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Zenith ZTG Series ATS, OPERATION, MAINTENANCE, AND INSTALLATION GUIDE
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2.5 Sequence of Operations
2.5.1 Switching sequence / Automatic
2.5.1.1 SOURCE 1 Priority
(SOURCE 2 = Generator)
The switching sequence can be
summarized in the following steps:
• An anomaly occurs on SOURCE 1
• Override momentary S1 outage delay
• Generator start
• SOURCE 2 OK
• Transfer from S1 to S2 delay
• Pre-transfer signal on
• Load shed signal on
• Pre-transfer S1 to S2 delay
• Load shed delay
• Transfer switch (SOURCE 1) to
position O
• Center-off delay (only with Delayed
transition I - O - II type)
• Transfer switch (SOURCE 2) to
position II
• Post-transfer S1 to S2 delay
• Pre-transfer signal off
The re-transfer sequence can be
summarized in the following steps:
• SOURCE 1 is restored
• Transfer from S2 to S1 delay
• Pre-transfer signal on
• Pre-transfer S2 to S1 delay
• Transfer switch (SOURCE 2) to
position O
• Center-off delay (only with Delayed
transition I - O - II type)
• Transfer switch (SOURCE 1) to
position I
• Load shed signal off
• Generator stop delay
• Post-transfer S2 to S1 delay
• Pre-transfer signal off
• Generator stop
• SOURCE 2 off
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