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9 – 11
9.1.5
Protective functions
9.1.5.1 Basic protective functions
The basic protective functions of the trip unit are ensured without additional auxiliary voltage. The required energy is supplied by the
circuit breaker's internal energy transformers.
To evaluate the currents, the electronic system of the trip unit calculates the r.m.s value.
The individual functions are parameterized according to the types via:
- rotary coding switch (ETU745)
- electronic data transfer (ETU776) via:
- TD400 and the software "powerconfig"
- the COM modules with a PC with the software “powerconfig” installed
- the control board (ETU776)
Overload protection – L-tripping
The current setting I
R
defines the maximum continuous current the circuit breaker can carry without tripping. The long-time delay t
R
determines the maximum duration of an overload without tripping.
The tripping characteristic is an I
2
t characteristic. Some trip units can be switched over to an I
4
t characteristic.
Short-time delayed short-circuit tripping – S-tripping
On trip units ETU745 - 776, tripping due to the short-circuit current I
sd
can be delayed by the time t
sd
.
This provides selectivity for short-circuit protection in switchgear with several grading levels.
1)
The delay time 0.02 sec. is not an I
2
t function.
The motor protection function is activated in this position.
2)
For settings t
sd
>0.4 sec., the maximum possible setting I
sd
is reduced automatically according to the frame size:
Frame size I
: 15 kA
Frame size II
: 20 kA
Frame size III : 30 kA
The setting "OFF" for trip units ETU745 and ETU776 is provided to deactivate the short-time delayed short-circuit protection.
If the zone selective interlocking (ZSI)
is used and the ZSI module is set to "S" or "S+G" the adjusted delay time t
sd
is auto-
matically set to 50 ms provided that in the event of short-circuit the circuit breaker does not receive a blocking signal from a downstream
circuit breaker. In this case regardless of the adjusted t
sd
value the circuit breaker will trip after 50 ms.
If a blocking signal exists the adjusted delay time tsd is valid. For safety reasons after 3 s the blocking signal is terminated.
Some trip units can be switched over to an I
2
t-characteristic.
Setting values for I
R
ETU745
I
R
= (0.4 / 0.45 / 0.5 / 0.55 / 0.6 / 0.65 / 0.7 / 0.8 / 0.9 / 1.0) x I
n
ETU776
I
R
= (0.4 - 1.0) x I
n
(given in Amps)
Setting values for t
R
ETU745
t
R
= 2 / 3.5 / 5.5 / 8 / 10 / 14 / 17 / 21 / 25 / 30 sec. (at 6 x I
R
)
ETU776
t
R
= 2 - 30 sec. (at 6 x I
R
)
Setting values for I
sd
ETU745
I
sd
= (1.25 / 1.5 / 2 / 2.5 / 3 / 4 / 6 / 8 / 10 / 12) x I
n
ETU776
I
sd
= 1.25 x I
n
- 0.8 x I
CW
(given in Amps)
Setting values for t
sd
ETU745
t
sd
= 0.02(M)
1)
/ 0.1 / 0.2 / 0.3 / 0.4 sec.; OFF
ETU776
t
sd
= 0.02(M)
1)
/ 0.08 - 4 sec.
2)
; OFF
Summary of Contents for UL 489
Page 36: ...5 21 Frame size II 3000 A Frame size III 1 Holes 14 mm 0720 1 0721_nu ...
Page 63: ...7 2 Horizontal connectors 0733_nu top view ...
Page 64: ...7 3 Rear vertical connectors 0734_nu top view rear view ...
Page 65: ...7 4 Front connectors 0736_nu front view top view ...
Page 66: ...7 5 Front connectors and pressure wire terminals 0737_nu top view front view ...
Page 67: ...7 6 7 2 Frame size II fixed mounted version 0494 3_nu ...
Page 68: ...7 7 Class C always 0494 5_nu top view rear view ...
Page 69: ...7 8 2500 0738_nu LH side view front view ...
Page 71: ...7 10 7 4 Frame size III fixed mounted version 0495 1_nu LH side view ...
Page 72: ...7 11 0495 2_nu top view top view ...
Page 73: ...7 12 0495 3_nu top view rear view ...
Page 75: ...7 14 7 5 Door cut outs fixed mounted circuit breaker Frame size I 0735_nu ...
Page 76: ...7 15 Frame size II III 0496_nu ...
Page 77: ...7 16 7 6 Frame size I draw out version 0745_nu ...
Page 78: ...7 17 0746_nu rear view top view ...
Page 79: ...7 18 0747_nu bottom view ...
Page 80: ...7 19 0748_nu ...
Page 81: ...7 20 0749_nu ...
Page 82: ...7 21 7 7 Frame size II draw out version 0490 1_ul ...
Page 86: ...7 25 7 8 Frame size III draw out version ...
Page 87: ...7 26 ...
Page 88: ...7 27 ...
Page 89: ...7 28 7 9 Door cut outs for draw out circuit breakers Frame size I 0750_nu ...
Page 91: ...7 30 7 11 External sensor for neutral conductor WLNCT2 ...
Page 92: ...7 31 WLNCT3 ...
Page 107: ...9 5 I tripping Ground fault tripping ...
Page 351: ......