11.1.1 Dual Power Supply Switching

(1) The power supply and distribution of the clean operating department must be an independent system, supplied directly from the central power distribution station of the building in which the operating department is located, and must not share the same line with any other power-consuming areas.

(2) The central power distribution station of the building where the operating department is located must be supplied by two or more power grids. These two or more power supply grids must be capable of automatic switchover between one another; when one power grid fails or is under maintenance, the supply can switch instantaneously (switching time less than 0.5s) to another grid to continue normal power supply. If two power grids are not available locally, other means may be used to ensure normal power supply to the operating department; a standby generator may be adopted. The generator should be interlinked with the power distribution center so that, when the mains power fails, it can automatically switch over to start the generator, putting the generator into operation in time to maintain the normal use of the operating department. If the generator cannot supply power normally within 1min, the system must automatically switch to the standby UPS (or EPS) emergency power supply within 1s to ensure normal power supply to the operating rooms. When the standby generator is supplying power normally, the UPS (or EPS) emergency power supply then switches back to the standby generator. If an EPS or other batteries are used as the emergency standby power supply, ventilation measures and fire safety measures must be provided. Figures 11.1 and 11.2 are schematic diagrams of standby power supply switching.

Figure 11.1 Schematic diagram of dual emergency standby power supply switching

(3) The transmission line from the central power distribution station to the clean operating department should use mineral-insulated cables wherever possible, so as to raise the fire-resistance rating.

(4) Electricity consumption within the operating department is a first-class load; the power supply to the instruments in the operating rooms, the shadowless lamps, and the emergency lighting must be ensured as a priority; power suppl

Figure 11.2 Schematic diagram of the switching principle of the EPS emergency standby power supply

  1. KM1, KM2, and KM3 are mechanical-electrical interlocks, located inside the EPS
  2. The charger can be connected to either the standby power supply or the normal power supply
  3. When there is no normal power supply, if the standby power is switched in for more than 0.1s, the EPS switches in first and switches out after the standby power comes on The busbar supplying power to the operating department and the power supply for the purification air-conditioning units serving the clean operating department shall be separated.

11.1.2 Power Distribution of the Clean Operating Department

Power shall be supplied using the TN-S system and the IT system; the TN-C system is not permitted for power supply.

[Reference] For a schematic diagram of the TN-S system, see Figure 11.3; for a schematic diagram of the IT system, see Figure 11.4.

Figure 11.3 Schematic Diagram of the TN-S System

Figure 11.4 Schematic Diagram of the IT System