Electrical power supply

Most of the tunnel equipment and systems require electrical energy to operate. Therefore, equipment for supplying power to the tunnel must be installed. This installation has to satisfy two essential requirements:

• Supply safe and sufficient power to allow all the equipment to operate
• Meet the needs under all operational situations (normal, degraded, critical, emergency).

The power required for supplying a tunnel is directly related to the nature and number of equipment installed in it. Depending on the amount of electrical energy required (kWh), power may be supplied in low voltage or high voltage (Fig. 1).

Each country has its own regulatory requirements with regard to tunnels and a specific structure in terms of distribution networks: therefore, the architectures retained may be significantly different in tunnels with similar characteristics. However, some identical principles can be noted, such as:

• The presence of a standby power supply (redundant supply, diesel generator, etc.),
• The installation of a device that can compensate for a total loss of power supply. This system (uninterruptible power supply (UPS), diesel generator., etc.) supplies electricity to equipment critical for safety, during a limited period of time.