Final answer:
Superconductors can maintain a current without the need to transform high to low voltage due to their ability to conduct electricity without resistance.
Step-by-step explanation:
The type of current flow that cannot be transformed from a higher voltage to a lower voltage is one in superconductors. Superconductors are materials that can conduct electricity without resistance; as such they can maintain a current without a continuous power input. This means that superconductors can keep a current flowing without needing to transform voltage from high to low, as they don't have the energy losses typically associated with other conductive materials.