transformertestinghk [read only]

Tools for Tran

G. Matthew Kennedy, Solutio

©2013 Doble Engineering Company. All Rights Reserved

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


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


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


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


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


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


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


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


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.


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


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


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


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


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%


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


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


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


Main-InsulatioStandard M

High-Voltage Cable

Test Includes•Main C1 Core Insulat

G d Low V

Test Mode: UST

Guard Low V

Groun

A


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


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


ABB Type O+C 230 kV bushing

ator

Watts 20°C %PF-0.007 -0.053

Exciting Currents


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


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


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


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


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


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


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


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.


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


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


You

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