lessons learned from loss of nuclear plant
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7/23/2019 Lessons Learned From Loss of Nuclear Plant
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David Penney, P.E., CISSP
Senior Reliability Engineer
Texas Reliability Entity, Inc.
Lessons Learned from Loss of
Nclear Plant
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Pr!ose
• Overview of the event• Review event analysis findings• Review of corrective actions and lessons
learned
Review lessons learned from theloss of a nuclear plant
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"ne#Line Diagram
#lant si$e %200 M
'ourtransmission
exits
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Se$ence of Events % Initial Conditions
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One transmissioncircuit out ofservice for
maintenance
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Se$ence of Events % Initial Conditions
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One transmissioncircuit out ofservice for
maintenance
)ingle line toground fault occurs
at the remoteterminal of
outgoingtransmission circuit
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Se$ence of Events % Initial Conditions
One transmissioncircuit out of service
for maintenance
)ingle line to ground
fault occurs at theremote terminal oftransmission circuit
+arge $ero se,uence
currents induced inthe unfaulted parallel
line due to mutualcoupling
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Se$ence of Events % Initial Conditions
One transmission circuit
out of service formaintenance
)ingle line to ground faultoccurs at the remote
terminal of transmission
circuit
+arge $ero se,uencecurrent induced in the
unfaulted parallel line dueto mutual coupling
.nfaulted line remoteterminal trips on grounddirectional instantaneous
overcurrent
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Se$ence of Events
)ingle line to ground fault
occurs at the remote terminalof transmission circuit
+arge $ero se,uence currentinduced in the unfaulted
parallel line due to mutual
coupling
.nfaulted line trips on grounddirectional instantaneous
overcurrent
enerator goes unsta1leRemaining line trips on
unsta1le power swing resultingin loss of unit and loss of offsite
power to the nuclear facility
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&nalysis by Entity
'ailure to consider effects of mutual coupling1etween ad4acent lines
'ailure to consider or simulate a line5end fault6with end open7 on the ad4acent line that wasmutually coupled to the protected line
8ncorrect setting of ground directionalinstantaneous overcurrent element
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Corrective &ctions
Revised relay settings
Conducted comprehensive review of transmission system
Changed protection system philosophy
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Lessons Learned
Mutual impedances 1etween all linepairs should 1e calculated andincluded in the system model
Out5of5$one simulations shouldensure 9one protection elements
do not operate
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"t#of#'one Simlations
#erform an out5of5$one simulation on each lineconnected to each remote terminal close to the remoteterminal with the remote line5end open and closed
• Then with the largest remaining remote terminal ground source outof service
)imulate a line5end fault 6with end open7 on all linesthat are mutually coupled with protected line for more
than 0 percent of the protected line:s length• Then with the largest remaining remote terminal ground source out
of service
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References
; NERC Event Analysis
http<==wwwnerccom=pa=rrm=ea=#ages=>A5#rogramaspx
; NERC Lessons Learned
http<==
wwwnerccom=pa=rrm=ea=#ages=+essons5+earnedaspx
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(estions)
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