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20
Terminal identification and base values
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Serial number, software version and the identification names and numbers for the sta-
tion, the object and the terminal (unit) itself can be stored in the REx 5xx terminal. Also
the ordering numbers of included modules are stored in the terminal. This information
can be read on the local HMI or when communicating with the terminal through a PC
or with SMS/SCS.
The base currents, voltages and rated frequency must be set since the values affect many
functions. The input transformers ratio must be set as well. The ratio for the current and
the voltage transformer automatically affects the measuring functions in the terminal.
The internal clock is used for time tagging of:
•
Internal events
•
Disturbance reports
•
Events in a disturbance report
•
Events transmitted to the SCS substation control system
This implies that the internal clock is very important. The clock can be synchronized
(see Time synchronization) to achieve higher accuracy of the time tagging. Without
synchronization, the internal clock is useful for comparisons among events within the
REx 5xx terminal.
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Uxr and Ixr (x = 1-5) are the rated voltage and current values for the analog input trans-
formers within the REx 5xx terminal. UxScale and IxScale are the actual ratio for the
main protection transformer at the protected object. These values will be used to calcu-
late the present voltage and current in the protected object. Uxb and Ixb defines base
voltage and current values, used to define the per-unit system used in the terminal for
calculation of setting values.
The current transformer secondary setting current (Is
I
SEC
⋅
Is
------------ - Is
=
SEC
I
PRIM
&KDSWHU
) is:
SEC
*HQHUDO
(Equation 10)
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