ABB Zenith ZTS T Series, Operation, Maintenance, And Installation Manual

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O PER AT I O N , M A I N T EN A N C E , A N D I N S TA L L AT I O N G U I D E
2.5.1.2 SOURCE 2 Priority (No generator)
The switching sequence can be
summarized in the following steps:
1. An anomaly occurs on SOURCE 2
2. Override momentary S2 outage delay
3. Transfer from S2 to S1 delay
4. Pre-transfer signal on
5. Load shed signal on
6. Pre-transfer S2 to S1 delay
7. Load shed delay
8. Transfer switch (SOURCE 2) to
position O
9. Center-off delay (only with Delayed
transition I - O - II type)
10. Transfer switch (SOURCE 1) to
position I
11. Post-transfer S2 to S1 delay
12. Pre-transfer signal off
And the re-transfer sequence can be
summarized in the following steps:
1. SOURCE 2 is restored
2. Transfer from S1 to S2 delay
3. Pre-transfer signal on
4. Pre-transfer S1 to S2 delay
5. Transfer switch (SOURCE 1) to
position O
6. Center-off delay (only with Delayed
transition I - O - II type)
7. Transfer switch (SOURCE 2) to
position I
8. Load shed signal off
9. Post-transfer S1 to S2 delay
10. Pre-transfer signal off