selectivity for distribution network
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Copyright © AEP and SEL 2015
Case Study: Achieving Selectivity ona Critical Distriution !et"or#
Jim Thomas American Electric Power
Andrew K. Burich, Michael J. Thompson,and Sneha Vasudevan
Schweitzer Engineering Laboratories, Inc.
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Agenda
• Introduction to AE distri!ution networ"
• #etwor" desi$n challen$es and $oals
•Implemented protection s%stem♦ &ircuit protection
♦ Bus protection
• &ontin$enc% anal%sis
• &onclusion
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$ntroduction to Distriution !et"or#
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Design Challenges and %oals
• T%pical overcurrent radial '(eeder)protection
• *ead+loop networ"
• ault current ma$nitude as (unction
o( location
• rotection $oals♦ Selectivit%
♦ Speed
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Location& Location& Location
Sin$le+-ine+to+round
ault on &ircuit /
Sin$le+-ine+to+round
ault on &ircuit /'Brea"er 0 1pen)
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Circuit Protection Syste'
• 1TT 2 *TT primar% microprocessor+!ased rela%s
• Alternate microprocessor+!ased and
electromechanical rela%s
• 1TT 2 *TT rela%s consistent with e3istin$
alternate rela%s
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(elay Coordination
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!eed )or Speed
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*us Di))erential Protection
• 4eplacement o( e3istin$ !us protection withtwo+restraint, dual+slope, microprocessor+
!ased rela%s at Su!stations B and &
• Various &+ratin$s on !rea"er &Ts
• -ar$e+ma$nitude (ault currents 5
&T saturation
• 4ecommendations
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E+isting Connections at Sustation *
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(eco''ended Connections
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$n)inite $ncrease in (estraint
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*us Di))erential %oalsDependaility
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*us Di))erential %oalsSecurity
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Sensitivity o) *us ProtectionLarge Slope Settings (esult in
Sacri)ice o) Sensitivity
• aults in volta$e re$ulator
• 6i$h+impedance !us (aults
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Contingencies
• -oss o( (i!er+optic communications
• -oss o( potential '-1)
• Brea"er (ailure
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!et"or# Co''unications Layout
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L,P at Sustation A -as !o E))ect
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L,P at Sustations * or C A))ects All
(elays at Sustation
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L,P at Sustations * or C A))ects All
(elays at Sustation
• -oss o( all directional elements
• 4eliance on *TT to clear (ault
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*rea#er .ailure
• ro$ramma!le lo$ic+implemented!rea"er (ailure
• -ocal !rea"er (ailure
• *TT to isolate remote end
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! / 2 ContingencyLoss o) .ier,ptic Co''unications and L,P
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Conclusion
• Selectivit% 5 "e% $oal o( protection scheme• &ontin$encies
• Bus di((erential up$rade
♦ &T saturation challen$e
♦ Sensitivit% compromise
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uestions