Manual MRG3
SEG Electronics GmbH
DOK-TD-MRG3, Rev. D
41
The generator has a rated voltage of 180 A. Voltage transformers with a rating of 200 A/5A shall be
applied.
Resulting from this, the parameter settings are as follows:
rated primary CT current:
0.20 kA
rated generator current:
0.18 kA
A parameter for the rated secondary CT current is not required since this parameter is equal to the
rated current of the protective device.
If the over current step is now adjusted to 120%, there will be excitation at a generator voltage of
1.2 x 180 A = 216 A and the display shows “k216”.
5.3.5 Voltage transformer connection for residual voltage measuring
(3pha/e-n/1:1)
Depending on the connection of the voltage transformer three possibilities of the residual voltage
measurement can be chosen (see chapter 4.7.4).
5.3.6 Nominal frequency
The adapted FFT-algorithm requires the nominal frequency of the object to be protected as a pa-
rameter for correct digital sampling and filtering of the input currents.
By pressing <SELECT> the display shows "f=50" or "f=60". The desired nominal frequency can be
adjusted by <+> or <-> and then stored with <ENTER>.
5.3.7 Selection between vector surge function or df/dt supervision
The MRG3 provides two methods for the supervision of short-term mains interruptions: the vector
surge supervision (see chapter 4.5.2) and the df/dt supervision (refer to chapter 4.5.1)
The above indicated functions (vector surge = dPhi and df/dt supervision) can be selected by
means of the arrow keys <+> and <-> .
5.3.8 Display of the activation storage
If after an activation of the relay, the existing current drops again below the pickup value, e.g. I>,
without a trip has been initiated, LED I> signals that an activation has occurred by flashing fast.
The LED keeps flashing until it is reset again (push button <RESET>). Flashing can be suppressed
when the parameter is set to NOFL.