Establishment of a Life Assessment and Decision ... · PDF fileTesting the Strategy Selection...
Transcript of Establishment of a Life Assessment and Decision ... · PDF fileTesting the Strategy Selection...
Gerhard Myburgh Namibian Power Corporation; Namibia
Graduate School of Technology Management, University of Pretoria; South Africa
Establishment of a Life Assessment and Decision
Methodology for Critical Network
Transformers/Reactors
Agenda
• Introduction
• Theory
– Problem Statement and Objective
– Research Study Process Design
• Application
– Development and Testing of the Life Assessment and Decision Methodology
– Implementation results (Year 1&2)
• Benchmarking
– Survey Methodology
– Survey Results
• Conclusion and Recommendations
General Information Area: 825 418 km2
People: 2,324,004
Density: 2.8 people/km2
(South Africa 42.4 people/km2)
Network Lines (Km) TRFRs
400 kV 988 15
350kV 952 10
330 kV 522 9
220 kV 2795 40
132 kV 2006 21
66 kV 3507 111
Introduction
A preliminary investigation suggested that The Namibian Power Corporation’s
(NamPower) maintenance plan lacked
• clear and documented life assessment criteria
• an approved methodology for maintenance strategy selection of critical
network transformers
Problem Statement and Objective
Problem statement
NamPower’s maintenance plan lacked clear
and documented life assessment criteria
and methodology for maintenance strategy
selection of critical network transformers.
Objective
To establish life assessment criteria and a
methodology for integration into a
maintenance strategy selection model in
order to improve system availability and
reliability.
Research Study Process Design
Phase 1
Criteria
development
Weighting and
scoring criteria
Information
sharing and
application
workshop
Final life assessment procedure
Life assessment
model
development
Deductive
reasoning
Deductive
reasoning
Objective
To establish transformer life assessment criteria and a methodology for integration into a maintenance strategy
selection model in order to improve system availability and reliability
Research
Research Study Process Design
Phase 2 & 3
NamPower internal assessments on
targeted critical transformers only
Summarise assessment results
Priority review session
Summarise assessment results
Feedback and benchmark review
session
Publish results
Criteria and maintenance strategy
questionnaire to target technology-
based organisations
Approval and induction of new
transformer life assessment
methodology
Development and Testing of the
Life Assessment and Decision
Methodology
TRFR Technical Condition (Input) Impact/consequence NamPower
Risk Profile (Input)
AHP (Processing)
Strategy
Selection Model
(Output)
Step 1
Step 2
Step 3
Technical Criteria Assessment
Evaluate Transformer Technical
Condition
Main criteria
Sub criteria
Elements
Historical experience
Availability (50%)
2.01 Maintenance/ Failure spare availability
(27%)
2.03 Transformer loading
(17%)
2.04 Transformer fault levels (10%) 2.02 OEM Support
(18%)
2.05 Network redundancy
(27%)
1.01 Age (5%)
1.02 Time in Service (6%)
1.03 Service History (17%)
1.04 Visual inspection (5%)
1.05 Chemical diagnostics (27%)
1.06 Electrical diagnostics (27%)
1.07 Failures (11%)
Product support (20%)
Performance (80%)
Reliability (50%)
Transformer Consequence/Impact A B C D E
Rating Financial Impact People Effect Legal and Compliance Continuity of Supply Environment
5 N$ 20-N$ 50mil
Multiple fatality and/or
Significant irreversible effects
to 10's of people
-Major litigation costing
N$10mil+
-Investigation by regulatory
body resulting in long term
interruption to operations
-Possibility of custodial
sentence
-Regional blackout lasting
<6hrs
-National load shedding
<2weeks
-Loss of critical supply to
critical customer (mines,
towns etc)
- Prolonged environmental
impact
-High profile community
concerns raised - requiring
significant rectification
measures
-Legislation agency enquiry
- Potential for significant legal
sanctions against NamPower
4 N$10 – N$20 mil
Single fatality and/or
irreversible disability or
impairment to one or more
persons
-Major breach of
regulationwith with punitive
fine.
-Significant litigation involving
many weeks of senior
management time
-Regional loss of supply to
large customers or affecting
>10 000 (50MW) customers
for >12hrs
-Loss of supply to major
centre or customer >12hrs
- Measurable environmental
harm - medium term recovery
- High potential for complaints
from stakeholders and
community
- Environmental directives
issued by authorities
3 N$10 – N$20 mil
Extensive injuries or
irreversible disability or
impairment to one or more
persons
-Breach of regulationwith
investigation or report to
authority with prosecution
and/or moderate fine possible
-Local loss of supply to large
customers or affecting >10
000 (50MW) customers for
>8hrs
- Medium term recovery,
immaterial effect on
environment / community
-Required to inform legislative
authority
2 N$ 100 - N$1 mil
- Medium term largely
reversible disability to one or
more persons
- Significant medical
treatment, disabling or lost
time injury <2weeks
-Minor legal issues, non-
compliance and breaches of
regulation
-Loss of supply to large
customers or affecting >5000
customers for <4hrs
Short term transient
environmental or community
impact - some cleanup costs
1 <N$100 000 loss- First Aid treatment or minor
medical treatmentNo breach
-Loss of supply to some
customers (normal
interruption) effects 1 000
customers for <4hrs
Negligible impact on the
environment, little or no
ecological effect and no
measurable impact on human
health
Impact Assessment Criteria
Sheet and Risk Matrix Input
Impact Assessment Criteria
Sheet and Risk Matrix Input Transformer Consequence/Impact
NAMPOWER ASSET MAINTENANCE RISK MATRIX
100 year event years to decades months to years Weeks to months Days to weeks
1 2 3 4 5
A5 B5 C5 D5 E5 5 6 7 8 9 10
A4 B4 C4 D4 E4 4 5 6 7 8 9
A3 B3 C3 D3 E3 3 4 5 6 7 8
A2 B2 C2 D2 E2 2 3 4 5 6 7
A1 B1 C1 D1 E1 1 2 3 4 5 6
>5%
probability
(Rare)
>20%
probability
(Can Happen)
>50%
probability
(Very Likely)
99%
probability
(Will Happen)
SUBSTATION NAME:
TRANSFORMER INSTALLATION DESCRIPTION:
COMPILED BY:
DATE COMPILED:
<5%
probability
(Highly
Unlikely)
FREQUENCY/PROBABILITY OF OCCURRENCE
En
vir
on
me
nt
CO
NS
EQ
UE
NC
ES
(5
CA
TE
GO
RIE
S)
Fin
an
cia
l Im
pa
ct
Pe
op
le E
ffe
ct
Le
ga
l a
nd
Co
mp
lia
nc
e
Co
nti
nu
ity
of
Su
pp
ly
Pairwise comparison scale
A 5-point scale is used
Description Score Process question example
Equal / no difference in importance 1
Moderately more important 2 Main criteria
Strongly more iomportant 3
Significantly more important 4
Extremely more important 5 Sub criteria
G P
1 0.50
1 0.50
G P
0.5 0.20
2 0.80
1.01 1.02 1.03 1.04 1.05 1.06 1.07 G P Lambda 5.9
1.01 1 1/3 1/3 2 1/5 1/5 1/3 0.48 0.05 CI -0.19
1.02 3 1 1/3 1 1/5 1/5 1/3 0.54 0.06 CR -0.13
1.03 3 3 1 2 1 1 1 1.51 0.17
1.04 1/2 1 1/2 1 1/5 1/5 1/2 0.47 0.05
1.05 5 5 1 5 1 1 4 2.43 0.27
1.06 5 5 1 5 1 1 4 2.43 0.27
1.07 3 3 1 2 1/4 1/4 1 1.02 0.11
1.00
2.01 2.02 2.03 2.04 2.05 Geom P
2.01 1 5 1 3 1/3 1.47 0.27 Lambda 7.2
2.02 1/5 1 1 1 5 1.00 0.18 CI 0.56
2.03 1 1 1 3 1/4 0.94 0.17 CR 0.491
2.04 1/3 1 1/3 1 1/3 0.52 0.10
2.05 3 1/5 4 3 1 1.48 0.27
1.00
G P
1 0.17
2.46 0.42
1 0.17
0.407 0.07
1 0.17
1.00
G P
1.414 0.67
0.707 0.33
Reliability Availability
Performance 4 1
Reliability
Availability 1
11
What is the relative importance of Availability compared to Reliability in terms of transformer technical condition based on
increased Risk Exposure ?
What is the relative importance of Product Support compared to Performance w.r.t transformer Availability?
Reliability
1
Product Support 1 1/4
Product Support Performance
3
Financial Impact 1 1/5
Availability
Financial Impact People Effects Legal and Compliance Continuity of Supply Environment
1/2 5 2
People Effects 5
1/3
Continuity of Supply 1/5 1/3 1/3 1 1/2
Legal and Complience
1 2 3
2 1/2 1 3
Technical Condition Consequence/Impact
1Environment 1/2 1/3 3 2
Technical Condition 1 2
Consequence 1/2 1
Technical/Impact Condition
Criteria Weighting
with AHP
Strategy Selection and Decision
Model (Output) Preventative
(TBM)
Predictive
(CBM)
Testing the Strategy Selection
and Decision Model
• Ruacana Generator Transformer (11/330 kV, 90
MVA)
• Auas TX Reactor
(400 kV, 100 MVAr)
• Kokerboom TX Transformer (400/220/132 kV,
315 MVA)
• Omburu TX Transformer
(220/66/22 kV, 40 MVA)
• Rossing TX Transformer
(220/11 kV, 40 MVA)
• Karas T-OFF Reactor/Transformer (220/22 kV
15 MVAr)
Input of Sample
Transformers/Reactors
NamPower Life Assessment and Decision Methodology
Input SheetCriteria
Criteria Weight
Subcriteria
Subcriteria Weight
Total weight 100% 100%
Substation Equipment Name Serial Voltage (kV) MVA/r ManufacturerTechnical
Condition
Impact/
Consequence
Priority
Distance
Ruacana TX Gen TRFR Gen T3 26807 11/330 90 ABB/Powertech 1.65 4.02 4.01
Auas TX Reactor K/B 29986 400 100 ABB/Powertech 1.96 2.57 3.21
Kokerboom TX Transformer T22 29977 400/220/132 315 ABB/Powertech 1.13 2.85 2.81
Omburu TX Transformer T12 H8914 220/66/22 40 GEC 1.75 1.83 2.53
Rossing TX Transformer T2 26676 220/11 40 ASEA 2.38 3.55 4.19
Karas T-Off TX Reactor R1 1447884 220/22 15 Elin 3.50 2.29 4.09
Strategy Selection and Decision
Model (Result)
0
1
2
3
4
5
0 1 2 3 4 5
Ruacana
Kokerboom
Karas T-Off
Rossing
AuasOmburu
Preventative
(TBM)
Predictive
(CBM)
Evaluation of 36 of NamPower’s
66 kV Fleet Transformers (Year 1)
Evaluation of 36 of NamPower’s
66 kV Fleet Transformers (Year 2)
Trending Individual Transformer
Data
3.00
1.00 1.00
3.81
2.55 2.55
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
2010 2011 2012 2013 2014
Omatando TX TRFR 1_66/11 kV
Technical Condition
Priority Distance
1.75
1.5
2.25
3.91
3.81
4.07
3.75
3.80
3.85
3.90
3.95
4.00
4.05
4.10
0.00
0.50
1.00
1.50
2.00
2.50
2010 2011 2012 2013 2014
Onunu TX TRFR 1_66/33 kV
Technical Condition
Priority Distance
Benchmarking Survey
Methodology
The sample reviewed had been allocated as follows: Respondents 63
Companies 39
Objective of the technical questionnaire:
To evaluate and benchmark the research rationale followed
in the study against industry practices for evaluating and
motivating practical implementation by NamPower
Technical criteria responses had been divided as per respondent’s
continent and organisation: Africa 38 Utilities 30
USA 12 Private Companies 20
Europe 7 OEM 7
Benchmarking Survey Results Which of the following maintenance strategies do you believe to be adequate for
integration in a decision model for critical transformer life assessment? (Run To
Failure, Fix Time Maintenance, Design Out Maintenance, Skill Level Upgrade,
Condition-Based Maintenance, All)
Run To Failure6%
Fixed Time Maintenance
23%
Design Out Maintenance
12%
Skill Level Upgrade11%
Condition Base Maintenance
39%
All9%
Benchmarking Survey Results Which of the following transformer risk criteria do you believe to be necessary for
integration in a decision model? Rank 1-6 (Effect on Personnel, Financial Impact,
Environment, Brand Reputation, Legal Compliance, Other)
Survey Respondents NamPower Respondents
Effect On Personnel, 1
Financial Impact, 2
Environment, 4Brand
Reputation, 5
Legal Compliance, 3
Effect On Personnel, 1
Financial Impact, 2
Environment, 2
Legal Compliance, 2
Continuity of Supply, 3
Benchmarking Survey Results
Which of the following transformer technical condition criteria do you believe to be necessary for
integration in an input decision model? Rank 1-14 ( Age, Time in Service, Service History, Network
Criticality, Visual Inspection, Chemical Diagnostics, Electrical Diagnostics, Failures, Spare
Availability, OEM Support, Transformer Loading, Transformer Fault Levels, Network Redundancy,
Other)
Survey Respondents NamPower Respondents
Most Important
Least Important
Most Important
Least Important
Conclusion
It is notable that chemical diagnostics, electrical diagnostic, network
criticality and service history (NamPower’s four main criteria) feature in
the response of the most important criteria from all respondents of all
continents reviewed. The criteria had thus been successfully
benchmarked and found to be valid for implementation against industry
best practices
Recommendations Further testing with the incorporation of a larger sample of transformers
as required data becomes available
Investigation for the re-programming of the current spread sheet
program to integrate and automate the decision methodology with the
current NamPower CMMS program.
A family tree of transformer failures per specific OEM is developed and analysed. The OEM’s rated
with the higher transformer family failing history can then be given higher priority in criticality and
action when referred to transformer technical condition.
Utilise sweep frequency response analysis (SFRA) with electrical diagnostics as baseline data
becomes more available
After final testing, approval and integration of the transformer life assessment and decision
methodology, the framework of the methodology to be utilised for the development of life assessment
and decision methodologies and models for all other NamPower network assets starting with
switchgear
SHARE 2013| 27
Gerhard Myburgh
Engineer: CBM and Projects
+264 61 2052024
+264 81 1224802