9 – 16
Short-time delayed short-circuit protection switchable to I
2
t
Trip units ETU745 - 776 make it possible to switch over from a constant delay time to an I
2
t-characteristic. In this way, the delay time
depends on the short-circuit current, but with a constant I
2
t
sd
-value, providing better coordination with downstream fuses.
In this case, the setting options for the short-time delay t
R
are as follows:
Switchover to the I
2
t
sd
characteristic can be made via:
-the t
sd
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).
Changeable parameter sets
Trip units ETU745 - 776 make it possible to store two different parameter sets for protective functions.
This enables new protection settings to be adopted when a transfer to another supply source takes place.
Switchover can be made manually via:
- the graphical display (ETU776)
- the test socket with the BDA
or automatically via:
-the CublicleBUS with an input signal at the digital input module.
-the PROFIBUS-DP
-the MODBUS.
Settings for t
sd
ETU745 - 748
t
sd
= 0.1 / 0.2 / 0.3 / 0.4 sec. (at 12 x I
n
)
ETU776
t
sd
= 0.1 - 0.4 sec. (bei 12 x I
n
)
To Next Page
Loading...
