Liebert Series 610 user manual Continuous Tie, Intersystem Sync and Power Sharing

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System Description

The Tie Control Unit also contains interlock and monitoring circuitry necessary to assure successful transfers of load between UPS systems. These consist of the following:

1.Sync Verification circuitry, similar to the circuitry employed in each UPS, provides the sync check function in two independent modes:

a.Phase Difference detection for ±3 degrees.

Phase Difference inhibits a transfer if limits are exceeded.

b.Voltage Difference detection for ±3%.

Voltage Differential inhibits transfers if limits are exceeded (if phase error is greater than ±3 degrees, the Voltage Difference will also exceed ±5%), making the differential voltage detec- tion a redundant phase detector.

2.Load Verification circuitry prohibits transfer if the resulting total system load will exceed the capacity of one UPS System (the system which will assume all the critical load once the transfer is complete).

1.5.3Continuous Tie

See Figure 3.

The Liebert Continuous Tie system is a topology that extends the concept of a manually initiated momentary tie of UPS critical load buses by providing the capability to continuously parallel the out- put buses of two otherwise independent UPS Systems.

All the performance features of a momentary tie system are available in the continuous tie system. In the unlikely event that one UPS system or both UPS systems have only partial available capacity (e.g., loss of one or more modules in an otherwise functional system), this partial capacity system can be continuously tied to a second full (or partial) capacity system, powering simultaneously the now- tied two critical buses.

This results in a single, fully redundant UPS system powering two different distribution strings through a single UPS critical output bus. When the off-line (whether for maintenance or repair) mod- ules are brought on-line again, the two UPS critical buses are again separated, all in a make-before- break manner, and without the need to transfer to bypass sources. For continuous-tied systems, mod- ule kVA/kW ratings must be identical.

There are two main control functions associated with the Continuous Tie:

•Intersystem synchronizing and load sharing;

•Intersystem transfer/parallel control and switch gear.

Intersystem Sync and Power Sharing

Synchronization between the UPS systems is accomplished in a two step process:

First, a line sync source is chosen. This will be the bypass power source of the UPS system that is the manually selected preferred bypass source. Generally, if one system is to be shut down for mainte- nance after the two systems and loads are paralleled, the preferred bypass source is the system remaining on line during the maintenance activities. Both systems are synchronized to the preferred bypass.

Second, once both UPSs are in sync with one bypass, inter-module sync is enabled. This is a digital sync bus that holds all modules of both systems in phase-lock operation, with or without a bypass ref- erence. This ensures that the individual modules of both systems are tightly controlled to enable par- alleling.

Load sharing between UPS systems is accomplished by interconnecting the load sharing circuitry— the combination of the System Output Voltage Adjustment Control plus the Module Load Sharing Control—of the two systems when the tie breaker between the systems is closed. This operation is analogous to bringing a module on-line in a multi-module system

The voltage synchronizing and load sharing loops also back up each other. Together, they hold module load sharing to within ±5% of load current. Should one or the other loop be inoperative, load sharing can still be maintained within acceptable limits.

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Contents Continuous POWER-TIE Configuration Page Table of Contents Initial System Start-Up 4.2 Basic Operation Operating InstructionsInter-System Isolation and Reliability FunctionSystem Flexibility Basic Dual-Bus Power-Tie one-line diagram Power-Tie systems fault isolation issues Power-Tie systems control interface diagram Operational Description Control System FeaturesMomentary Tie Transfer Controls Momentary Tie OperationIntersystem Synchronizing Continuous Tie Intersystem Sync and Power SharingTie System Components Continuous Tie/Transfer/Parallel ControlModes of Operation Power-Tie system one-line diagram Synchronizing the UPS Systems Continuous Power-TieChecking for Phase, Voltage, and Capacity Selecting a Line Sync SourceControl panel layout Load Transfers Between UPS Systems Separating Tied SystemsDesign Criteria Combined Loads on One System from Continuous Tie OperationCombined Loads on One System to Continuous Tie Operation Line Sync Signal Power-Tie system fault isolation issues Power-Tie systems fault tolerance Tie Operation Improper User OperationTransfer Operation Hardware Failures Tie Circuit Breaker or Logic FaultsWhat Happens If a Failure Occurs During a Power Transfer Recommendations Tie Circuit Breaker SelectionMimic Panel Load Transfer Controls Transfer Function Available OK to Transfer Load 2 to System Transfer Control DisabledTransfer Function Available Transfer Function Available OK to Transfer Load 1 to SystemControl Inhibits Continuous Tie ControlManual Controls Basic Operation Normal Transfer Operation ConfigurationsMaintenance Procedures Isolating Each UPS System Initial System Start-UpTransfer of Load Between Two Systems Maintenance Procedures Tie Control Logic Components Maintenance Procedures Maintaining Power-Tie ComponentsCircuit Breaker Failure Trouble RecoveryAbnormal Operations Improper TransferTying the UPS Systems Continuous Parallel Operations Normal Operating ConfigurationContinuous Tie-Systems Abnormal Operations Isolation for Maintenance Power-Tie system one-line diagram Operation Scenarios/Transfer Procedures See 4.2.5 Transfer of Load Between Two Systems See 4.2.4 Isolating a UPS System for MaintenanceCombined Loads Operation Parallel Operations See 4.2.11 Tying the UPS Systems ContinuousUPS System See 4.2.3 Maintenance Procedures Isolating EachOne system in bypass to Continuous Tie operation Option Operating Instructions Page Locations Technical Support/ServiceCompany Behind the Products
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