Woodward
Manual MRI3-ITER GB
30
DOK-TD-MRI3 ITERE Rev.A
5.4.6 Time current characteristics for phase overcurrent element (CHAR I>)
By setting this parameter, one of the following 6 messages appears on the display:
DEFT
-
Definite
time
NINV
-
Normal
inverse
VINV
-
Very
inverse
EINV
-
Extremely
inverse
RINV
-
RI-Inverse
LONG
-
Long Time Inverse
Anyone of these four characteristics can be chosen by using <+> <->-pushbuttons, and can be
stored by using <ENTER>-pushbutton.
5.4.7 Trip delay or time multiplier for phase over current element (tI>)
Usually, after the characteristic is changed, the time delay or the time multiplier should be changed
accordingly. In order to avoid an unsuitable arrangement of relay modes due to carelessness of the
operator, the following precautions are taken:
After the characteristic setting, the setting process turns to the time delay setting automatically. The
LED tI> is going to flash yellow to remind the operator to change the time delay setting accordingly.
After pressing the <SELECT>-pushbutton, the present time delay setting value is shown on the
display. The new setting value can then be changed by using <+> <-> -pushbuttons.
If, through a new setting, another relay characteristic other than the old one has been chosen (e.g.
from DEFT to NINV), but the time delay setting has not been changed despite the warning from the
flashing LED, the relay will be set to the most sensitive time setting value of the selected characte-
ristics after five minutes warning of flashing LED tI>. The most sensitive time setting value means
the fastest tripping for the selected relay characteristic. When the time delay or the time multiplier is
set out of range (Text "EXIT" appears on the display), the low set element of the over current relay
is blocked. The "WARN"-relay will not be blocked.
5.4.8 Reset setting for inverse time tripping characteristics in the phase
current path
To ensure tripping, even with recurring fault pulses shorter than the set trip delay, the reset mode
for all tripping characteristics can be switched over. If the adjustment tRST is set at 60 s, the trip-
ping time is only reset after 60 s faultless condition. This function is not available if tRST is set to 0.
With fault current cease the trip delay is reset immediately and started again at recurring fault cur-
rent.
5.4.9 Current setting for high set element (I>>)
The current setting value of this parameter appearing on the display is related to the nominal cur-
rent of the relay. This means: I>> = displayed value x I
N
.When the current setting for high set ele-
ment is set out of range (on display appears "EXIT"), the over current high set element is blocked.
5.4.10 Trip delay for high set element (tI>>)
Independent from the chosen tripping characteristic for I>, the high set element I>> has always a
definite-time tripping characteristic. An indication value in seconds appears on the display.
