定价： 923元 / 折扣价： 785 元

Certain synthetic dielectric fluids are used in the manufacture of capacitors because of their chemical, thermal, and electrical properties as well as their environmental acceptability.Properties of a synthetic dielectric fluid differ from those of petroleum based fluids. Design considerations and quality control are influenced by these properties as measured by the appropriate tests.Each test method has its own brief statement describing its significance.1.1 These test methods cover testing synthetic dielectric fluids currently in use for capacitors. The methods are generally suitable for specification acceptance, factory control, referee testing, and research. Their applicability to future fluids has not been determined.1.2 The scope of some of the test methods listed here apply to petroleum oils, but have been found suitable for synthetic fluids.1.3 For methods relating to polybutene fluids refer to Specification D 2296.1.4 For methods relating to silicone fluids refer to Test Methods D 2225.1.5 A list of properties and standards are as follows:This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

定价： 0元 / 折扣价： 0 元

4.1 The dielectric breakdown voltage and dielectric strength of an insulating gas in a uniform field depends primarily on the molecular structure of the gas. As different gases are mixed either by plan or by contamination, any change in dielectric breakdown voltage and dielectric strength will depend on both the nature and proportion of the individual gases. This test method uses plane and spherical electrodes which provide a nearly uniform field (see Appendix) in the area of electrical discharge. It is suitable for determining the dielectric breakdown voltage and dielectric strength of different gases and mixtures thereof for research and application evaluations and also as a field test. A more complete discussion of the significance of the dielectric strength test is given in the Appendix.1.1 This test method covers the determination of the dielectric breakdown voltage and dielectric strength of insulating gases used in transformers, circuit breakers, cables, and similar apparatus as an insulating medium. The test method is applicable only to gases with boiling points below room temperature at atmospheric pressure.1.2 This standard may involve hazardous materials, operations, and equipment. 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.1.3 Mercury has been designated by EPA and many state agencies as a hazardous material that can cause central nervous system, kidney and liver damage. Mercury, or its vapor, may be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury containing products. See the applicable product Material Safety Data Sheet (MSDS) for details and EPA's website — http://www.epa.gov/mercury/faq.htm for additional information. Users should be aware that selling mercury and/or mercury containing products into your state may be prohibited by state law.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车

This specification establishes the requirements for the material, dimensions and tolerances, and property values of polymeric resin films, in sheet or strip form, for use in electrical insulation and dielectric applications. Type I are flexible unsupported films for general purpose, while Type II are heat-sealable coated on one (Grade 1) or both (Grade 2) sides. Materials covered here are (A) poly(N,N'-p,p'-oxydiphenylene pyromellitimide), (B) poly(N,N'-p,p'-oxydiphenylene biphenyltetracarboxylimide, (C) poly(N,N'-p-phenylene biphenyltetracarboxylimide), (D) FEP-fluorocarbon, (E) polyethylene terephthalate, (F) polyethylene naphthalate, and (G) polyetherimide. Individual materials class of films shall be tested and conform accordingly the following property values: tensile strength; elongation; shrinkage; moisture absorption; dielectric strength; volume resistivity; permittivity; and dissipation factor.1.1 This specification covers requirements for the material, dimensions and tolerances, and property values of film, in sheet or strip form, with or without heat-sealable coatings.1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.NOTE 1: This document is similar to IEC 60674, Part 3, Sheets 2, 4, 5, 6, and 7.1.3 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.

定价： 590元 / 折扣价： 502 元 加购物车

7.1 The electrical and mechanical characteristics of circuits produced from flexible composites of copper foil with dielectric materials will, to a large extent, depend on the properties of the dielectric portion of the composite. Measurement of these properties is essential for predicting performance of the circuit.1.1 These test methods cover procedures for testing flexible materials consisting of copper foil combined with either dielectric film or with treated or impregnated fabric to form flexible composites used in the manufacture of flexible or multilayer circuitry, or both.1.2 The procedures appear as follows:Procedure Section ASTM Reference MethodConditioning 5  Flex Life of the Composite 20 – 25  Peel Strength of the Composite 11 – 19  Specimen Preparation 6 D1825Strain Relief Due to Etching 26 – 32  Testing of the Dielectric Portion of      the Composite 7 – 10 D1825, D2305, D902  1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.4 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 and health practices and determine the applicability of regulatory limitations prior to use.

定价： 0元 / 折扣价： 0 元

4.1 Dielectric withstand voltage testing is useful for design verification, quality control of materials, and workmanship.4.2 This test method is used to verify that the membrane switch or printed electronic device can operate safely at its rated voltage, and withstand momentary overpotentials due to switching, surges and other similar electrical phenomena.4.3 Specific areas of testing are, but not limited to:4.3.1 Conductor/dielectric/conductor crossing point,4.3.2 Close proximity of conductors, and4.3.3 Any other conductive surface such as shielding or metal backing panel.4.4 Dielectric withstand voltage testing may be destructive and units that have been tested should be considered unreliable for future use.4.5 Testing using ac voltage may be useful for switches intended for control circuits powered by ac voltages.1.1 This test method covers the verification of a specified dielectric withstand voltage or dielectric breakdown voltage of a membrane switch or printed electronic device.

定价： 0元 / 折扣价： 0 元

5.1 The soil permittivity probe is used for the following purposes:5.1.1 The test method described is useful as a rapid, nondestructive technique for bulk measurements of the water mass per unit volume of soil and soil-aggregate which may, in conjunction with an independent bulk density determination, be used in the determination of dry density.5.1.2 The test method is used for quality control and acceptance testing of compacted soil and soil-aggregate mixtures as used in construction and also for research and development. The nondestructive nature allows repetitive measurements at a single test location and statistical analysis of the results.5.1.3 Volumetric Water Content—The fundamental assumptions inherent in the test method are that the dielectric constants value measured by the system in a given test site composed of soil or soil-aggregate are directly correlated to the volumetric water content of the soil or soil-aggregate, and that the material is homogeneous. (See 6, “Interferences.”)NOTE 2: The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.1.1 This test method describes the procedures for measuring the water mass per unit volume of soil and soil-aggregate by use of an in situ permittivity probe. Measurements are taken at a depth beneath the surface of the soil determined by the design of the probe.1.1.1 For limitations see Section 6 on Interferences.1.2 The permittivity probe is inserted into a hole drilled or punched into the soil being measured. As its name indicates, the probe measures the dielectric permittivity of the soil into which it is placed. Two electrodes, connected to an oscillating circuit, are mounted a predetermined distance apart. These electrodes act as the plates of a capacitor, with the soil between the plates forming the capacitor dielectric.1.2.1 The probe circuit creates an oscillating electric field in the soil. Changes in the dielectric permittivity of the soil are indicated by changes in the circuit’s operating frequency. Since water has a much higher dielectric constant (80) than the surrounding soil (typically around 4), the water content can be related by a mathematical function to the change in dielectric permittivity, and, consequently, the changes in the circuit’s operating frequency.1.2.2 The construction, deployment, and operating principle of the device described in this test method differ from other methods that measure the dielectric constant, bulk electrical conductivity, complex impedance, or electromagnetic impedance (see Test Methods D6780/D6780M, D7698, and D7830/D7830M) of the soil and relate the results to water mass per unit volume and/or water content.1.2.3 The water content of the soil measured by the permittivity probe is the volumetric water content, expressed as the ratio of the volume of water to the total volume occupied by the soil. This quantity is often converted, and displayed, by the probe in units of mass of water per volume of soil, or water mass per unit volume. This conversion is performed by multiplying the water content (in volume of water per volume of soil) by the density of water.1.3 Water content most prevalent in engineering and construction activities is known as the gravimetric water content, ω, and is the ratio of the mass of the water in pore spaces to the total mass of solids, expressed as a percentage. To determine this quantity, the bulk density of the soil under measurement must also be determined.1.4 Units—The values stated in SI units are to be regarded as the standard. Reporting the test results in units other than SI shall not be regarded as nonconformance with this standard.1.5 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026.1.5.1 For purposes of comparing, a measured or calculated value(s) with specified limits, the measured or calculated value(s) shall be rounded to the nearest decimal or significant digits in the specified limits.1.5.2 The procedures used to specify how data are collected/recorded and calculated in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that should generally be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.1.6 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.1.7 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.

定价： 646元 / 折扣价： 550 元 加购物车

4.1 Permittivity and dissipation factor are sensitive to changes in chemical composition, impurities, and homogeneity. Measurement of these properties is, therefore, useful for quality control and for determining the effect of environments such as moisture, heat, or radiation.1.1 This test method covers the determination of the relative permittivity (dielectric constant) and dissipation factor of solid dielectrics from 50 Hz to 10 MHz over a range of temperatures from −80 to 500 °C.2,3 Two procedures are included as follows:1.1.1 Procedure A—Using Micrometer Electrode.1.1.2 Procedure B—Using Precision Capacitor.NOTE 1: In common usage the word “relative” is frequently dropped.1.2 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.1.3 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.

定价： 515元 / 折扣价： 438 元 加购物车

4.1 Design calculations for such components as transmission lines, antennas, radomes, resonators, phase shifters, etc., require knowledge of values of complex permittivity at operating frequencies. The related microwave measurements substitute distributed field techniques for low-frequency lumped-circuit impedance techniques.4.2 Further information on the significance of permittivity is contained in Test Methods D150.4.3 These test methods are useful for specification acceptance, service evaluation, manufacturing control, and research and development of ceramics, glasses, and organic dielectric materials.1.1 These test methods cover the determination of relative (Note 1) complex permittivity (dielectric constant and dissipation factor) of nonmagnetic solid dielectric materials.NOTE 1: The word “relative” is often omitted.1.1.1 Test Method A is for specimens precisely formed to the inside dimension of a waveguide.1.1.2 Test Method B is for specimens of specified geometry that occupy a very small portion of the space inside a resonant cavity.1.1.3 Test Method C uses a resonant cavity with fewer restrictions on specimen size, geometry, and placement than Test Methods A and B.1.2 Although these test methods are used over the microwave frequency spectrum from around 0.5 to 50.0 GHz, each octave increase usually requires a different generator and a smaller test waveguide or resonant cavity.1.3 Tests at elevated temperatures are made using special high-temperature waveguide and resonant cavities.1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are inch-pound units that are provided for information only and are not considered standard.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.

定价： 646元 / 折扣价： 550 元 加购物车

This test method permits interlaboratory comparison and intralaboratory correlation of instrumental temperature scale data.Dielectric analyzers are used to characterize a broad range of materials that possess dielectric moments. One of the desired values to be assigned by the measurement is the temperature at which significant changes occur in the properties of the test specimen. In order to obtain consistent results from one period of time to another and from one laboratory to another, the temperature signal from the apparatus must be calibrated accurately over the temperature range of interest.1.1 This test method covers the temperature calibration of dielectric analyzers over the temperature range from -100 to 300°C and is applicable to commercial and custom-built apparatus. The calibration is performed by observing the melting transition of standard reference materials having known transition temperatures within the temperature range of use.1.2 Electronic instrumentation or automated data analysis and data reductions systems or treatment equivalent to this test method may be used.1.3 The values stated in SI units are to be reported as the standard.1.4 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 and health practices and to determine the applicability of regulatory limitations prior to use.

定价： 0元 / 折扣价： 0 元

Dielectric measurement and testing provide a method for determining the permittivity and loss factors as a function of temperature, frequency, time, or a combination of these variables. Plots of the dielectric properties against these variables yield important information and characteristics about the specimen under test.This procedure can be used to do the following:5.2.1 Locate transition temperatures of polymers and other organic materials, that is, changes in molecular motion (or atomic motion in the case of ions) of the material. In temperature regions where significant changes occur, permittivity increases with increasing temperature (at a given frequency) or with decreasing frequency (at constant temperature). A maximum is observed for the loss factor in cases where dipole motions dominate over ionic movement.35.2.2 Track the reaction in polymerization and curing reactions. This may be done under either isothermal or nonisothermal conditions. Increasing molecular weight or degree of crosslinking normally leads to decreases in conductivity.45.2.3 Determine diffusion coefficients of polar gases or liquids into polymer films on dielectric sensors. The observed change in permittivity typically is linear with diffusant concentration, as long as the total concentration is relatively low.5This procedure can be used, for example, to evaluate by comparison to known reference materials:5.3.1 The mix ratio of two different organic materials. This may be determined either through use of permittivity or loss factor values. In early studies, permittivity has been found to be linear with concentration.65.3.2 The degree of phase separation in multicomponent systems.5.3.3 The filler type, amount, pretreatment, and dispersion.This test method can be used for observing annealing and the submelting point crystallization process.This test method can be used for quality control, specification acceptance, and process control.1.1 This test method describes the gathering and reporting of dynamic dielectric data. It incorporates laboratory test method for determining dynamic dielectric properties of specimens subjected to an oscillatory electric field using a variety of dielectric sensor/cell configurations on a variety of instruments called dielectric, microdielectric, DETA (DiElectric Thermal Analysis), or DEA (DiElectric Analysis) analyzers.1.2 This test method determines permittivity, loss factor, ionic conductivity (or resistivity), dipole relaxation times, and transition temperatures, and is intended for materials that have a relative permittivity in the range of 1 to 105; loss factors in the range of 0 to 108; and, conductivities in the range 10 16to 1010S/cm.1.3 The test method is primarily useful when conducted over a range of temperatures for nonreactive systems (160C to degradation) and over time (and temperature) for reactive systems and is valid for frequencies ranging from 1 mHz to 100 kHz.1.4 Apparent discrepancies may arise in results obtained under differing experimental conditions. Without changing the observed data, completely reporting the conditions (as described in this test method) under which the data were obtained, in full, will enable apparent differences observed in another study to be reconciled.1.5 SI units are the standard.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 and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 10.

定价： 0元 / 折扣价： 0 元

3.1 The dielectric breakdown voltage is a measure of the ability of an insulating liquid to withstand electrical stress. The power-frequency breakdown voltage of a liquid is reduced by the presence of contaminants such as cellulosic fibers, conducting particles, dirt, and water. A low result in this test method indicates the presence of significant concentrations of one or more of these contaminants in the liquid tested. See Appendix X1.3.2 A high breakdown voltage measured in this test method does not necessarily indicate that the amount of the contaminants present in a liquid from which the sample was taken is sufficiently low for the sampled liquid to be acceptable in all electrical equipment. Test Method D877 is not sensitive to low levels of these contaminants. Breakdown in this test method is dominated by events occurring at the electrode edges. The voltage stress distribution between the parallel disk electrodes used in this test method are quasi-uniform and there is substantial stress concentration at the sharp edges of the flat disk faces.3.3 This test method may be used for evaluation of insulating liquids in equipment that is designed to be filled with unprocessed liquids as delivered by a vendor.3.4 This test method is not recommended for evaluation of the breakdown voltage of liquids used in equipment that requires the application of vacuum and filtering of the oil before being placed into service. Test Method D1816 should be used to determine the breakdown voltage of filtered and degassed liquids.3.5 This test method is used in laboratory or field tests. For field breakdown results to be comparable to laboratory results, all criteria including room temperature (20 to 30 °C) must be met.1.1 This test method describes two procedures, A and B, for determining the electrical breakdown voltage of insulating liquid specimens. The breakdown test uses ac voltage in the power-frequency range from 45 to 65 Hz.1.2 This test method is used to determine the electrical discharge voltage of in-use electrical liquids. It is no longer applicable to new insulating liquids upon receipt, in which case Test Method D1816 shall be used.NOTE 1: It is understood that long-term histories for this test method exist, but this test method is no longer considered applicable as numerous deficits exist that affect its usefulness. It is recommended to move all new and in-service electrical discharge voltage testing of electrical insulating liquids to Test Method D1816.1.3 Limitations of the Procedures: 1.3.1 The sensitivity of this test method to the general population of contaminants present in a liquid sample decreases as applied test voltages used in this test method become greater than approximately 25 kV rms.1.3.2 If the concentration of water in the sample at room temperature is less than 60 % of saturation, the sensitivity of this test method to the presence of water is decreased. For further information refer to RR:D27-1006.21.3.3 The suitability for this test method has not been determined for a liquid's viscosity higher than 900 cSt at 40 °C.1.4 Procedure Applications 1.4.1 Procedure A: 1.4.1.1 Procedure A is used to determine the breakdown voltage of liquids in which any insoluble breakdown products easily settle during the interval between the required repeated breakdown tests. These liquids include petroleum oils, hydrocarbons, natural and synthetic esters, and askarels (PCB) used as insulating and cooling liquids in transformers, cables, and similar apparatus.1.4.1.2 Procedure A may be used to obtain the dielectric breakdown of silicone fluid as specified in Test Methods D2225, provided the discharge energy into the sample is less than 20 mJ (milli joule) per breakdown for five consecutive breakdowns.1.4.2 Procedure B: 1.4.2.1 This procedure is used to determine the breakdown voltage of liquids in which any insoluble breakdown products do not completely settle from the space between the disks during the 1-min interval required in Procedure A. Procedure B, modified in accordance with Section 17 of Test Methods D2225, is acceptable for testing silicone dielectric liquids if the requirements of 1.4.1.2 can not be achieved.1.4.2.2 Procedure B should also be applied for the determination of the breakdown voltage of liquid samples containing insoluble materials that settle from the specimen during testing. These may include samples taken from circuit breakers, load tap changers, and other liquids heavily contaminated with insoluble particulate material. These examples represent samples that may have large differences between replicate tests. The use of Procedure B will result in a more accurate value of breakdown voltage when testing such liquids.1.4.2.3 Use Procedure B to establish the breakdown voltage of an insulating liquid where an ASTM specification does not exist or when developing a value for an ASTM guide or standard. Procedure A may be used once the single operator precision of 13.1 has been demonstrated.1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.1.6 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.1.7 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.

定价： 590元 / 折扣价： 502 元 加购物车

4.1 Electrical contact injuries to workers may involve a current path through the feet of the worker. The footwear covered by this specification is dielectrically rated to provide additional insulation and isolation to the wearer. This test method will determine that dielectric footwear has dielectric integrity at the time of the test.1.1 This test method covers testing to determine the “Dielectric Strength” of dielectric overfoot and overshoe footwear. Testing is done over the maximum possible area of the dielectric footwear without permitting flashover between electrodes.1.2 The use and maintenance of dielectric footwear is beyond the scope of this test method.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements appear in 5.2.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 515元 / 折扣价： 438 元 加购物车

This specification covers acceptance testing of dielectric overfoot and overshoe footwear designed to provide additional isolation or insulation of workers if in accidental contact with energized electrical conductors, apparatus, or circuits. Styles of overshoe footwear covered under this specification shall be designated as: Rubbers, designed to be worn over existing footwear and to cover only the foot of the worker; Boots, designed to be worn over existing footwear and to cover the foot and lower leg of the worker to below the knee; and Galoshes, designed to be worn over existing footwear and to cover the foot and lower leg of the worker to below the knee and having fasteners to close the folded front flaps. Each article of overshoe footwear shall be given a proof test and shall withstand the 60-Hz ac proof-test voltage (rms value) or the dc proof-test voltage (average value).1.1 This specification covers acceptance testing of dielectric overfoot and overshoe footwear designed to provide additional isolation or insulation of workers if in accidental contact with energized electrical conductors, apparatus, or circuits.1.2 Three styles of overshoe footwear are provided and are designated as rubbers, boots, and galoshes.1.3 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.

定价： 515元 / 折扣价： 438 元 加购物车

3.1 This test method is most commonly performed using a negative polarity needle or a sharp defined point to an opposing grounded sphere (NPS). The NPS breakdown voltage of fresh unused liquids measured in the highly divergent field in this configuration depends on the insulating liquid composition, decreasing with increasing concentration of aromatic, particularly polyaromatic, hydrocarbon molecules in liquids of petroleum origin and decreasing with ester molecular structure, either natural or synthetic.3.2 This test method may be used to evaluate the continuity of composition of an insulating liquid from shipment to shipment. The NPS impulse breakdown voltage of an insulating liquid can also be substantially lowered by contact with materials of construction, by service aging, particulate matter, and by other impurities. Test results lower than those expected for a given fresh liquid may also indicate use or contamination.3.3 Although polarity of the voltage wave has little or no effect on the breakdown strength of an insulating liquid in uniform fields, polarity does have a marked effect on the breakdown voltage in nonuniform electric fields.3.4 Transient voltages may also vary over a wide range in both the time to reach crest value and the time to decay to half crest or to zero magnitude. The IEEE standard lightning impulse test (see 2.2) specifies a 1.2 by 50-μs negative polarity wave.1.1 This test method covers the determination of the dielectric breakdown voltage of insulating liquids in a highly divergent field under impulse conditions and has been found applicable to liquids of petroleum origin, natural and synthetic esters.1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 515元 / 折扣价： 438 元 加购物车