wind collector

8/3/2019 Wind Collector

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POWER Engineers, Inc.

Western Protective Relaying Conference

Wind PlantWind Plant

Collector Substation ProtectionCollector Substation Protection

Mr. John J. Kumm, P.E.POWER Engineers, Inc.


Wind Generation Resources


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Renewable Portfolio Standard: 20% by 2030


Introduction & Outline

Background & Objectives

Utility Interface

Transmission Line Protection

Transmission-Voltage Bus Protection

Collector Substation Transformer

Protection Collector-Voltage Bus Protection

Collector Protection

Capacitor Bank Protection


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The Wind Plant

Intertie

Switchyard

Collector

Substation

Collector System


Background & Objectives

Wind plants now have planned build-outsto 1,000 MW, interconnect voltages to345 kV

Plants represent a large investment andappreciable production resource

Protection objectives of Dependability,Security, Selectivity, Speed, Simplicity,Economics all apply


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Typical Collector Substation Topology


Wind Turbine Generator Types

Type A Simple Induction Machine

Type B Wound Rotor Induction withVariable Resistance

Type C Doubly-fed Induction

Type D Full Converter Interface

generator

full power

Plant

Feedersac

to

dc

dc

to

ac

generator

partial power

PlantFeeders

acto

dc

dcto

ac

generator

Slip power

as heat loss

PlantFeeders

PF controlcapacitors

ac

to

dc

generator

PlantFeeders

PF controlcapacitors

Type A Type B Type C Type D


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Utility Interface

Utility requirements for protection &control vary with location, voltage level

Determine protection scheme,communication, control, & datarequirements as early as possible

Consider protection signaling, breakerfailure transfer trip, remote metering &

control



WTGs may not provide large or enduringcurrents for line faults

Frequently, the wind park is served by anew OPGW-equipped line

Dual, high-speed protection schemes are

typical and increasingly likely withincreasing line voltage and/or decreasingline length


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In POTT schemes, use weak-infeed logicat the wind plant terminal

DCB and line-current differential schemesare only impacted in sensitivity

In all cases, a time-stepped backupscheme should be provided for whencommunications are out

Many lines are initiallyor are likely tobecomethree-terminal lines.


Three-Terminal Line Protection

DCB over fiber with channel-lossmonitoring is preferred

Several modern line-current differentialrelays support three-terminalapplications, consult with your vendor(s)

POTT performs acceptably but needsweak-infeed logic to improvedependability

Inter-tie utility will have the final word


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Transmission-Voltage Bus Protection

Frequently not required as a result ofstation topology and placement ofinstrument transformers to protect thebus in the line or transformer zones

When required, this protection needntbe exotic, high-impedance busdifferential will typically serve


Collector Sub Transformer Protection

Transformer top ratings from 100 MVA to230 MVA

Usually the key single wind plant asset

Dual differential is typically desired andemployed


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Collector Sub Transformer Protection

Ground faults near the neutral ofgrounded wye windings may not drawsignificant phase current

Consider restricted earth fault protectionfor improved sensitivity to low-windingground faults

Monitor non-electrical trips (sudden

pressure, temperature) using thetransformer relay for SOE & reporting


Collector-Voltage Bus Protection

34.5 kV buses may have very high faultduties (>40 kA)

Bus faults yield high arc flash hazard,particularly in indoor switchgearinstallations

Smaller installations may or may notinclude a bus main breaker

Fast bus fault clearing is desirable


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Collector-Voltage Bus Protection

High-speed bus protection through high-impedance differential or zone-interlockprotection is usually employed

Particularly in switchgear applications,match the CT ratio and C-rating of CTsemployed in high-impedance schemes.The C-rating should be at least C200

Backup bus time-overcurrent should be

employed in the bus main-breakerprotection set, or in the transformer relay


Collector Protection (Phase Faults)

Coordinate with WTG step-uptransformer fuses

Coordination with other WTGprotection is not a concern

Cold-load pickup is not a concern,but transformer inrush may be


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Directional supervision may permit moresensitive pickup settings

Fault duties may not offer discriminationneeded to employ an instantaneouselement



Skinny laterals near the substation cancause challenges

High available fault duties make itdifficult to protect lateral cable andcoordinate with WTG fuse.


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Collector Protection (Ground Faults)

Ground fault protection can be mademore sensitive than distribution feederprotection; no single-phase laterals andlittle natural unbalance

Be aware of cable neutral I2t rating

Account for the effects of the WTGs andtheir step-up transformers


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Overcurrent-based protection detectscatastrophic faults

Coordinate phase overcurrent elementswith capacitor fuses and trip thecapacitor breaker

Capacitor breaker must be rated forthis duty



Voltage-balance-based protection detectsnon-catastrophic capacitor fuseoperations

Alarm/Trip before voltage on remaininghealthy capacitors exceeds 110% of

rating Refer to IEEE C37.99 Guide for Shunt



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Key Points

Negotiate transmission protection,signaling, and data exchangerequirements early in the project

Consider transmission relay selection andperformance for three-terminal lines

Analyze protection scheme for gaps dueto single-point failures


Key Points

Confirm transformer and collector-voltage bus protection speed andadequacy

Examine collector cable and neutral faultwithstand capabilities when coordinating

collector elements

wind collector

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