ASTM D3755-20 PDF Download

The ASTM D3755-20 standard provides guidelines for determining the dielectric breakdown voltage and dielectric strength of solid electrical insulating materials when subjected to direct-voltage stress.

The test method described in the standard is intended for use as a control and acceptance test for direct-voltage applications, as well as for evaluating materials for specific end uses and detecting changes in material due to deteriorating causes. The standard notes that the breakdown value obtained with direct voltage is usually about 2 to 4 times the rms value of the 60-Hz alternating-voltage breakdown.

The standard explains that for a nonhomogeneous test specimen, the distribution of voltage stress is primarily capacitive with alternating voltage, but becomes resistive after steady application of direct voltage. The choice between direct and alternating voltage depends on the purpose of the breakdown test and the intended application of the material.

The standard also refers to Appendix X1 of Test Method D149 for a more comprehensive discussion of the significance of dielectric breakdown tests, noting that the sections in Test Method D149 that relate to alternating voltage are not applicable to the direct-voltage method.

Additionally, the standard points out that special treatment or reference to other ASTM specifications or test methods may be necessary for certain materials. It also mentions that the test method is similar to IEC Publication 243-2, with any differences between the two standards being largely editorial.