Technical data

Siemens SIP · 2008
12 Motor Protection / 7SK80
12
12/21
Typical connections
Connection for compensated networks
The figure shows the connection of two
phase-to-ground voltages and the V
E
volt
-
age of the broken delta winding and a
phase-balance neutral current transformer
for the ground current. This connection
maintains maximum precision for direc
-
tional ground-fault detection and must
be used in compensated networks.
Fig. 12/22 shows sensitive directional
ground-fault detection.
Connection for all networks
The figure shows the connection to three
current transformers and two voltage
transformers in V-connection. Directional
ground overcurrent protection is not pos
-
sible since the displacement voltage cannot
be calculated.
Fig. 12/21
Sensitive directional
ground-fault detec-
tion (no directional
element for phase)
Fig. 12/22
Sensitive directional
ground-fault detec-
tion
Fig. 12/23
Residual current
circuit with voltage
functions (no direc
-
tional element for
phase)