The Short-Time Electric Breakdown Behavior of Polyethylene

The measurement of dielectric strengths is generally beset with numerous difficulties, and results depend to a large extent upon experimental conditions and sample geometry. The development of so-called cylindrical samples, in which spherical electrodes are almost completely embedded in the dielectric to be measured, and observation of stringent cleanliness, have resulted in distributions of the measured breakdown field strengths which can no longer be described by simple distribution functions. The results can, however, be consistently interpreted with multiplicatively mixed distribution, functions consisting of two Weibuli distributions, one of which reprelents the so-called technological breakdown due to macroscopic imperfections, and the second of which represents the material or intrinsic breakdown. On the basis of this differentiation, the influence of various parameters on the electrical breakdown behavior of polyethylene is discussed.