Voltage endurance of coated electrical sleeving by statistical analysis

Historically, coated electrical sleeving has been offered in several grades characterized by prescribed minimum voltage breakdown levels determined by means of short time dielectric testing. Various empirical criteria have been used to determine the Jevel of continuous applied voltage which could be considered a safe level for intended applications for these grades in service. To date, no significant quantitative studies have been made to relate the short time tests to actual long term capability of the coated sleeving. One obvious reason for this lies in the difficulty and cost of constructing test models that would possess reliable similarities to actual service. As an alternative, the authors present data obtained from short time breakdown testing in which the rate of voltage application is varied. By treatment of these data, using accepted mathematical relationships, a method of estimating the constant stress performance of the sleeving is developed. This method has promise for providing statistically significant data on lot-to-lot variability, effects of aging, modeling of service environments, etc.