
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Neutral conductor protection – N-tripping
Trip units ETU745 - 776 also make it possible to protect the neutral conductor against overload. This requires a current transformer for the
neutral conductor, which can be retrofitted if necessary.
For tripping, the same long-time delay t
R
applies as for overload tripping.
9.1.5.2 Additional functions
Load monitoring (load restore / load shedding)
Trip units ETU745 - ETU776 offer the possibility of additional load monitoring. Two current values, "load shedding" and "load restore", as
well as a delay time t
x
, can be set.
If the setting value "load restore" is undershot, and the lower limit value for current transmission is exceeded at the same time, a signal is
output by the
Cublicle
BUS
after the set delay time t
x
has elapsed. If the setting value "load shedding" is exceeded, a signal is output by the
Cublicle
BUS
after the set delay time t
x
has elapsed. These signals can be used to connect or disconnect loads, thereby preventing an over-
load tripping of incoming circuit breakers.
Load monitoring can be adjusted via:
- the alphanumeric display (ETU745)
- the graphical display (ETU776)
- TD400 and the software "powerconfig"
- the COM modules with a PC with the software “powerconfig” installed
Leading signal for L-tripping
Trip units ETU745 - 776 provide a leading signal for "L-tripping", which is transmitted via the
Cublicle
BUS
100 milliseconds before overload
tripping. In this way it is possible e.g. to disconnect thyristor controllers.
Phase loss sensing
When phase loss sensing is active and the load current on the least-loaded phase is at least 50% below that of the highest loaded phase,
the long-time pickup value I
R
is automatically reduced to 80% of its set value. This is designed to prevent overheating conditions in motor
loads when a single phase of voltage is lost and the motor is operating on 2 phases. If the highest and lowest load phase currents return to
differing by less than 50%, I
R
returns to its set value.
In the trip unit ETU776, phase loss sensing can be activated independently from the motor protection t
sd
setting of 20ms.
Setting values for I
N
ETU745
I
N
= (0.5 / 1.0) × I
n
; OFF
ETU776
I
N
= (0.2 - 2.0) × I
n
; OFF
NOTICE
Neutral Conductor Overheating.
Neutral conductor or insulation may be damaged.
Settings I
N
> 1 x I
n
should only be used if the neutral conductor has been properly sized.
Setting values for load monitoring
"Load shedding" and "load restore"
40 A - 1.5 x I
n
Delay time
t
x
= 1 - 15 sec.
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: ......