ABB REG670 - Page 310

U
1
/ U
2
Y
C
stat
R
N
+
U
inj
-
I
inj
R
d
a
b
IEC11000011-2-en.vsdx
Y
Y
2
1
2
3
Nd
U
RR
U
∑⌡

√

√<
IEC11000011 V2 EN
Figure 162: Injection via open delta VT connection
It must be observed that the resistor R
d
is normally applied for ferro-resonance
damping. The resistance R
d
is will have very little contribution to the earth fault
current as it has high resistance. This injection principle can be used for applications
with various generator system earthing methods. It is therefore recommended to make
the injection via the open delta VT on the terminal side in most applications.
Accuracy for STTIPHIZ is installation dependent and it mainly depends on the
characteristic of grounding or voltage transformer used to inject signal into the stator.
Note that large variation of the ambient temperature and variation of stator
Section 8 1MRK 502 071-UEN -
Impedance protection
304 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual