Download - TransformerTestingHK [Read Only]
Tools for Tran
G. Matthew Kennedy, Solutio
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nsformer Maintenance
ons Director – Enterprise and Data Technolog
ivation for Testing
• Field Testing provides the maintools to assess the condition otools to assess the condition o
• Benefit for each test must be cinterpretedinterpreted
• Data may relate to different ar
– DielectricDielectric
– Thermal
Mechanical– Mechanical
• Engineer should choose the rig
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ntenance engineer a group of of the transformerof the transformer
clear and results able to be
reas
ght tool for the right job
vation for Testing
• Identify unsatisfactory conditions– General Condition– Effective Broadband Techniques
R di t t hi h• Responding to an event which qu– Fault Investigation– Focused testing– Focused testing
• Ranking by status for reason of re– Condition AssessmentCondition Assessment
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s during normal routine testing
ti th t f ’ h lthuestions the transformer’s health
eplacement or asset management
sformer Tests
• Dissolved Gas Analysis (DGA)• Dissolved Gas Analysis (DGA)• DP and Furanic Compounds
P f t d C it• Power factor and Capacitance• Turns Ratio
L k R• Leakage Reactance• Winding Resistance• SFRA• Partial Discharge
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hanical Integrity Techniques
• Sweep Frequency Response Anal• Sweep Frequency Response Anal• Leakage Reactance
C it• Capacitance• Excitation Current (Core Integrity
• These independent diagnostic mett f dititransformer condition
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ysis (SFRA)ysis (SFRA)
y)
thods have their place in ascertainin
port Apparatus Tests
B hi C1 AND C2• Bushing C1 AND C2• Bushing Hot-Collarg• Surge Arrester Dielectric L
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Loss
en & Why Field Testing?
• Acceptance• Establish a BaselineEstablish a Baseline• Routinely to Establish a • Determine Dryness of InDetermine Dryness of In• Assess Condition after E• Isolate a Problem Areaso e ob e e• Assess Condition after a• Asset Management - Rang• Reduce Catastrophic Fai
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Condition TrendnsulationnsulationElectrical Disturbance
a Relocationnking and Prioritizingg gilures
Categories
• Tests can be divided into two c
– Broad: Test provides a general c
– Narrow: Test provides focused tea much more searching manner.diagnose our understanding of th
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categories:
condition assessment of an apparatus
esting and looks at specific parameter Often, these test are used to enhanche broad condition
ad Testing
• Broad Testing:– Power FactorPower Factor– Oil Quality– Infrared– Excitation Current– DC Resistance– DGA– DGA The most predominant type
Provides an overall/general under test. Well understo
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e of broad testing is PF/Tan(D).
condition of any insulation system ood and accepted in the industry.
used Testing
• Focused Tests– Special oil & lab testsSpecial oil & lab tests– Sweep Frequency Respon– Leakage Reactance– Partial Discharge
Often there are se erOften there are severthat can individuallan apparatus but ean apparatus, but einsight.
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nse Analysis
ral different foc sed testsral different focused tests ly tell us the condition of ach can provide uniqueach can provide unique
ad and Focused Testing
• Generally, most test progtesting techniquestesting techniques– Best “Bang” for your buc– Usually short duration tesy– Provide reasonable level
results are good– Test analysis is usually si
• Focused tests usually req– Can be part of a routine t– Often used to analyze a s
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grams concentrate on broad
ckstof confidence that unit is good if
imple or easy to train
quired specialized equipmentest program ymptom
Broad and Narrow Focu
Problem Broad Focus Mechanical Capacitance
Exciting CurrentsExciting Currents Turns Ratio
Di l t i P F tDielectric (Insulation)
Power FactorInsulation ResistanceDissolved Gas Analy(DGA) PD DetectionExciting Currents/ TuRatio
Thermal DGAThermal Imaging
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s Chart
Narrower Focus Leakage Reactance SFRASFRAWinding Resistance Internal Inspection Acoustic Emission Di l t i F
e ysis
Dielectric Frequency Response Partial Discharge
urns FFA AnalysisyWinding Resistance
Triggered TestingProblem Trigger/Identifier DMechanical Impact recorder
Maintenance ResultsRelay Operation
LSCRelay Operation CEWTV
Dielectric(Insulation)
Annual DissolvedGas Analysis (DGA)Relay operation
PWIDPP
Thermal Annual DGAHigh OperatingTemperatures
D
General Maintenance Results PGeneral Maintenance ResultsBushings in piecesBulge in tankOdd soundsFire
P
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Oil all over the place
DiagnosticLeakage ReactanceSFRACapacitanceCapacitanceExcitationWinding ResistanceTurns RatioVisual InspectionPower FactorWinding Resistancensulation Resistance
Dissolved Gas Analysis (DGA)PD D t tiPD DetectionDGA
Pick an appropriate set of toolsPick an appropriate set of tools
What is a Doble test?
Basic Insulation CharacBasic Insulation Charac• Percent PF/Tan(D)• Capacitance (Total Cha• Dielectric (Watts) Loss• Transformer Excitation• Transformer Voltage Ra• Oil Quality & DGA
L k R t ( k• Leakage Reactance (ak• Sweep Frequency Resp
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cteristicscteristics
arging Current)
n Currentatio (aka TTR)
k Sh t i it I d )ka Short-circuit Impedance)ponse Analysis (SFRA)
Basic Insulation Power Fac
IT=Total Current I =Resistive CurrenIR=Resistive Curren
ITI0% PF θ =Power
TIC
IR E
O100%
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IR E
ctor Measurement
IC=Capacitive Currentnt E=Applied Voltage
IT
nt E=Applied Voltager Factor Angle
ICIR
E CP RP
% PF
wer and Distribution Transfor
The dielectric-loss and power factthe most comprehensive tests for i
M
Doble Test
MMThe test technique makes it possiblcomponents for more effective ana
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mers
tor test as applied to transformers are insulation assessment.
Moisture/Contamination
Carbonization
Mechanical FailureMechanical Failurele to segregate the specimen into major lysis of test results.
Problem Revealed in LFPE, 3-φ, 2-winding , Δ13.8/4.3 kV, 7 MVA
Insulation kV mCH + CHL 10 28CH 10 7.CHL (UST) 10 2CHL 2Localized moisture/contamCL +CHL 2 39CL 2 17CHL (UST) 2 2
Localized moisture/contam
CHL 2
High CL % P.F. & disagreement b
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LV WindingΔ-Y transformer
mA Watts % P.F.8.5 1.45.05 0.38 0.391.5 0.95 0.321.45 1.07 0.36mination in the L V winding9.5 5.57.65 2.85 1.181.5 3.55 1.2
mination in the L.V. winding
1.85 2.65
etween HV & LV CHL %P.F.s
Bushing Problem gCase Studies
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Main-InsulatioStandard M
High-Voltage Cable
Test Includes•Main C1 Core Insulat
G d Low V
Test Mode: UST
Guard Low V
Groun
A
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on/C1 TestMethod
tion
Voltage LeadVoltage Lead
nd Lead
Bushing andApparatus Ground
Dielectric Circuit - MC1 Tes
High Voltage Lead
Low-VoltagLead
Test Mode: UST
GuardIC1
Test Mode: UST
I & W Meter
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Main Insulationst
Test TapC
entege C1
C2
er Conducctor
Ground Lead
Test Ground
Staining of the Lower Insul
Test kV I (mA)10 1.313
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ABB Type O+C 230 kV bushing
ator
Watts 20°C %PF-0.007 -0.053
Exciting Currents
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Magnetic Circuit and W
• Exciting Current and Loss• Exciting Current and Loss– Factory Tests at Rated Voltage.– Field Tests at the Lesser of Rat
Test Set.• Simple measurement of single-pha
ll th HV id ith th thusually the HV side, with the othegrounded neutral).
• The tests should be performed at te es s s ou d be pe o edexceeding the voltage rating of the
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Winding Tests
.ted Voltage or Highest Capability of the g g p y
ase current on one side of the transformerid l ft fl ti ( ith th ti fer side left floating (with the exception of a
the highest possible test voltage without e g es poss b e es vo ge w oue excited winding.
Transformer Excitation CurreDelta-connected Primary, H1-
Test 1: MeasurEnergize H3 Measure H1 (GrouEnergize H3, Measure H1, (Grou
Also: Ground X0 on the Wye-Conn
HV Cable
UST
Test Set
Guard Low Voltag
IEC
Ground LeaUST
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Guard Low VoltagI & W Meter
ent Test Connection-H2 on Center Core Leg
re H3 to H1und H2 Float X1 X2 & X3)und H2, Float X1,X2, & X3)nected Low Voltage Winding.
H2
L H
H2
ge Lead
ad H1 H3H
ge Lead
netic Circuit and Winding Tests
• Exciting Current and Loss– Examine phase patternsExamine phase patterns– Typical pattern is two high sim
and one lower result on the ceexceptions due to core design
– Residual magnetism can affecDC tests can magnetize co• DC tests can magnetize co
• Can be a result of being de– Subsequent tests should be pSubsequent tests should be p
with same connections
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milar results on the outer phases enter phase however there are n, etc.ct resultsoreoree-energized from the systemerformed at same test voltage anderformed at same test voltage and
Leakage Impedance a
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and Reactance
Equivalent Circuit of
Primary winding dcPrimary winding dc resistance measurement
R LR
Lm C
R L-1 L 1R DC-1
Exciting Current and L t ZLoss measurement, Zm
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f a Transformer
Secondary winding dcSecondary winding dc resistance measurement
L R RCUST
R
L 2 R L-2 R DC-2
Leakage Reactance and Loss
Rm
measurement, ZL
Leakage C
The leakage flux path includes the rleakage reactance may be sensi
Top yok
Outer winding
Inner winding
B tt
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Bottom yo
Channel
regions occupied by the windings. The tive to deformations in the windings.
ke
Leakage channel
Core leg
koke
Transformer Test
• Each test is sensitive to a sproblems.
• Motivation for testing shobefore arbitrarily performibefore arbitrarily performi
• Routine testing should prolevel of comfort with trans
• Investigative testing needsthorough
• Test results should always• Test results should alwaysseriously
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Summary
specific set of
uld always be determined ing a variety of testsing a variety of testsovide owner with a high sformer conditions to be more focused and
s be scrutinized and takens be scrutinized and taken
ansformer Test Summaryy
• Planning discussions forgimportant in making goo
• There are cases where soidentify a problemidentify a problem.
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r contingencies are god decisions
ome tests will fail to
clusionLocation
Problem Overall Test Capacitance
Overall Test Power Factor
Insulation Deteriorated, High Wet, Contaminated Between Phases
Winding Distortion High Turn To TurnTurn To Turn Fault Shorted Strands High Resistance Connections
OOpen Conductors
Load Tap Changer
Contact Problems
Turn To Turn Fault Connection Errors in the PA or Taps
Core Not Grounded High
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gMovement Low
Partial Dsicharge
Exciting Current and Loss
DC Conductor Resistance
LRT/ SFRA
Leakage Loss
High
Low High Low High High
High Low High LowHigh Low High Low
Low High Low High High High High
L Hi h Hi h Hi hLow High High High
High High High High
High Low High High
High Low Low Low
Thank Y
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You
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