1. Ground selection connector for IO, screw terminals, 2-pole
2. Ground pin
3. Soft ground pin, see figure 540
4. X.21 Micro D-sub 15 pole male connector according to the V11 (X:27) balanced
version
I/O
100kW
100nF
Soft ground
en07000242.vsd
IEC07000242 V1 EN
Figure 540: Schematic view of soft ground
Grounding
At special problems with ground loops, the soft ground connection for the IO-ground
can be tested.
Three different kinds of grounding principles can be set (used for fault tracing):
1. Direct ground - The normal grounding is direct ground, connect terminal 2 direct
to the chassi.
2. No ground - Leave the connector without any connection.
3. Soft ground - Connect soft ground pin (3), see figure
539
X.21 connector
Table 710: Pinout for the X.21 communication connector
Pin number
Signal
1 Shield (ground)
2 TXD A
3 Control A
4 RXD A
6 Signal timing A
Table continues on next page
1MRK505222-UUS C Section 19
IED hardware
1127
Technical reference manual
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