Direct Earthed System - ABB REQ650 Applications Manual

1MRK 505 291-UEN A
7.3.3.3
Application manual
IEC07000190 V1 EN
Figure 74: Earth fault in Non-effectively earthed systems

Direct earthed system

In direct earthed systems, an earth fault on one phase indicates a voltage collapse in
that phase. The two healthy phases will have normal phase-to-earth voltages. The
residual sum will have the same value as the remaining phase-to-earth voltage. See
Figure 75.
Section 7
Voltage protection
163