The aim in this project is to find a design space for a condenser type bushing given by HitachiEnergy. The design space shows which combinations of air and silicon-rubber (SiR) conductivity remain under a specified electric field strength value. This range of value represents how humidity affects air and SiR conductivity. Hitachi energy provided two different models, one with foils and one without foils. The design space for these models consists of how humidity affects the conductivity of both air and SiR. The values of air conductivity are gathered from different studies with different air humidity and external effects that affect the conductivity such as high aerosol concentration and high radon concentration. The values used for simulation will be approximated because of the different external effects and will range from 10^(−12)–10^(−13) S/m for humid conditions, 10^(−14) S/m for average humidity conditions and 10^(−15)–10^(−16) S/m for dry conditions. The range of SiR conductivity and the correlated weather conditions was given by Hitachi Energy and range from 10^(−11)–10^(−15) S/m where 10^(−11) S/m is for humid conditions, 10^(−12)–10^(−14) S/m for average humidity conditions and 10^(−15) S/m for dry conditions. For each of these combinations of conductivity the maximum electric field strength is calculated using COMSOL Multiphysics and compared to the threshold value of 2 kV/mm. Using these parameters the maximum electric field strength on the sheds of the bushing was calculated using COMSOL Multiphysics for all combinations of SiR and air conductivity. The results shows a pattern for both models. SiR conductivity must be higher or equal to the air conductivity to be below the threshold of 2 kV/mm.

Electrical bushings are a type of hollow or solid conductor withinsulation designed to allow a conductor to pass through a conductingbarrier without making electrical contact and are very important forsafe transportation of electricity. The bushings vary in size, but allbushings have a solid or hollow conductor.This project aims to investigate which resistivities of the siliconerubber, in combination with different air conditions for the airsurrounding the bushing (dry, average and humid air) and theirrespective resistivities, to see which combinations allow for anelectrical field that allows the bushing to safely work without beingdamaged. The different air conditions are an important factor since theyall correspond to different absolute humidities present in the air,which have a direct impact on the strength of the electrical fieldsurrounding the bushing. Since this cannot be done by hand, a computersoftware called COMSOL Multiphysics will be used. COMSOL is aMultiphysics software, meaning one can simulate many types of physics atonce. With the help of this software, and a model provided by HitachiEnergy, results could be found stating that dry air overall is the bestcondition of air for the bushing, followed by average (not either dry orhumid) air and lastly humid air.