Thermal mechanical performance test on suspended insulators for transmission line
This study described some basic performance tests and accelerated ageing test by cool-heat cycling methods and thermal mechanical performance test methods on alumina porcelain insulators (new and aged) used for transmission lines in Korea. There were no failures in electrical and mechanical performance tests such as high voltage strength, flashover voltage, impact strength, etc. in any of the samples. However in the case of accelerated ageing tests above 90 /spl deg/C temperature gradient, fracture phenomena occurred by a thermal shock in the aged samples with low aluminous porcelain body. It was found that sample A was more severely aged than other samples. According to results of the HRB test and microstructural analysis, it was reasoned that insulator bodies with the matrix reinforced with alumina crystalline phase have advantages in the suppression of crack propagation. Cool-heat aging and mechanical thermal aging tests show that a temperature gradient is more effective for acceleration of the aging than variation in the number of cycles.
High voltage insulator mechanical load limitations to dielectric material damage
The paper discusses the mechanical load limitations to dielectric material damage of high voltage suspension type insulators. For ceramic insulators, discussed are the design aspects of cap-and-pin insulators that play a role in the limits of time-load and thermal mechanical loads to prevent damage to the dielectric material. Brittle fracture, weathershed seals, interfaces between dielectric materials, and temperature, are discussed in terms of limiting the mechanical loads of non-ceramic insulators in order to prevent dielectric material damage.
Portland cement curing and volume characteristics
This paper describes the volume change characteristics of neat portland cement paste as used in the assembly of high voltage porcelain insulators. Many tests were made to determine volume changes under a variety of physical conditions. The effect on the electrical and mechanical integrity of the insulators subjected to these cement volume changes was investigated and reported.