Introduction: Emergency Diesel Generator is basically required, in the event of prolonged power failure on the power plant, the emergency diesel generator shall be capable of ensuring a safe shutdown of plant, maintaining emergency supplies of the plant and black start in case of GTGs. Commonly fed Loads from EDG- • Emergency Lighting • AC / DC UPS • Communication System • Emergency shutdown and Fire & Gas System • Plant & Personal Safety System • All Material Handling equipment (in Offshore Platform) • Building HVAC • Black Start Motor (in case of GTGs) • Convenience Receptacles • Emergency Lube Oil Pump Motors Main Components of a Generator: An Electric Generator is a device that converts mechanical energy obtained from an external source into electrical energy as the output. • Engine: It converts fuel into Mechanical energy. It is the source of input mechanical energy to the generator. • Alternator: It produces Electrical output from the Mechanical input supplied by engine. • Fuel System: The fuel tank usually has capacity to keep the generator operational for 6 to 8 hours on an average. • Voltage Regulator: This component regulates the output of the generator by regulating DC voltage applied to armature. • Cooling System: Raw/ fresh water and or air is generally used as a coolant. • Exhaust Systems: Exhaust fumes emitted by a generator contain highly toxic chemicals that need to be properly managed. Hence, it is essential to install an adequate exhaust system to dispose of the exhaust gases. • Lubrication system: It ensures durability and smooth operations for a long period of time. • Battery charger: The start function of a generator is battery-operated. The battery charger keeps the generator battery charged by supplying it with a precise ‘float’ voltage. • Control Panel: This is user interface of the generator. Different manufacturers have varied features to offer in the control panel. • Main Assembly / Frame: It is customized housing that provides a structural base support. Applicable International Codes & Standards • IEC-60034 • IEEE-387 – IEEE Standard criteria for DG applied as standby power supplies for Nuclear Power Generating Stations • ANSI / NEMA MG1 • ISO 8528 – Generator Ratings