SEG Electronics GmbH
Manual MRG3
40
DOK-TD-MRG3, Rev. D
5.2 Setting procedure
In this paragraph the settings for all relay parameters are described in detail. For parameter setting
a password has to be entered first (please refer to 4.4 of description "MR-Digital Multifunctional Re-
lays").
5.3 Systemparameters
5.3.1
/Y
– Change-over switch
Depending on the mains voltage conditions, the input voltage transformers can be operated in delta
or Y connection. Changeovers are effected via the <+> and the <-> keys and stored with
<ENTER>. (See chapter 4.3.1)
5.3.2 Display of measurement values as primary quantity
By means of this parameter it is possible to indicate measured values as primary values. For this
purpose the parameter must be set to be equal with the rated primary CT current. If the parameter
is set to "SEK", the measured value will be displayed as rated secondary CT voltage or as a multi-
ple of the rated secondary CT current.
5.3.3 Setting of measured secondary values for the voltage transformers
By means of this parameter, the nominal secondary value of the voltage transformer has to be ad-
justed. If no voltage transformer is available, t
he parameter for “Indication of measured values as
primary values on the display” has to be set to SEK (see chapter 5.3.2).
With the aid of this parameter, the MRG3 is capable of recognizing whether the calculation has to
be based on 0
– 150 V or on the voltage range from 0 – 600V.
Upon adjustment of a rated secondary voltage of >= 138 V, all switching points of the measuring
range 0
– 600 V will be calculated. If this parameter is set to <= 138 V, all switching points ranging
from 0
– 150 V are calculated.
Please note: It has to be made sure that
– for switching over to the different voltage ranges - the
coding plugs are always properly plugged in (see chapter 3.1.8).
5.3.4
Setting of the generator’s nominal values
Before the following parameters for the protective functions of current and voltage can be shown in
percent, the nominal generator values for current and voltage have to be adjusted.
Example:
The generator has a nominal value of 8.2 kV. Voltage transformers with a rating of 10 kV/110 V are
applied.
The resulting parameter settings are as follows:
rated primary CT voltage:
10 kV
rated secondary CT voltage:
110 V
rated generator voltage:
8.2 kV
If the generator is now operated at rated voltage, the measured voltage rating of “8k20” is dis-
played. If an under voltage step is then adjusted to 80%, there will be excitation at a generator volt-
age of 0.8 x 8.2kV = 6.56 kV.