51 of 124  Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 08: Electrical Works  • Grid OK  • Static Bypass  • Manual Bypass.  8.9.6 Earthing system and equipotential bonding  A five-conductor earthing system (TN-S) pursuant to IEC 60364 with separate protective conductor (PE) and  neutral (N) conductor shall be established from the power transformer(s) and throughout the new installations to  be established. The solution shall be approved by the electricity company.  A common equipotential bonding bar (CEBB) shall be installed connecting:  Foundation earth shall be firstly applied to the reinforcement of buildings / units via galvanized steel strip in  30x3,5 mm. Afterwards second circle shall be created around the buildings / units via copper conductors in at  least 70 mm2 in a way that distance between galvanized strips and copper conductors will be around 1 meter.  Both circles shall be connected each other from each corner via copper conductors in at least 70 mm2. Every building / unit shall be connected to other building / unit from at least 2 points via copper conductors in  at least 50 mm2 by using equipotential bars.  The common equipotential bonding bar shall be made of copper and have a cross sectional area such that it can  act as the circuit protective conductor on each item of the plant and equipment connected to it. The bar shall be  clearly labelled to identify its purpose and bolted firmly to the building wall mounted on 50 mm distance  pieces. Cable termination shall be made with compression-type cable lugs bolted to the bar. An equipotential zone shall be created throughout all installations encompassing all metal structures.  Extraneous metalwork, building reinforcement, metal supporting structures and machinery equipment i.e. pipes,  conduits, pumps, motors etc. shall be cross-bonded and connected to the common equipotential bonding bar.  An earthing system for power transformers shall be established as specified in this specification.  The earth resistance of the earthing system shall be as low as practicable but shall in any event be such that the  electrical resistance between the common equipotential bonding bar and the general mass of one earth group  shall not exceed 5 ohm when any one group of electrodes is disconnected. Connections to copperweld ground  rods will be made by the Cadweld process.  Distance between 2 different earth groups shall be at least 20 m. Electrodes of earth socket shall be buried with  the superior part at the minimal depth of 0.8 m. Every construction shall be connected to the earth group through at least two points. Protective conductors (PE) shall be made of stranded copper with overall green/yellow plastic covering.  8_Vol3_d4 3_Section 8 electrical works_en_GIR rev6.doc  • Power transformer low voltage (LV) earthing points.  • Plant protective conductor system (PE).  • Building reinforcement.  • Plant cross-bonding system.  • Earthing system for external lightning protection system.  • Lightning and overvoltage arresters. 