Emax Low voltage air circuit-breakers - ABB Download Center

Solution with the PR123 trip unit with “double S”LV/LV Trans. 315kVATime-Current Curve @ 400V1SDC200315F0001MV CB (PR521)50 (I>): 50 A t=0.5s51 (I>>): 500 A t=0sE2N 1250 PR123 T5V 630 PR222DS/PLSIG R1250LSIG R630L Setting 0.8 0.74Curve 108s 12sS t=constant Setting - 4.2Curve - 0.25sS1 t=constant Setting 3.5 -Curve 0.5s -S2 t=constant Setting 5 -Curve 0.05s -I Setting OFF 76As is evident, by means of the “double S” function, selectivitycan be achieved both with the T5 circuit-breaker on the loadside as well as with the MV circuit-breaker on the supply side.A further advantage obtained by using the “double S” functionis the reduction in the time of permanence of high current valuesunder short-circuit conditions, which results in lower thermaland dynamic stresses on the busbars and on the other installationcomponents.ABB SACE 6/7