Functions
2.1 General
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
37
Figure 2-3
Measurement of two ground currents, example
The phase currents
I
A
and
I
C
must be connected to the first current input (terminals Q1, Q2) and to the third
(terminals Q5, Q6). At the fourth input (terminals Q7, Q8) the ground current
I
N
or
I
NS
is connected as usual, in
this case the ground current of the line. A second ground current, in this case the transformer starpoint current,
is connected to the second current input
I
N2
(terminals Q3, Q4).
The settings
A,G2,C,G; G->B
or
A,G2,C,G; G2->B
must be used here. Both define the connection of a
ground current
I
N2
at the second current input (terminals Q3, Q4). The settings only differ in the calculation of
I
B
. In case of
A,G2,C,G; G->B
, the phase current
I
B
is determined by phase currents
I
A
and
I
C
as well as the
measured ground current
I
N
or
I
N sens.
at the fourth current input. In case of
A,G2,C,G; G2->B
, the phase
current
I
B
is determined by phase currents
I
A
and
I
C
as well as the measured ground current
I
N2
at the second
current input. The setting must be set according to system requirements.