1.1 本试验方法涵盖在冲击条件下在高度发散场中测定绝缘液体的介电击穿电压，并适用于石油来源的液体、天然酯和合成酯。 1.2 以英寸-磅为单位的数值应视为标准值。括号中给出的值是到国际单位制的数学转换，仅供参考，不被视为标准值。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 3.1 该试验方法通常使用负极针或指向相对接地球体（NPS）的尖锐定义点进行。在该配置的高度发散场中测量的新鲜未使用液体的NPS击穿电压取决于绝缘液体成分，随着石油来源液体中芳香族分子（尤其是多环芳烃）浓度的增加而降低，并随着酯分子结构（天然或合成）而降低。 3.2 本试验方法可用于评估绝缘液体成分在不同运输过程中的连续性。绝缘液体的NPS冲击击穿电压也可以通过与结构材料接触、使用老化、颗粒物质和其他杂质大幅降低。 低于给定新鲜液体预期值的测试结果也可能表明使用或污染。 3.3 虽然电压波的极性对均匀电场中绝缘液体的击穿强度影响很小或没有影响，但极性对非均匀电场中的击穿电压确实有显著影响。 3.4 瞬态电压在达到峰值的时间和衰减到半峰值或零幅值的时间上也可能在很大范围内变化。IEEE标准雷电冲击试验（见 2.2 )指定 1.2 通过50μs负极性波。

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. ====== Significance And Use ====== 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.