descrizione delle correnti di cortocircuito

Short circuit current

I_cc =C V / ( k Z_cc )

where for I_cc three-phase:

V=phase voltage

C=voltage factor

k=1,732

Z_cc= sqr(ᓬR²_FASE+ᓬX²_FASE)

where for I_ccphase-phase:

V=phase voltage

C=voltage factor

k=2

Z_cc= sqr(ᓬR²_FASE+ᓬX²_FASE)

for I_cc phase-neutal:

k =1,732

Z_cc =sqr((ᓬR²_FASE+ᓬR²_NEUTRO)²+(ᓬX²_FASE+ᓬX²_NEUTRO)²)

for I_cc fase-protection:

k =1,732

Z_cc =sqr((ᓬR²_FASE+ᓬR²_PROT)²+(ᓬX²_FASE+ᓬX²_PROT)²)

The voltage factor and the resistance of the cables assume different values depending on the current

Calculated short-circuit. The values assigned are as follows:

I_ccMAX:

C=1

R=> (Tab.Cable Resistance and Reactance)

I_ccmin:

C=1

R=> (Calculated with the 'increase of conductivity' to the final temperature of short circuit from table of

the resistance and reactance of the cables.)