Siemens SIPROTEC 7SJ62 Manual page 45

Current Connection (Power System)
Via parameter 251 CT Connect. a special connection of the current transformers can be determined.
The standard connection is A, B, C, (Gnd). It may only be changed if the device is set to measure one or
more ground currents via two current inputs. The standard connection applies to all other cases.
The following diagram illustrates a special connection.
Figure 2-3
The phase currents I
(terminals Q5, Q6). At the fourth input (terminals Q7, Q8) the ground current I
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
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
. In case of A,G2,C,G; G->B, the phase current I
I
B
measured ground current I
current I is determined by phase currents I
B
current input. The setting must be set according to system requirements.
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
Measurement of two ground currents, example
and I must be connected to the first current input (terminals Q1, Q2) and to the third
A C
N2
at the second current input (terminals Q3, Q4). The settings only differ in the calculation of
N2
at the fourth current input. In case of A,G2,C,G; G2->B, the phase
or I
N N sens.
(terminals Q3, Q4).
is determined by phase currents I
B
and I as well as the measured ground current I
A C
Functions
2.1 General
or I is connected as usual, in
N NS
and I as well as the
A C
at the second
N2
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