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Figure 2-2
Nominal values of the transformers
If voltage transformers are connected, the device obtains information on the primary and secondary nominal
voltage (phase-to-phase voltage) in addresses 203 Unom PRIMARY and 204 Unom SECONDARY, and infor-
mation about the primary and secondary nominal currents of the current transformers (phases) 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.
Correct entry of the primary data is a prerequisite for the correct computation of operational measured values
with primary magnitude. If the settings of the device are performed with primary values using DIGSI, these
primary data are an indispensable requirement for the correct function of the device.
The differential protection is designed such that it can operate without measured voltages if it is configured as
the main protection function without distance protection 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-
essary, they can also serve for determining the line voltage in case of automatic reclosure. During configuration
of the device functions (Section 2.1.1), it has been determined whether the device is to work with or without
measured voltages.
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
Polarity of current transformers
Functions
2.1 General
45
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