Siemens SIPROTEC 4 7UT6 Series Manual page 66

Functions
2.1 General
The device requests also the polarity and rated currents of the connected 1-phase CTs. The clarifications below
comprise all possible settings, in the actual case only those addresses will appear which are available in the
actual version and defined in the topology.
Enter the primary rated current of each further 1-phase current transformer which is connected and assigned
to a further 1-phase current input of the device. Please note the previous assignment of the measuring loca-
tions (see Section
Locations").
Distinction must be made for the secondary rated currents whether the 1-phase current input is a "normal" or
a "high-sensitive" input of the device:
If a "normal" input is concerned, set the secondary current in the same way as for the 3-phase current inputs.
Please make sure that the rated secondary CT current matches the rated current of the corresponding current
input of the device. Rated secondary currents of the device can be matched.
If a "high-sensitive" current input is used, no rated secondary current is defined. In order to calculate primary
values for such measuring inputs (e.g. for setting in primary values or for output of primary measured values),
the conversion factor Ι
The polarity of a 1-phase current input is important for correct function of the differential protection and the
restricted earth fault protection. If only the magnitude of the current is of interest (e.g. for earth overcurrent
protection or single-phase overcurrent protection) the polarity is irrelevant, Even though a high-sensitive 1-
phase current input has been selected, the polarity setting is omitted as it only processes the current amount.
For polarity information, set to which device terminal the side of the current transformer facing the earth elec-
trode is connected, i.e. not the side facing the starpoint itself. The secondary earthing point of the CT is of no
interest. Figure 2-16
current ΙX1.
[anlagendaten-polaritaetseinstellung-iz1-020904-st, 1, en_GB]
Figure 2-16
The following applies for the (max. 4, dependent on device version on connections) 1-phase current inputs:
For the auxiliary measuring input X1
•
Address 711 EARTH IX1 AT with the options Terminal Q7 or Terminal Q8,
•
Address 712 IN-PRI CT IX1 = primary rated CT current,
•
Address 713 IN-SEC CT IX1 = secondary rated CT current.
For the auxiliary measuring input X2
•
Address 721 EARTH IX2 AT with the options Terminal N7 or Terminal N8,
•
Address 722 IN-PRI CT IX2 = primary rated CT current,
•
Address 723 IN-SEC CT IX2 = secondary rated CT current.
For the auxiliary measuring input X3
66
2.1.4 Power System Data
/Ι of the current transformer is set.
Nprim Nsec
shows the alternatives using as an example an earthed transformer winding for auxiliary
Polarity check for 1-phase current inputs ΙX1
1, margin heading "Assignment of Auxiliary 1-phase Measuring
SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016