Breaker Contacts

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Dynamic Contac t Resis tance Measurementson HV Circu i t BreakersbyMic hel Landry , IREQFouad Bri kc i , Zenso l Automa t i on Inc .

IEEE/PES Sw i tc hgear Comm it t ee Meet ing(Montral , Oc t ober 4, 2005)

Zensol Automation Inc.

2 Zensol Automation Inc.

Interrupting chamber of an SF6 circuit breaker

Fixed contacts Moving contacts


2/13


Measuring system and sensors for DynamicContact Resistance Measurements (DRM)

3 signals to be recorded

The injected current (IDC) of at least 100 A

The voltage drop (VD) across the breaker contacts

The breaker contact travel curve

Features of the acquisition unit

3 analog 12-bit resolution inputs

Sampling frequency 10 kHz Total acquisition time = 30-100 s

Connection to a portable computer

Sensors

Hall-effect current sensor (LEM type)

Voltage sensor Linear or rotary contact travel sensor


Measuring parameters

DRM during closing operations is impractical

Abrupt resistance variation from infinity (opencontacts) to arcing contact resistance value ( 200 )

Undesired noise level due to transient DC current at themoment of arcing contact touch

DRM during opening operations

Low contact speed ( 0.002 - 0.2 m/s) Reproducible measurements

Easy to interpret Adequately simulates the actual operating condition of

an in-service HV circuit breaker


3/13


Not obvious resistance transition from infinityto arcing contact resistance value ( 200 )

Impractical DRM during closing operations

R(m)

0

2

4

6

8

0 0.5 1.0 1.5t (ms)


DRM on a break of a 315-kV

capacitor-bank SF6 circuit breaker

No

reproducible

measurements

0.5 ms

500

Main contact

part

At rated speedArcing

contact

part

t

R(

)

Main contact part

Contact speed=0.2 m/s 0.15 m/s

50 ms

100

At low speed

Arcing

contact

part

t

R(

)


4/13


DRM on a break of a 120-kVcapacitor-bank SF6 circuit breaker

2 ms

500

Presumed

main contact

part

Arcing

contact part

t

R(

)

At rated speed5 s

500

Main contact part

Arcing

contact part

Contact speed= 0.002 m/s

t

R(

)

At low speed


735-kV 8-break air-blast PK circuit breaker


5/13


Relatively newfixed contact

(F1)

New movingcontact

(M1)

Slightly wornmoving contact

(M2)

Contact sets of PK b reakers used fordeveloping new contact wear algorithm


Seriously damaged

moving contact

(M4)

Worn moving

contact(M3)

Contact sets of PK b reakers used for

developing new contact wear algorithm


6/13


Laboratory test set-up usinga vertical CNC milling machine


Contact wear analysis by evaluating the

area beneath the dynamic resistance curve

1

2

34

43

2

1 1:Contact set F1-M1

2:Contact set F1-M2

3:Contact set F1-M3

4:Contact set F1-M4

R(m)

Ar

(m

.s)

0.5 s

1 m

0.5 s

1 m.s

2.7 m.s

5.4 m.s

3.9 m.s

2.8 m.s

t

t


7/13


Rm

Dm

Da

Pa

Time

Ra

Ra * Da

Rm

Da

Pa

Dm

Parameters to be extractedfrom dynamic resistance curve

Arcing contact partArcing contact part

Main

contact part

Main contact

part

Dynamic

resistance curve

Contact travel

curve

t0

Contact travel (mm)

R(m)

RandContacttravel


Case Study No. 1

315-kV capacitor-bank SF6 circuit breaker


8/13


Case Study No. 1DRM on a 315-kV capacitor-bank SF6 circuit breaker

15 25 355Contact travel (mm)

0

1

3

2

R(m)

Arcing contact in excellent condition

3.6Ra*Da(m. mm)

34.6Pa

(mm)

19.5Da(mm)

15.1Dm(mm)

185Ra()

29Rm()

2492Operationcounterreading

Main

contact

part


Contact travel (mm)

R(m)

Case Study No. 2

DRM on a 120-kV capacitor-bank SF6 circuit breaker

10.3Ra*Da(m. mm)

45.9Pa(mm)

24.6Da(mm)

21.3Dm(mm)

420Ra()

37Rm()


0

1

3

2

20 300 10 40 50

Defective arcing contact

Main

contact

part


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1 off-center moving arcing contact tip Damaged fixed arcing contact

Case Study No. 2Damaged moving and fixed arcing contacts


Case Study No. 2

DRM on the same break after contact overhaul

3.4Ra*Da(m. mm)

50.5Pa(mm)

19.7Da(mm)

30.8Dm(mm)

173Ra()

33Rm()

< 20Operationcounterreading

Normal arcing contact

R(m)

0

1

3

2

25 355 15 45 55

Contact travel (mm)

Main

contact

part


10/13


Case Study No. 3230-kV reactor SF6 circuit breaker


Case Study No. 3

DRM on a 230 -kV reactor SF6 circuit breaker

60.3Ra*Da(m. mm)

65.7Pa(mm)

34.2Da(mm)

31.4Dm(mm)

1768Ra()

74Rm()


Internal restrike

R(m)

0

1

3

2

20 400 60

Contact travel (mm)


11/13


Case Study No. 3Arcing spots on the fixed contacts


Case Study No. 3DRM on a healthy break of another phase of a

230-kV reactor SF6 circuit breaker

3.1Ra*Da(m. mm)

67.2Pa(mm)

33.5Da(mm)

33.8Dm(mm)

93Ra()

34Rm()


R(m)

0

1

3

2

20 400 60

Contact travel (mm)

Main

contact

part

Normal arcing contact


12/13


Dynamic Resistance Measurement KitZ-DRM-2

Stable DC current source

Data acquisition system

Voltage and current sensors


Resdyn software

(R as a function of the breaker contact travel)


13/13


Dynamic Resistance Measurement KitZ-DRM-2 (Contact travel sensors)


Conclusion

New DRM method

Opening operations at low contact speed

Reproducible curves easy to analyze and interpret

Vital information about the breaker contact condition

Useful tool for maintenance planning

Six vital diagnostic parameters

Average main contact resistance

Average arcing contact resistance

Main contact wipe

Arcing contact wipe

Position of the breaker contact at the arcing contact part

Cumulative area beneath the resistance curve(m.mm)

Breaker Contacts

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