4.1　General Requirements

4.1.1　Comprehensive telecommunication buildings shall be built on the principle of common earthing，and the foundation of buildings shall be connected with earthing systems of various equipment and devices，including all electrical connection and metal parts of buildings，low-voltage distribution earthing conductors，static electricity protective earthing and so on.Besides，ring earth electrodes shall be welded and connected with rebars in horizontal foundation of buildings.

4.1.2　When a comprehensive telecommunication building is comprised of many buildings，earth grids of buildings shall be interconnected via horizontal earth electrodes，forming a closed ring configuration.When they are far from each other or it is difficult for interconnection，these buildings may be handled separately as independent bureaus（stations）.

4.1.3　The comprehensive telecommunication building shall adopt comprehensive lightning protection systems such as external lightning protection systems，internal equipotential bonding and lightning electromagnetic pulse protection and the like.

4.1.4　For the earthing system inside the comprehensive telecommunication building，a complete equipotential bonding system shall be comprised of a main earthing terminal，floor earthing bar，local earthing bar and the earthing terminal preinstalled in the pillar，and respective sub-earthing system shall be connected via earthing conductors，forming different earthing reference points.

4.1.5　For earthing system inside the comprehensive telecommunication building，one or more lines may be led out from the main earthing conductors at the first floor to the high-rise vertical Riser，and the branched main earthing conductor at each floor shall be led out from the place nearby，finally forming the vertical riser network.

4.1.6　When transformers are installed in the buildings，neutral points of transformers and main earthing conductors should be connected via double lines.

4.1.7　The common earthing system of comprehensive telecommunication building may be designed according to Fig.4.1.7.

Fig.4.1.7　Connection mode of common earthing system of comprehensive telecommunication building