ABB Relion 670 Series Applications Manual page 233

1MRK 505 370-UUS Rev. K
ANSI07000190 V1 EN-US
Figure 117: Ground fault in Non-effectively grounded systems
8.3.4.5 Direct grounded system
In direct grounded systems, an ground fault on one phase is indicated by voltage collapse in that phase.
The other healthy phase will still have normal phase-to-ground voltage. The residual sum will have the
same value as the remaining phase-to-ground voltage, which is shown in Figure 118.
ANSI07000189 V1 EN-US
Figure 118: Ground fault in Direct grounded system
8.3.4.6 Settings for two step residual overvoltage protection
Operation: Disabled or Enabled
Busbar protection REB670
Application manual
ANSI07000190-1-en.vsd
ANSI07000189-1-en.vsd
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Section 8
Voltage protection
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