Impact of low voltage bushings diameter on single-phase distribution transformers losses

This paper analyses steel tank wall losses of pole-mounted single-phase distribution transformers due to high currents crossing through the bushing holes of the low voltage terminals, and evaluates the impact of the holes diameter on load losses. The study also includes a description and comparison of analytical and empirical approaches used by other authors. The analysis was performed using simulations obtained by finite element method. The finite element model was validated reproducing results found in literature and simulations obtained for a 37.5kVA single-phase transformer model. The study was motivated by a reduction of diameter (from 4.6cm to 3.6cm) in the bushings supplied by manufacturers that represented a cost reduction. Results show no appreciable change of load losses with 1cm diameter reduction and consequently the decrease in manufacturing cost means a beneficial impact.