power transformer asset management · engineering to project equipment remaining useful life •...
TRANSCRIPT
![Page 1: Power Transformer Asset Management · engineering to project equipment remaining useful life • Requirements: non-invasive, continuous degradation indicators, and a pre-defined threshold](https://reader030.vdocuments.mx/reader030/viewer/2022040101/5e081d9c15bfc1283a730cc4/html5/thumbnails/1.jpg)
© 2016 Electric Power Research Institute, Inc. All rights reserved.
1. Michael Fourman – Georgia Transmission Company
2. Matt Walther & JinMing Liu – Con Edison, New York
3. Bhavin Desai - EPRI
Power Transformer
Asset Management
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© 2016 Electric Power Research Institute, Inc. All rights reserved.
A Little About Georgia Transmission Corporation (GTC)
GTC is a “T” only cooperative.
Our fleet of transformers consists of just under 1000 units with an
average age of 26 years.
Average annual failure rate of 0.6% (about 6 a year)
With so few units and about 40 years of experience (GTC
formed in 1974) GTC does not have the breadth of expertise.
Use Transformer Oil Analyst (TOA) to store our oil results.
Acetylene triggered proactive action.
Other gasses might catch our attention.
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© 2016 Electric Power Research Institute, Inc. All rights reserved.
Power Transformer Asset Management Issues
Consistent repeatable method for evaluating our fleet.
When to pull the trigger and replace a gassing or aged unit.
Finding the sweet spot is a function of risk tolerance.
Justification to replace a unit.
Objective justification tells a better story.
What to replace it with.
New versus used and the industries experience.
Budgeting.
Executives appreciate data supporting budgetary requests.
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© 2016 Electric Power Research Institute, Inc. All rights reserved.
EPRI Tools to Address the Issues
Consistent repeatable method for evaluating our fleet.
Power Transformer Expert System (PTX)
When to pull the trigger and replace a gassing or aged unit.
PTX
Justification to replace a unit.
PTX, Industry-wide Database (IDB)
What to replace it with.
IDB
Budgeting
PTX, IDB
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5© 2016 Electric Power Research Institute, Inc. All rights reserved.
Power Transformer Expert System (PTX)
What Is?
EPRI
PTX
Algorithms
Measurements• DGA
• Oil Quality
• Routine Electrical
Design
Information• Manufacturer
• Vintage
• Nameplate Data
Past
StressesMaintenance
History
Ab
no
rmal
Co
nd
itio
n In
dex
Paper Degradation Index
Readily Available
Data
Condition Indices -
Transformer Fleet
Risks
Belief & Likelihood of
Fault Conditions
Present
Basis for Operational and Asset
Management Decisions
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6© 2016 Electric Power Research Institute, Inc. All rights reserved.
Hazard Rates Failure ProjectionsUtility Data
0
0.002
0.004
0.006
0.008
0.01
0 20 40 60 80
HA
ZA
RD
RA
TE
AGE
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0 1 2 3 4 5 6 7 8 9 10
PR
OB
AB
ILIT
Y
NUMBER OF FAILURES
0
2
4
6
8
10
12
14
1 6 11 16 21 26 31 36 41 46 51 56
CO
UN
T
AGE
Industry-wide Transformer Database (IDB)
What is?
IDB analysis can assess random and wear-out failures using calendar age as proxy for
transformer condition
Calendar age does not account for variations in operating history (primarily thermal stresses)
of specific transformers
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© 2016 Electric Power Research Institute, Inc. All rights reserved.
GTC’s Vision for Asset Management Analytics
Continue using PTX and IDB as a supplemental tool for
decision making.
Use PTX.DLL to integrate with TOA, Doble, eDNA, and
Maximo.
Bring DGA, Power Factor, Load, Faults into PTX analysis.
Auto-creation of work orders if certain criteria met.
EPRI staff extremely helpful in using these tools!
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Challenge
• How to relate observed wear out failure rates as a function
of calendar age to actual paper condition as reflected by
NDI?
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Theoretical “Bathtub” Curve
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Available Tools And Techniques
• IDB analysis can assess random and wear-out failures using calendar age as proxy for transformer condition. Calendar age does not account for variations in operating history (primarily thermal stresses) of specific transformers
• Normal (End of Life and Wear out) Failure: PTX assesses Normal
Degradation Index (NDI) to reflect insulation condition as function of evidence of degradation
• Abnormal (Infant and Quasi-Random) Failure: PTX also provides
indices to reflect potential incipient faults due to non-age related mechanism. Corresponds to “random” failures in the bathtub curve
0
0.005
0.01
0.015
0.02
0.025
0.03
0 20 40 60 80 100
Pro
bib
ilit
y o
f F
ailu
re
Age
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Approach
• Retrospective studies of failed transformers and calibration
with constant “random” failure rate from IDB curves
provides assessment of individual transformer failure
probability due to non-age related failure mechanisms
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Con Edison: Using PTX For Capital
Planning-Advanced Analytics
1. Correlation analysis on PTX NDI scores and transformer
failures* —using a snapshot of historical fleet NDI scores
To establish NDI as a proxy for overall transformer health/risk
2. Degradation analysis using NDI scores—using time
series of individual units
To identify transformers for future repair/replacements
To generate a forward looking transformer replacement plan
To project future transformer fleet risk profile
12*Transformer Failures as defined in EPRI’s Transformer Industrywide Database
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A snapshot: correlation analysis on PTX
NDI scores and transformer failures
13
Failure rates increase exponentially as NDI scores increase.
*Our proactive replacement activities masked the possible correlation with NDI>0.3, as most of them were replaced
later on.
y = 0.0052e8.4482x
R² = 0.9845
0.0%
0.5%
1.0%
1.5%
2.0%
2.5%
3.0%
3.5%
4.0%
4.5%
5.0%
0 0.05 0.1 0.15 0.2 0.25
An
nu
al
Fa
ilu
re R
ate
NDI
(257, 15)
(58, 6)
(15, 3)
(5, 2)
(population, failures)
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0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 10 20 30 40 50 60
ND
I
In Service Age (year)
36-T3
36-T5
A-T3
13-T14
MH-T3
Degradation analysis using NDI scores
• Degradation analysis is commonly used in reliability
engineering to project equipment remaining useful life
• Requirements: non-invasive, continuous degradation
indicators, and a pre-defined threshold of failure/end of
useful life
14
Predefined
Threshold Of
High Risk of
Failure
Retired in 2014
Winding damage Failed in 2012
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Time Series degradation analysis
—Project Remaining Useful life
15
Transformer: 36-T3
Energized 4/25/1975
Projected date to reach NDI of 0.5: 2030
Estimated useful life remaining: 14
y = 0.0088e0.0730x
R² = 0.9410
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
10 15 20 25 30 35 40 45
ND
I
In-service age (year)
Extrapolating NDI growth trend may project the remaining
useful life of transformers with acceptable risk.
Transformer: MH-T3
Energized: 8/11/2004
Projected date to reach NDI of 0.5: 2019
Estimated useful life remaining: 3
y = 0.004974e0.311874x
R² = 0.992980
0
0.04
0.08
0.12
0.16
0.2
0 2 4 6 8 10 12
ND
I
In-service age (year)
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Using PTX For Capital Planning
• The combination of the correlation between NDI and
transformer failures, and degradation analysis (trending of
NDI) may help us to forecast the risk profiles
– Identify future risky units
– Based on NDI scores, its trend and conditions of other components,
assign/forecast risk for today and future.
– Project proper annual replacement rate—avoiding replacement wall
16
y = 0.0088e0.2441x
R² = 0.9393
0.00
0.05
0.10
0.15
0.20
0.25
0 2 4 6 8 10 12 14
ND
I
In-service age (year)
y = 0.0052e8.4482x
R² = 0.9845
0.0%
0.5%
1.0%
1.5%
2.0%
2.5%
3.0%
3.5%
4.0%
4.5%
5.0%
0 0.05 0.1 0.15 0.2 0.25
An
nu
al F
ailu
re R
ate
NDI
Annual Failure Rate (2007-2015) vs. 2006 NDI
(257, 15)
(58, 6)
(15, 3)
(5, 2)
(population, failures)
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17© 2016 Electric Power Research Institute, Inc. All rights reserved.
Ongoing and Future Research
0
0.005
0.01
0.015
0.02
0.025
0.03
0 20 40 60 80 100
Pro
bib
ilit
y o
f F
ailu
reAge
Normal Degradation Index
= f (Paper Insulation)Age Based Failure Rates Through fault Risk
Condition Based Failure Rates
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18© 2016 Electric Power Research Institute, Inc. All rights reserved.
Ongoing and Future Research
Integration: Enterprise Systems Algorithms Development
Validation Use of On Line Monitoring Data
Online
Offline
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19© 2016 Electric Power Research Institute, Inc. All rights reserved.
Together…Shaping the Future of Electricity