Optical Sensing in Power Transformers

242 Pages·2021·11.328 MB·English

by  Junfeng Jiang, Guoming Ma

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OpticalSensinginPowerTransformers
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Optical Sensing in Power Transformers
JunJiang
NanjingUniversityofAeronauticsandAstronautics,Nanjing,China
GuomingMa
NorthChinaElectricPowerUniversity,Beijing,China
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Thiseditionfirstpublished2021
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Contents
Foreword ix
Preface xi
Acknowledgments xiii
AbouttheAuthors xv
Acronyms xvii
ListofFigures xxi
ListofTables xxix
1 PowerTransformerinaPowerGrid 1
1.1 TypicalStructureofaPowerTransformer 2
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1.2 InsulationOilinaPowerTransformer 3
1.3 ConditionMonitoringofanOil-ImmersedPowerTransformer 7
1.3.1 Temperature 7
1.3.2 Moisture 8
1.3.3 DissolvedGasesAnalysis 9
1.3.4 PartialDischarge 10
1.3.5 CombinedOnlineMonitoring 11
1.4 Conclusion 11
References 12
2 TemperatureDetectionwithOpticalMethods 15
2.1 ThermalAnalysisinaPowerTransformer 15
2.1.1 HeatSourceinaPowerTransformer 15
2.1.2 HeatTransferinaPowerTransformer 16
2.2 Fluorescence-BasedTemperatureDetection 18
2.2.1 DetectionPrinciple 18
2.2.2 FabricationandApplication 20
2.2.3 MeritsandDrawbacks 21
2.3 FBG-BasedTemperatureDetection 22
2.3.1 DetectionPrinciple 22
2.3.2 FabricationandApplication 24
2.3.3 MeritsandDrawbacks 25
2.4 DistributionMeasurement 27
2.4.1 Quasi-DistributedTemperatureSensing 27
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vi Contents
2.4.2 DistributeTemperatureSensing 28
2.4.2.1 LightScattering 28
2.4.2.2 RamanBasedDistributedTemperatureSensing 28
2.4.2.3 Rayleigh-BasedDistributedTemperatureSensing 32
2.4.3 MeritsandDrawbacks 33
2.5 Conclusion 33
References 34
3 MoistureDetectionwithOpticalMethods 37
3.1 OnlineMonitoringofMoistureinaTransformer 37
3.1.1 DistributionofMoistureinthePowerTransformer 38
3.1.2 TypicalMoistureDetectionTechniques 40
3.2 FBG-BasedMoistureDetection 42
3.2.1 DetectionPrinciple 42
3.2.2 FabricationandApplication 45
3.2.3 MeritsandDrawbacks 48
3.3 EvanescentWave-BasedMoistureDetection 49
3.3.1 DetectionPrinciple 49
3.3.2 FabricationofMNF 53
3.3.2.1 ChemicalEtchingMethod 53
3.3.2.2 FusedBiconicalTaperMethod 54
3.3.3 MNFMoistureDetection 56
(cid:2) 3.3.4 MeritsandDrawbacks 57 (cid:2)
3.4 Fabry–Perot-BasedMoistureDetection 58
3.4.1 DetectionPrinciple 58
3.4.2 FabricationandApplication 59
3.4.3 MeritsandDrawbacks 61
3.5 Conclusion 61
References 62
4 DissolvedGasesDetectionwithOpticalMethods 65
4.1 OnlineDissolvedGasesAnalysis 65
4.1.1 GeneralQuantitiveRequirementsofOnlineDGA 67
4.1.2 AdvantagesofOpticalTechniquesinDGA 70
4.2 PhotoacousticSpectrumTechnique 70
4.2.1 DetectionPrincipleofPAS 70
4.2.2 ApplicationofaPAS-BasedTechnique 73
4.2.3 MeritsandDrawbacks 74
4.3 FourierTransformInfraredSpectroscopy(FTIR)Technique 76
4.3.1 DetectionPrincipleofFTIR 76
4.3.2 ApplicationoftheFTIR-BasedTechniques 80
4.3.2.1 FTIRTechnique 80
4.3.2.2 OnlineFTIRApplication 85
4.3.2.3 CombinationofFTIRandPAS 86
4.3.3 MeritsandDrawbacks 88
4.4 TDLAS-BasedTechnique 89
4.4.1 DetectionPrincipleofTDLAS 89
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Contents vii
4.4.2 ApplicationoftheTDLAS-BasedTechnique 92
4.4.2.1 OpticalLasers 94
4.4.2.2 Multi-passGasCell 95
4.4.2.3 TopologyofMulti-gasDetection 96
4.4.2.4 LaboratoryTests 99
4.4.2.5 FieldApplication 103
4.4.3 MeritsandDrawbacks 105
4.5 LaserRamanSpectroscopyTechnique 106
4.5.1 DetectionPrincipleofRamanSpectroscopy 106
4.5.2 ApplicationofLaserRamanSpectroscopy 107
4.5.3 MeritsandDrawbacks 109
4.6 FiberBraggGrating(FBG)Technique 110
4.6.1 DetectionPrincipleofFBG 110
4.6.2 ApplicationoftheFBGTechnique 110
4.6.2.1 StandardFBGSensor 110
4.6.2.2 EtchedFBGSensor 114
4.6.2.3 Side-PolishedFBGSensor 118
4.6.3 MeritsandDrawbacks 121
4.7 DiscussionandPrediction 123
4.7.1 ComparisonofOpticalFiberTechniques 123
4.7.2 FutureProspectsofOptic-BasedDiagnosis 125
4.8 Conclusions 127
(cid:2) References 128 (cid:2)
5 PartialDischargeDetectionwithOpticalMethods 137
5.1 PDActivitiesinPowerTransformers 137
5.1.1 OnlinePDDetectionTechniques 138
5.1.2 PDInducedAcousticEmission 139
5.2 FBG-BasedDetection 142
5.2.1 FBGPDDetectionPrinciple 142
5.2.2 PS-FBGPDDetection 144
5.2.3 HighResolutionFBGPDDetection 148
5.2.4 MeritsandDrawbacks 149
5.3 FP-BasedPDDetection 150
5.3.1 FP-BasedPrinciple 150
5.3.2 ApplicationofFPPDDetection 152
5.3.3 SensitivityofanFP-BasedSensor 155
5.3.3.1 TheDiaphragmThickness 155
5.3.3.2 TheDiaphragmMaterial 156
5.3.3.3 TheDiaphragmShape 156
5.3.4 MeritsandDrawbacks 157
5.4 Dual-BeamInterference-BasedPDDetection 158
5.4.1 PrincipleofDifferentInterferenceStructures 158
5.4.1.1 Mach-ZehnderInterference 158
5.4.1.2 MichelsonInterference 159
5.4.1.3 SagnacInterference 160
5.4.2 ApplicationCases 162
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5.4.2.1 PDDetectionBasedonMach-Zehnder 162
5.4.2.2 PDDetectionBasedonMichelson 162
5.4.2.3 PDDetectionBasedonSagnac 163
5.4.3 SensitivityofanInterference-BasedSensor 166
5.4.3.1 SensorParameterVariation 166
5.4.3.2 PhaseModulationandDemodulationTechniques 168
5.4.4 MeritsandDrawbacks 171
5.5 MultiplexingTechnologyofanOpticalSensor 171
5.5.1 MultiplexingTechniquewiththeSameStructure 171
5.5.2 MultiplexingTechniquewiththeDifferentStructures 175
5.5.3 DistributedOpticalSensingTechnique 176
5.6 Conclusion 179
References 182
6 OtherParameterswithOpticalMethods 189
6.1 WindingDeformationandVibrationDetectioninOpticalTechniques 189
6.1.1 WindingDeformationDetection 189
6.1.1.1 WindingDeformationinPowerTransformer 189
6.1.1.2 WindingDeformationDetectionwithanOpticalTechnique 190
6.1.2 VibrationDetection 192
6.1.2.1 VibrationinPowerTransformers 192
6.1.2.2 VibrationDetectionwithOpticalTechniques 194
(cid:2) 6.1.3 MeritsandDrawbacks 197 (cid:2)
6.2 VoltageandCurrentMeasurementwithOpticalTechniques 198
6.2.1 CurrentMeasurementwithOpticalTechnique 199
6.2.1.1 PrincipleofOpticalCurrentTransducer 199
6.2.1.2 All-FiberOpticalCurrentTransducer 200
6.2.2 VoltageMeasurementwiththeOpticalTechnique 200
6.2.2.1 PrincipleoftheOpticalVoltageTransducer 200
6.2.2.2 All-FiberOpticalVoltageTransducer 202
6.2.3 MeritsandDrawbacks 202
6.3 ElectricFieldMeasurement 203
6.4 Conclusion 205
6.5 Outlook 207
6.5.1 ProfoundandExtensiveInterdisciplinaryCombinations 208
6.5.2 MatureSchemeandLowCostManufacturing 208
6.5.3 ReliableMeasurementandLong-TermStability 208
6.5.4 Pre-factoryInstallationandIntegrationintoaMonitoringSystem 209
6.5.5 RapidExpansionandDevelopment 209
6.5.6 AdvancedAlgorithmsandNovelDiagnosis 210
References 210
Index 213
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ix
Foreword
Ibelievethatthepresentbookisthefirstbookrelatedtoapromisingoptic-basedonline
monitoringforpowertransformersinthepowergrid.
Powertransformersareessentialequipmentforpowerdelivery,whichdirectlyinflu-
encethesecurityandstabilityofthelargeelectricnetwork.Therefore,thetransformer
condition assessment and failure analysis are very important issues for the electric
power utilities. There is a very complicated environment in the transformer, which is
related to the Multiple Physical Field and its coupling, such as intense electric field,
intensemagneticfield,heattransferfield,oilflowfield,andsoon.Thecurrentsensing
systemsaremostlylocatedontheoutsideofthetransformerinordertopreventsenses
from electromagnetic, chemical, and heating effects, resulting in less physical fields
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fault location. It is believed that optical sensing, especially optic fiber sensors, has an
advantage of passive, lightweight, small size, EMI immunity, and is able to work in
environmentswithmultiplephysicalfieldsandchemicalcorrosioninthetransformer.
Therefore,Ibelievethatopticalsensingtechnologywillbepromisingtechnologyfora
powertransformer,notonlyinanon-lineconditionmonitoringaspectbutalsoinfault
protectionissues.
Thisbookisaimedtocomprehensivelypresentthedifferentcutting-edgeopticalprin-
ciples and methodologies adopted for online monitoring of power transformers and
coversthebasicprinciple,keypoints,possibleinstallations,andsomeresults.Although
some opticaltechniques are currently still not mature enoughfor in-situ applications
inpowertransformers,thebooktriestoinspirenewchancesandpossibilities.Inaddi-
tion,thereareabundantfirst-handinformation,experience,andknowledgeontheopti-
caltechniquesappliedinpowertransformerscontributedbyDr.JiangJunandDr.Ma
Guominginthisbook,whichmaymakeitmoreattractivetothereaders.
Ireallyhopethisbookwillbeinterestingtotheaudienceofscientificresearchers,tech-
nicalR&Dstaff,manufacturers,frontlineengineers,postgraduatestudents,etal.,andwe
encourageeveryreadertoexploremorenewpossibilitiesappliedinpowertransformers.
August,2020 ChengrongLi
Professor
NorthChinaElectricPowerUniversity
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xi
Preface
Transformers are one of the most important pieces of equipment in a power grid.
Its health index can significantly impact both the reliability and functionality of the
powergrid. However, partialin-servicetransformersworldwidehavealreadyreached
orexceededtheirdesignlifeexpectancy.Thus,real-timeonlinemonitoringandassess-
ment have been prioritized on the agenda among utilities around the globe to allow
foratimelymaintenanceactionandtoavoidanypotentialcatastrophicfailures.Many
newdetectiontools are being investigatedcontinuously by researchers andengineers
in the field. In particular, with advances in optical engineering and communications
technology,thelastfewdecadeshavewitnessedtheemergenceanddevelopmentofa
newgenerationofopticalapproachesforpowerapparatusconditionmonitoring.The
(cid:2) inherentadvantagesoffibreopticsensorsincludelightweight,compatibility,passivity, (cid:2)
low attenuation, low power, immunity to electromagnetic interference (EMI), high
sensitivity, wide bandwidth, and environmental ruggedness. These advantages are
utilizedtocompromiseforitshighcostandunfamiliaritytotheconsumer.Therefore,
theyhavebecomecommonlyusedandappliedinhighvoltageapplications.
This book presents the concepts and current industry practice of various popular
condition monitoring techniques such as temperature measurement, moisture analy-
sis, dissolved gas analysis, partial discharge, winding deformation, vibration analysis,
voltage/currentmeasurement,andelectricfieldmeasurement.Thebookalsoprovides
fundamental knowledge of optical principles and some practical techniques for opti-
calprobesdesign,circuittopology,alternativeschemes,andthecomprehensivemerits
anddrawbacks.Primarily,thebookoffersacomprehensiveandvaluablesourceofinfor-
mationforresearchers,utilityengineers,operators,andtechnicians.Itreflectsasolid
understandingofstrategicconceptstomaintainassets,optimizeplannedreplacements,
andminimizethepossibilityofcatastrophicfailures.Finally,itoffersadvancedmaterial
for undergraduate and postgraduate research students, and advanced teaching in the
emergingfieldofadvancedsensorsandelectricengineering.
Thisbookisorganizedintosixchapters.
1. Chapter 1 gives an overview of power transformers in power grids, their typical
structure, as well as an overview of oil-immersed insulation systems. This chapter
alsoprovidesafoundationforunderstandingconditionmonitoringofoil-immersed
powertransformerstoprovideabasicoutlineoftraditionaltechniquesandassistthe
readerinunderstandingthenecessityofnovelsensing.
2. Chapter2focusesontemperaturedetectionwithopticaltechniques,alongsideheat
sourcingandtransferringinpowertransformers.Opticalfibersensorsaredeveloped
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xii Preface
todetecthotspottemperature(HST)andpreventa“fever”ofpowertransformers,
withpointmeasurement,quasi-distributedmeasurement,anddistributionmeasure-
ment.
3. Chapter 3 primarily explains moisture measurements by optical sensors, with a
comprehensive guideline for three types: FBG, evanescent wave and Fabry–Perot
(FP)-based moisture measurements. To build a reasonable and practical online
moisturedetection,thefactorsofinferencingthemeasurementareconsideredand
theprosandconsofeachopticaltechniqueareweighedrespectively.
4. Chapter 4 presents fundamentals of dissolved gas analysis (DGA) and its require-
mentsforonlinemonitoring.Italsoshowsthecategorizationofopticalschemesfor
dissolvedgasanalysisasphotoacousticspectrum(PAS),Fouriertransforminfrared
spectrum (FTIR), tunable diode laser absorption spectrum (TDLAS), laser Raman
spectroscopy(LRS),andfiberBragggrating(FBG).Finally,itprovidesacomparison
betweencurrentlyusedopticalfibertechniques.
5. Chapter 5 concentrates on partial discharge (PD) activities detection with optical
techniquesonthebasisofthePD-inducedweakacousticemissioneffect.Threemain
optical techniques, based on different principles, are analyzed for PD detection,
namelyFBG,FP,anddual-beaminterferencetopology.Thesensitivityenhancement,
merits,anddrawbacksofthesetechniquesarepresentedaswell.
6. Chapter6providesthemeasurementofmechanicalandelectricalparametersonthe
basisofopticalsolutions,suchaswindingdeformation,highvoltage,largecurrent,
and contactless electric fields. It also highlights the current condition monitoring
(cid:2) limitationwithopticaltechniquesandtheimportanceoffutureresearch. (cid:2)
The research work presented in this book is supported and funded by the National
NaturalScienceFoundationofChinaandshowscollaborativeworkandprojectsfrom
severalpowerutilitiesinChinaoveraperiodofabout10years.Thebookaimstoprovide
thestate-of-the-artknowledgerelatedtoopticalsolutionsforconditionmonitoringand
faultdiagnosisofpowertransformers.
Opticalfibersmayseemirrelevanttopowertransformersatfirstglance;however,itis
extremelybeneficialtocombinetheinterdisciplinarysubjects.Theauthorshopeitcan
be a “must have” reference book and an adequate reference for anyone working with
condition monitoring of power transformers. Nevertheless, a continuing effort in the
academicresearchandindustrialworkisstillnecessarytoemphasizethelong-termreli-
abilityoftheinformationprovidedandimprovetheprecisionofopticalmeasurements,
respectively.Therefore,interests,efforts,opinions,andcollaborationsfromenthusiastic
readersarehighlyappreciated,inordertoofferpotentialfeasiblesolutionsandimprove
theopticalpresenceinthepowerindustry.
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