The paper gives some specific instances of the wide variations which can occur in the measured electric strength of industrial insulating materials, arising partly within the material itself and partly on account of differences in the test conditions. Some of the results are subjected to an elementary statistical analysis. It is shown that short-time tests may be quite misleading as an indication of the relative merits in service of materials of different kinds, and it is concluded that the performance of a material can be found only by trial over a prolonged period. The paper includes the results of electric-strength tests at 50 c/s for periods up to two years, and these are compared with the results of tests lasting for only a few minutes.
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机译：本文给出了工业绝缘材料测得的电气强度可能发生大范围变化的一些具体实例，部分原因是材料本身内部存在，部分是由于测试条件的差异引起的。其中一些结果经过基本统计分析。结果表明，短时测试可能会误导不同种类材料在使用中的相对优势，并得出结论，只能通过长时间试用才能确定材料的性能。本文包含了长达两年的50 c / s的电强度测试结果，并将这些结果与仅持续了几分钟的测试结果进行了比较。
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