ITU-T Recommendations

This Recommendation deals with lightning protection of the dedicated transformer for Radio Base Station (RBS).

RBSs are usually powered by the local power utility with a dedicated power line operating at medium voltage (e.g., from 10kV to 20 kV). A dedicated transformer is installed at the RBS for transforming the medium voltage to low voltage (e.g., 380V or 240 V), which is then used to power the RBS.

Frequently, the dedicated transformer is installed in a pole, and the associated overhead lines (medium and low voltage lines) have poor earthing conditions. Therefore, these transformers are exposed to lightning effects and, consequently, the power interruptions caused by lightning flashes can severely affect normal operations of the RBS.

The main objective of this Recommendation is to reduce risk of damage to RBS dedicated transformer due to lightning flashes, which will improve the safety and reliability of the RBS itself and its related equipment.

This Recommendation includes the following features:

1) Need of protection for dedicated transformer ;

2) Earthing and bonding of transformer and RBS;

3) Direct lightning protection for transformers;

4) Transformers insulation requirements;

5) MV/LV arresters and LV SPDs;

6) Protection of ancillary facilities.