SEG Electronics GmbH
Manual MRG3
48
DOK-TD-MRG3, Rev. D
5.6 Parameter protection earth fault supervision
5.6.1 Pick-up value for residual voltage
Regardless of the preset earth current, an earth fault is only identified if the residual voltage ex-
ceeds the set reference value. This value is indicated in % of the generator rated voltage.
For the relay version MRG3-IER, this protection has only a warning function; for the relay version
MRG3-IU0 und MRG3-U0 it takes place in two steps and is accompanied by the following LEDs
when being adjusted.
U
0
>
U
0
+ 1 + >
U
0
>>
U
0
+ 2 + >
5.6.2 Trip delay for residual voltage (only MRG3-IU0 and MRG3-U0)
When setting the appropriate tripping delays, the LEDs will be flashing up as follows:
t
U0
>
U
0
+ 1 + > + t>
t
U0
>>
U
0
+ 2 + > + t>
5.6.3 Pick-up value for earth fault element
For the relay version MRG3-IE, the setting
values of this parameter relate to the earth current’s ap-
parent portion. The indicated value is shown as percentage of the generator’s nominal earth fault
current. For the relay version MRG3-IER, the indicated value relates to the effective portion of the
earth current for compensated grids (cos.-procedure) or to the reactive portion for isolated grids
and it is also displayed as percentage of the nominal earth current (see chapter 4.7.3)
The setting is accompanied by the LEDs I
E
+ 1 + >.
5.6.4 WARN/TRIP changing-over
(applies to MRG3-IE; MRG3-IU0 and MRG3-U0)
A detected earth fault can be parameterized as follows. After expiry of the delay time.
a) the alarm relay responds "warn"
b) the tripping relay responds "trip" and the tripping values are stored.
Upon this setting, the LEDs I
E
+ 1 or U0 + 1 will be flashing.
5.6.5 Time current characteristics for earth fault element (only MRG3-IE)
By setting this parameter, one of the following 7 messages appears on the display:
DEFT -
Definite Time
NINV -
Normal inverse (type A)
VINV
-
Very inverse (type B)
EINV
-
Extremely inverse (type C)
RINV
RI-Inverse
LINV
Long time inverse
RXID
Special characteristic
Any of these characteristics can be chosen by using <+> <->-pushbuttons, and can be stored by
using <ENTER>-pushbutton. The setting is accompanied by the LEDs IE + 1 + >.
