ABB RELION 620 Series Technical Manual page 294

Section 4
Protection functions
288
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Figure 142: Logic diagram for phase selection module
When the Number of start phase setting is set to "1 out of 3" and the fault is in one or
several phases, the phase selection logic sends an enabling signal to the faulty phase
timers. If the fault disappears, the related timer-enabling signal is removed.
When the Number of start phase setting is "2 out of 3" or "3 out of 3", single-phase
faults are not detected. The value "3 out of 3" requires the fault to be present in all three
phases.
Timer A, Timer B, Timer C
The function design contains three independent phase-segregated timers which are
controlled by common settings. This design allows a true three-phase overcurrent
protection which is useful in some applications.
The common START and OPERATE outputs are created by "ORing" the phase-
specific starting and operating outputs.
1MRS757644 F
620 series
Technical Manual