Paul Dyer

Condition Criticality Risk Rating and Condition

Monitoring in a Distribution Network

PAUL DYERPAUL DYERDAVE OPENSHAWDAVE OPENSHAW

London Electricity GroupLondon Electricity Group

Paul Dyer

What am I going to talk aboutWhat am I going to talk about ??

Risk ManagementRisk ManagementMaintenance strategiesMaintenance strategies

Plant specific diagnosticsPlant specific diagnosticsWhat are the benefitsWhat are the benefits

SummarySummary

Paul Dyer

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

Asset Condition Importance is:

f: Asset Population

f: Probability of Failure

f: Impact of Failure on Business

Population = 35,000

Population = 1,100

The probability and failure impact when considering (say)quality of supply effects may be very different to that whenconsidering (say) environmental effects

For any generic group of assets, asset condition importancecan be expressed as a function of three things:

Paul Dyer

m = Maintenance or Replacement Window

f = Critical Failure (or Uncertainty) Period

m + f = ‘P-F’ Interval

Asset Condition

Time or Duty

Functional Failure

As New

Potential Failure (Fails ConditionAcceptance Criteria)

Unacceptable Risk of Failure

m f

Risk-AverseMaintenance /Replacement Strategy

Hi-Risk (Reactive) Maintenance/ Replacement Strategy

Optimum Maintenance /Replacement Strategy

Paul Dyer

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40 50 60 70 80 90

Infant Mortality

How long ?

How long ?

BATHTUB CURVE

FAIL

UR

E R

ATE

Paul Dyer

Reactive Reactive

FORFOR Considered to be Considered to be

cheapcheap No policy to developNo policy to develop No routine No routine

maintenance to maintenance to budget forbudget for

AGAINSTAGAINST Safety riskSafety risk Unscheduled down Unscheduled down

timetime Damage to plantDamage to plant Teams always to be Teams always to be

readyready Loss of confidenceLoss of confidence

Paul Dyer

FORFOR Easy to predict Easy to predict

labour and planlabour and plan Can ensure Can ensure

maintained before maintained before failurefailure

AGAINSTAGAINST Not easy to predict Not easy to predict

failurefailure Easy to over or Easy to over or

under maintainunder maintain

Time basedTime based

Paul Dyer

Duty basedDuty based

FORFOR Tailored to actual Tailored to actual

usageusage Minimises workMinimises work

AGAINSTAGAINST Needs development Needs development

work to set duty work to set duty levelslevels

Requires hours run Requires hours run or other duty or other duty counterscounters

Paul Dyer

Condition basedCondition based

FORFOR Tailored to plant Tailored to plant

conditioncondition Minimises work and Minimises work and

knowledge of plant knowledge of plant conditioncondition

AGAINSTAGAINST Needs development Needs development

work to set condition work to set condition levels levels

Requires diagnostic Requires diagnostic equipmentequipment

Requires some skill Requires some skill to assess conditionto assess condition

Paul Dyer

Transformer diagnosticsTransformer diagnostics

Moisture and dielectric testsMoisture and dielectric tests Dissolved gas in oil analysisDissolved gas in oil analysis Furfuraldehyde analysisFurfuraldehyde analysis Hydran on/off lineHydran on/off line Metal in oilMetal in oil Particle analysisParticle analysis

Paul Dyer

Maintenance strategiesMaintenance strategiesSwitchgearSwitchgear

So what diagnostics do we have available?So what diagnostics do we have available?1. Discharge1. Discharge

Transient Earth Voltage monitoringTransient Earth Voltage monitoring Ultrasonic detectionUltrasonic detection Radio frequency detectionRadio frequency detection Discharge sensitive gelDischarge sensitive gel

Paul Dyer

Paul Dyer

Maintenance strategiesMaintenance strategiesCable diagnosticsCable diagnostics

Why are we interested in cables?Why are we interested in cables?

Main cause of loss of supplyMain cause of loss of supply Failure is commonFailure is common Adversely affects KPIsAdversely affects KPIs Main nuisance to customersMain nuisance to customers

Paul Dyer

Maintenance strategiesMaintenance strategiesCable diagnosticsCable diagnostics

So what can we do?So what can we do?

Monitor failures Monitor failures Off line partial discharge testsOff line partial discharge tests On line partial discharge monitoringOn line partial discharge monitoring

Paul Dyer

SUMMARYSUMMARY

What measurements are important?What measurements are important? Evaluate the risk to the systemEvaluate the risk to the system

What data tells me most about equipment What data tells me most about equipment operating condition?operating condition?

Do I need to take measurements from each itemDo I need to take measurements from each item How much will it cost ?How much will it cost ?

How much time interpreting the results?How much time interpreting the results? Will the measurements be acted upon?Will the measurements be acted upon?

Paul Dyer

Maintenance strategiesMaintenance strategies

THE ENDTHE END

Any questions?Any questions?