20
TB MRIK3 12.00 E
Important note:
When functioning as parameter change over facility,
the external input RESET is not available for resetting.
When using the external input BLOCKING the protec-
tion functions must be deactivated by software blocking
separately (refer to chapter 5.7.1).
5.4
Parameter protection
5.4.1
Pickup current for phase
overcurrent element (I>)
The setting value for this parameter that appears on the
display is related to the nominal current (I
N
) of the relay.
This means: pickup current (Is) = displayed value x
nominal current (I
N
) e.g. displayed value = 1.25 then, Is
= 1.25 x I
N
.
5.4.2
Time current characteristics for
phase overcurrent element
(I> + CHAR)
By setting this parameter, one of the following 6 mes-
sages appears on the display:
DEFT -
Definite Time (Type A)
NINV -
Normal Inverse (Type B)
VINV -
Very Inverse (Type C)
EINV -
Extremely Inverse
LINV
-
Long Time Inverse
RINV
-
RI - Inverse
Anyone of these four characteristics can be chosen by
using <+> <->-push buttons, and can be stored by us-
ing <ENTER>-push button.
5.4.3
Trip delay or time multiplier for
phase overcurrent element (t
I>
)
Usually, after the tripping characteristic is changed, the
time delay or the time multiplier should be changed ac-
cordingly. In order to avoid an unsuitable arrangement
of relay modes due to carelessness of the operator, the
following precautions are taken:
After the change of 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 press-
ing the <SELECT>-push button, the present time delay
setting value is shown on the display. The new setting
value can then be changed by using <+> <-> -push but-
tons.
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 characteristics after five minutes warning
of flashing LED tI>. The most sensitive time setting value
means the fastest tripping for the selected relay charac-
teristic. 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 overcurrent relay is blocked. The
"WARN"-relay will not be blocked.
5.4.4
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 ad-
justment RST is set at 60 s, the tripping time is only re-
set after 60 s faultless condition. This function is not
available if RST is set to 0. With interruption of the fault
current the trip delay is reset immediately and started
again at recurring fault current.
5.4.5
Current setting for high set element
(I>>)
The current setting value of this parameter appearing on
the display is related to the nominal current of the relay.
This means: I>> = displayed value x I
N
.
When the current setting for high set element is set out
of range (on display appears "EXIT"), the high set ele-
ment of the overcurrent relay is blocked.
The high set element can be blocked via terminals
E8/D8 if the corresponding blocking parameter is set to
BLOC (refer to 5.7.1).
