ABB Zenith ZTG 30 Operation, Maintenance And Installation Manual page 26

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Z e n i t h Z T G S e r i e s AT S , O P E R AT I O N , M A I N T E N 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:
• An anomaly occurs on SOURCE 2
• Override momentary S2 outage delay
• Transfer from S2 to S1 delay
• Pre-transfer signal on
• Load shed signal on
• Pre-transfer S2 to S1 delay
• Load shed 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
• Post-transfer S2 to S1 delay
• Pre-transfer signal off
And the re-transfer sequence can be
summarized in the following steps:
• SOURCE 2 is restored
• Transfer from S1 to S2 delay
• Pre-transfer signal on
• Pre-transfer S1 to S2 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 I
• Load shed signal off
• Post-transfer S1 to S2 delay
• Pre-transfer signal off