Short-time delayed short-circuit protection switchable to I
Trip units ETU745 - 776 make it possible to switch over from a constant delay time to an I
depends on the short-circuit current, but with a constant I
In this case, the setting options for the short-time delay t
Settings for t
sd
ETU745
t
ETU776
t
2
Switchover to the I
t
characteristic can be made via:
sd
- the t
rotary coding switch (ETU745); this must be set to a value in the white area.
sd
.
- the graphical display (ETU776)
- TD400 and the software "powerconfig"
- the COM modules with a PC with the software "powerconfig" installed
Changeable parameter sets
The trip unit ETU776 contains two complete sets of protective parameters and can be switched between them locally or remotely.
This enables lowering instantaneous and short-time settings for arc flash mitigation as well as changing parameters when the source
of supply changes between utility and generator.
Switching between parameter sets can be made manually via:
- the graphical display (ETU776)
or remotely via:
- the
CublicleBUS
with an input signal at the digital input module.
- the PROFIBUS DP
- the PROFINET IO, Modbus TCP and Modbus RTU.
2
R
= 0.1 / 0.2 / 0.3 / 0.4 sec. (at 12 x I
sd
= 0.1 - 0.4 sec. (at 12 x I
)
sd
n
2
t
t
-value, providing better coordination with downstream fuses.
sd
are as follows:
)
n
(page
29-2).
2
t-characteristic. In this way, the delay time
9 – 15