Operation Manual 37107F
MFR 3 - Multi Function Relay
Page 100/165
© Woodward
Parameter
138
Gen.overcurr. 2
resp.value 000%
Time-overcurrent: limit 2
0 to 300 %
The value configured in this screen is a percentage of the configured generator
rated current. If this level is reached or exceeded for the configured delay time, the
unit issues an alarm and opens the GCB.
Tripping of class F3 alarm
Parameter
139
Gen.overcurr. 2
Delay 00.00s
Time-overcurrent: delay 2
0.02 to 99.98 s
The generator time-overcurrent monitoring threshold limit 2 must be exceeded,
without interruption, for the time period configured here before the configured re-
lay will be energized.
Inverse Time-Overcurrent Monitoring
NOTE
All percentage indications of the current are in relation to the generator rated current (Parameter 29).
Function:
Monitoring of overcurrents including inversely proportional time dependent tripping characteristic.
The selected trip curve defines the tripping time according to the measured current. The tripping time will be de-
creased according to a defined curve the higher the measured current is. According to IEC 255 three different
characteristics are available.
normal inverse:
]
[
*
1
)
/
(
14
.
0
02
.
0
s
t
I
I
t
p
P
−
=
high inverse:
]
[
*
1
)
/
(
5
.
13
s
t
I
I
t
p
P
−
=
extreme inverse:
]
[
*
1
)
/
(
80
2
s
t
I
I
t
p
P
−
=
Variables:
t
tripping
time
t
p
time set point value
I
fault current / monitored current
I
n
rated (nominal) current (Parameter 29)
I
p
current set point value
If t is greater than 650 s the system trips at 650 s. If t is lower than t
min
the tripping time is t
min
. The reaction time
for t
min
depends on the time it takes to monitor the fault and the operating time of the relays. t
min
is at least 20 ms.
Please consider during configuration:
for I
start
: I
start
> I
n
and I
start
> I
p
for I
p
the smaller I
p
is, the steeper is the slope of the tripping curve
