Insulation system is one of the most important parts of power transformer. Theoretical background for insulation design is given, which includes explanation of dielectric properties of main insulation materials, their withstand to breakdown voltage, their verification by dielectric tests, and statistical data based theory for breakdown probability. Two known numerical methods (BEM and FEM) for calculation of electric field are used and for each numerical method an appropriate model of transformer is made. Safety factors for main insulation between HV and LV winding are calculated after which the oil gap width is reduced. Additional analysis of safety factors and field nonuniformity along windings is performed.Index Terms-numerical calculation, boundary element method, finite element method, electric field, power transformer
Snowdrifts caused by wind gusts reduce visibility on the road which endangers traffic safety, increases travel time and road maintenance costs. Based on previous experience and research it has been proven that living snow fence is an economical, ecological and efficient solution for protection of roads from snowdrifts. Living snow fences with their above-ground part, reduce the wind speed, act as a mechanical barrier for the snow and accumulate a certain amount of snow. This study presented use and efficiency of living snow fence in controlling snowdrifts on the road section Paraćin-Zaječar, locality – crest Čestobrodica. Analysis of environmental conditions, which are resented main endangering factor for snowdrifts, included the determination of indicators of possibility of snowdrifts: snowfall water equivalent (Swe), snow transport (Q) and ability of living snow fence to prevent snowdrifts: snow storage capacity of the fance (Qc). Snow storage capacity for living snow fence is analyzed for ten year period. Using equation for estimation of length of snowdrifts on downwind side of fance, a change in length of snowdrifts during the analyzed period are determin, and the efficiency of living snow fence in protection of the road from snowdrifts with increasing age.The results of this study represent a contribution to using living snow fence in solving the problem of roads protection from snowdrifts and increasing traffic safety during winter conditions.
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