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Operation 79
3.2.2 OK To Transfer
The OK to Transfer status message will be displayed when the bypass line and UPS system output power are
both available, their voltage, frequency, and phase synchronization are matched within specifications, and the
Static Switch Disconnects are closed (ON). An alarm message may be displayed to indicate Load On Bypass. If
no alarm is displayed, the operating status is Load On UPS.
When the OK to Transfer message is displayed, you can perform a manual transfer of the load from the UPS sys-
tem to bypass, or a manual retransfer of the load from bypass to the UPS system.
Use the Load Transfer Procedures screen at the SCC when performing a manual transfer. Refer to 3.3.2 - Load
Transfer Procedures.
The UPS system control logic at the SCC will initiate an automatic transfer to bypass if an overload condition
exceeds the system current versus time window, or if a UPS module is taken off line while the system is operat-
ing in the non-redundant mode. An automatic retransfer to the UPS system may be initiated when recovering
from system overloads lasting less than five minutes. Refer to 3.4 - Automatic Operations.
Figure 48 Load on Bypass (UPS Available)
NOTE
When the critical load is being supplied power from the bypass line, it is exposed to
utility power disturbances.
BIB
SKRU
MIB
MBB
I
R
#2UPS
CB1
CB2
I
R
#1UPS
CB1
System
Controls
I
R
#3UPS
CB1
CB2
RIB RIB
CB2
RIB BFB
Output
SBB
SBS
SCCT
SCCT
(can accommodate up to 6 UPS modules)
To CriticalLoad
Battery
MBD
Battery
MBD
Battery
MBD