Power engineering is a subfield of electrical engineering that looks at the transmission and distribution of electric power and the electrical devices connected to such systems such as, generators, motors and transformers. Many fields are concerned with the problems of three-phase AC power; the standard for large-scale power transmission and distribution across the modern world.
Electric power is the mathematical product of two quantities: current and voltage. These quantities can vary with respect to time (AC) or they can be kept at a constant level (DC). Most refrigerators, air conditioners, pumps and industrial machinery use AC power; whereas digital equipment uses DC power. AC power has the benefit of being easy to transform between voltages and is able to be generated and utilised by brushless machinery. DC power remains the practical choice in digital systems and can be more economical to transmit over long distances at high voltages.
Power engineering looks at the generation, transmission and distribution of electricity and the design of a range of related devices. These include transformers, electric generators, electric motors and power electronics. Power engineers also work on systems that do not connect to the grid. These systems are called off-grid power systems and may be used in preference to on-grid systems for a variety of reasons.