2.1 General
45
7SD5 Manual
C53000-G1176-C169-1
2.1.2
General Power System Data (Power System Data 1)
The device requires certain network and power system data so that it can be adapted
to its intended functions in accordance with application. This comprises, e.g., nominal
system data, nominal data of transformers, polarity ratios and their physical connec-
tions, in certain cases circuit breaker properties, and similar. Furthermore, there are
a number of settings associated with all functions rather than a specific protection,
control or monitoring function. These data can only be changed from a PC running
DIGSI
®
and are discussed in this section.
2.1.2.1
Setting Notes
Polarity of Current
Transformers
In address
201
CT Starpoint
, the polarity of the wye-connected current transform-
ers is specified (the following figure also goes for only two current transformers). This
setting determines the measuring direction of the device (forwards = line direction). A
change in this setting also results in a polarity reversal of the earth current inputs
I
E
or
I
EE
.
Figure 2-2
Polarity of current transformers
Nominal Values of
the Transformers
If voltage transformers are connected, the device obtains in addresses
203
Unom
PRIMARY
and
204
Unom SECONDARY
information on the primary and secondary
nominal voltage (phase-to-phase voltage), and in addresses
205
CT PRIMARY
and
206
CT SECONDARY
information on the primary and secondary nominal currents of
the current transformers (phases).
Address
206
CT SECONDARY
must correspond to the nominal current of the device,
otherwise the processor system cannot be started.
The correct primary data are required for the calculation of the proper primary infor-
mation of the operational measured values. If the settings of the device are performed
with primary values using DIGSI
®
, these primary data are an indispensable require-
ment for the fault-free operation of the device.
In principle, the differential protection is designed such that it can operate without mea-
sured voltages if it is configured as the main protection function without distance pro-
tection function. However, voltages can be connected. These voltages allow to display
and log voltages, to calculate various components of power and to locate faults. If nec-
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