Superhydrophobicity in Power Applications ICC - Sub B Fall 2008 Nigel Hampton, Frank Lambert NEETRAC
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Lotus Effect - Superhydrophobicity Contact angle: > 150˚ Hysteresis smaller than 10˚ (Hysteresis= γa- γr ) Dir
ect ion of D
γr
rop
Mo vem en
γa
A droplet on a superhydrophobic surface: The droplet touches the leave only in a few points and forms into a ball. It completely rolls off at the slightest declination.
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Why This Is Interesting • Lotus effect surface: Dust with a particle size larger than the surface roughness is complete cleaned with a water droplet, rough surface in effect. • Smooth surface: Dirt is only moved by the droplet.
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Contact Angle Measurement • Goniometer for Contact Angle and Hysteresis measurements
Starting Structures • Superhydrophobic coatings were prepared on various insulating polymer materials using CF4 and SF6 plasma etching. 100 W, 5 min 200W, 5 min
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Multi Factor Ageing
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Looks Good But !!!!!!
Contact Angleact (Degree) Wat er cont angl e
170 160 150 140 130 120 110 100 90
Superhydrophobicity Lost But Still Looks Good Though Heading for the Floor
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Uncur ed Cur ed
0
50 100 150 Multi Factor Ageing UV exposur e t Time i me ( (h) h)
200 8
Degradation Of Polymer Film • After 48 hours exposure the superhydrophobicity is totally lost. The contact angle drops from 160˚ to only 80˚.
After exposure
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Next Step - An Inorganic Film Inorganic material, stable under multifactor ageing. Low energy surface can be achieved. Roughness control through diameter control.
Contact angle: ~162˚ hysteresis: < 5˚ ICC Fall 2008
SEM image: Surface roughness
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Can Control Particle Sizes 700
Calculated Particle Size (nm)
600 500
Perfect Correlation
400 300 200 100 4 components
0 0
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200
300 400 500 Actual Particle Size (nm)
600
700
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One species, too perfect packing, not enough roughness Contact angle: 134˚
TiO2: ~800 nm SiO2: 90 nm Enough roughness can be achieved
Contact angle: 168.3˚, hysteresis < 4˚ ICC Fall 2008
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Multi Factor Ageing - Results Hysteresis (degree)
50
Contact Angle (degree)
180
Material M T
40 160 Superhydrophobic
30
150 140
20
10
10
Normal Silicone Level
120 0
120
Superhydrophobic 0
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1000 2000 3000 4000 5000
0
1000 2000 3000 4000 5000
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Recovery Hysteresis 0
40
314
670
20
Hysteresis (degree)
10 0 1000
40
1947
2113
20 10 0 4531
40
4797
0
7
20 10 0 0
7
14
21
0
7
14
21
Measurement Delay (Days)
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Sample No 1 1 2 2 3 3 4 4
Test A B A B A B A B
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Transition to “Real Life”
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Salt Fog
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Salt Fog
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HiVARC
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Semi Quant STRI Classifications
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STRI Assessment Bad 6
MEDIAN STRI
5
4
3
2
1
Good
1
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3
4
5
6 7 SAMPLE
8
9
10
11
12
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Full Size Insulator Test Device
Salt Fog Endurance
HiVARC
STRI Hydrophobicity
Tracking Wheel Endurance
Suspension Insulator Phase I
12.5kV 1382 hours
YES
YES
-
Suspension Insulator Phase II
20kV 1233 hours
YES
YES
-
Polymer Cut Out
-
-
-
YES
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Tracking Wheel
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Let There Be Light
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Tracking Wheel Failures
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Tracking Wheel Test on Cutout 99
Treated Untreated
90 80 70 60 50
Percent
40 30 20 10
End of Tracking Wheel Test
5 3 2 1
10000
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15000
20000 Cycles to Failure
30000
40000
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Tracking Wheel Test on Cutout 99
Treated Untreated
90
Same Gradients Indicate Same Failure Mechanism
80 70 60 50
Percent
40 30 20 10
End of Tracking Wheel Test
5 3 2 1
10000
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15000
20000 Cycles to Failure
30000
40000
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Tracking Wheel Test on Cutout 99 Treated Untreated
90 80 70 60 50
Treated Fail later Than Untreated see 10% probabilities
Percent
40 30 20
10 5
2 1
10000
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15000
20000 Cycles to Failure
23886
18677
3
End of Tracking Wheel Test
30000
40000
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Field Test Participants •Polymer Silicone Insulators •Southern Company Transmission Lines •Hubbell
MISSISSIPPI CHEMICAL MOSS POINT EAST 115 KV T.L. ICC Fall 2008
Insulator Installation Site 28
Field Test Site
MISSISSIPPI PHOSPHATE
X X
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CHEVRON PLANT
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Solution Applied To New Insulators
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Installing New Insulator At Str.# 54
Performance is being monitored on a 3 monthly basis ICC Fall 2008
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Conclusions • • • • •
Robustness and longevity are very important Coatings work on all of the main insulations Accelerated tests are underway Coatings are in use at 15 & 115 kV Work planned for EHV