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)�� SafetySafety�� Handling & processingHandling & processing�� Fault identification/failure mode processesFault identification/failure mode processes�� Wear outWear out

AACCEPTANCE TESTINGCCEPTANCE TESTING

�� Numerous new suppliers have entered Numerous new suppliers have entered marketmarket

�� SF6 is manufactured for different SF6 is manufactured for different applicationsapplications

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 products

�� SFSF66 severely contaminated with SFseverely contaminated with SF66breakdown productsbreakdown products

�� SFSF66 contaminated with moisturecontaminated with moisture�� SFSF66 slightly contaminated with airslightly contaminated with air�� SFSF66 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

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 ppm

�� Water 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 ppm

�� Water content: 120 Water content: 120 ppmvppmv.ppmv. .

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

051015202530354045

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 �s 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 filling�� Absorbed & Adsorbed OAbsorbed & Adsorbed O22, N, N22, H, H22OO�� Ingress 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

CF4

Cu

(copper) CuF2 (solid)

W

(tu

ngste

n)

WF6

C

(c

arbo

n)H2O WO3 (solid)

SF6

Al(aluminum)

Al, O

2 , C

SOF2 + AlF3 (solid) + CF4

AlF3 (solid)

Key SFKey SF6 6 GasesGases

�� ActivityActivity�� SOFSOF22

�� SOFSOF44

�� SOSO22FF22

�� SOSO2

�� Wear OutWear Out�� CFCF44

�� WFWF66

2

CasesCases

Case 1 Case 1 -- Circuit BreakerCircuit Breaker

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

�� AirAir�� MoistureMoisture�� Reactive surfacesReactive surfaces�� Sample pressureSample pressure

Sampling SFSampling SF66

Sampling SFSampling SF66