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DIR 1000587R0002 (Version 02)
I
f
0.9 xI
1
No alarm, all settings possible. No time delay in progress.
0.9 xI
1
< I
f
< (1.05...1.2) xI
1
Prealarm L signal, all settings possible. No opening time delay in progress.
(1.05...1.2) xI
1
I
f
Alarm L signal, no setting possible. Opening time delay in progress.
ATTENTION: the protection L threshold entry range ensures that:
-
the trip unit does not set to the alarm status for current values less than 1.05 xI
1
;
-
the trip unit will set to the alarm status for current values exceeding 1.2 xI
1.
3.6.2.1.
Thermal memory L
The thermal memory function can be enabled for cable protection. It is based on the “
L” parameter, defi ned as the tripping time
of the curve (t1) selected at 1.25xI1.
The tripping time of the trip unit will certainly be 100% of the selected value after time
L has elapsed since the last overload or
the last trip, otherwise the tripping time will be reduced in relation to the overload that has occurred or the time that has elapsed.
LSIG-MM trip unit has two instruments for processing the thermal memory. The fi rst only operates when the trip unit is energized
(it also records overloads that have not lasted long enough to trip the CB), while the second operates even when the trip unit is
not energized, reducing any trip times in the case of immediate reclosing and activating the moment the circuit-breaker trips.
It is the trip unit that decides which of the two to use, depending on the situation in question.
ATTENTION: The thermal memory function can only be activated if the standard type of curve has been selected
(t=k/I
2
).
.
3.6.3. Protection
S
This protection can be disabled; it can be of the fi xed time (t=k) or inverse time (t=k/I
2
); in the latter case, the trip time is given by
the expression.
The tripping time with inverse time curve is given by the expression: t(s)=
. If the calculated value is less than t
2
, the
real tripping time is forced to t
2
(t(s)= t
2
.)
DEFINITIONS:
t(s):
estimated tripping time
I
f
:
fault current; given in [In] (example: 1.4In)
I
2
, t
2
:
protection S parameters set by the user, given in [In] and [s]
3.6.3.1.
Thermal memory S
The thermal memory function can be enabled for cable protection in the case where the curve with inverse time is selected. This
is based on the “tS” parameter defi ned as the trip time of the curve (t2) selected at 1.5xI2. The other characteristics are the same
as those for thermal memory L.
3.6.3.2.
Start-up threshold S
The start-up function can be selected in the case where the curve with fi xed time is selected.
The start-up function enables the protection threshold (S, I and G) to be changed during a time interval lasting “ts”, starting from
“start-up”. The latter must be intended as follows:
- Passage of at least one of the phase currents above the activation threshold of the adjustable Start-Up (0.1…10In, by 0.1In
steps); A new start-up is possible after the current has dropped below this threshold.
3.6.4. Protection
"I"
The protection is enabled/disabled from the menu.
I
t
Start-Up Threshold I2
ts
Threshold I2
Activation of Start-Up
Threshold Start-Up activation
