Siemens UL 1066 - Page 97

9 – 17
Ground-fault protection switchable to I
2
t characteristic
The ground-fault protection modules for trip units ETU745 - 776 make it possible to switch over from a constant delay time to an 
I
2
t characteristic.
This provides an inverse-time tripping characteristic with a constant I
2
t
g
value, providing better selectivity of the ground-fault protection in
systems with several grading levels.
The setting options for the delay time remain unchanged.
Switchover to the I
2
t
g
characteristic can be made via:
-the t
g
rotary coding switch (ETU745 - 748);
this must be set to a value in the white area.
- the graphical display (ETU776)
- the BDA (ETU776)
-the PROFIBUS-DP (ETU776)
- the MODBUS (ETU776).
Ground-fault alarm
 Ground-fault protection modules (page 9-45)