A Study on the Reliability of Polyester Insulators Blended with Borax
Tracking is the main factor which limits the safe working electric stress of insulation in power system applications. Polymer samples have been tested in laboratory conditions according to ASTM D2303 on accelerated inclined plane tracking test. In this paper, a model based on improved Weibull statistics is proposed for estimating the breakdown time of polymeric insulating materials with borax. The confidence intervals of the Weibull shape parameter and the Weibull scale parameter are determined for the borax concentration values using the Weibull 7++ program.
A study on the ageing process for polyester resin using improved Weibull statistics
Surface tracking on organic solid insulators is one of the main reasons for failure in high voltage systems. Due to various factors, such as humidity, pollution, ice load, increase in local voltage, etc., it is hard to estime the lifetime of an insulator. For many years, Weibull statistics have been widely used and accepted as a successful mathematical method of predicting the remaining lifetime of an insulating material. The basic reliability function can perform well for predefined conditions. However, it might be insufficient in lifetime prediction in multi-variable conditions. In this research, a model based on improved Weibull statistics is proposed for estimating the breakdown time of polymeric insulation material. By using appropriate parameters, this improved model can estimate the remaining lifetime within a reasonable accuracy in varying external conditions such as voltages, contaminant flow rates and applied load. To determine the model parameters, several tests are performed according to the IEC 587 accelerated inclined plane tracking test method by investigating the breakdown times of polyesters under various external conditions generated artificially in the laboratory. The calculated results are found to be in good agreement with the experimental data.
Warm Hands in Cold Age – On the Need of a New World Order of Care
The world is aging as fertility and mortality are both decreasing. This article focuses on practical care work for the elderly. Such work is done primarily by women even though a larger portion than previously is paid rather than unpaid. All over the world, most elderly care work is organized within the family, most often unpaid. Men receive more care from partners than women, while women receive more care from female relatives. When care work is paid, the payment is generally low. A comparison between Germany, Spain, and Sweden demonstrates similar gender patterns, even though the role of the state in supporting care differs considerably as do care workers' conditions. The sustainability of today's distribution and organization of care work is questioned as the need for care increases, and the possibility of more equal sharing of care work between women and men is explored.