OMICORN SFRA

Condition Based Assessment/ Incipient Fault Detection Aradhana Ray, OMICRON, India

Charles Sweetser OMICRON, USA

© OMICRON

24. November 2009

Page: 1

Agenda g • Sweep Frequency Response Analysis (SFRA) • Advanced Diagnostic Measurements on Power Transformers by Electrical Methods • Dielectric Freq Frequency enc Response • Partial P ti l Discharge Di h Measurements M t

© OMICRON

24. November 2009

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Advanced Diagnostics g • Field use and recognition is becoming standard accepted standard, accepted, and/or popular • Fueled by technology and the proliferation of modern instrumentation • Extension of Standard Tests that add value • PF/TD, Tip-Up, Variable Frequencies

© OMICRON

24. November 2009

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Transformer Test Categories g • Dielectric • Thermal • Mechanical

© OMICRON

24. November 2009

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Transformer Tests Dielectric

Thermal

Mechanical

DGA Oil Screen PF/TD CAP Exciting Ima TTR DFR Partial Discharge

DGA Oil Screen IR DC Winding RES

SFRA Leakage Reactance PF/TD CAP Exciting Ima DC Winding RES

© OMICRON

24. November 2009

Page: 5

SFRA Diagnostics Measurements and Analysis Aradhana Ray, OMICRON, India

Charles Sweetser OMICRON, USA

© OMICRON

24. November 2009

Page: 6

What is SFRA?

¨Powerful and sensitive tool to assess the mechanical ec a ca a and de electrical ect ca integrity teg ty o of po power e transformers active part ¨Measurement of the transfer function over a wide frequency range

© OMICRON

24/11/2009

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Transformer Test Categories g • Dielectric • Thermal • “Mechanical” Mechanical

© OMICRON

24. November 2009

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Transformer Tests Dielectric

Thermal

Mechanical

DGA Oil Screen PF/TD CAP Exciting Ima TTR DFR Partial Discharge

DGA Oil Screen IR DC Winding RES

SFRA Leakage Reactance PF/TD CAP Exciting Ima DC Winding RES

© OMICRON

24. November 2009

Page: 9

Diagnostic g Note • Tests should be p part of a protocol • More than 1 test should provide supporting evidence.

© OMICRON

24. November 2009

Page: 10

Transformer Tests Dielectric

Thermal

Mechanical

DGA Oil Screen PF/TD CAP Exciting Ima TTR DFR Partial Discharge

DGA Oil Screen IR DC Winding RES

SFRA Leakage Reactance PF/TD CAP Exciting Ima DC Winding RES

© OMICRON

24. November 2009

Page: 11

When to use SFRA? ¨ quality check during manufacturing ¨ proof the transformer after short circuit testing ¨ check the integrity of transformers after transport ¨ routine diagnostic g measurement ¨ condition assessment after the occurrence of high transient fault currents ¨ diagnosis after transformer alarm or protection tripping ¨ testing after significant changes of monitored values (e.g. combustible gases) ¨ further inspection p after the observation of unusual routine test results © OMICRON

24/11/2009

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When to use FRA? Manufacturer Workshop

•Quality Assuring

D li Delivery P t Port

Truck Transport 1

•Transport Checking

•After Short Circuit Test

Trafo o

•Failure Investigation

Ship Transport

Reception Port •Routine Measurement •After Transients/Overcurrents •Failure Investigation (DGA)

Truck Transport 2

•Transport Checking © OMICRON

24/11/2009

Page: 13

Which problems can be detected? ¨ Winding deformation axial&radial (b kli tilti (buckling,tilting…), ) partial ti l winding i di collapse ll ¨ Displacement between high and low voltage windings ¨ Shorted or open p turns ¨ Faulty grounding of core or screens ¨ Core movement and / or shorted laminates ¨ Broken or open p internal connections © OMICRON

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Videos © OMICRON

24/11/2009

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Radial Failure

© OMICRON

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Axial Failure 5. 000e+001

1 . 0 0 0 e +0 0 2

5 . 0 0 0 e +0 0 2

1.000e+003

5.000e+ +0 003

1 . 0 0 0 e +0 0 4

5.000e+004

1.000e+005

5 . 0 0 0 e +0 0 5

1 . 0 0 0 e +0 0 6

5. 000e+006

5. 000e+001

1 . 0 0 0 e +0 0 2

5 . 0 0 0 e +0 0 2

1.000e+003

5.000e+003

1 . 0 0 0 e +0 0 4

5.000e+004

1.000e+005

5 . 0 0 0 e +0 0 5

1 . 0 0 0 e +0 0 6

5. 000e+006

f/H z

-1 0

-1 5

-2 0

-2 5

-3 0

-3 5

-4 0

-4 5

-5 0

dB

150

100

-5 0

f/H z

-1 0 0

° 1V 1U

1W 1V

© OMICRON

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Conductor Tilting

© OMICRON

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Core Faults

© OMICRON

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???????

© OMICRON

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SFRA Measuring Method

© OMICRON

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The SFRA Measurement Principle 3

3

Transformator

2 Spannu ung U2/U1 in V/V

Spannu ung U1/U1 in V/V

2 1

0 0

50

100

-1 -2

1

0 0

50

100

-1 -2

-3

-3 Zeit t in µs

Zeit t in µs

Erregungssignal Input signal (variable Frequenz)

2 Spannung U/U1 in V/V

(sine wave of variable frequency)

OutputAntwortsignal signal 3

1-|TF(f1)| ^ U1

1

^ U2

0 0 -1

50

ϕ(f1)/2πf

-2

|TF(f1)| =

-3

arc(TF(f1)) =

100

^ U2 ^ U1

ϕ(f1) Zeit t in µs

Betragsfunktion |TFU2/U1(f)|Magnitude 1.0

1.000e+002

1.000e+003

1.000e+004

1.000e+005

0.8

-30

-40

-50

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

-20

°

200.0

150

150 0 150.0

100

100.0

f/Hz

-10

50

0.6

0 0.4

-50

-60

-100

0.2

arc(TFU2/U1(f)) in deg

dB

Phasenfunktion

Phase arc(TFU2/U1(f))

50.0

1.000e+002

1.000e+003

1.000e+004

f/Hz

1.000e+005

0.0 -50.0 -100.0

-70

-150

-150.0

-80

0.0

-200.0 0.0

-90

NV

0.2

0.4

0.6

0.8 f in MHz

1.0

1.2

1.4

NV

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

f in MHz

© OMICRON

24/11/2009

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Theoretical Background transformer

900 800

0.80 0.60

700

0.40

600 U (V)

0.20

500

1

400

1

1

1

I (A) 0.00 -0.20

300

-0.40

200

-0.60

100 0 0.0

20.0

40.0

60.0

80.0

-0.80

complex RLCM-Network

100.0

Zeit (µs)

0.0

20.0

40.0

60.0

80.0

100.0

Zeit (µs)

input signal

response signal

FRA with impulses (IFRA) filtering, sampling, windowing, FFT, quotient

2.5

transfer function (phase)

transfer function (magnitude)

3.0 20 2.0

20 2.0

1.0

1.5 |TF(f)| 1.0

arc(TF(f)) 0.0

0.5

-2.0

00 0.0

-3.0 30

-1.0

0.0

0.2

0.4

0.6

0.8

Frequenz f frequency

1.0

1.2 MHz

1.4

0.0

0.2

0.4

0.6

0.8

1.0

1.2 1.4 MHz

Frequenz ff frequency

© OMICRON

24/11/2009

Page: 23

Theoretical Background Cables Grounding

Measurement cable bl

x (t ) = X sin ω t

Measurement cable bl

RMC12

y (t ) = Y sin( ω t + φ )

RMC34

TF = CMC

CMC

CMC

Rm U 2 (s) = U1 ( s ) Rm + Z specimen

CMC

k = 20 log10 (U 2 / U1 )

Complex RLC Network

ϕ = tan −1 (∠U 2 / ∠U1 ) 50Ω

dB

U1

50Ω 50

U2

50Ω 50

°

Magnitude (k)

10 0 1.000e+002

-10

1.000e+003

1.000e+004

1.000e+005

Phase

150 1.000e+006

f/H f/Hz

100

-20

50

-30 -40

0

-50 -60

1.000e+002

-50

1.000e+003

1.000e+004

1.000e+005

1.000e+006

f/Hz

-70

-100

-80 -90

-150

-100 -110

-200 -120

H1 H2

H2 H3

H3 H1

H1 1H H2

H2 2H H3

H3 3H H1

Swept Frequency Response Analysis (SFRA) © OMICRON

24/11/2009

Page: 24

SFRA Principle p C = ε * A/d

The transformer as a RLC network © OMICRON

24/11/2009

Page: 25

SFRA RLC Basics

TF =

U o ( s) Rm = U i ( s ) Rm + sL

TF = 0 Amplitude [dB]

Amplitude [dB]

0 -50 L=200 mH L=2 mH L=20 H

-100 -150 1 10

2

10

3

10

4

10 Frequency (Hz)

5

10

6

10

-100 C=1uF C=20nF C=1pF

-150 2

10

3

10

4

10 Frequency (Hz)

5

10

6

10

7

10

100 L=200 mH L=2 mH L=20 H

-50

2

10

3

10

4

10 Frequency (Hz)

5

10

6

10

Phase [°]

Phase [°]

-50

-200 1 10

7

10

0

-100 1 10

U o (s) Rm sC = U i ( s ) Rm sC + 1

7

10

C=1uF C=20nF C=1pF

50

0 1 10

2

10

3

10

4

10 Frequency (Hz)

5

10

6

10

© OMICRON

7

10

24/11/2009

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RLS Basics • Parallel RLC - VALLEY • Series RLC – PEAK • 0 dB = 0 Ohms = Short • -100 dB = ∞ = Open © OMICRON

24. November 2009

Page: 27

Typical yp Results 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

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

f/Hz

-20

-30

-40

-50

-60

-70

dB

150

100

f/Hz

-50

-100

° N W sec

N V sec

NU

© OMICRON

24/11/2009

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Measurement Types yp • Open Circuit - Exciting Ima • Short Sh t Circuit Ci it - Leakage L k Reac R • Interwinding - CAP • Transfer Voltage - TTR © OMICRON

24. November 2009

Page: 29

Measurement Setup

Open Circuit

© OMICRON

24/11/2009

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HV vs. LV Winding Responses

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Open p Circuit Tests

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24. November 2009

Page: 32

Measurement Setup

Short Circuit Test

© OMICRON

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Open p vs. shorted tests

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Short Circuit Tests

© OMICRON

24. November 2009

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Measurement Setup

I t Inter-winding i di measurements: t C Capacitive iti (l (left) ft) IInductive d ti (right) ( i ht)

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Capacitive Inter Inter--Winding Test

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24/11/2009

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Inductive InterInter-Winding g Test

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Usable Frequency q y Ranges g

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The General Curve Structure

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Analysis y Strategies g • Baseline • Similar Si il Unit U it • Phase Comparison

© OMICRON

24. November 2009

Page: 41

U

W

V

Date X

Phase ba ased comp parison

Time ba ased comp parison

7. SFRA Interpretation p Date Y Trafo A 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

f/Hz

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

f/Hz

-10 -10

20 -20 -20

-30 -30

-40 -40

-50

-50

-60

-60

-70

-70

-80

-80

dB

dB

Failure investigation

Fingerprint

Integrity verification

U

W

V

Trafo A 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

f/Hz

-10

-20

-30

-40

-50

-60

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

-70

f/Hz

-10

-80

dB

-20

-30

Failure investigation

-40

-50

-60

U vs. V

-70

-80

dB

Integrity verification

Construction based comparison U

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

f/Hz

Trafo A

V

W

U

V

W

Trafo B

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

f/Hz

-10

-10

-20 -20

-30 -30

-40 -40

-50 -50

-60 -60

-70 -70

-80 -80

dB

dB

© OMICRON

24/11/2009

Page: 42

SFRA & Transformer Transportation p

An Example of a typical SFRA use case: The evaluation of a transformer after it's transportation.

© OMICRON

24/11/2009

Page: 43

Transportation is not allways easy

© OMICRON

24/11/2009

Page: 44

First indication of transport damage

© OMICRON

24/11/2009

Page: 45

SFRA - Results

Suspect unit

Sister transformer

W-U (blue) is not OK!

Everything is OK! © OMICRON

24/11/2009

Page: 46

After opening the transformer

Limb W was displaced to the right

Bent clamping rod, Ruptured clamping f frame © OMICRON

24/11/2009

Page: 47

Possible Testing Issues • Oil • Residual Magnetization • Poor Connections and Grounding

© OMICRON

Influence of the insulating g oil

Bl Blue: With Oil - Green: G Without With t Oil © OMICRON

24/11/2009

Page: 49

Comparison: p with / without Tank 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

f/Hz

10 -10

10 -10

-20

-20

-30

-30

-40

-40

-50

-50

-60

-60

-70

-70

dB

dB

150

150

100

100

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

-50

-100

2.000e+006

3.000e+006

4.000e+006

5.000e+006

6.000e+006

7.000e+006

8.000e+006

9.000e+006

1.000e+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

-50

f/Hz

f/Hz

-100

° UV

f/Hz

1.000e+006

° U V (1)

Logarithmic Representation

UV

U V (1)

Linear Representation © OMICRON

24/11/2009

Page: 50

Standardisation in the World PC57.149/D5

WG A2.26

DL 911/2004

CHINA

© OMICRON

24/11/2009

Page: 51

IEC Standard 6007660076-18

© OMICRON

24. November 2009

Page: 52

Test Connections

© OMICRON

Test Recommendations (IEEE) • LTC Extreme Raise • DETC as Found • Open Circuit Test • Short Circuit Test

© OMICRON

Radial Deformation (IEEE)

© OMICRON

Axial Deformation

© OMICRON

Core Defects

© OMICRON

Turn--to Turn to--Turn Short

© OMICRON

Open Winding

© OMICRON