Liebert Series 610 Function, System Flexibility, Inter-System Isolation and Reliability

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System Description

1.0SYSTEM DESCRIPTION

1.1Function

The Liebert Continuous Power-Tie™ system provides the capability to momentarily or continuously parallel the output buses of two otherwise independent UPS Systems (See Figure 1). It also provides manually initiated, uninterrupted transfers of a critical load bus between the two UPS Systems.

This topology permits one UPS and its associated distribution system to be shut down for mainte- nance while the load continues to be supplied by another UPS, without the necessity of transferring the load to bypass during shutdown or restart of the UPS being maintained.

1.2System Flexibility

In the unlikely event that one 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 continu- ously tied to a second full (or partial) capacity system, powering simultaneously the now-tied two crit- ical buses.

This results in a single, fully redundant UPS system powering two different distribution strings through a single UPS critical bus.

When the off-line (whether for maintenance or repair) modules are brought on-line again, the two UPS critical buses are again separated without the need to transfer to the bypass source. For continu- ous-tied systems, module kVA and kW ratings must be identical.

1.3Inter-System Isolation and Reliability

For multiple UPS installations at a single site, best total system reliability is achieved when system- to-system independence is maximized. However, to transfer loads or parallel critical buses between multiple UPS systems, a certain amount of cross-connected system-to-system power and signal con- ductors are required. See Figure 2.

Proper implementation of power conductor runs and circuit breaker placement will minimize the risk that a catastrophic critical bus fault (e.g., a dropped wrench) on one system will cause a failure in a second system.

Liebert has minimized the risk of system-to-system electrical noise susceptibility and faults in sys- tem-to-system copper wire control circuitry through the use of fiber-optic technology as well as trans- former and impedance isolation techniques in critical control circuits.

The possibility of signal and ground loops through control interconnections has been eliminated by isolating all control signals between each UPS system and the Tie Controls (See Figure 3). For exam- ple, a water leak over one UPS could effectively short all the control conductors together, causing a catastrophic fault in one system. Through the noted isolation techniques, this fault will not be propa- gated through intersystem (e.g., load sharing control conductors) control wiring to the second system.

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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 Checking for Phase, Voltage, and Capacity Continuous Power-TieSelecting a Line Sync Source Synchronizing the UPS SystemsControl 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 What Happens If a Failure Occurs During a Power Transfer Tie Circuit Breaker or Logic FaultsRecommendations Tie Circuit Breaker Selection Hardware FailuresMimic Panel Load Transfer Controls Transfer Function Available Transfer Control DisabledTransfer Function Available OK to Transfer Load 1 to System Transfer Function Available OK to Transfer Load 2 to SystemControl Inhibits Continuous Tie ControlManual Controls Maintenance Procedures Isolating Each UPS System Normal Transfer Operation ConfigurationsInitial System Start-Up Basic OperationTransfer of Load Between Two Systems Maintenance Procedures Tie Control Logic Components Maintenance Procedures Maintaining Power-Tie ComponentsAbnormal Operations Trouble RecoveryImproper Transfer Circuit Breaker FailureTying 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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