Siemens UL 489 Operating Instructions Manual page 118

Ground-fault protection switchable to I
The ground-fault protection modules for trip units ETU745 - 776 make it possible to switch over from a constant delay time to an 
2
I t characteristic.
This provides an inverse-time tripping characteristic with a constant I
systems with several grading levels.
The setting options for the delay time remain unchanged.
2
Switchover to the I t characteristic can be made via:
g
- the t rotary coding switch (ETU745);
g
this must be set to a value in the white area.
- the graphical display (ETU776)
- TD400 and the software "powerconfig"
- the COM modules with a PC with the software "powerconfig" installed
Ground-fault alarm
 Ground-fault protection modules (page 9-44)
9 – 16
2
t characteristic
2
t value, providing better selectivity of the ground-fault protection in
g
 (page
29-2).