ABB REG670 - Stator Earth Fault Protection Function

For all the alternatives the 100% stator earth fault protection can be applied.
7.9.9.3 100% Stator earth fault protection function
The injection to the stator is schematically shown in figure
136. It should be observed
that in this figure injection equivalent circuit is also shown with all impedances and
injection generator related to the primary side of the neutral point voltage transformer.
Points a & b indicate connection terminals for the injection equipment. Similar
equivalent circuit can be drawn for all other types of generator stator earthing shown
in latter figures.
Z
Bare
Z
Measured
+
U
inj
-
I
inj
R
N
C
stat
R
fault
+
U
inj
-
I
inj
R
N
C
stat
Stator Reference
Impedance Z
Ref
R
f
Z
series
Z
mT
a
b
a
b
U
N
IEC11000008-4-en.vsd
Û
IEC11000008 V1 EN
Figure 136: High-resistance generator earthing with a neutral point resistor
There are some alternatives for connection of the neutral point resistor as shown in
figure 137 (low voltage neutral point resistor connected via a DT).
Section 7 1MRK502052-UEN B
Impedance protection
306
Technical manual