3.13　Power Distribution System

3.13.1　The setting of high-voltage transmission lines and transformers shall be in accordance with the following requirements：

1　The high-voltage power lines at telecommunication bureaus（stations）led in from the terminal poles of overhead high-voltage power lines should be armour cables；when entering distribution transformers of telecommunication bureaus（stations），armour cables at the high voltage side shall be led in by wholly buried.

2　When distribution transformers is inside the buildings of telecommunication bureaus（stations），high-voltage armour cables shall be led in via underground，and armour layers at two ends shall be earthed nearby.

3　The distribution transformers of microwave stations and mobile telecommunication base stations built at the suburbs or mountainous regions should not be mounted with telecommunication equipment in the same equipmentrooms.

3.13.2　At the junctions of terminal poles of overhead high-voltage power lines and armour cables，three-phase power lines shall be separately added with AC gapless zinc oxide arresters with a nominal voltage thereof at 12.7kV（system nominal voltage at 10kV）or 7.6kV（system nominal voltage at 6.6kV）to ground nearby.For telecommunication bureaus（stations）at middle keraunic zones or above，and built at the suburbs or mountainous regions，enhanced AC gapless zinc oxide arresters with the nominal discharge current not lower than 20kA shall be adopted.

3.13.3　At the high-voltage side of distribution transformers，the AC gapless zinc oxide arresters of corresponding nominal voltage shall be mounted at the place near to transformers，and at the lowvoltage side of transformers，SPDs shall be mounted.

3.13.4　SPD earthing terminals，transformers enclosure，neutral lines and armor layers of power cables at the high-voltage side or the low-voltage sides of distribution transformers shall be earthed nearby.

3.13.5　When special transformers are installed in the bureaus（stations）building s countyard，earth electrodes of transformers shall be connected with those of buildings.Earthing conductors shall be connected with the main earthing conductors in bureaus（stations）.When special transformers are installed in buildings，their earthing system may share the same earth-termination system with bureaus（stations）.

3.13.6　All exposed conductive parts of distribution equipment equipmentbureaus（stations）under normal conditions shall be earthed.Neutral protection must not be adopted.