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Using SFUsing SF66 Analysis forAnalysis forCondition Based Maintenance ofCondition Based Maintenance of
Circuit Breakers andCircuit Breakers andGas Insulated SubstationGas Insulated Substation
Antony GiacominTJ|H2b Analytical Services, Pty. Ltd.
Reasons for TestingReasons for Testing
Acceptance testing (purity)Acceptance testing (purity)SafetySafetyHandling & processingHandling & processingFault identification/failure mode processesFault identification/failure mode processesWear outWear out
AACCEPTANCE TESTINGCCEPTANCE TESTING
Numerous new suppliers have entered Numerous new suppliers have entered marketmarketSF6 is manufactured for different SF6 is manufactured for different applicationsapplications
ASTM SFASTM SF66 SpecificationSpecification
Moisture 8.0 ppm w/w
Air 500 ppm w/w
CF4 500 ppm w/w
Assay 99.8% wt
IEC SFIEC SF66 SpecificationSpecification
Moisture 15 ppm w/w
Air 500 ppm w/w
CF4 500 ppm w/w
SAFETYSAFETY
Numerous decomposition products formed Numerous decomposition products formed –– many toxicmany toxic
Threshold Limit Values in Threshold Limit Values in ppmppm of SFof SF66Gaseous Decomposition ProductsGaseous Decomposition Products
SF6 Sulfur hexafluoride 1000SO2 Sulfur dioxide 3SF4 Sulfur tetrafluoride 0.1SOF2 Thionyl fluoride 1SO2F2 Sulfuryl fluoride 5SOF4 Thionyl tetrafluoride 0.5WF6 Tungsten hexafluoride 0.1CF4 Carbon tetrafluoride 1000
Threshold Limit Values in Threshold Limit Values in ppmppm of SFof SF66Solid Decomposition ProductsSolid Decomposition Products
AlF3 Aluminum fluoride 2.5CuF2 Cupric fluoride 1CuF Cuprous fluoride 1
Handling & ProcessingHandling & Processing
Uncontaminated SFUncontaminated SF66
SFSF66 slightly contaminated with SFslightly contaminated with SF66breakdown productsbreakdown productsSFSF66 severely contaminated with SFseverely contaminated with SF66breakdown productsbreakdown productsSFSF66 contaminated with moisturecontaminated with moistureSFSF66 slightly contaminated with airslightly contaminated with airSFSF66 severely contaminated with airseverely contaminated with air
UncontaminatedSF6
Slightlycontaminated
SF6 with breakdownproducts
Severelycontaminated
SF6 with breakdownproducts
Slightlycontaminated
With air
Severelycontaminated
With air
ContaminatedWith moisture
AssessSF6
condition
Collect SF6Sample
Store and reuse
As needed
Filter and retest until
acceptable, then reuse
Reprocess SF6
Filter and retest until
acceptable, then reuse
Add new SF6 untilresidual air acceptable.
Reuse as needed
Reprocess SF6
CigreCigre SF6 Recycling GuideSF6 Recycling Guide
50 50 ppmvppmv totaltotalReactive ComponentsReactive Components
160 Pa @ 0ºC 160 Pa @ 0ºC Equivalent to120 Equivalent to120 ppmvppmv ((liqliq))320 320 ppmvppmv @ 500 @ 500 kPakPa1600 1600 ppmvppmv @ 100 @ 100 kPakPa
H2OH2O
2% 2% volvol totaltotalAir and CF4Air and CF4
Proposed LevelsProposed LevelsComponentsComponents
CIGRE 23.10 CIGRE 23.10 -- “SF6 Guidelines” “SF6 Guidelines” ELECTRA No. 173 (1997)ELECTRA No. 173 (1997)
InIn--service service guidelinesguidelines..
Total Air (O2 & N2): Total Air (O2 & N2): 30,000 ppm30,000 ppmWater content: 200 Water content: 200 ppmv.
Recycling or reRecycling or re--use use guidelines.guidelines.Total Air (O2 & N2): Total Air (O2 & N2): 20,000 ppm20,000 ppmWater content: 120 Water content: 120 ppmvppmv.ppmv. .
Comparison of Australian and NZ Comparison of Australian and NZ data against these guidelinesdata against these guidelines
59% of equipment tested met the 59% of equipment tested met the recycling guidelines of CIGRE 23.10 for recycling guidelines of CIGRE 23.10 for both air and water content.both air and water content.76% of equipment the CIGRE 23.10 76% of equipment the CIGRE 23.10 inin--service guidelines.service guidelines.Correct and careful sampling is required Correct and careful sampling is required to meet these specifications.to meet these specifications.
DIAGNOSTIC TESTINGDIAGNOSTIC TESTING
Measuring various levels of Measuring various levels of decomposition products enables decomposition products enables detection of failure modes, faults and detection of failure modes, faults and wear activity.wear activity.
SFSF66 ChemistryChemistry
ChemistryChemistry
S
F
F
F
F F
F
F
S
F
F
F F
F
FF
F S FFSF
F
SF FF
FF FF SF S
F
FF
SF6
SF5
SF4
SF3
SF2
SF
S
F
F
F
F
F
e
e
e
e
e
F
e
Population DistributionPopulation Distribution
05
1015202530354045
SF6 SF5 SF4 SF3 SF2 SF S
ELECTRIC DISCHARGESELECTRIC DISCHARGES
Type Occurrence Characteristics
Partial Discharge Electrically floating component Free conducting particles 0.01 – 0.010 J
102 – 104 Hz
Spark Capacitive discharge Disconnect switch 0.010 – 100 J
a few µs duration
Arc Breaker switch In-service fault 105 – 107 J
50 – 150 ms
Contamination with AirContamination with Air
Residual OResidual O22, N, N22, H, H22O from fillingO from fillingAbsorbed & Adsorbed OAbsorbed & Adsorbed O22, N, N22, H, H22OOIngress of OIngress of O22, N, N22, H, H22O through leaksO through leaks
Graham’s Law of EffusionGraham’s Law of Effusion
Vacuum
H2O
O2
N2
1 atm <0.001 atmp ≈ 1 atm
Graham’s Law of EffusionGraham’s Law of Effusion
SF6 @ 5 atm
p ≈ 5 atm<0.001 atm 5.0 atm
Graham’s Law of EffusionGraham’s Law of EffusionZWA0=pA0/(2πmkT)1/2
SF6
H2O
O2
N2
SF6
SF5
SF4
SF3
SF2
SF
S
OH SOF4
SOF3
SOF2
SOF
SO
OH SO2F2
O
SOF4
SOF2
SO2F2
SO2F2
SO2F2SOF2
SO2F
SO2
SO2
OH
OH
OH
OH
H 2O
H 2O
H 2O
O2
O2O
O
O
O
O
F
F
F
F
F
e
Fe
O
e
O
e
e
F
e
Materials of ConstructionMaterials of Construction
Cu
(copper) CuF2 (solid)
W
(tu
ngste
n)
WF6
C
(c
arbo
n)H2O
CF4
WO3 (solid)
SF6
Al(aluminum)
Al, O
2 , C
SOF2 + AlF3 (solid) + CF4
AlF3 (solid)
Key SFKey SF6 6 GasesGases
ActivityActivitySOFSOF22
SOFSOF44
SOSO22FF22
SOSO2
Wear OutWear OutCFCF44
WFWF66
2
CasesCases
Case 1 Case 1 -- Circuit BreakerCircuit Breaker161 kV, 2000 amp161 kV, 2000 amp
Compound Pole 1 Pole 2 Pole 3SF6 Sulfur hexafluoride 998191 995848 996190N2 Nitrogen 964 649 2917O2 Oxygen 341 136 638CF4 Carbon tetrafluoride 504 3365 255SOF2 Thionyl Fluoride ND 1 NDCO2 Carbon dioxide ND 1 ND
Case 2 Case 2 -- Gas Insulated Gas Insulated SubstationSubstation
Compound Segment 26 Segment 31SF6 Sulfur hexafluoride 825686 820579N2 Nitrogen 173657 178674CF4 Carbon tetrafluoride 184 329CO2 Carbon dioxide 255 254SOF4 Thionyl tetrafluoride 8 17H2 Hydrogen 210 146
Case 3 Case 3 –– 245kV Live Tank CB245kV Live Tank CB Compound SF6 Sulfur hexafluoride 670011N2 Nitrogen 144898O2 Oxygen 44409CF4 Carbon tetrafluoride 8719CO2 Carbon dioxide 18174SO2F2 Sulfuryl fluoride 3445SO2 Sulfur dioxide 109812COS Carbonyl Sulfide 533
Moisture 180 ppm
SamplingSampling
Sampling IssuesSampling Issues
AirAirMoistureMoistureReactive surfacesReactive surfacesSample pressureSample pressure
Sampling SFSampling SF66
Sampling SFSampling SF66
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