Liebert Series 610 2.2 Separating Tied Systems, 2.3 Load Transfers Between UPS Systems

Operation Description

2.2 Separating Tied Systems

The following sequence of operations describes the actions taken to separate two tied UPS systems.

From the CONTINUOUS TIE CONTROL section, press the SYNCHRONIZE SYSTEMS button. The

button’s light turns off to provide a visual indication of the operator’s intention to separate the sys-

tems. The SYNCHRONIZE SYSTEMS button toggles between indicating the intention to parallel or

separate the two UPS systems.

The Power-Tie logic checks the UPS systems and their loads to verify both systems have sufficient

capacity to maintain their loads once the systems are separated. If both UPS systems have sufficient

capacity, the OK TO OPEN TIE light turns on in the TIE CONTROLS section of the control panel.

After the OK TO OPEN TIE light turns on, press the PUSH TO OPEN TIE AFTER OK button. The

tie breaker trips to separate the two UPS systems. Both systems automatically resynchronize to their

own bypass source; and all control loops between the systems separate.

2.3 Load Transfers Between UPS Systems

Functionally, load transfers are a continuous tie operation followed by an immediate selective separa-

tion of the systems. The following sequence of operations describes the actions taken to transfer a load

between UPS systems.

Select the system you want to receive the load, system 1 or system 2. Press the TRANSFER LOAD TO

button (for system 1 or system 2) on the LOAD TRANSFER CONTROL section of the control panel.

The system 1 or system 2 light turns on to indicate your selection.

You can cancel your selection by pressing the system button again. The button toggles between select

and deselect.

The two UPS systems synchronize to the proper bypass source to perform the selected transfer. With

the line sync controls tied, the Continuous Power-Tie logic checks the inter-module sync signals for

coincidence. The Power-Tie logic ties the inter-module sync signals when coincidence occurs.

The SYNCHRONIZING light in the CONTROL STATUS section of the MIMIC panel turns on to let

the operator know synchronization is still in progress.

The Power-Tie logic checks these UPS system parameters, phase, voltage, and capacity, to determine

when they have reached their proper limits. The OK TO TRANSFER LOAD (#) TO SYSTEM (#) indi-

cator turns on in the LOAD TRANSFER CONTROL section of the control panel on when these

parameters reach their proper limits.

After the OK TO TRANSFER LOAD (#) TO SYSTEM (#) light turns on, press the PUSH TO TRANS-

FER AFTER OK button.

The Power-Tie logic operates the proper circuit breakers in a make-before-break manner to transfer

the load.

Once the transfer starts, the TRANSFERRING light in the CONTROL STATUS section of the MIMIC

panel turns on indicating a transfer in progress. With the two UPS systems in parallel, the voltage

synchronization and power sharing loops become tied.

When transfer is complete, both systems automatically resynchronize to their own bypass source; and

all control loops between the systems separate.