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Power-systemarchitecture

Selection criteria 0

Protection of a power system depends on

its architecture and the operating mode.

This chapter compares typical structuresof power systems.

Power-system architectureThe various components of a power system can be arranged in different ways.The complexity of the resulting architecture determines the availability of electricalenergy and the cost of the investment.Selection of an architecture for a given application is therefore based on a trade-offbetween technical necessities and cost.

Architectures include the following:b radial systemsv single-feeder,v double-feeder,v parallel-feeder,v dual supply with double busbars.

b loop systemsv open loop,v closed loop.

b systems with internal power generationv normal source generation,v replacement source generation.

The table below lists the main characteristics of each architecture for comparison.Illustrations are provided on the next page.

Architecture Use Advantages Drawbacks

Radial

Single-feeder radial Processes not requiringcontinuous supplyE.g. a cement works

Most simple architectureEasy to protectMinimum cost

Low availabilityDowntime due to faults may be longA single fault interrupts supply to the entirefeeder

Double-feeder radial Continuous processes: steel,petrochemicals

Good continuity of supplyMaintenance possible on busbarsof main switchboard

Expensive solutionPartial operation of busbars duringmaintenance

Parallel-feeder Large power systems

Future expansion is limited

Good continuity of supply

Simple protection

Requires automatic control functions

Double busbars Processes requiring highcontinuity of serviceProcesses with major loadchanges

Good continuity of supplyFlexible operation: no-break transfersFlexible maintenance

Expensive solutionRequires automatic control functions

Loop systems

Open loop Very large power systemsMajor future expansionLoads concentrated indifferent zones of a site

Less expensive than closed loopSimple protection

Faulty segment can be isolated during loopreconfigurationRequires automatic control functions

Closed loop Power system offering highcontinuity of serviceVery large power systemsLoads concentrated indifferent zones of a site

Good continuity of supplyDoes not require automatic controlfunctions

Expensive solutionComplex protection system

Internal power generation

Normal source

generation

Industrial process sitesproducing their own energyE.g. paper plants, steel

Good continuity of supplyCost of energy (energy recoveredfrom process)

Expensive solution

Replacement source

(source changeover)

Industrial and commercialsitesE.g. hospitals

Good continuity of supply for priorityoutgoing feeders

Requires automatic control functions