Power System Data 1 - Siemens siprotec 7SA6 User Manual

6.1.1

Power System Data 1

Polarity of Current
Transformers
Instrument
Transformer
Nominal Values
Voltage
Transformer
Connection
7SA6 Manual
C53000-G1176-C133-1
Some system and plant data are required by the device, so that it may adapt its
functions to these data, according to its mode of operation. Amongst others, the plant
and instrument transformer ratings, polarity and termination of the measured values,
parameters of the circuit breaker, etc. These data are summarized in 3RZHU 6\VWHP
'DWD  36\VWHP 'DWD  .
If the key is operated, the main menu is displayed. With the key
MENU
6HWWLQJV is selected and by pushing the key
confirmed. To enter the plant data 3RZHU 6\VWHP 'DWD  36\VWHP 'DWD 
must be selected in the menu 6HWWLQJV.
® 4 the corresponding selection is reached by double click on 6HWWLQJV.
With DIGSI
In address  &7 6WDUSRLQW the polarity of the current transformers must be
entered, in other words, the location of the CT star-point (Figure 6-8). This setting
determines the measuring direction of the device (forward = line direction). A change
of this parameter also results in the polarity reversal of the earth current input.
I
L1
I
L2
I
L3
I
N
Gvr
6qq…r††Ã! Ã2
‡‚h…q†ÃGvrÃ
Figure 6-8 Current transformer polarity
In the address  8QRP 35,0$5< and  8QRP 6(&21'$5< the device is
informed of the primary and secondary rated voltage (line voltage) of the voltage
transformers. In the address  &7 35,0$5< and  &7 6(&21'$5< the
primary and secondary rated current (phase current) of the current transformers are
entered.
Please observe that the rated current transformer secondary current must
corresponds to the rated current of the device, as the device would otherwise compute
incorrect primary data.
Correct entry of the primary data is a prerequisite for the correct computation of
operational measured values with primary magnitude. If DIGSI
parameters as primary quantities, the correct entry of the primary data is an important
prerequisite for the correct operation of the device.
The device contains four voltage measuring inputs, three of which are connected to
the set of voltage transformers. For the fourth voltage transformer U
options are available:
• Connection of the U
4
transformers, refer to Appendix A, Figure A-25:
6qq…r††Ã! Ã2
‡‚h…q†Ã7ˆ†ih…
input to the open delta connection e–n of a set of voltage
the option
the selection of 6HWWLQJV is
7ˆ†
I
N
I
L1
I
L2
I
L3
Gvr
®
4 is used to enter
input several
4
Functions
6-7