Certain auxiliary equipment (such as lighting) used during the loading and unloading process at airports, as well as electrical system tests during maintenance checks, require power supply. Although the aircraft's battery can provide power to on-board equipment for a short period and even start the engine, its capacity does not permit widespread use on the ground. Therefore, ground power sources are commonly used to service on-board electrical equipment or start the engine, with aviation power sources/aviation ground power units available in the form of ground power vehicles or fixed power sources that directly convert municipal electricity into the required form of energy.
The ground power vehicle is equipped with a battery or a generator, depending on the type of aircraft's main power supply. The generator is driven by the vehicle's engine and is fitted with voltage regulation, frequency stabilization, and protection devices. Ground power is delivered to the aircraft's ground power socket via a cable. The ground power monitor on the aircraft is used to check the polarity, phase sequence, and quality of the ground power. The aircraft's ground power contactor is only connected when the ground power meets the technical requirements of the aircraft, thereby connecting the ground power to the aircraft's electrical grid.
The fixed power supply consists of a central power source and an overhead or underground distribution network. The central power source is an electrical conversion device, transforming civilian power into 400Hz AC or DC electricity.
