Transformers in distribution systems can be broadly categorized into distribution substation transformers and other distribution transformers. They are crucial for stepping down high transmission voltages to levels suitable for distribution and end-user applications.

Distribution substation transformers come in various ratings and typically use mineral oil for insulation and cooling. To prevent moisture and air from entering the oil, some transformers use an inert gas like nitrogen to fill the space above the oil.

Transformers with load tap changers (LTCs) automatically regulate voltage levels to ensure consistent voltage delivery despite fluctuations in demand. Sealed transformers often have a pressure-relief diaphragm designed to rupture when internal pressure exceeds a specified threshold.

Outdoor transformers include a conservator tank for oil expansion and contraction due to temperature changes. This feature maintains transformer longevity by preventing moisture and sludge formation. These transformers are typically rated based on their maximum continuous load capacity, as indicated by MVA ratings. These ratings ensure the transformers operate within safe temperature limits. Distribution transformers link the primary high-voltage system to the secondary low-voltage system. They can be installed outdoors, indoors, or underground, and come in various types:

Pole-mount Transformers: These can be either single-phase or three-phase, are usually liquid-filled, and are self-protected. They are often used in overhead distribution networks.

Padmount Transformers: Placed at ground level, these can be liquid-filled or dry-type. They are commonly used in underground distribution systems and can be single-phase or three-phase.

Network Transformers: These are large, liquid-filled three-phase transformers typically installed in underground vaults. They are used in urban areas to handle high load densities.

Transformers in distribution systems ensure that voltage levels are appropriately stepped down and regulated for safe and efficient distribution to end-users.