11
ENGLISH
LOOP TT e TN
Re
Rt
L
N
Pe
RCD
Rt
L
N
Pe
TERRA
BT
MT
BT
MT
RCD
FUSE
Rt ≤
Vc
I∆n
Re
Rt
L
N
Pe
RCD
Rt
L
N
Pe
TERRA
BT
MT
BT
MT
RCD
FUSE
TT SYSTEM
TN-S SYSTEM
Z line - PE impedance measurement in TT system
Z: Global Earth Resistance
Vc: Contact Voltage
NOTA: Limit for earth ground resistance is defined as:
Vc:Contact Voltage Limit (50V o 25V)
I∆n: Nominal RCD current
Impedance measurement Zs L-pe in TN system
Z: Fault Ground Impedance L-Pe
Ipsc: Prospective short circuit current (for check correct sizing of MCB or FUSE
protecting the system)