An emergency power system is an independent source of electrical power that supports important electrical systems on loss of normal power supply. A standby power system may include a standby generator, batteries and other apparatus. Emergency power systems are installed to protect life and property. Emergency power systems were used as early as on naval ships. In combat, a ship may lose the function of its boilers, which power the for the. In such a case, one or more The use of emergency power systems in aviation can be either in the aircraft or on the ground. In commercial and military aircraft it is critical to maintain power to essential systems during an emergency. This can be done via Ram air. In recent years, large units of a utility power station are usually designed on a unit system basis in which the required devices, including the boiler, the turbine generator unit, and its power (step up) and unit (auxiliary) are solidly connected as one unit. A. • • can be lost due to downed lines, malfunctions at a sub-station, inclement weather, planned or in extreme cases a -wide failure. In modern buildings, most emergency power systems have been and are still based on. Computers, communication networks, and other modern electronic devices need not only power, but also a steady flow of it to continue to operate. If the source voltage drops significantly or drops out completely, these devices will fail, even if the power loss is only for a fraction. For a 208 VAC emergency supply system, a central battery system with automatic controls, located in the power station building, is used to avoid long electric supply wires. This central battery system consists of cell units to make up a 12 or 24 VDC.