Siemens SIPROTEC 4 7XT71 Series, Manual, Page: 94 / 122

²
Unscrew the 4 screws used to attach the Z-shaped angle brackets to the housing and remove the Z-
shaped angle brackets (see
Figure 4-2 ).
²
Pull off the 2 covering caps on the front cover upward or downward as appropriate (see Figure 4-1 ).
²
Unscrew and remove the screws located in the center at the top and bottom of the front cover.
[scabbaufront, 1, en_US]
Figure 5-1 Removing the Front Cover
²
Carefully pull the pluggable printed circuit board assembly from the housing and put it down so that the
DIP switch S1 is accessible.
²
Once you have performed the necessary work on the printed circuit board assembly, reinstall the plug-
gable printed circuit board assembly using similar steps in reverse order.
Injection Unit in the Flush-Mounting Housing 7XT7100-0EA00
²
Switch off the plant providing the auxiliary voltage for the injection unit 7XT71.
²
Switch off all signaling voltages fed to the device.
²
Pull off the 2 covering caps on the front cover upward or downward as appropriate (see Figure 4-1 ).
²
Unscrew and remove the screws located in the center at the top and bottom of the front cover (see
Figure 5-1 ).
²
Carefully pull the pluggable printed circuit board assembly from the housing and put it down so that the
DIP switch S1 is accessible.
²
Once you have performed the necessary work on the printed circuit board assembly, reinstall the plug-
gable printed circuit board assembly using similar steps in reverse order.
Setting the Frequency
You can set the polarity-reversal frequency (frequency of the square-wave generator) using the DIP switch S1
on the printed circuit board assembly.
5.2.3
Commissioning
5.2 Changing the Polarity-Reversal Frequency
32 SIPROTEC 4/5, Injection unit 7XT71, Manual
C53000-B1174-C128-8, Edition 05.2020