DC systems are great for moving bulk power at really high voltages. They are just not feasible for power distribution, however. AC systems provide easy means to deliver power to remote users from remote generating stations. A mix of both technologies is viable for the future power system.
Power transformers are widely used in a power system to transform voltage. The most common type, a two winding transformer, has one winding connected to a high voltage – low current circuit while the other winding is connected to a low voltage – high current circuit.
Coordinating and setting protective devices is an art in itself. It’s mostly at the engineer’s discretion and the clients priority when finding the middle ground for device settings. In any case, the following items should be considered when coordinating protective devices: