Define 'substation'.

A substation is indeed a facility that transforms voltage levels from high to low, which is essential for the distribution of electricity to homes and businesses. High voltage transmission lines carry electricity over long distances efficiently, but before it can be utilized by consumers, the voltage needs to be stepped down to safer levels. This step-down transformation process occurs at substations, allowing the electricity to be safely distributed throughout the power grid. Substations also play critical roles in regulating and controlling electrical flow, ensuring the stability and reliability of the power supply.

The other options refer to different aspects of the power system. Generating facilities are responsible for producing electrical power, while high voltage transmission locations refer to the distribution of power over long distances without mentioning transformation. A center for storing energy during peak demand describes energy storage systems, which are different from the transformation functionality of substations. Thus, the definition highlighting the voltage transformation is the most accurate representation of what a substation is.