backup power :
Buildings with a higher power supply level should be able to provide sufficient power under normal conditions and have sufficient backup power in the event of normal use of the power supply. In the event of an emergency (such as a fire or an earthquake) in a building, There must also be emergency power to ensure disaster relief and evacuation of personnel. Any building needs a large amount of electric energy to be able to be used and operated normally. The main source of electric energy consumed by a building is a national or regional power grid. When the grid can not guarantee power supply or has its own special conditions, it will also use its own small-scale power plant as the main power source or Supplementary power supply; in many cases, diesel generator sets and battery energy storage devices will be set as backup and emergency power supplies.