ABB OTM C 21D - Page 7

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AUTOMATIC TRANSFER SWITCH, OTM_C_21D
The transfer sequence of OTM_C21D can be sum-
marized in following steps:
• An anomaly occurs on the Line 1 (LN1)
• Generator start, immediately start generator
in case of black-out, phase-loss, overvoltage or
undervoltage (If Generator mode is selected)
• The Line 2 start the normal functioning,
transfer delay Ts
• Change-over switch (Switch I) to the position 0
• Change-over switch (Switch II) to the
position II
Figure 4. Automatic Switching Sequences in OTM_C_21D, Manual return mode
And the return sequence can be summarized in
the following steps:
• The Line 1 will start the normal functioning
• Change-over switch stays in position II
• An anomaly occurs on the Line 2 (LN2)
• Change-over switch stays in position II
• Change-over switch can be transferred
manually back to position I
2.2.3 Manual return mode