Rockwell Automation 140G-NTK-E12 LSIG and LSIG-MM Release User Manual
Page 14
DIR 1000587R0002 (L3821)
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3.1.6.3
Circuit-breaker state
The LSIG-MM units record the state of the circuit breaker by means of specific wiring on the circuit breaker. When presence of current is determined
with the circuit-breaker in the “OPEN” position, a state error is signaled by a warning message being displayed
(see par. 3.5) and “warning” LED lighting up.
3.1.7 Measurement functions
The current measuring (ammeter) function is available.
The display shows histograms with three phase and neutral currents on the main page. In addition, the current of the phase under the greatest
load is given in numerical form. Where applicable, the earth fault current is displayed on a separate page.
The ammeter functions both in self-powering mode and with auxiliary voltage. In the latter case, ammeter and backlighting are always on. Tolerance
for the ammeter measuring chain (current sensor plus ammeter) is described in paragraph 3.1.9.10.
The LSIG-MM releases provide a complete set of measurements:
- Currents: three phases (L1, L2, L3), neutral (Ne), earth fault
- Maintenance: number of operations, percentage of contact wear, opening data storage
3.1.8 Watchdog
The LSIG-MM units provide some watchdog functions which can guarantee proper management of relay malfunctions. These functions are as follows:
Watchdog for presence of Auxiliary power supply with “plug” icon displayed”.
Rating Plug validity.
Watchdog for proper connection of Trip Coil (TC). Any faults are indicated by a special alarm message and “alarm” LED coming on; if the
communication module is installed, this activates the opening coil command (Y0) which opens the CB when trip is enabled.
3.1.9 Description of protection functions
3.1.9.1
Protection “L”
“L” is the only protection that cannot be disabled because it is for self-protection against overloading of the relay. The types of trip curves that can
be set are divided into two groups according to the standard they refer to.
Standard trip curve according to IEC 60947-2
Only one type of curve can be set (t=k/I
2
) as defined by IEC 60947-2 standard.
Protection trip time - inverse time - is given by the expression:
where l
f
≤ 12ln and 1s where l
f
> 12ln where I
f
is the fault current and I
1
the protection threshold.
NB: Time expressed in seconds.
Standard trip curve according to IEC 60255-3
There are 3 types of curves that can be set, defined by IEC 60255-3 standard as A, B and C.
Protection trip time - inverse time - is given by the expression:
NB: Time expressed in seconds.
a and k are two parameters, suggested by the standard, which vary according to type of slope selected (e.g. for type B slope a = 1 and k=13.5);
b is a parameter introduced by AB to increase the number of curves with the same slope. This parameter is automatically calculated by setting
parameter t1 (required trip time 3xI1).
3.1.9.1.1 Thermal memory “L”
The thermal memory function can be enabled for cable protection. It is based on the “τL” parameter defined as the trip time of the curve (t1)
selected at 1.25xI1.
Release trip time certainly is 100% of the one selected, after a time interval τL has passed since last overload or since last trip. Otherwise, trip time
will be reduced, depending on overload occurred and time elapsed.
LSIG-MM is fitted with two instruments to make up this thermal memory. The first instrument operates when the release is powered (it also records
overloads that have not lasted long enough to trip the release), while the second works even when the release is not powered, reducing any trip
times in case of an immediate re-closing, and is enabled as soon as the CB is tripped.
It is the LSIG-MM release that automatically decides which of the two to use, according to the various situations.
NB: The thermal memory function can only be set if the type of curve selected is the standard one (t=k/I
2
) (see par. 3.1.9.1).
3.1.9.2
Protection “S”
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
3.1.9.2.1 Thermal memory “S”
The thermal memory function can be enabled for cable protection in the event that the curve with inverse time is selected. This is based on the
“tS” parameter defined as trip time of the curve (t2) selected at 1.5xI2. The other characteristics are the same as those for thermal memory “L”
(see par. 3.1.9.1.1).
where
( )
b
I
k
t
•
−
=
1
α
I
f
is the fault current and I
1
the protection threshold set by user.
1
I
I
I
f
=
where I
f
is the fault current and I
2
the protection threshold.
where
max
100 t
2
(I
)
f
2
, t
2
/ I
n