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DIR 1000587R0002 (Version 02)
3.6.8. Load control function
Single loads can be enabled/disabled on the load side before the overload protection L intervenes and trips the circuit-breaker on
the supply side. This is performed by means of contactors or switch-disconnectors controlled by the trip unit via contact S51/P1.
The current thresholds are lower than those available with the protection L, so that the load control can be used to prevent trip-
ping due to overloads. The function is active when an auxiliary power supply is present.
The operating logic involves the activation of three contacts when the preset thresholds LC1, LC2 and I
w
are exceeded.
Thresholds LC1 and LC2 are expressed as a percentage of I
1
(current threshold specifi ed for protection L) while the “warning
current” I
w
is expressed as an absolute value. The allowable values are given in the following table:
Threshold LC1 50%...100% x I1 step 1% I1
Threshold LC2 50%...100% x I1 step 1% I1
Threshold Iw 0.3 ...10.0 x In step 0.05 In
Contact S51/P1 can be associated with thresholds LC1 and LC2, and the confi guration (NO or NC), delay time and latch settings
can be entered via the trip unit.
3.6.9. Neutral Protection
LSIG-MM allows the current signal of the neutral pole to be processed with different ratios in relation to the value of the phases.
The following values can be set for this protection: I
n
N =Off - 50% - 100% - 150% - 200% * I
n
.
The adjustments can be made via the menu in the Settings-Circuit-breaker-Neutral Protection section.
Regulation of the neutral value (I
n
N) must conform to the following formula: (I
1
x I
n
N) Iu.
With four-pole circuit-breakers, the trip unit performs the test automatically and transmits a fault signal following failure to conform
to this formula. If the circuit-breaker is the three-pole type with external neutral, no tests will be performed by the trip unit and
correction of the settings is at the user’s charge.
E.g.: With 140G-N 1200 with Rating Plug at 400A, Iu=1200A and I1=1In, adjustment of I
n
N may be 50-100-200%
With 140G-N 1200 with Rating Plug at 800A, Iu=1200A and I1=1In, adjustment of I
n
N may be 50-100%
The I
1
=1I
n
setting is the maximum setting of the protection against overload. The real permissible maximum setting setting must
take account of derating due to the temperature, the terminals used and the altitude, or In (rating plug) 50% of the size of the
circuit-breaker.
ATTENTION: In some installations, where particularly high harmonics occur, the current circulating on the neu-
tral may be higher than that of the phases.
ATTENTION: For three-pole circuit-breakers without external neutral, the Neutral protection setting must be OFF,
otherwise the sensor presence error will be signalled (Error CS).
In these cases, short-circuit T5-T6 on the sliding contacts, as shown in the wiring diagrams.
ATTENTION: Failure to comply with the setting limits of “I1” and “InN” may result in damage to the circuit-
breaker and consequent risks even for the operator.
ATTENTION: the protection setting is automatically 100% when the current value exceeds 15.5xIn on the neutral.
3.6.10. Protection MM
The protection, available with LSIG-MM trip unit, protects against short-circuit.
In order to function, it must be enabled via the display menu and activated by means of a signal supplied to inputs K14/K15:
- Signal High: protection activated;
- Signal Low: protection deactivated.
The trip unit handles output contacts 95S/98s as feedback of the protection state, so as to communicate whether it is activated
(contacts closed) or deactivated (contacts open).
The state of the input contacts is available in the Test-MM Test-Input menu.
Further details about the electrical characteristics of the inputs and outputs are available in chapter 3.8.3.
3.6.11. Protection against instantaneous short-circuit “Iinst”
Iinst is a software override protection. The purpose of this protection is to maintain the integrity of the circuit-breaker and instal-
lation in the case of particularly high current values requiring shorter reaction times than those provided by the instantaneous
short-circuit-protection.
The protection cannot be disabled. It has a single fi xed time protection curve and the threshold level.
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