ABB REG670 Applications Manual page 437

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
Under unfavorable conditions the blind zone may extend to 20% from the neutral.
Some different earth fault protection solutions are shown in figure
figure 214.
IEC06000317 V2 EN
Figure 213: Broken delta voltage transformer measurement of 3U
Alternatively zero sequence current can be measured as shown in fig
- U +
0
IEC06000318 V2 EN
Figure 214: Neutral point voltage transformer measurement of neutral point
voltage (that is U
In some applications the neutral point resistor is connected to the low voltage side of
a single-phase distribution transformer, connected to the generator neutral point. In
such a case the voltage measurement can be made directly across the secondary
resistor.
+
3U
0
voltage)
0
Section 10
Voltage protection
213 and
Generator unit transformer
IEC06000317-2-en.vsd
voltage
0
215
Generator unit transformer
IEC06000318-2-en.vsd
431