If mounted on a utility pole, they are called pole-mount transformers. When placed either at ground level or underground, distribution transformers are mounted on concrete pads and locked in steel cases, thus known as distribution tap pad-mounted transformers.OverviewA distribution transformer or service transformer is a that provides a final reduction in the system, stepping down the voltage used in the distribution lines to the level used. Distribution transformers are classified into different categories based on factors such as: • Mounting location – pole, pad, underground vault• Type of insulation – liquid-imme.