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Condition Criticality Risk
Rating and Condition
Monitoring in a Distribution
Network
PAUL DYER
DAVE OPENSHAW
London Electricity Group
Paul Dyer
What am I going to talk about ?
Risk Management
Maintenance strategies
Plant specific diagnostics
What are the benefits
Summary
Paul Dyer

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Ensure safety of staff and members of the
public
Prevent interruption to supply
Extend the useful life of the asset
Ensure that the most cost effective solutions
in place
Enable informed asset replacement policy
Paul Dyer
F o r a n y g e n e ric g ro u p o f a sse ts, a sse t co n d itio n im p o rta n ce
ca n b e e xp re sse d a s a fu n ctio n o f th re e th in g s:
A sse t C o n d itio n Im p o rta n ce is:
f:
A sse t P o p u la tio n
f:
P ro b a b ility o f F a ilu re
f:
P o p u la tio n = 3 5 ,0 0 0
Im p a ct o f F a ilu re o n B u sin e ss
T h e p ro b a b ility a n d fa ilu re im p a ct w h e n co n sid e rin g (sa y)
q u a lity o f su p p ly e ffe cts m a y b e ve ry d iffe re n t to th a t w h e n
co n sid e rin g (sa y) e n viro n m e n ta l e ffe cts
Paul Dyer
P o p u la tio n = 1 ,1 0 0
As New
m = Maintenance or Replacement Window
Asset Condition
Potential Failure (Fails Condition
Acceptance Criteria)
Unacceptable Risk of Failure
Functional Failure
f = Critical Failure (or Uncertainty) Period
Risk-Averse
Maintenance /
Replacement Strategy
Optimum Maintenance /
Replacement Strategy
Hi-Risk (Reactive) Maintenance
/ Replacement Strategy
Time or Duty
Paul Dyer
m + f = ‘P-F’ Interval
m
f
20
BATHTUB CURVE
18
16
Infant
Mortality
FAILURE RATE
14
12
10
8
6
How long ?
4
2
0
0
10
20
30
40
50
60
70
How long ?
Paul Dyer
80
90
Reactive



FOR
Considered to be cheap
No policy to develop
No routine maintenance
to budget for
AGAINST
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Paul Dyer
Safety risk
Unscheduled down time
Damage to plant
Teams always to be
ready
Loss of confidence
Time based


FOR
Easy to predict labour
and plan
Can ensure maintained
before failure
Paul Dyer
AGAINST


Not easy to predict
failure
Easy to over or under
maintain
Duty based


FOR
Tailored to actual usage
Minimises work
AGAINST


Paul Dyer
Needs development
work to set duty levels
Requires hours run or
other duty counters
Condition based


FOR
Tailored to plant
condition
Minimises work and
knowledge of plant
condition
AGAINST



Paul Dyer
Needs development
work to set condition
levels
Requires diagnostic
equipment
Requires some skill to
assess condition
Transformer diagnostics
Moisture and dielectric tests
 Dissolved gas in oil analysis
 Furfuraldehyde analysis
 Hydran on/off line
 Metal in oil
 Particle analysis

Paul Dyer
Maintenance strategies
Switchgear
So what diagnostics do we have available?
1. Discharge
Transient Earth Voltage monitoring
 Ultrasonic detection
 Radio frequency detection
 Discharge sensitive gel

Paul Dyer
Paul Dyer
Maintenance strategies
Cable diagnostics
Why are we interested in cables?
Main cause of loss of supply
 Failure is common
 Adversely affects KPIs
 Main nuisance to customers

Paul Dyer
Maintenance strategies
Cable diagnostics
So what can we do?
Monitor failures
 Off line partial discharge tests
 On line partial discharge monitoring

Paul Dyer
SUMMARY
What measurements are important?

Evaluate the risk to the system
What data tells me most about equipment operating
condition?

Do I need to take measurements from each item

How much will it cost ?

How much time interpreting the results?

Will the measurements be acted upon?
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Paul Dyer
Maintenance strategies
THE END
Any questions?
Paul Dyer
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