Rockwell Automation 140G-NTK-E12 LSIG and LSIG-MM Release - Manual (Page 15)

DIR 1000587R0002 (L3821)
(15)
3.1.9.2.2 Start-up threshold “S”
The start-up function can be selected in the case where the curve with fixed time is selected.
This function can be disabled; it is a setting characteristic of the single protection units.
The start-up function enables the protection threshold (S and G) to be changed during a “ts” time interval, starting from “start-up”. The latter must
be intended as follows:
- RMS value of maximum current passing over one single adjustable threshold (0.1...10In, by 0.1In steps). A new start is possible after the current
has dropped below this threshold.
I
t h
Start Up
Start Up
Programmed time t s
Threshold I 2
• Start-up time
Start-up time is different for all protections concerned.
Range: 0.1 s ... 30 s, with steps of 0.01 s.
3.1.9.3 Protection “I”
The protection is enabled/disabled from the menu.
In the event zone selectivity “S” is active, during tripping of the relay for “I”, the ZSO output signal is activated to guarantee correct operation of
the relay on supply side (and on load side).
3.1.9.4 Protection for maintenance mode “MM”
The protection is enabled/disabled from the menu.
The protection is activated when is enabled and when binary input is high (24 Vdc see par. 3.1.4.1).
3.1.9.5 Protection “G”
This protection can be disabled; it can be of the fixed time (t=k) or inverse time (t=k/i 2 ) type. In the latter case, trip time is given by the expression
ч
ч
ш
ц
з
з
и
ж
,
2
I
2
max t
4
where I=I
f
/I
4
, I
f
is the fault current and I
4
the protection threshold.
NB: Time expressed in seconds.
It is possible to disable trip control of protection (“Enable Trip: Off”).
For the whole duration of the earth fault, circuit-breaker opening does not take place, but only the alarm condition is signaled
(“Alarm” LED lit and alarm message).
The unit can provide two different types of earth fault protection, simultaneously:
Internal protection G
This is provided inside the relay by vectorially summing phase and neutral currents. Fault current is defined by the following formula:
If the circuit shows no faults, the module of the sum of these currents is always nil; vice versa, the value of the fault current takes on a larger and
larger value depending on size of fault. This operating mode is enabled by default.
N.B.: it can be used also with CS for an external neutral.