Abstract
Insulators serve bi-fold objectives of holding the conductor and electrical segregation from the grounded structure. For reliable operation of utility, electrical and mechanical strength of insulators are equally significant. The mechanical load is governed by weight of conductor, tension and environmental conditions like wind, snow, rain and typhoons etc. However, electrical strength is determined by survival of insulators against system voltage and transient over-voltages. A simulated power arc test was conducted on porcelain insulator samples by passing 72 kA/cycle surge current to evaluate for sudden lightning conditions after conducting insulation measurement of insulator samples. All cristobalite samples broke during power arc test. Power arc test revealed the thermal expansion coefficient of cristobalite samples were1.6 times higher as compared to alumina samples. Followed to arc test, X-Ray Diffraction (XRD), and Scanning Electron Microscope (SEM) were performed on insulator samples to evaluate consequences of power arc test on both cristobalite and alumina insulators. XRD reveals doubling of peak of cristobalite phase of fractured cristobalite insulators due to flow of high surge current through insulator body. X-Ray Fluorescence (XRF) was performed to investigate the elemental composition of Alumina and cristobalite porcelain insulators. Results of XRF show 5% increased Al 2 O 3 in alumina samples as compared to cristobalite samples. Finally SEM was carried to study microstructure of samples before and after power arc test. SEM analysis depicts the maximum pore size in cristobalite porcelain insulators were increased to 200 μm unlike alumina insulators. This article outline layout of research strategy to study behavior of alumina and cristobalite porcelain insulators.
Highlights
The concept of insulators has been come into existence before 1942
The insulators evaluated were removed from utilities operated at 154 kV
The insulation resistance was measured before the power arc tests
Summary
The concept of insulators has been come into existence before 1942. Since the inception, it has been strictly managed as international standards like ANSI and IEC [1], [2]. It has been strictly managed as international standards like ANSI and IEC [1], [2] These standards are globally acceptable [3]. The lifespan of porcelain insulators are approximately 30 years. Insulators were exposed to continuous electrical and mechanical stresses such as lightning, wind, rain, ice etc.
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