Siemens SIPROTEC 7SJ62 User Manual

Functions
2.1 General
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
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 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.
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Siemens SIPROTEC 7SJ62 Specifications

General

Brand	Siemens
Model	SIPROTEC 7SJ62
Category	Relays
Language	English