TB MRM3 07.01 E
17
5.4.12
Trip Characteristics for the Earth-
Fault Element (I
E
>+CHAR)
When adjusting the trip characteristics one of the fol-
lowing 7 abbreviations is displayed:
DEFT
-
Definite Time (definite time over-
current protection)
NINV -
Normal inverse (Type A)
VINV
-
Very inverse (Type B)
EINV
-
Extremely inverse (Type C)
RINV
-
RI-Inverse
LINV
-
Long-term inverse
RXID
-
Special purpose characteristics
The displayed text can be changed by push-buttons
<+><-> . By pressing <ENTER> the required trip
characteristics is selected. The allocated LED I
E
> is red,
the LED CHAR green.
5.4.13
Tripping Time or Time Factor for
the Earth Fault Element (IE>+t>)
The setting procedure outlined in chapter 5.4.7 ap-
plies here as well.
5.4.14
Reset Time for the Earth Fault
Element (I
E
>+CHAR+t>)
The setting procedure outlined in chapter 5.4.8 ap-
plies here as well.
5.4.15
Tripping Time for the CB Failure-
Protection (CB+t>)
This protection is activated after a protective trip and it
monitors if all phase currents have dropped within the
set time t
CBFP
to <2% x I
N
. If not, CB failure is detected
and the allocated relay triggered. (CBFP= Circuit
Breaker Failure Protection
)
.
5.4.16
External Trip (delayed)
(Trip+t>)
Via the digital input A8/D8 an external trip with time
delay can be activated. Trip is initiated if the <signal
existed for at least the set time. The external trip func-
tion can be allocated to a relay.
5.4.17
Trip Blocking in case of Excessive
Phase Current (Trip+Block)
This function is important where power contactors are
used and they are not designed to disconnect high
short-circuit currents. In such a case no function of the
MRM3
must initiate tripping. The trip function is then
allocated to a preceding protective element (e.g.
fuse).
Trip blocking is activated as soon as the set current is
exceeded. When this threshold is undershot, all func-
tion are released again.
If the circuit breakers used are able to disconnect the
short-circuit current to be expected, the function is set
to EXIT.
5.5
Start Supervision
The
MRM3
can offer two start supervision methods:
•
Automatically by means of the thermal load
•
By a limited number of starts per time interval
5.5.1 Duration of a Start Cycle (No.+Start)
AUTO
If this mode is selected, a start is always possible if suf-
ficient start reserves are available according to the
thermal image. This function operates dynamically on
the data of the previous starts (see chapter 4.1.1).
Time Adjustment
By this the interval of the permissible number of starts is
timed.
The number is defined in the next parameter.
EXIT
The element is de-energised.
5.5.2 Number of Starts per Cycle
(No.+Start)
This parameter is only visible if a time was selected
with the preceding parameter which defines the num-
ber of permissible starts during the respective interval.
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