The anti-electric equipment is supplied by the main power supply when it is normal, and should be supplied by the emergency power supply in the event of a fire; when the main power supply is cut off in the fire for whatever reason, the emergency power supply should be automatically input to ensure the reliability of the fire power supply.The switching methods of fire power supply are:
1.Head-end switch
Each independent feeder of the fire load is respectively connected to the emergency bus, which receives power in a centralized manner and supplies power to the fire-fighting electrical equipment in a radial manner.Diesel generator sets provide emergency power to the emergency bus.The emergency bus is connected to the low-voltage bus of the main power substation through an automatic switch (called a tie switch) through a separate feeder.Under normal circumstances, the automatic switch is closed.Fire-fighting electrical equipment is powered by the main power supply via the emergency bus.When the main power supply fails or is disconnected due to a fire, the main power supply low-voltage bus will lose power, and the tie switch will be automatically disconnected after a delay. The diesel generator set will only supply power to the emergency bus after 30s is started, thus realizing the purpose of first-end switching , To ensure the reliable power supply of fire-fighting electrical equipment.
2.End switch
Two independent feeders drawn from the emergency bus and the main power low-voltage bus can be switched in the accident power switch box at the respective ends.Since each feeder is independent, the reliability of power supply is improved, but the feeder is doubled compared to the head-end switching.When the main power supply is cut off during a fire, the diesel generator set starts to supply power.If the emergency feeder fails, it is also possible to lose power to the fire-fighting electrical equipment.For Uninterruptible Power Supply (UPS).Due to the two-stage switching, no matter which circuit of the two feeders fails, it is reliable for the fire load.