BN-20 Power Supply System provides uninterruptible 48V DC power supply for the DT-10TS Remote Terminal and Switchgear apparatus. It is built in a 600x600x350 mm cabinet. The BN-20 consists of a rectifier / charger and a high frequency voltage converter, NAP-2 Power Unit, battery packs, and automatic switches in each power supply output. In normal operation, the high frequency converter powers the switchgear apparatus, the DT-10TS Remote Terminal and charges the batteries from an external 230V AC supply. In the event of a 230V AC supply voltage failure, the power is supplied from the battery.

The NAP-2 unit is used for battery undervoltage and deep discharge protection. NAP-2 does not allow the battery to discharge below the safety level (according to battery characteristics) and switches off the battery via the K1 contactor when safety level is exceeded. When the external 230V AC supply is reestablished, NAP-2 recharges the battery.

In the DC distribution there are automatic switches (6 – 10 pcs) for the protection of individual power supply output, with auxiliary contact for remote signalling.