27 of 124  Construction of Giresun Wastewater Treatment Plant  Tender Dossier Volume 3 Employer’s Requirements  Section 08: Electrical Works  PLC analog cards will have galvanic isolation. Analog signals which are delivered and received from and to  exproof areas will be protected by serial surge arrester when there is equipment.  Assemblies shall be equipped with separate earthing and neutral busbar. Busbars shall be of hard drawn electrolytic copper.  Ends and joints must be protected against corrosion. The buses shall be painted and supported on flame- retardant, track-resistant and nonhygroscopic insulators strong enough to withstand the stresses caused by  magnetic forces when faults occur. 8.7.9 Busbars  Busbars must be sized for the prospective fault current level and duration. Due regard shall be given to the  method of supporting, regarding current withstand and thermal/mechanical stresses. The busbars shall have a  continuous current rating in accordance with IEC 298 standard of temperature rise.  The dimensions of the busbar copper work shall be of one size throughout the complete assembly and the  busbars shall be the same rating as the incoming supply switch.  Busbars shall be enclosed in a separate chamber and shall be continuous over each shipping section.  Riser bars shall be of the same construction and be fault rated to the same level as the main busbars.  Easy access shall be available to the busbars for future connections.  Circuit connections to the ground bus shall be made so that it is not necessary to open circuit the ground bus to  remove any connection made to the ground bus.  Connections between transformers in 1000 kVA or greater and main TR circuit breaker inside the Main  Distribution Panel shall be with isolated busbar. Copper busbars shall be used.  8.7.10 Assembly ventilation  All sections that contain equipment susceptible to heat that may be generated in normal operation shall be fitted  with forced air-cooling.  Filters shall be provided to maintain the integrity of the dust and moisture protection rating of the assembly.  Fans shall be thermostatically controlled and automatically switched on, on rising temperature level in the  section.  Indication of fan failure or section over temperature shall be included on the section door and signalled to the  PLC.  8.7.11 Circuit breakers (CBs)  Circuit breakers (CBs)for supply of final sub-circuits to equipment shall be in accordance with EN 60947, type  2, and have a rated switching capacity at least equal to the total load of the circuit they supply. CBs greater than  800 A shall be draw-out type and CBs greater than 100 A shall be air circuit breaker.  Miniature circuit breakers (MCB) shall be provided with fixed instantaneous short circuit and overload trips,  and be of the single, double or triple pole type as required. The prospective fault level must not be higher than  the breaker capacity, and the time/current tripping characteristics shall be chosen with due regard to the  equipment performance and circuit data, and to assure discrimination between the miniature circuit breaker and  the moulded case circuit breaker. The choice of miniature circuit breaker shall ensure basic protection against  indirect contact when used on a circuit with earthed equipotential bonding.  Inlet circuit breakers shall be 4-poles and motorized in MDP and have residual current protection.  8_Vol3_d4 3_Section 8 electrical works_en_GIR rev6.doc 