A newly constructed residential area introduces a 10kV power line to a substation. From the transformer's low-voltage side (0. 4kV), power is distributed to a main distribution panel (primary distribution box). An American. Each substation, whether existing or new, can have different configurations or equipment construction depending on what is needed, and to comply with regulations. Useful key terms and equipment definitions: Security and. Primary distribution systems consist of feeders that deliver power from distribution substations to distribution transformers.