collector system design

8/7/2019 Collector System Design

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Collector System DesignCollector System DesignConsiderations for Wind FarmsConsiderations for Wind Farms

Sean CarrSean Carr

Ernst CammErnst Camm

S&C Electric Co.S&C Electric Co.


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OverviewOverview

Challenges in wind farmChallenges in wind farm

collector systemscollector systems Design considerationsDesign considerations

for collector systemsfor collector systems

SummarySummary

The presentation will discuss theThe presentation will discuss themost prevalent collector systemmost prevalent collector systemdesign for land based wind farmsdesign for land based wind farmswith underground collectorwith underground collectorsystems.systems.


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Challenges in Wind Farm CollectorChallenges in Wind Farm Collector

SystemsSystems

Location and terrain of windLocation and terrain of wind

farm sitefarm site Installation methodologyInstallation methodology

and constructabilityand constructability

Ice throw from windIce throw from windturbinesturbines

Length of collector systemLength of collector system

cable circuitscable circuits

Cable testing and faultCable testing and fault

locating of collector circuitslocating of collector circuits


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Design Considerations for CollectorDesign Considerations for Collector

SystemsSystems

Most common voltage levels for collector systemsMost common voltage levels for collector systems

15 kV15 kV

25 kV25 kV

35 kV (most typical)/46 kV (Canada)35 kV (most typical)/46 kV (Canada) 35 kV is the most common system voltage utilized35 kV is the most common system voltage utilized

for wind farm collector systems because of the longfor wind farm collector systems because of the longcircuit lengths and loading requirementscircuit lengths and loading requirements

UK voltages typically 11 kV and 33 kVUK voltages typically 11 kV and 33 kV


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Cable DesignCable Design

Cable insulation levelsCable insulation levels

Cable type and sizesCable type and sizes CableCable ampacitiesampacities

Load factorLoad factor

Number of circuitsNumber of circuits Cable installation geometryCable installation geometry

and methodand method

ThermalThermal resistivityresistivity andand

temperaturetemperature

Cable shield voltages andCable shield voltages and

bonding methodbonding method


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Circuit Configuration and Soil ThermalCircuit Configuration and Soil Thermal

ResistivityResistivity Impact on AmpacityImpact on Ampacity

1 Circuit, 3 Cables, Trefoil, 90 C, 1/3 Neutral, 35 kV, 40 Direct Buried,Spaced 12 Between Circuits

270

241

2

20

19

5

162

142

134

117

0

50

100

150

200

250

300

Ampacity

90 150 300 450

RHO

Ampacity vs RHO for Single and Parallel Circuits

Trefoil

Double Ckt. Trefoil


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Cable Sheath Bonding and GroundingCable Sheath Bonding and Grounding

Three basic methods ofThree basic methods of

sheath bondingsheath bonding singlesingle--point bondingpoint bonding

solid bondingsolid bonding

cross bondingcross bonding

NESC Sec. 9 Rule 92CNESC Sec. 9 Rule 92C

4 grounds per mile4 grounds per mile includes grounds atincludes grounds at

transformers, splices, etc.transformers, splices, etc.

Parallel groundingParallel groundingconductorconductor


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Surge Protection Considerations for CollectorSurge Protection Considerations for Collector

SystemsSystems

Surge protection typically installed at last padSurge protection typically installed at last pad--

mounted transformer on each feeder string ofmounted transformer on each feeder string ofcollector circuitcollector circuit

Considerations in application of surge arrestersConsiderations in application of surge arresters location of arresters, type of mountinglocation of arresters, type of mounting

system groundingsystem grounding

circuit lengthcircuit length

transient analysis (EMTP) may be requiredtransient analysis (EMTP) may be required


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System Protection Considerations forSystem Protection Considerations for

Collector SystemsCollector Systems Considerations for protection of collector systemsConsiderations for protection of collector systems

long circuit lengths may not allow for easy detection oflong circuit lengths may not allow for easy detection ofground faultsground faults system grounding (grounded vs. ungrounded)system grounding (grounded vs. ungrounded) selective coordination of collector system circuitsselective coordination of collector system circuits selective coordination with upstream padselective coordination with upstream pad--mountedmounted

transformers at WTGtransformers at WTG temporary overvoltages caused by ground faultstemporary overvoltages caused by ground faults

loss of phase during fault with single phase tripping andloss of phase during fault with single phase tripping andreclosingreclosing on transmission system or downed conductoron transmission system or downed conductor WTG may feed faults for several cyclesWTG may feed faults for several cycles


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Collection SwitchgearCollection Switchgear

Underground distributionUnderground distribution

switchgearswitchgear MetalMetal--enclosed switchgearenclosed switchgear

Circuit breakersCircuit breakers


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Reactive Power CompensationReactive Power Compensation

Reactive powerReactive power

compensation systems forcompensation systems formeeting interconnectmeeting interconnectrequirements (FERC 661requirements (FERC 661--A)A)for power factor and LVRT:for power factor and LVRT:

powerpower--electronicallyelectronicallyswitched capacitorsswitched capacitors

distributed staticdistributed static

compensatorscompensators mechanicallymechanically--switchedswitched

capacitorscapacitors


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Other ConsiderationsOther Considerations

FerroresonanceFerroresonance

can occur in collector system circuits with ungrounded wyecan occur in collector system circuits with ungrounded wyeor delta primary transformer connections because of:or delta primary transformer connections because of:

single pole switching or reclosingsingle pole switching or reclosing

single phasing during faulted conditionssingle phasing during faulted conditions

preventing ferroresonance on collector systemspreventing ferroresonance on collector systems

provide grounding transformersprovide grounding transformers size of grounding transformers > 5% of feeder loadsize of grounding transformers > 5% of feeder load


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Fault locatingFault locating

long circuit lengths can make locating and isolation oflong circuit lengths can make locating and isolation offaults difficultfaults difficult

provide sectionalizing points for circuits that do notprovide sectionalizing points for circuits that do not

exceed capabilities of fault locating equipmentexceed capabilities of fault locating equipment

include sectionalizing points for isolation and restorationinclude sectionalizing points for isolation and restoration

Use directional fault indicators at WTG transformers toUse directional fault indicators at WTG transformers to

provide for fault detection and isolationprovide for fault detection and isolation


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SCADA systemsSCADA systems

typically installed as a part of the collector systemtypically installed as a part of the collector system design considerationsdesign considerations

circuit lengthcircuit length number of turbines on a circuitnumber of turbines on a circuit

communications protocolcommunications protocol

fiber typefiber typesinglesingle--mode fibermode fiber

multimulti

--mode fibermode fiber


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Analytical Studies for Collector SystemsAnalytical Studies for Collector Systems

Analytical studies typically performed during theAnalytical studies typically performed during the

design phase:design phase:

cable ampacitycable ampacity

system lossessystem losses voltage drop/regulationvoltage drop/regulation

shortshort--circuit and coordinationcircuit and coordination

transients and insulation coordination (EMTP)transients and insulation coordination (EMTP)

harmonicsharmonics


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SummarySummary

Key considerations in collector system designKey considerations in collector system design

system voltagesystem voltage insulation levelsinsulation levels

cable ampacity parameterscable ampacity parameters

load factor, installation method, bonding method,load factor, installation method, bonding method,thermal considerationsthermal considerations

other factorsother factors

surge protection, system protection, ferroresonance,surge protection, system protection, ferroresonance,SCADASCADA

collection switchgear and compensation requirementscollection switchgear and compensation requirements


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IEEE PES Support for Wind Farm CollectorIEEE PES Support for Wind Farm Collector

System DesignSystem Design

Recommended practices/standardsRecommended practices/standards

Equipment application guidelinesEquipment application guidelines

Development and validation of equipment modelsDevelopment and validation of equipment models

TrainingTraining

collector system design

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