Dielectric Materials Moisture Resistance Study

Solid Dielectric Breakdown Techniques

“…Specimen and electrodes are immersed in transformer oil in order to increase the voltage level at which corona appears in the region around the high voltage electrode, where the electrode meets the surface of the specimen. At 60 cycles it is possible to use larger electrodes of smooth contour and thereby eliminate the troublesome effects of corona in the case of materials of moderate dielectric strength, tIowever, larger electrodes cannot be used at high frequencies because the resulting specimen capacitance would normally be beyond the limit imposed by the requirements of the resonant test circuits which must be employed (1,2). Moreover, at 60 cycles, recourse to such electrodes will not solve the corona problem for all materials; the very high dielectric strength plastics require a more perfect arrangement.…”

“…However, where specimen thickness permitted, the use of recessed cavities to contain the high voltage electrode provided the most homogenous and certain field configuration. Various types of recessed electrodes have been used by many investigators (1,2,4,5). The fact that the preparation of such cavities for the purpose of careful research is difficult has caused the authors to seek improved techniques that would serve a wide range of practical materials as well as those most promising for theoretical study.…”

“…Both methods have been used with considerable success (1), although the former one is restricted to low-frequency investigations. At higher frequencies it proved necessary to use fillets of high dielectric strength material.…”

“…Since the usual problems associated with dielectric strength measurements become more critical with increasing frequency, the test methods, which can be used successfully at the higher fre- 1 Manuscript received Jun~c 28, 1954. 67 quencies, afford improvements in conventional lowfrequency techniques.…”