RIP vs OIP

Omicron Workshop – Diagnosemessungen an Leistungstransformatoren

© OMICRON electronics GmbH 1/42

Assessment of the Condition of High Voltage Bushings

PAGE 4

Definitions

Dielectric Losses are caused by:• Conductive losses

• Polarization losses

• Partial discharges

0.00E+00

5.00E-04

1.00E-03

1.50E-03

2.00E-03

2.50E-03

0 50 100 150 200 250 300 350 400

SerialParallelSum

Parallel circuit Serial circuit

RPCP

RS

CStot

R

SSC

R

U

U

CRU

U

=

⋅⋅==

ϕ

ωδ

cos:PF

tan:DF

||

||cos:PF

1

||

||tan:DF

tot

RP

PPCP

RP

I

I

CRI

I

=

⋅⋅==

ϕ

ωδ

PAGE 5

Capacitance Values

• Bushings:

• Partial breakdowns between layers

• Incoming oil into cracks of solid insulation (RBP)

• Between transformer windings:

• Change of the geometry between winding

• Between windings and tank

• Displacement of the active part within the tank

• Between windings and core

• Displacement of the winding or the core (if the core

ground can be disconnected)

• Core to tank

• Movement of the core (if the core ground can be

disconnected)

PAGE 6

Power (Dissipation) Factor

•Bushings:

•Aging and decomposition of insulation

•Water content

• Bad contacted electrodes or capacitive layers

• Cracks in the insulation

• (Partial) discharges

• Transformers:

•Aging

•Water content in the oil and in the paper

• Contamination by particles

PAGE 7

Condenser Type Bushings

RBP Resin Bonded Paper

RIP Resin Impregnated PaperOIP

Oil Impregnated Paper

PAGE 8

Limits

* at 1.05 Um/√3 and 20°C

Typ RIP OIP RBP Gas

InsulationResin

impregnated paper

Oil

impregnated paper

Resin bonded

paper

SF6 or other

gases

DF tan δ (RT)(IEC 60137)

< 0,7% * < 0,7% * < 1,5% * -

PF cos ϕ (RT)IEEE C57.19.01

< 0,85% * < 0,5% * < 2% *-

Typical new values 0.3-0.4% * 0.2-0.4% * 0.5-0.6% * -

Partial discharges

(IEC 60137)Um1.5 Um/√31.05 Um/ √3

< 10pC

< 5cC< 5pC

< 10pC

< 5pC< 5pC < 300pC

< 10pC

< 5pC< 5pC

< 0.7% < 0.7% <1.5%

< 0.3-0.4% <0.2-0.4% <0.5-0.6%



PAGE 9

Capacitive Bushings (1)

Emax= high

A

Emax= smaller

A

without capacitive layers

with capacitive layers

Earthing Cap

PAGE 11

Bushing Measuring Tap

PAGE 12

Measuring Taps

MICAFIL

ABB

PAGE 13

Measuring Taps

HSP

PAGE 14

Measuring Taps

GE

PAGE 15

C-Tan Delta Progression of a Bushing

C Tan-Delta Progression of a 220 kV RBP (Hard Paper ) BushingYear of Manufacturimg 1961, horizontal mounted, oi l filled

-5

0

5

10

15

20

25

30

75 77 79 81 83 85 87 89

Date of Measurement

Tan

Del

ta x

10

-3

Cha

nge

of C

apac

itanc

e %

Tan Delta Change of Capacitance

Source: RWE



PAGE 16

Bushing Fault

Source: RWE

PAGE 18

• Not free of cavities – Partial Discharges possible also at rated voltage

• Higher dielectric losses can feed to thermal instability

• RPB has cavities and cracks in the paper which are normally filled with the surrounding oil

• Increase of capacitance

• After a longer storage period this oil is running out. The PD level is increasing and the capacitance is getting smaller

RBP - Bushings

PAGE 19

RBP 220kV Bushing (1971)

Guard

PAGE 20

RBP Bushing 220kV (1971)

PAGE 21

RBP Bushing Oil-filled Cracks

PAGE 23

Micafil RBP Bushing 123kV

?



PAGE 24


PF (V) A, B, C

0.5%

0.6%

0.7%

0.8%

0.9%

1.0%

1.1%

0.0V

2000

.0V

4000

.0V

6000

.0V

8000

.0V

1000

0.0V

1200

0.0V

1400

0.0V

A

B

C

PAGE 25


PF (f) A, B, C

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

0.0H

z

50.0

Hz

100.

0Hz

150.

0Hz

200.

0Hz

250.

0Hz

300.

0Hz

350.

0Hz

400.

0Hz

450.

0Hz

A

B

C

PAGE 26


Bushing has to be exchanged

• defective contact on the measuring tap or

• defective connection between the innermost layer and the HV conductor or

• partial breakdown between layers

PAGE 27

Measurement Tap O.K.

PAGE 28

Innermost Layer Was Not Properly Connected to the HV Conductor.

123kV RBP Bushing

Page: 29



Dissipation Factor Measurement

Page: 30

0,0%

1,0%

2,0%

3,0%

4,0%

5,0%

6,0%

7,0%

8,0%

0,0H

z

50,0

Hz

100,

0Hz

150,

0Hz

200,

0Hz

250,

0Hz

300,

0Hz

350,

0Hz

400,

0Hz

450,

0Hz

DF (f) A, B, C

A

B

C

Measurement of the Removed Bushing

Page: 31

Measurement of the Removed Bushing

Page: 32

0,0%

2,0%

4,0%

6,0%

8,0%

10,0%

12,0%

14,0%

16,0%

0,0H

z

50,0

Hz

100,

0Hz

150,

0Hz

200,

0Hz

250,

0Hz

300,

0Hz

350,

0Hz

400,

0Hz

450,

0Hz

DF (f)

C1

Active Part of the Bushing

Page: 33

PAGE 34

OIP Bushings

• Paper of the OIP bushings ages particularly at high temperatures

• Through aging the dielectric losses will increase -> this increases the power factor

• Temperature dependent aging decomposes the Paper and produces additional water -> this accellerates the aging

PAGE 35

420kV OIP Bushings



PAGE 38

33kV OIP Bushings

New bushings

Removed bushings

C-Tan-Delta Meas.

PAGE 39

Tan Delta (T) at 50Hz (OIP Bushings)

0.10

1.00

10.00

20 30 40 50 60 70 80 90°C

[%]0.1-0.3% Water in paper

0.4-0.6% Water in paper

1% Water in paper

Source: ABB, Bushing diagnostics and conditioning

PAGE 40

Tan Delta (f) at 30°C (33kV OIP Bushings)

Tan Delta (f) A, B, C

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0 50 100

150

200

250

300

350

400

450Hz

%

ABCA RemovedB RemovedC Removed

PAGE 41

123kV OIP Bushings

PAGE 42

123kV OIP Bushings

PF (V) A, B, C

0.4%

0.5%

0.6%

0.7%

0.8%

0.9%

1.0%

1.1%

1.2%

1.3%

0.0V

2000

.0V

4000

.0V

6000

.0V

8000

.0V

1000

0.0V

1200

0.0V

1400

0.0V

A

B

C

PAGE 43

123kV OIP Bushings

PF (f) A, B, C

0.0%

0.2%

0.4%

0.6%

0.8%

1.0%

1.2%

1.4%

1.6%

1.8%

2.0%

0.0H

z

50.0

Hz

100.

0Hz

150.

0Hz

200.

0Hz

250.

0Hz

300.

0Hz

350.

0Hz

400.

0Hz

450.

0Hz

A

B

C



PAGE 44

123kV OIP Bushings

PAGE 45

123kV OIP Bushings

Bushing has to be exchanged

PAGE 46

Aging of RIP Bushings

• Partial breakdowns between capacitive layers are ra ther seldom

• Decrease of the power factor with increasing test v oltage can be an indicator for partial breakdowns

• Also defective connections of the measurement layer to the test tap or of the innermost layer to the high voltage conductor may be the reason for a decrease of the p ower factor with increasing test voltage

• Increase of the capacitance after a partial breakdo wn between two layers:

Cnew = Cold x n / (n-1)

n= number of layers approx. 4-7 kV per layer

PAGE 47

220kV RIP Bushing Stored Outside

PAGE 48

220kV RIP Bushing Stored Outside

0.25 %

0.35 %

0.45 %

0.55 %

0.65 %

0.75 %

0.85 %

0.0 Hz 100.0 Hz 200.0 Hz 300.0 Hz 400.0 Hz 500.0 Hz

Tan

Del

ta

31.03.200415.07.200408.10.2004

Minimum

Minimum

Minimum

PAGE 55

• The oil side of RBP and RIP bushings doesn't need a housing

• Cellulose near to the surface can absorb water, if bushings are not stored properly

• Incoming water, also from the ambient air reduces the dielectric strength – this causes an increase of the dielectric dissipation factor

Moisture in RBP and RIP Bushings



PAGE 56

Water in RBP and RIP Bushings

RIP wet RIP dry

Drying of RBP and RIP bushings is limited

PAGE 57

Micafil UTXF 24 (Drysomic) RBP Bushings

• A,B,N humid after storage

• C dryed

PAGE 58

New Micafil UTXF 24 RBP Bushings A,B,N Stored Under Wet Conditions, C Dried

Messung bei 20°CDF (f) A, B, C, N

0.0%

1.0%

2.0%

3.0%

4.0%

5.0%

6.0%

0.0H

z

50.0

Hz

100.

0Hz

150.

0Hz

200.

0Hz

250.

0Hz

300.

0Hz

350.

0Hz

400.

0Hz

450.

0Hz

A

B

C

N

dryed

humid

PAGE 60

Drying of a 145kV RBP Bushing PF Measurement

PAGE 61

Drying of a 145kV RBP Bushing

TanDelta (V)

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

0 2 4 6 8 10 12 14

kVTanDelta (f)

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

0 50 100 150 200 250 300 350 400 450

Hz

1. Measurement before drying

2. Measurement after drying

1. Measurement before drying

2. Measurement after drying

Drying:

1200h at 90°C / 200°F

PAGE 62

PD Measurement



PAGE 63

PD Measurement

OMICRONmtronix MPD 600

Quadrupole

Measuring Tap

PAGE 64

PD Measurement - Phase Resolved Pattern @ 157kV

PAGE 66

Separation of PD Sources in 3CFRD

fC

fL

fR

fL

fC

fR

A(fL)> A(fC)>A(fR)3CFRD

timeframe 1 µs

5

500

kHz

2 M

Hz

8 M

Hz

3CFRD = 3 Center Frequency Relation DiagramPAGE 67

PD Measurement Cluster 1

500 kHz

2.8 MHz

8 MHz

500

kHz

2.8

MH

z

8 M

Hz

PAGE 68


500 kHz

2.8 MHz

8 MHz

500

kHz

2.8

MH

z

8 M

Hz

PAGE 69


500 kHz

2.8 MHz

8 MHz

500

kHz

2.8

MH

z

8 M

Hz



PAGE 75

50 Hz Tan δδδδ dependent on the Temp.

PAGE 76

Assessment and Interpretation

Indication RBP OIP RIP

increase of capacitance

oil in cracksor partial breakdowns

partial breakdowns partial breakdowns

high dissipation factor

partial breakdowns;insulator surface wet or dirty (clean the insulator);

ageing of the inner insulation;

water in the inner insulation;







dissipation factor is decreasing withincreasing voltage

bad potential connections;partial breakdowns



dissipation factor isstrongly increasing

with increasing temperature

high moisture in the insulation;

high degree of ageing





partial discharges normal, if constant

Discharges produce gasses;

Errosion of the cellulose;production of x-wax

partial breakdowns;cracks or voids after

electrical or mechanical stress;

PAGE 77

• Periodical on-site measurements are essential to get a picture of the aging status.

• With beginning of on-site measurements the fault rate could be continously reduced.

• A lot of information is necessary to assess the reliability of bushings.

• The tan delta measurement is an important tool. Particularly the tan delta sweep over a wide frequency range give a better indication of many kinds of faults.

• RIP- bushings have become very common due to the long life time expectation and a minimum of maintenance.

Conclusions

PAGE 78

Thank you for your interest !

RIP vs OIP

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Transcript of RIP vs OIP