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Condition Based Assessment/Condition Based Assessment/

Aradhana Ray,Aradhana Ray, Charles SweetserCharles Sweetser

OMICRON, IndiaOMICRON, India OMICRON, USAOMICRON, USA

© OMICRON 24. November 2009 Page: 1



A endaA enda• Sweep Frequency Response Analysis (SFRA)

• Advanced Diagnostic Measurements on Power

• u n y n

• ar a sc arge easuremen s

© OMICRON Page: 224. November 2009



Advanced Dia nosticsAdvanced Dia nostics• Field use and recognition is becoming

, ,

modern instrumentation

• Extension of Standard Tests that add value

• PF/TD, Tip-Up, Variable Frequencies




Transformer Test Cate oriesTransformer Test Cate ories

•

• Thermal

• M h ni l




Transformer TestsTransformer TestsDielectric Thermal Mechanical

DGA DGA SFRAOil Screen Oil Screen Leakage Reactance

Exciting Ima DC Winding RES Exciting Ima

TTR DC Winding RES

Partial Discharge




SSFRA DiagnosticsFRA Diagnostics

Aradhana Ray,Aradhana Ray, Charles SweetserCharles Sweetser

OMICRON, IndiaOMICRON, India OMICRON, USAOMICRON, USA

© OMICRON 24. November 2009 Page: 6



What is SFRA?What is SFRA?

Powerful and sensitive tool to assess themechanical and electrical inte rit of owertransformers active part

Measurement of the transfer function over awide frequency range

© OMICRON Page: 724/11/2009



Transformer Test Cate oriesTransformer Test Cate ories

•

• Thermal

• “M h ni l ”







TTR DC Winding RES

Partial Discharge




Dia nostic NoteDia nostic Note• Tests should be art of a

protocol

• supporting evidence.







TTR DC Winding RES

Partial Discharge




When to use SFRA?When to use SFRA? quality check during manufacturing

proof the transformer after short circuit testing

check the integrity of transformers after transport

routine dia nostic measurement

condition assessment after the occurrence of high transient

fault currents

diagnosis after transformer alarm or protection tripping

. .

combustible gases)

further ins ection after the observation of unusual routine test

© OMICRON Page: 1224/11/2009

results



WhenWhen to use FRA?to use FRA?e very ort

•Quality Assuring•Transport CheckingTruck Transport 1

T

r af

•After Short Circuit Test

•Failure InvestigationShip Transport

•Routine Measurement

© OMICRON Page: 1324/11/2009

•Transport Checking

•Failure Investigation (DGA)

Truck Transport 2



Which problems can be detected?Which problems can be detected?

Winding deformation axial&radialuc ng, ng… , par a w n ng co apse

Displacement between high and low voltagewindings

Shorted or o en turns

Faulty grounding of core or screens

Core movement and / or shorted laminates

Broken or o en internal connections

© OMICRON Page: 1424/11/2009



Radial FailureRadial Failure

© OMICRON Page: 1624/11/2009



Axial FailureAxial Failure

5 000 +001 1 000 +002 5 000 +002 1 000 +003 5 000 +003 1 000 +004 5 000 +004 1 000 +005 5 000 +005 1 000 +00 5 000 +00f/Hz

. + . + . + . + 3 . + 3 . + . + . + . + . + . +

-25

-20

-15

-10

-40

-35

-30

dB

-50

-45

100

150

1V 1U 1W 1V

f/Hz5. 000e+001 1. 000e+002 5 .000e+002 1 .000e+003 5 .000e+003 1 .000e+004 5 .000e+004 1 . 000e+005 5 .000e+005 1. 000e+006 5 . 000e+006

°

-100

-50

© OMICRON Page: 1724/11/2009



Conductor TiltingConductor Tilting

© OMICRON Page: 1824/11/2009



Core FaultsCore Faults

© OMICRON Page: 1924/11/2009



??????????????

© OMICRON Page: 2024/11/2009



SFRA Measuring MethodSFRA Measuring Method

© OMICRON Page: 2124/11/2009



The SFRAThe SFRA Measurement PrincipleMeasurement Principle

Transformator

0

1

2

3

0 50 100ung U1/U1 in V/V

0

1

2

3

0 50 100ung U2/U1 in V/V

Erregungssignal(variable Frequenz)

Antwortsignal

-3

-2

-1

Zeit t in µs

Spann

3

-3

-2

-1

Zeit t in µs

Spann

Input signal Output signal

-

-1

0

1

2

0 50 100

Span

nung U/U1 in V/V

U2^U1^

1-|TF(f1)|

U2^| |

ϕ(f1)/2πf

variable frequency)

1.0

1500

200.0

Betragsfunktion|TFU2/U1(f)|

Phasenfunktionarc(TFU2/U1(f))

-3

-

Zeit t in µs

U1^| |

=ϕ

f/Hz1.000e+002 1.000e+003 1.000e+004 1.000e+005

dB

-10

°

150

PhaseMagnitude

0.2

0.4

0.6

0.8

|TFU2/U1(f)| in V/V|

-150.0

-100.0

-50.0

0.0

50.0

100.0

.

arc(TFU2/U1(f)) in deg

-70

-60

-50

-40

-30

-20

f/Hz1.000e+002 1.000e+003 1.000e+004 1.000e+005

-150

-100

-50

0

50

100

© OMICRON Page: 2224/11/2009

0.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

f in MHz

-200.0

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

f in MHzN V

-90

-80

N V



TheoreticalTheoretical BackgroundBackground

400

500

600

700

800

900

U (V)

transformer

-0.20

0.00

0.20

0.40

0.60

0.80

I (A)

0

100

200

300

0.0 20.0 40.0 60.0 80.0 100.0

Zeit (µs)

complex RLCM-Network -0.80

-0.60

-0.40

0.0 20.0 40.0 60.0 80.0 100.0

Zeit (µs)

input signal response signal

filtering, sampling, windowing, FFT, quotient

2.5

2 0

3.0transfer function (magnitude) transfer function (phase)

0.5

1.0

1.5

.

|TF(f)|

-2.0

-1.0

0.0

1.0

.

arc(TF(f))

© OMICRON Page: 2324/11/2009

.

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Frequenz f

MHz

- .

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Frequenz f

MHz

frequency f frequency f



TheoreticalTheoretical BackgroundBackground

Measurement Measurement

Cables Grounding

t X t x ω sin)( =

ca e ca e

CMC CMC

RMC12 RMC34

specimenm

m

Z R

R

sU

sU TF +

==)(

)(

1

2

CMC CMC

Complex RLC Network )/ (log20 1210 U U k =

U1 50Ω U2 50Ω

50Ω

)/ (tan 12 U U ∠∠=−ϕ

/1 .0 00e +0 02 1. 000 e+ 00 3 1 .0 00 e+ 004 1. 000 e+ 00 5 1 .0 00 e+ 006

dB

0

10

°

150Magnitude (k) Phase

H1 H2 H2 H3 H3 H1

/ z

-120

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

f/Hz1.000e+002 1.000e+003 1.000e+004 1.000e+005 1.000e+006

-200

-150

-100

-50

0

50

100

© OMICRON Page: 2424/11/2009

Swept Frequency Response Analysis (SFRA)Swept Frequency Response Analysis (SFRA)



SFRA Princi leSFRA Princi le

C = ε * A/d

© OMICRON Page: 2524/11/2009

The transformer as a RLC networkThe transformer as a RLC network



SFRA RLC BasicsSFRA RLC Basics

sLR

R

sU

sU TF

m

m

i

o

+==

)(

)(

0

1)(

)(

+==

sC R

sC R

sU

sU TF

m

m

i

o

0

101

102

103

104

105

106

107

-150

-100

-50

Frequency (Hz)

Amplitude [dB]

L=200 mH

L=2 mH

L=20 H

101

102

103

104

105

106

107

-200

-150

-100

-50

Frequency (Hz)

Amplitude [dB]

C=1uF

C=20nF

C=1pF

-100

-50

0

Phase [°]

L=200 mH

L=2 mH

L=20 H

0

50

100

Phase [°]

C=1uF

C=20nF

C=1pF

© OMICRON Page: 2624/11/2009

10 10 10 10 10 10 10

Frequency (Hz)

10 10 10 10 10 10 10

Frequency (Hz)



RLS BasicsRLS Basics• Parallel RLC - VALLEY

• Series RLC PEAK

• 0 dB = 0 Ohms = Short

• -100 dB = ∞ = Open




T ical ResultsT ical Resultsf/Hz

5.000e+001 1.000e+002 5.000e+002 1.000e+003 5.000e+003 1.000e+004 5.000e+004 1.000e+005 5.000e+005 1.000e+006

-20

-40

-30

-60

-50

dB

-70

100

150

N W sec N V sec N U

f/Hz5.000e+001 1.000e+002 5.000e+002 1.000e+003 5.000e+003 1.000e+004 5.000e+004 1.000e+005 5.000e+005 1.000e+006

°

-100

-50

© OMICRON Page: 2824/11/2009



Measurement T esMeasurement T es

• Open Circuit - Exciting Ima

• or rcu - ea age eac

• Interwinding - CAP

© OMICRON

• rans er o age -

Page: 2924. November 2009



MeasurementMeasurement SetupSetup

Open Circuit

© OMICRON Page: 3024/11/2009



HVHV vs. LVvs. LV Winding ResponsesWinding Responses

© OMICRON Page: 3124/11/2009



O en Circuit TestsO en Circuit Tests





Short Circuit Test

© OMICRON Page: 3324/11/2009



O en vs. shorted testsO en vs. shorted tests

© OMICRON Page: 3424/11/2009



Short Circuit TestsShort Circuit Tests





n er-w n ng measuremen s: apac ve e n uc ve r g

© OMICRON Page: 3624/11/2009



CapacitiveCapacitive InterInter--Winding TestWinding Test

© OMICRON Page: 3724/11/2009



InductiveInductive InterInter--Windin TestWindin Test

© OMICRON Page: 3824/11/2009



Usable Fre uenc Ran esUsable Fre uenc Ran es

© OMICRON Page: 3924/11/2009



TheThe General Curve StructureGeneral Curve Structure

© OMICRON Page: 4024/11/2009



Anal sis Strate iesAnal sis Strate ies

• Baseline

• m ar n

• Phase Comparison




7. SFRA Inter retation7. SFRA Inter retation

arison

arison

U V W U V W

Date XDate Y

sed c

om

sed c

om

f/Hz1 . 00 0 e +0 0 2 5 . 0 00 e +0 0 2 1 . 0 00 e +0 0 3 5 . 00 0 e+ 0 0 3 1 . 0 00 e +0 0 4 5 . 0 00 e + 00 4 1 . 0 00 e +0 0 5 5 . 0 00 e +0 0 5 1 . 0 00 e +0 0 6

-10

f/Hz1 . 00 0e + 00 2 5 . 00 0 e+ 0 02 1 . 00 0e + 00 3 5 . 00 0e + 00 3 1 . 00 0e +0 0 4 5 . 00 0 e+ 00 4 1 . 00 0 e+ 0 05 5 . 00 0e +0 0 5 1 . 00 0e + 00 6

20

-10

f/Hz1 . 0 00 e +0 0 2 5 . 0 00 e + 00 2 1 . 0 00 e +0 0 3 5 . 0 00 e +0 0 3 1 . 00 0 e +0 0 4 5 . 0 00 e +0 0 4 1 . 00 0 e +0 0 5 5 . 00 0 e +0 0 5 1 . 00 0 e+ 0 06

-20

-10

Trafo A Trafo A

Fingerprint Failure investigationTime b

Failure investigation

Inte rit verificationP

hase b

dB

-80

-70

-60

-50

-40

-30

-20

dB

-80

-70

-60

-50

-40

-30

-20

dB

-80

-70

-60

-50

-40

-30

f/Hz1 .0 0 0 e+ 0 0 2 5 .0 0 0 e+ 0 0 2 1 .0 0 0e + 0 0 3 5 .0 0 0 e+ 0 0 3 1 .0 0 0 e+ 0 0 4 5 .0 0 0 e+ 0 0 4 1 .0 0 0 e+ 0 0 5 5 .0 0 0e + 0 0 5 1 .0 0 0 e+ 0 0 6

dB

-80

-70

-60

-50

-40

-30

-20

-10

U vs. V

U V WU V W

Construction based comparison

Trafo ATrafo B

f/Hz1 . 00 0 e +0 0 2 5 . 0 00 e +0 0 2 1 . 00 0 e +0 0 3 5 . 00 0 e+ 0 03 1 . 0 00 e +0 0 4 5 . 00 0 e+ 0 0 4 1 . 0 00 e +0 0 5 5 . 0 00 e +0 0 5 1 . 0 00 e +0 0 6

-30

-20

-10

f/Hz1 . 00 0e + 00 2 5 . 00 0 e+ 0 02 1 . 00 0 e+ 00 3 5 . 00 0e + 00 3 1 . 00 0e +0 0 4 5 . 00 0 e+ 00 4 1 . 00 0e +0 0 5 5 . 00 0e + 00 5 1 . 00 0e + 00 6

-40

-30

-20

-10

© OMICRON Page: 4224/11/2009

dB

-80

-70

-60

-50

-40

dB

-80

-70

-60

-50



SFRASFRA -- ResultsResults

Suspect unitSuspect unit Sister transformerSister transformer

--

© OMICRON Page: 4624/11/2009

Af i h fAf i h f



After opening the transformerAfter opening the transformer

Bent clamping rod,Bent clamping rod,Ruptured clampingRuptured clamping

© OMICRON Page: 4724/11/2009

to the rightto the right

ramerame



Com arison: with / without TankCom arison: with / without Tank

f/Hz5 .0 00 e+ 00 1 1 .0 00 e+ 00 2 5 .0 00 e+ 00 2 1 .0 00 e+ 00 3 5 .0 00 e+ 00 3 1 .0 00 e+ 00 4 5 .0 00 e+ 00 4 1 .0 00 e+ 00 5 5 .0 00 e+ 00 5 1 .0 00 e+ 00 6

1

f/Hz1. 000e+006 2. 000e+006 3. 000e+006 4. 000e+006 5. 000e+006 6. 000e+006 7. 000e+006 8. 000e +006 9. 000e+006

1

-30

-20

-10

-30

-20

-10

-60

-50

-40

-60

-50

-40

dB

-70

100

150

dB

-70

100

150

U V U V (1)

f/Hz5 .0 00 e+ 00 1 1 .0 00 e+ 00 2 5 .0 00 e+ 00 2 1 .0 00 e+ 00 3 5 .0 00 e+ 00 3 1 .0 00 e+ 00 4 5 .0 00 e+ 00 4 1 .0 00 e+ 00 5 5 .0 00 e+ 00 5 1 .0 00 e+ 00 6

°

-100

-50

U V U V (1)

f/Hz1. 000e+006 2. 000e+006 3. 000e+006 4. 000e+006 5. 000e+006 6. 000e+006 7. 000e+006 8. 000e +006 9. 000e+006

°

-100

-50

© OMICRON Page: 5024/11/2009



StandardisationStandardisation in the Worldin the World

DL 911/2004DL 911/2004PC57.149/D5PC57.149/D5WG A2.26WG A2.26

CHINA

© OMICRON Page: 5124/11/2009

IEC S d d 60076IEC S d d 60076 1818



IEC Standard 60076IEC Standard 60076--1818


T t C tiT t C ti



Test Recommendations (IEEE)Test Recommendations (IEEE)

•

• DETC as Found

• Open Circuit Test

• Short Circuit Test

© OMICRON

RadialRadial Deformation (IEEE)Deformation (IEEE)

omicorn sfra

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