12 Koch Monitoring TR

8/20/2019 12 Koch Monitoring TR

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Maik KOCH, Dr.-Ing. FKH, Switzerland

1. Monitoring approaches

2. Bushing monitoring

3. Partial discharges

On-Line Monitoring of Transformers –

A New Method and Experiences


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Scope of Monitoring – Expectations and Needs

ContinuousDiagnostics

Condition basedmaintenance

Full utilizationof life span

F a

i l u r e

R a

t e

time / a0 10 20

Classical

Diagnostics

Temporary

Monitoring

PermanentMonitoring

5a

3a


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Brand-New: Cigré A2.37

• Preliminary results published 2012• Failure mode based on 913 failures

Dielectric

37 %

Electrical

15 %

Thermal

11 %


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Transformer Monitoring – Mult iple Parameters

0. Operational

1. DGA

2. Bushings

3. OLTC


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Case Study: 600 MVA Transformer


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DGA Gas Measurements

0,1

1

10

100

1000

10000

15.6.12 20.6.12 25.6.12 30.6.12 5.7.12 10.7.12 15.7.12 20.7.12 25.7.12 30.7.12

AmbientTemp

C2H2

C2H4

C2H6

CH4CO

CO2

H2

H2O

OilTemp

On-line monitoring results

Confirmed by off-line results


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Analysis and Decision

• Decision: Removal and

Repair in Workshop• Advantages:

– Not visible with oil sampling

– Avoided over-saturation

and Buchholz alarm

– Planned outage of only 2w

Dörnenburg: Local overheating

Rogers: Thermal failure >700°CMSS: Not defined

IEC60599: Overheating >700°C

Duval: Overheating 300-700°C

Cigre: Overheating

http://diagnostic.ieh.uni-stuttgart.de/duval/800/466


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Failure Mechanisms and Diagnostics

• Partial breakdowns

– Capacitance – Partial discharges

Voltage

[kV]

No. of

layers

%

change

123 14 7.1

245 30 3.3

420 40 2.5

550 55 1.8

A

Emax= high

Emax= low

A

without

layers

with layers


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Failure Mechanisms and Diagnostics

• Voids, cracks

– Partial discharges – Capacitance

• Ageing by-products, moisture

– Dissipation factor / power factor

0,0

0,2

0,4

0,6

0,8

1,0

D i s s i p a t i o

n F a c t o r ( % )

typ: 0,25

OIP

typ: 0,35

IEC60137

max: 0,7 %

RIP

0,0

0,2

0,4

0,6

0,8

1,0

P o w e r F a c t o r ( % )

typ: 0,25

OIP

typ: 0,35

max: 0,85

RIP

max: 0,5

IEEE C57.19.01


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Where Can I Get the Reference from?

• Off-line test: Reference from HQ capacitor

• On-line test: Reference?

u

UX(t)UR(t) Z1

Z2

CX,CR

0(t)

Reference Measurement path

I R I X

Im

ϕ

δ

Uo

IXIR


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Relative C/DF Measurement

> Sum of the bushing currents

> Three phase vectors are added up

> Bushing-to-bushing comparison

> Vectors of bushings in same phase are

compared

L1

L2L3


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from 2011-02-13 to 2011-02-15

[P. Picher “Integration of New Transformer Monitoring Technologies ...”

TechCon Asia-Pazific 2011]

Systematic error

0.65 %

plus instrumentinaccuracy 0.5 %

Capacitance?

DF impossible!

0,0

0,20,4

0,6

0,8

1,0

D F ( % )

typ: 0,25

OIP

typ: 0,35

Systematic error

RIP


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VTBushing

Data Storage and

Analysis Unit

Connection Diagram VT Reference

ϕ

δ

IB

UVT+

90°


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TanDelta Measurement Phase U

Comparison to accurate

off-line tests:

DF 2.701 E-3

C (pF) 467.1


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C/DF Measurement over 1.75 Years

0,0

0,2

0,4

0,6

0,8

1,0

D F ( % )

typ: 0,25

OIP RIP

400

467 +/- 2 pF

Measurement

478 pF Warning

500

C a p a c i t a n c e (

p F )

0,27 +/- 0,05 %

Measurement

0.7 % IEC Warning


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PD Activity

over 4 Days

10

1

0.1

0.01

00:00:00 01:00:00 02:00:00 03:00:00 04:00:00 05:00:00

Q i

n n C

t in dd:hh:min

L1

L2L3


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Fighting PD Noise: UHF Gating

Electr. PD

UHF PD

InternalPD

Corona

EM Field


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3PARD: PD Discrimination by Amplitude

MPD1

InternalPD

Corona

EM Field

MPD2 MPD3

1

23


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3PARD and Back Transformation


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20 10 0 t in ms

10

1

0.1

0.01

Q I E C

i n n C

Ph. U Ph. W

Ph. V

Ph. U Ph. W

Ph. V

On-Line Application of 3PARD

10

1

0.1

Q I E C

i n

n C

100

20 10 0 t in ms


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PD Risk Assessment

Noise rejectionSource

separationPattern

classificationPD localization

• Galvanic

decoupling

• Gating

• UHF

• RTD

• 3 PARD

• 3 FREQ

• Manual

• Automatic

• Asset

• Phase

• Acoustic

localization


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G

Grid

400 kV

GSU

1100 MVA

Generator

900 MW

21 kV

Transmission line

400 kV

6 km

Substation

Transformer 2Transformer 1

ca. 10 m

UMTS

Generator

OMS843

- PD

- Transients

- C/DF

UHF620 + UVS

OMS843

- PD

- Transients

- C/DF

Voltag Transformers

OMS843

- C/DF

(Reference)

UHF620 + UVS

PDM600

Case Study: Combined Generator and

Transformer Monitoring


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C/DF and PD Couplers

Generator:

Capacitive couplersTransformer:

Capacitive bushing

adapters and UHF

drain valve sensor


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Transformer 2Transformer 1

ca. 10 m

UMTS

Generator

OMS843

- PD

- Transients

- C/DF

UHF620 + UVS

OMS843

- PD

- Transients

- C/DF

Voltage Transformers

OMS843

- C/DF

(Reference)

UHF620 + UVS

PDM600

Monitoring Results

20 10 0 t in ms

1

0.1

0.01

Q I E C

i n

n C

10

20 10 0 t in ms

100

1

.001

U i n µ V

1000500 0 f in MHz

P i n d B

m

-120

-100

-60

0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

11-20-2012 11-25-2012 11-30-2012

D F / %

U

V

W


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Influence of Environmental Conditions

0 5 10 150

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

d i s s i p a t i o n f a c t o r i n %

0

5

10

15

20

25

30

35

40

t e m p e r a t u r e i n C °

V-phase

U-phaseW-phase

IEC60137 max: 0,7 %

time / days


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G

Grid

400 kV

GSU

1100 MVA

Generator

900 MW

21 kV

Transmission line

400 kV

6 km

Substation

0

V o l t a g e i n k V

18t in ms1260

200

-400

400

-200

C Phase

B Phase

A Phase

BAT20

BAT10

0

V o l t a g e i n

k V200

-400

400

-200

Transient Over-Voltages

> Oszillation frequency 10 kHz,

beat frequency 600 Hz

> Several times a day

t in ms 1260

BAT10

18t in ms1260


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Switching Transients

0

V o l t a g e i n k V

t in ms80400

200

-200

2417t in ms

0

V o l t a g e i n

k V

t in ms 100500

200

-2002915 t in ms


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DGA Monitoring


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User Interface: Asset Page

• Capacitance /

dissipation factor:

IEC limits• Transients: 2.5 p.u.

• Partial discharges

transformer: Yes/no

• Partial discharges

generator: Expert

analysis (remote)


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Summary

• On-line monitoring as

future trend• C/DF monitoring

– The reference problem

– Solution: VT reference

– Accuracy +/- 2pF• On-line PD monitoring

– The noise problem

– Possible solutions:

• UHF-gating

• Software separation

• Pattern recognition

• Outlook

– Commoditization of on-line

monitoring

12 Koch Monitoring TR

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