nesc subcommittee 5 changes to the 2017 nesc · nesc subcommittee 5 changes to the 2017 nesc joseph...
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Re-format Rule 241.C. At Crossings
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241. Application of grades of construction to different situations
2012version
Re-format Rule 241.C. At Crossings
3
241. Application of grades of construction to different situations
2012version
2017version
Re-format Rule 241.C. At Crossings
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241. Application of grades of construction to different situations
2012version
2017version
SameWords
EasiertoComprehend
Grade N
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CPIntention:
ChangeGradeNEmergency&Temp
EliminateGradeNfromTable242-1
FinalModification:
KeepGradeN
AddNOTE toRule240.A.General:NOTE: For emergency or temporary installations,
see Rule 014.
Grade Cx
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CPIntention:MakeGrade“Catcrossings”anofficialGrade:Callit“Cx”
ListinSection24-GradesofConstruction
Grade Cx
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CPIntention:MakeGrade“Catcrossings”anofficialGrade:Callit“Cx”
ListinSection24-GradesofConstruction
PotentialModification:EliminateGrade“Catcrossings”
Grade Cx
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CPIntention:MakeGrade“Catcrossings”anofficialGrade:Callit“Cx”
ListinSection24-GradesofConstruction
PotentialModification:EliminateGrade“Catcrossings”
FinalAction:Rejectanychange
Revise Table 242-1Grades of Construction Applications
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CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
Revise Table 242-1Grades of Construction Applications
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CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
FN3reversed;highergradeinthetable
3 Grade B C construction shall may be used if the supply circuits will not be promptly de-energized, both initially and following subsequent breaker operations, in the event of a contact with lower supply conductors or other grounded objects.
Revise Table 242-1Grades of Construction Applications
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CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
FN3reversed;highergradeinthetable
AddFN11– GradeNfordielectricfiber-opticsupplycables
Revise Table 242-1Grades of Construction Applications
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CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
FN3reversed;highergradeinthetable
AddFN11– GradeNfordielectricfiber-opticsupplycables
Meet Rule 230F1b – Insulated Comm Cables in Supply Space
andSupported by effectively grounded messenger
orBonded at intervals specified in Rule 092C to Supply messengers supporting cable meeting Rule 230C1
Revise Table 242-1Grades of Construction Applications
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CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
FN3reversed;highergradeinthetable
AddFN11– GradeNfordielectricfiber-opticsupplycables
FinalAction:Accept
k-factor
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Introducedin1941§DistrictLoadswerereduced
Clearancesbasedonprevioushigherloads
K-factorapproximatedthesameresultantloadingonthewiretocreatethesamesags§Clearancesbasedonsags,nottension
Resultingincreaseintensionnotintendedforstructuraldesign
2007NESCaddedDistrictLoadMaptoSec23
k-factor
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CPIntention: Setk=0insection25
Onlyaffectsguyedstructures
Iftensionssetat%limit,designtensionsincrease -everydaytensionsincrease
Affectonstructuresconsideredsmall
k-factor
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CPIntention: Setk=0insection25
Onlyaffectsguyedstructures
Iftensionssetat%limit,designtensionsincrease -everydaytensionsincrease
Affectonstructuresconsideredsmall
FinalAction:Reject
WillcoordinateeffortwithSC4innextcycle
Delete Rule 243.C.4
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When communication conductors are required tomeet Grade B or C, only the requirements formechanical strength for these grades are required.
Delete Rule 243.C.4
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Two new grades of construction:Undefined Loads + Grade B StrengthUndefined Loads + Grade C Strength
Rule 250C: Add Wind Return Period
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NOTE: The commentary to ASCE 7-2005 indicates thatthese wind speeds represent a 50-to-90 year meanrecurrence interval.
Rule 250C: Add Wind Return Period
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NOTE: The commentary to ASCE 7-2005 indicates thatthese wind speeds represent a 50-to-90 year meanrecurrence interval.
FinalAction:Accept
Non-linear analysis
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CPIntention:
Rule250BGradeB IncreaseStrengthFactorwhenusenon-linear
Rule250BGradeC DecreaseStrengthFactorwhenuselinear
Rule250C&D .75to.79
Non-linear analysis
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Intention:Rule250BGradeB IncreaseStrengthFactor
whenusenon-linear
Rule250BGradeC DecreaseStrengthFactorwhenuselinear
Rule250C&D .75to.79
AsModifiedin2013:Rule250B ReduceLFfornon-linear
Rule250C&D IncreaseLFforlinear
Non-linear analysis
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Furtheranalysisshowedinconsistenciesintheresultsofapplyingthesevalues.
-SomeofGradeCrequirementshigherthanGradeB
-Reducedrequirementsexceedincreased loadduetonon-linear
Non-linear analysis
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Furtheranalysisshowedinconsistenciesintheresultsofapplyingthesevalues.
-SomeofGradeCrequirementshigherthanGradeB
-Reducedrequirementsexceedincreased loadduetonon-linear
FinalAction:Reject
“Clarification”Determining Gust Response Factor
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Clarifiesusing“spanlength”todetermineGRF
Previouslystatedas“designwindspan”
FinalAction:Accept
Clarify when ice is appliedRule 250D
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…………
Addiceto:WiresConductorsCablesMessengers
Donotaddiceto:StructureOthersupportedfacilities
Clarify when ice is appliedRule 250D
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…………
Addiceto:WiresConductorsCablesMessengers
Donotaddiceto:StructureOthersupportedfacilities
FinalAction:Accept
New ASCE ReferenceExtreme Wind Map Figures 250-2
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2012NESC
2017NESC
ASCE7-05MinimumDesignLoadsforBuildingsandOtherStructures
ASCE74-10GuidelinesforElectricalTransmissionLineStructuralLoading
New ASCE ReferenceExtreme Wind Map Figures 250-2
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SameMap
NewlyrevisedASCEstandard
2012NESC
2017NESC
ASCE7-05MinimumDesignLoadsforBuildingsandOtherStructures
ASCE74-10GuidelinesforElectricalTransmissionLineStructuralLoading
FinalAction:Accept
New ASCE ReferenceExtreme Ice Map Figures 250-3
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2012NESC
2017NESC
ASCE7-05MinimumDesignLoadsforBuildingsandOtherStructures
ASCE7-10MinimumDesignLoadsforBuildingsandOtherStructures
New ASCE ReferenceExtreme Ice Map Figures 250-3
50
2012NESC
2017NESC
ASCE7-05MinimumDesignLoadsforBuildingsandOtherStructures
ASCE7-10MinimumDesignLoadsforBuildingsandOtherStructures
SameMap
NewEditionofASCE7
FinalAction:Accept
Longitudinal Capability Rule 252.C.6
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It is recommended that structures having a longitudinal strength capability be provided at reasonable intervals along the line.
Longitudinal Capability Rule 252.C.6
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LongitudinalcapabilityrecommendationmovedtheissuetoaRECOMMENDATION
FinalAction:Accept
Insulators – New Rating System
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OldLinePostratings:
Ratingequaltoaverage
Lowestnolessthan85%ofaverage
NewLinePostratings:
Rating=Minimumofallinsulators
Insulators – New Rating System
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OldTransmissionSuspensionratings:
1.2standarddeviations
NewTransmissionSuspensionratings:
3.0standarddeviations
Exception AddedInsulator Factory Tests Rule 274
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EXCEPTION:
Guyinsulatorsmanufacturedperdesigns
forwhichvalidationtestshavebeenperformed
and
avalidqualityassuranceprogramisfollowed,
thisruledoesnotrequirethat
dryandwetflashovertestsbeperformed
oneachguyinsulatorunit.
Insulators
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CPIntention:
IntroduceLoadfactors(LRFD)
Adjustallowablestresses
Mostlyequivalentinsulatorapplications
IntroduceClasses:Distribution&Trans
Differentallowables forRule250Bvs250C,D
Table 277-1 cont’d
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FN 3: This percentage shall be supplied by the manufacturer.
FinalAction:Accept
Subcommittee 5 Works in Progress
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StandardizeTerminology
ImproveClarityandConsistency
K-factor
60ftexclusion
Non-linearAnalysis
GradeN
GradeCx