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JOHNSON_CA_author_ALPHA1_BLOCK1

Barcelona 12-15 May 2003

EVALUATION OF HIGH-TEMPERATURE FLUORINATED ETHERS (PFPE) FOR

POWER CONNECTORS OPERATING AT EXTREME SERVICE CONDITIONS

Barry JOHNSON and Dmitry LADIN Tyco Electronics – Canada

[email protected]

Milenko BRAUNOVICMB Interface - Canada,

[email protected]



Competitive Industry

• From system growth to prolonging the operating life

• Increased energy consumption in densely populated areas

• Transmission/Distribution lines carry greater loads

• Operating temperature of conductors raised beyond 1300C

• New type of high temperature conductor (ACSS)

• Stability of power connections at extreme operating conditions



Lubrication of Power Connections

• Contact aid compounds commonly used for Al and Cu

• Contact zone protection

• Low thermal stability of currently used compounds

• Inertness and low viscosity of fluorinated ethers

• PFPE-based lubricants can sustain operating temperatures as high as 2000C



Lubricants Selection

• Maximum operating temperature range• Formulation: base oil and additives• Thickeners:

– not melting– improved adhesion to the substrate– lower wear rates

Composition

Base/Thickener

N1 from -50 to +225 PFPE/PTFE



S1 from -43 to +232 Teflon

C1 from -20 to +300 PFAE/PTFE

Lubricant Temperature

Range (°C)



UV Resistance

• Per ASTM G-53-95 and ASTM D-638-95• Accelerated Weathering Tester: cycles of 4 hrs UVB at

600C, followed by 4 hrs of condensation at 500C• Lubricant failed: no longer can be spread and/or has severe

cracking

N1 >2051

N2 >2051

N3 >2051

S1 305

C1 >2051

Lubricant Time to Failure

(hrs)



WEATHERING TESTER



Long-Term Temperature Exposure

• Forced Air Oven set to 2000C• Exposure time: more than 2000 hrs• Material Examination:

– Discoloration– Cracking– Hardening

N1 720

N2 720

N3 >2400

S1 504

C1 >2400

Lubricant Time to Failure

(hrs)



Appearance of the Lubricants (Thermal Ageing)

BEFORE EXPOSURE AFTER EXPOSURE

PASSED

FAILED



Thermogravimetric Analysis (TGA)

• Determination of thermal stability

• Weight change measurement

• Heating rate: 10 0C/min

• N3 is stable up to 4000C

0 50 100 150 200 250 300 350 400 450 500

WE

IGH

T L

OS

S

0

20

40

60

80

100

120

140

LUBRICANT S1

0 50 100 150 200 250 300 350 400 450 500

WE

IGH

T L

OS

S

0

20

40

60

80

100

120

140

TEMPERATURE (°C)

0 50 100 150 200 250 300 350 400 450 500

WE

IGH

T L

OS

S

0

20

40

60

80

100

120

140

LUBRICANT N3

LUBRICANT C1



Current Cycling Tests

• Test I: measured contact resistance and temperature of lubricated Al-to-Al busbar bolted joints:– Thin layer of the lubricant spread over overlapping

zones

– Joints repeatedly heated up to 2000C (for 5 min) and cooled to ambient temperature



Current Cycling Tests

• Test II: wedge connectors assembled with 336.4 kcmil ACSS conductors:– Followed modified ANSI 119.4 Class AA procedure

– Temperature of the control conductor was raised to 2000C



Results of the Current Cycling Tests

• Typical data sample: lubricated Al to Al wedge connectors

• N3 and C1 lubricants are the base formulation for effective high temperature applications

0 100 200 300 400 500 600

TE

MP

ER

AT

UR

E (

oC

)

0

50

100

150

200

250

300

0 100 200 300 400 500 600

RE

SIS

TA

NC

E

( m

)

0

3

6

9

12

15

LUBRICANT C1LUBRICANT C1

NUMBER OF CURRENT CYCLES

0 100 200 300 400 500 600

RE

SIS

TA

NC

E

(m

)

0

3

6

9

12

15

NUMBER OF CURRENT CYCLES

0 100 200 300 400 500 600

TE

MP

ER

AT

UR

E (

oC

)

0

50

100

150

200

250

300

LUBRICANT N3 LUBRICANT N3

BETWEEN EQUALIZERS

ACROSS CONNECTOR

BETWEEN EQUALIZERS

ACROSS CONNECTOR

CONTROL CONDUCTOR

CONNECTOR

CONTROL CONDUCTOR

CONNECTOR

µµ



Discussion & Conclusions• Two PFPE lubricants with sufficient UV and thermal

ageing stability are identified

• The lubricants were effectively utilized as contact-aid compounds in current cycling tests

• Results obtained under controlled laboratory conditions

• Suggested materials should be subjected to the field service conditions

• Necessary fillers and metallic additions are to be incorporated to make HT contact-aid compounds

Documents

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