Which banks serve a specialized function for stepping down voltages for Subtransmission?

The specialized function for stepping down voltages for Subtransmission is best associated with power banks. Power banks are designed to reduce the higher transmission voltages from the transmission system to lower subtransmission levels, making the electricity more suitable for local distribution.

Power banks typically consist of transformers that effectively manage voltage levels, ensuring that the distribution of electricity is safe and efficient for consumers and the local grid. This role is critical in the management of electric power systems, as it allows for the reliable delivery of electricity from bulk power sources to areas where it can be distributed to end users.

Other types of banks like distribution banks, line banks, and utility banks serve different purposes, and thus are not specialized for the function of stepping down voltages specifically within the subtransmission context.