Life Expectancy Bridging the gap between Lab Tests … Expectancy Spring ICC 2017 A6D Nigel Hampton,...
Transcript of Life Expectancy Bridging the gap between Lab Tests … Expectancy Spring ICC 2017 A6D Nigel Hampton,...
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Life Expectancy
Spring ICC 2017 A6D
Nigel Hampton, Josh Perkel, Thomas Parker
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Bridging the gap
between Lab Tests
and estimates of
Service Performance
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Life Expectancy
Spring ICC 2017 A6D
Feedback shows its important to
estimate / assure the longevity of
an installed cable system
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Life Expectancy
Spring ICC 2017 A6D
Limited field data
but have accelerated tests
ACLT
Cores in water - tanks
??yr
AWTT
Cores in water - tubes
1yr
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Life Expectancy
Spring ICC 2017 A6D
Details of accelerated tests
ACLT
Cores in water - tanks
??yr
Time to Failure metric
Continuum of un defined times
Moderate samples (#*l)
AWTT
Cores in water - tubes
1yr
Breakdown metric
Multiple defined times
Small samples (#*l)
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Life Expectancy
Spring ICC 2017 A6D
Details of accelerated tests
ACLT
Cores in water - tanks
??yr
Time to Failure metric
Continuum of un defined times
Moderate samples (#*l)
AWTT
Cores in water - tubes
1yr
Breakdown metric
Multiple defined times
Small samples (#*l)
Time to Failure Data
seems like a good place
to start
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Life Expectancy
Spring ICC 2017 A6D
Details of accelerated tests
ACLT
Cores in water - tanks
??yr
Time to Failure metric
Continuum of un defined times
Moderate samples (#*l)
AWTT
Cores in water - tubes
1yr
Breakdown metric
Multiple defined times
Small samples (#*l)
Time to Failure Data
seems like a good
place to start
Unfortunately when
you start looking
around there is not
much data out there &
available
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Life Expectancy
Spring ICC 2017 A6D
Details of accelerated tests
ACLT
Cores in water - tanks
??yr
Time to Failure metric
Continuum of un defined times
Moderate samples (#*l)
AWTT
Cores in water - tubes
1yr
Breakdown metric
Multiple defined times
Small samples (#*l)
Time to Failure Data
seems like a good
place to start
Unfortunately when
you start looking
around there is not
much data out there &
available
Can anything be done
with Breakdown
Strengths at defined
times
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Life Expectancy
Spring ICC 2017 A6D
What is there to work with?
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=
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Life Expectancy
Spring ICC 2017 A6D
Still some concerns
Are they representative only 3 numbers at each time
Are they sensible lengths 15ft is wet
How do we handle uncertainty
Are the failure modes translatable
Is acceleration reasonable
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Life Expectancy
Spring ICC 2017 A6D
Meta Analysis
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Are they representative YES
Are the failure modes translatable - YES
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Life Expectancy
Spring ICC 2017 A6D
Approaching Service Length Weibull Scale
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Sensible
lengths?
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1 4
873
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Life Expectancy
Spring ICC 2017 A6D
Length extension of Meta Analysis
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Sensible
lengths?
=
1 4
873
Are they sensible lengths - YES
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Life Expectancy
Spring ICC 2017 A6D
Uncertainty: Shape & Scale @ 300ft
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=
n 3
How do we handle uncertainty YES, with confidence limits
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Life Expectancy
Spring ICC 2017 A6D
B63 stress by which 63% of the population is expected to fail
B10 stress by which 10% of the population is expected to fail
B1 stress by which 1% of the population is expected to fail
Utility Risk Acceptance @ 300ft
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Is acceleration reasonable
NOT UN REASONABLE
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Life Expectancy
Spring ICC 2017 A6D
In Conclusion
Utilities remain interested in life expectancy
Need to use test data, but some steps are required
Are they representative
Are they sensible lengths
How do we handle uncertainty
Are the failure modes translatable
Is acceleration reasonable
There likely is some approximate translation between
test performance and service expectation
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Life Expectancy
Spring ICC 2017 A6D
More Information
The New Weibull Handbook Bob Abernethy
IEEE Guide for the Statistical Analysis of Electrical
Breakdown Data Fothergill, Montanari, Hampton,
Ross, Stone
Statistical Treatment of Fatigue Experiments Leonard
Johnson
Water Treeing Fred Steenis
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