3.2　Composition of Earthing System

3.2.1　The earthing system of telecommunication bureaus（stations）may be designed according to Fig.3.2.1.

Fig.3.2.1　Earthing system of telecommunication bureaus（stations）

3.2.2　Main earthing conductors and earthing conductors shall be connected in a layer-by-layer radiation mode，and should be connected in a layer-by-layer dendritic mode or a mesh connection mode.Following requirements shall be met：

1　The vertical main earthing conductor shall run through each floor of the buildings of telecommunication bureaus（stations）.One end thereof shall be connected to the earthing connection，and the other end to the rebar and the horizontal branched main earthing conductor at each floor of buildings.And a radiation structure shall be formed.The vertical main earthing conductor should be connected with the ring main earthing conductor at the first floor of buildings（structures），and shall be vertically led to the horizontal branched main earthing conductor of each equipment room.

2　The horizontal main earthing conductors shall be layered.The earthing conductors of respective telecommunication equipments shall be led in from an adjacent horizontal main earthing conductor at the same floor.

3.2.3　The common earth grids of telecommunication bureaus（stations）shall maintain mutual electrical connection by utilizing rebars inside foundation concrete of buildings，ring earth electrodes laid at the surrounding of buildings，and cable shields and various pipelines connected thereto.