In order to have low losses and enhanced reliability in the distribution system, bus-ducts are preferred over cables for higher current ratings and shorter lengths at different voltage levels. Though Sandwich Bustrunking System with rated operational voltage (Ue) 1000 Volt are easily available, when it comes to economics–Air insulated bus ducts have an edge. This article focuses on the types of air insulated busducts and their selection guidelines, design requirements, de-rating factors and sizing requirement.