Guide to Construction of ArTu switchgear - Abb

8 Protection against the effects of short-circuit8.3 Distribution system selected in relation to the short-circuit withstand currentGENERALSTANDARDS ANDCHARACTERISTICSVERIFYING THEOVERTEMPERATURESPROTECTION AGAINSTSHORT-CIRCUIT ANDELECTRIC SHOCKSExamplePlant data: Vn=400 V fn=50Hz Icc=45kAT2 160T2 160T3 250T3 250T3 250ArTuArTuPRACTICAL INDICATIONSCERTIFICATION ANDCONSTRUCTIONCERTIFICATESDECLARATION OFCONFORMITYLet us consider the switchgear in the figure, from wherethe vertical distribution busbars are branched from themain busbars.These are 800 A busbars with shaped section as indicatedin the Distribution Switchgear General Catalogue:In (IP65) 800,Icw max 35 kABeing a rigid system with spacers, for the CEI EN 60439Standard, the short-circuit between the busbars is a remotehypothesis.It must, in any case, be checked that the stresses reducedby the circuit-breakers located on the load side of thesystem are compatible with the system.Let us suppose that the following are in the compartmentsTmax T3S250Tmax T2S160It must be checked that, in the case of a short-circuit on any output, the limitations producedby the circuit-breaker, are compatible with the busbar system.It must therefore be checked that the circuit-breaker which limits the peak and energy least,in any case limits it sufficiently for the busbar system.In our case this is the T3S250 In250Therefore we carry out the check in the same way as in the previous paragraph:From the Icw of the busbar system it turns out that:IP syst= Icw . n = 35 . 2.1 = 73.5 [kA]I 2 t syst= Icw 2 . t = 35 2 . 1 = 1225 [(kA) 2 s]From the limitation and specific let-though energy curves.With Icc 45kA here is corresponding Ipcb