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TD_MRN3-3_08.06_GB
4.8 Voltage threshold value for
frequency- df/dt measuring
At low measuring voltages, e.g. during generator start-
up, frequency or df/dt-measuring is perhaps not de-
sired.
By means of the adjustable voltage threshold value
U
B
<, functions f
1
- f
3
or df/dt are blocked if the meas-
ured voltage falls below the set value.
4.9 Blocking
function
No. Dynamic
Behaviour
U</<< U>/>> f
1
, f
2
, f
3
∆Θ
df/dt
1
voltage to external
blocking input is
applied
can be set acc.
to requirement
can be set
acc. to re-
quirement
can be set
acc. to re-
quirement
can be set
acc. to re-
quirement
can be set
acc. to re-
quirement
2
blocking input is
released
Instantaneously
released
released
instantane-
ously
released after
1 s
Released after
5 s
released after
5 s
3
supply voltage is
switched on
blocked for
200 ms
blocked for
200 ms
blocked for 1 s blocked for 5s blocked for 1
s
4 3ph
measuring
volt.
is suddenly applied
released
released
blocked for 1 s blocked for 5s blocked for 5
s
5 one
or
several
measuring voltages
are suddenly
switched off (phase
failure)
released released blocked blocked blocked
6 measuring
voltage
smaller U
B
< (adjust-
able voltage thresh-
old value)
released released blocked
blocked
Table 4.1: Dynamic behaviour of
MRN3-3
functions
Blocking function set according to requirements:
The
MRN3-3
has an external blocking input. By ap-
plying the auxiliary voltage to input D8/E8, the re-
quested protection functions of the relay are blocked
(refer to 5.7.1).
