.2.2 Range of Testing Pressure. Since alti-

tude is the main natural factor affecting air pressure, it is customary to specify a range of altitude rather than air pressure for testing. For pressures and altitudes encountered near the earth's surface, the preferred range for use is

sea level to 1800 m (6000 ft)

which corresponds to average pressures of 101.3 kPa to 81.5 Wa (760 mm Hg to 611 mm Hg at 0 "C).

Test values for some parameters obtained outside this range of conditions may be corrected to the standard reference pressure. How- ever, a determination should first be made that the correction factors are known with the required accuracy.

NOTE: The Rotating Machinery and Transformers Committees have traditionally used the more limited range of sea level to 1000 m.

4.3 Special Considerations. Established prac- tices in dealing with the effect of pressures and altitude vary with the nature of tests. In temperature-rise tests on apparatus, no corrections are made for altitudes in a specified range. In flashover and sparkover tests, corrections are made at all nonstandard pressures. For dielectric tests involving solid or liquid insulation only, pressure has a negligible effect.

Barometric pressure should be recorded during all tests, even if correction factors are unknown or in doubt, so that data will be available to permit corrections to be applied when and if it becomes possible.

5 . Altitude

5.1 Definitions 5.1.1 standard reference altitude. A suitably

selected value for which performance data 4.2 Preferred Values

erence value for barometric pressure has been established as altitude levels.

are given in standards and which is established 4.2.1 Standard Reference Pressure. The ref- for purposes of standardization, particularly

in the application of apparatus at different

5.1.2 altitude testing range. The range of altitudes considered suitable for acceptance and check tests and reduction of measured values to the standard reference altitude.

101.3 kPa (760 mm Hg)

which corresponds to the average barometric pressure at sea level. This value is universally

8

CONDITIONS FOR TEST MEASUREMENTS OF ELECTRICAL APPARATUS IEEE

Std 3-1982

5.2 Preferred Values 5.2.1 Standard Reference Altitude. Sea level

is universally accepted as the reference value for altitude. The value corresponds to the reference barometric pressure of 101.3 kPa (760 mm Hg). 5.2.2 Altitude Testing Range. The range of

altitude for testing purposes is, preferably, sea level to 1800 m (6000 ft)

NOTE: See note under 4.2.2.

5.2.3 Standard Atmosphere. Table 1 shows the variations of temperature, pressure, and density of air with altitude for average conditions over the United States.

Table 1

Altitude Temperature Pressure Relative (m) (" C) (kPa) Qensity

0 15.0 101.3 1.000 500 11.8 95.5 0.953 1000 8.5 89.9 0.907 1500 5.3 84.6 0.864 2000 2.0 79.5 0.822 2500 -1.2 74.7 0.781

NOTE: Extracted from US Standard Atmosphere, 1962 [4].3 In the range of concern to the present document this is in full agreement with both the Inter- national Civil Aviation Organization (ICAO) standard atmosphere (1954) and with the Committee on Space Research (COSPAR) international reference atmosphere (1965). For more complete tables showing variations with latitude and seasons see US Standard A tmos- phere Supplements, 1966 [ 51.

6. Relative Air Density

6.1 Definitions 6.1.1 relative air density. The effects of

temperature and pressure on the density of the air have been combined into a single factor known as relative air density which is unity for the standard conditions of temperature to and pressure P o : 20 "C (68 OF) and 101.3 kPa (760 mm Hg). For other conditions the relative air density pr is given by the formula

P r = p, 273 + t P 273+to

Numbers in brackets correspond to those of the references listed in Section 2 of the standard.

in which P is the barometric pressure in kPa and t the temperature in "C at test conditions. The quantity thus defined is strictly the density of a given mass of air relative to that of the same mass of air at standard pressure and temperature and with the same content of water vapor. It does not indicate the true density of the gas, which is influenced by water vapor content.

6.2 Corrections for Relative Air Density. Rela- tive air density affects the electrical characteristics of air, particularly the flashover and sparkover of insulation and corona losses and radio influence voltages (RIV) on conductors. These quantities have been found to vary with relative air density to some power less than 1. Convection cooling and windage losses in rotating machinery also vary with relative air density. In all cases, for the small depatures from unity usually encountered, values may be considered to vary directly with the relative air density, and the relat@e air density in- herently includes altitude considerations through the medium of the barometric pressure. For variations from unity relative air density greater than approximately lo%, it is sometimes desirable to specify the correspond- ing correction factors as in 5.5.3.2.2 of ANSI/

Where insulation temperatures are involved, it is the practice to consider temperatures and altitudes separately.

Temperature and barometric pressure should be recorded during all tests, even if correction factors are unknown or in doubt so that data will be available to permit corrections to be applied when and if it becomes possible.

IEEE Std 4-1978 [3].

7. Humidity

7.1 General. The effects of humidity on electrical apparatus and insulating materials are complex. Some phenomena correlate better with relative humidity, others with absolute humidity, and there are some that are influenced, but for which no correlation with either absolute or relative humidity has been demon- strated. The electric breakdown or air in non- homogeneous electric fields, for example varies with absolute humidity, and correction factors have been evaluated and correlated for values of absolute humidity for many types of apparatus. On the other hand, the conditioning

9


of insulating materials for test, and the testing of finishes, cements, and adhesives are generally based on values of relative humidity. There- fore i t is necessary to recognize these practical conditions by establishing reference and limit- ing values for both absolute and relative humidity.

7.2 Definitions 7.2.1 absolute humidity. The mass of water

vapor in a unit volume of air, usually expressed as g/m3, or as the partial pressure of the water vapor in air in kPa.

7.2.2 relative humidity. The ratio of the partial pressure of water vapor in air at a given temperature, expressed as a percentage, to the saturation vapor pressure at that temperature. With adequate accuracy it may also be defined as the ratio of the mass of water vapor actually present in a specified volume of air a t a given temperature to the mass that would saturate it a t that temperature.

7.2.3 standard reference humidity. A suitably selected value for which performance data are given in records and standards and to which results of tests made at different humidities are corrected for purposes of comparison and standardization.

7.2.4 range of testing humidity. The zone of humidity conditions considered suitable for acceptance and check tests.

7.3 Preferred Values 7.3.1 Standard Reference Absolute Humid-

ity. The reference value for absolute humidity adopted by the International Electrotechnical Commission, and in the United States by the American National Standards Institute Com- mittee C68, is

11 grams of water vapor/m3 (a vapor pressure of 1.52 kPa)

This corresponds to a relative humidity of 65% at 20 "C and is intended to represent the average testing condition throughout the year in temperate zones. Until recently the accepted reference value in the United States was 15 g/m3. However, continue use of this value is discouraged.

7.32 Range of Testing Absolute Humidity. No widely accepted limits of absolute humidity can be set for the testing of apparatus and conductors. Where correction factors for particular apparatus are known, the apparatus

committee should specify the limits. The range of 0 kPa to 3.3 kPa (0 mm Hg to 25 mm Hg) vapor pressure covers practically all climatic conditions for humidity in the United States.

7.3.3 Standard Reference Relative Humidity. Since no basis for using the performance of electrical insulation at one value of relative humidity as a means of predicting behavior at another has been established, there is less merit in specifying standard reference values for relative humidity than for absolute humidity. However, the relative humidities of 50% and 65% have achieved a degree of acceptance as standard values for some tests, as indicated in 7.3.1 and Section 8.

7.3.4 Range of Testing Relative Humidity. For much electric apparatus testing, limits for relative humidity are of no practical interest, but they may be important in electronic and other equipment where minute operating currents are involved. Operation may be affected by leakage currents caused by humidity, especially with direct currents.

The relative humidity of the air may also be of importance in tests of electrical insulating materials. Since correction factors for different degrees of humidity are not known, it becomes necessary to conduct such tests at definite natural or controlled values of relative humidity, with suitable tolerances. Usually it will be expedient to combine these tolerances for humidity with specified tolerances for temperature.

Since requirements and capabilities for con- trolling humidity vary widely, it is not considered practical to suggest standard ranges here. Relative humidity should be recorded during all tests, even if correction factors are unknown or in doubt, so that data will be available to permit corrections to be applied when and if i t becomes possible.

8. Standard Laboratory Atmosphere

In high-voltage breakdown testing the standard reference atmosphere is defined as fol- lows:

Temperature, 20 "C Pressure, 101.3 kPa (760 mm Hg at 0 "C) Absolute humidity, 11 grams of water/m3

and its use, wherever possible, is recommended. However, for the reasons indicated in 3.2, con-

10


Std 3-1982

tinued use in restricted applications of the definition humidity may be specified."

". . .an atmosphere having a temperature of 23 f 2 "C (73.4 f 3.6 O F ) and a relative humidity of 50 f 5 percent. If closer tolerances are

required, k1 "C (1.8 O F ) and +2 percent relative

issued by the American Society for Testing and Materials, is to be expected (see ANSI/ASTM E171-63 (R1972) [l] and also ANSI/ASTM D618-61 (R1977) [2]).

11


Appendixes

(These appendixes are not a part of IEEE Std 3-1982, IEEE Recommended Practice in the Selection of Reference Ambient Conditions for Test Measurements of Electrical Apparatus.)

Appendix A

The Underground Thermal Environment

Al. General Considerations

Numerous complexly interrelated ambient earth conditions influence the performance of electric equipment in subsurface installations. Among others are such properties of the earth as temperature and thermal resistivity.

A l . l Universally recognized underground reference conditions are not generally to be found in connection with equipment performance. However, a discussion of the ranges of temperature and thermal resistivity which can be encountered in the field may aid where a reference value must be cited.

Certain reference values that have been adopted for particular purposes are cited below, It is urged that they also be used in other con- texts in which standard reference conditions must be cited, unless there are overriding considerations to the contrary.

A1.2 As is true of in-air equipment, underground installations which are in actual service must be designed to operate satisfactorily in the existing environment, rather than under standard reference conditions. For the values that must be applied in a specific installation, a field survey should be taken of the significant parameters, with full consideration given to the changes that must be expected in those parameters as the weather, the seasons, and other factors change.

Various techniques for measuring thermal resistivity and certain other parameters are dis- cussed in [ 11 and [ 21 .4

The numbers in brackets in Appendix A correspond to those of the Bibliography in Section A4.

A2. Ambient Earth Temperature

The surface layers of the earth absorb solar energy during the summer and release it to the air during the winter. The resulting cyclic variations in ambient earth temperature are most evident near the surface, as seen in Figs A1 and A2.

A2.1 Ranges and Examples. The two figures also demonstrate that climate as reflected in locality has a significant bearing on extreme and mean temperatures. As a further example, maximum temperatures at 2 ,4 , and 6 f t depths at an Arizona location were recorded as 34,31, and 30 "C, respectively [ 51.

Earth ambient temperatures do not fluctuate significantly on a daily basis as depths greater than 1 f t [ 41.

A2.2 Preferred Values. An ambient earth temperature of 25 "C is recommended as a reference condition. It has been selected as the basis for the cable ampacity tables of the Insulated Cable Engineers Association (ICEA). These tables also provide corrections for temperatures of 20 "C and 30 "C [6].

A3. Earth Thermal Resistivity

The thermal resistivity of soil is influenced by such factors as its constituents, density, and moisture content.

A3.1 Constituents. As examples of the influence of constituents, randomly oriented quartz averages 11 "C cm/W, and granite varies from 26 "C cm/W to 58 "C - cm/W.

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Std 3-1982

Fig A1 Ambient Earth Temperatures

Near Detroit, MI [3]

Fig A2 Ambient Earth Temperatures

at an Unspecified Location [ 41

13


Water measures 165 "C - cm/W, but the air it displaces measures 4000 "C cm/W [ 71.

tioned Arizona site were recorded as 150,130, and 120 "C cm/W, respectively [ 51.

A3.2 Density. Other factors remaining con- stant, each increase in dry density of 16 kg/m3 (1 lb/ft3 ) decreases thermal resistivity by about 3% [8].

A3.3 Moisture Content. In addition to displac- ing air and acting as a thermal bridge between soil particles, water serves as a lubricant, in- creasing soil density [9]. As an example of the effect of water, the average thermal resistivity of 1 4 dry soil samples was 213 "C cm/W. When the samples were moistened, each to its optimum extent, the average was reduced by a factor of 4.6:1, to 46.6 "C cm/W [8].

Under some conditions, the moisture content of soil in the vicinity of operating equipment can be altered markedly by the dissipation of heat in the equipment, through the mechan- ism of thermal moisture migration. This phenomenon has been treated at length in several references [ 71 , [ 91 - [ 121 . A3.4 Examples from the Field. The following values of measured soil thermal resistivity have been reported, in "C cm/W [ 131 :

(1) Composite sand (919 values):

Range Average 70.9 Median 56.0 50% within 44- 77 band

Approximately 10 to over 250

(2) Composite clay (801 values):

Range Approximately 20 to approximately 150

Average 54.9 Median 54.0 50% within 49- 62 band

(3) Composite sandy clay (329 values):

Range Approximately 20 to 110 Average 53.1 Median 50.0 50% within 40- 63 band

(4) Cinder-ash fill (76 values):

Range Average 191

A "typical" soil thermal resistivity during the summer in one area of California is reportedly 100 "C - cm/W [14]. The thermal resistivities at 2, 4, and 6 f t depths at the previously men-

85 (saturated) to 485 (dried out)

A3.5 Preferred Values. Thermal resistivities of 90 "C * cm/W and 120 "C cm/W are recommended as reference values. They have been selected as the basis for the ICEA cable ampacity tables [6]. Those tables also incorporate a value of 60 "C cm/W, associated with thermal backfill material.

A4. Bibliography

[l] IEEE Std 422-1977, IEEE Guide for the Design and Installation of Cable Systems in Power Generating station^.^ [2] CAMERON, A. W. W., and BROOKES, A. S. Soil Thermal Characteristics in Relation to Underground Power Cables. AIEE COMMIT- TEE REPORT, Pt VI - Measurement Tech- niques. AIEE Transactions, pt 111, vol 79,

[3] SANDERSON, W. D., STICHER, J., and McGRATH, M. H. Thermal Characteristics of a 120 kV High-pressure, Gas-Filled Cable In- stallation, AIEE Transactions, vol 67, pp 487- 502,1948.

[ 41 Underground Systems Reference Book. Edison Electric Institute, 1957, pp 10-7 and

[5] THOMAS, J. F. and SCHULTZ, N. R. Dapper Thermal Report. Joint Arizona Public Service Company - General Electric Company Dapper Committee, 1965, p 58.

[6] ICEA P-53-426, 2nd ed, NEMA WC 50- 1976 Ampacities Including Effect of Shield Losses for Single-Conductor Solid-Dielectric Power Cable 1 5 kV through 69 kV (Copper and Aluminum Conductors). Insulated Cable Engineers Association and National Electrical Manufacturers Association, pp III-IV.

[7] WINTERKORN, H. F. Behavior of Moist Soils in a Thermal Energy Field, in Clays and Minerals, vol 9. Oxford-London-New York- Paris: Pergamon 1962, pp 85-103.

[8] DEL MAR, W. A., BURRELL, R. W. and BAUER, C. A. Soil Thermal Characteristics in

While this edition of this standard does not discuss thermal resistivity measurements, the next edition, now in preparation will do so.

pp 836444,1960.

10-8.

14


Std 3-1982

Relation to Underground Power Cables. AIEE COMMITTEE REPORT, Pt I1 - Soil Types; Identification and Physical Properties. AIEE Transactions, pt 111, vol 79, pp 795-803,1960.

[9] FINK, L. H. Soil Thermal Characteristics in Relation to Underground Power Cables. AIEE COMMITTEE REPORT, pt 111 - Soil Moisture Characteristics. AIEE Transactions,

[lo] NEHER, J. H. The Temperature Rise of Buried Cables and Pipes. AIEE Transactions,

1111 MICKLEY, A. S. The Thermal Movement of Moisture in Soil. AIEE Transactions, pt I,

pt 111, V O ~ 79, pp 803-819,1960.

V O ~ 68, pp 9-21,1949.

V O ~ 68, pp 330-335,1949.

[123 MICKLEY, A. S. The Thermal Conductiv- ity of Moist Soil. AIEE Transactions, vol 70,

[13] SINCLAIR, W. A., BULLER, F. H. and BENHAM, C. B. Soil Thermal Characteristics in Relation to Underground Power Cables. AIEE COMMITTEE REPORT, Pt IV - Soil Thermal Resistivity; Typical Field Values and Calculating Formulas. AIEE Transactions, pt

[14] STOLPE, J. Emergency Ampacities for Underground 66 kV Extruded Dielectric Cables. Undergrounding, vol 3, pp 48-58, Max/Apr 1974.

pp 1789-1797,1951.

111, V O ~ 79, pp 820-832, 1960.

Appendix B Related Standards

Partial List of Other Standards which Specify Reference Ambient Conditions

ANSI B89.6.2-1973 (R1979), Temperature and Humidity Environment for ~ i ~ ~ ~ ~ i ~ ~ a l M ~ ~ - surement

Defines a standard reference atmosphere identical with that defined in Section 8, although presented some- what differently. Also recommends ranges of atmospheric conditions for measurement and defines stan-

Specifies 20 "C as the reference temperature. dard atmospheres for conditioning and for referee measurements.

ANSI/IEEE 112-1978, Test Procedure for IS() 1314-1973,7 Gas Turbines - Acceptance Polyhase Induction Motors and Generators

This and other rotating machinery standards specify 25 "C as a standard reference ambient temperature.

IEC 160 (1963),6 Standard Atmospheric Con- ditions for Test Purposes

Tests

Specifies as standard reference conditions, 1 5 "C, 60% relative humidity, and 101.3 kPa.

IEC Standards are available in the US from Amer- ' IS0 Standards are available in the US from Amer- ican National Standards Institute, 1430 Broadway, ican National Standards Institute, 1430 Broadway, New York, NY 10018. New York, NY 10018.

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