A procedure for validating the use of lathed tapes for electrical breakdown testing

摘要

The use of lathed tapes has been objectively assessed as a means of obtaining representative electrical strength data for commercially produced, extruded polymeric dielectrics. This was accomplished by melting appropriate specimens such that any internal stresses were able to relax. Comparison of virgin and processed specimens from XLPE cable sample 1 provides strong evidence mat the procedures employed do not greatly affect the structure of the material. However, breakdown measurements indicate that, whilst recrystallization does not lead to an appreciable change in electrical strength, the lathing process does affect the behaviour of this material to a statistically significant extent; ie the 95% confidence intervals do not overlap. Conversely, recrystallizing XLPE cable 2 results in a dramatic change in morphology, which is accompanied by an appreciable reduction in breakdown strength. This effect is of such a magnitude that any changes associated with lathing are not detected.