Bibliography Style Ieeetransformercommittee

Presentation on theme: "Maintenance for HV Cables & accessories, practical guidelines"— Presentation transcript:

1 Maintenance for HV Cables & accessories, practical guidelines
Wim BooneFrank de Wild

2 Program Introduction Definitions Maintenance strategies
Survey of presently used maintenance programsFailure modes / Related detection meth. / Maint. actionsAvailable diagnostic toolsMaintenance case studiesRemaining Life EstimationRecommendationsFuture developmentsConclusionsEvaluation

3 IntroductionCIGRE WG B1-04 completed a report in 2005, dealing with the following aspects of maintenance on HV cables, resulting in replying the following main questions:What maintenance practices are being applied at present?What are the causes of failure for cables and accessories?How can potential failures be detected?What guidelines can be given to improve?

4 Introduction (2)The CIGRE report TB 279 contains the following main chapters:A survey of presently used utility maintenance programsA list of common failure modes for cable systems, related diagnostic detection methods and maintenance actionsA list of available diagnostic toolsRecommendations for effective and efficient maintenance

5 Introduction (3)Attention has been focussed on predictive maintenance because:Predictive maintenance (to avoid failures) may contribute to higher reliability and reduced maintenance costsThe application of predictive maintenance is not yet common utility practiceMore tools are now becoming available for a successful application of predictive maintenance

6 Introduction (4)The economics of a predictive maintenance program has not been considered, because:Wide variations in operating frameworks between different countries and/or companiesMore important to focus on assisting cable users to identify diagnostic tools and methodologies

7 Definitions (IEC 60050)Maintenance: the combination of all technical and administrative actions, including supervision actions, intended to retain an item in, or restore it to, a state in which it can perform a required functionPredictive Maintenance: an equipment maintenance strategy based on measuring the condition of equipment in order to assess whether it will fail during some future period, and then taking appropriate action to avoid the consequences of that failure

8 Definitions (2)Preventive maintenance: the maintenance carried out at predetermined intervals or according to prescribed criteria and intended to reduce the probability of failure or the degradation of the functioning item

9 Definitions (3)Corrective Maintenance: to repair or to replace broken componentsTime Based Maintenance: to perform maintenance on a predetermined schedule= preventive maintenanceCondition Based Maintenance: to perform maintenance, based on the results of condition assessment of the component= predictive maintenance

10 Why maintenance? To avoid failures To avoid environmental damage
To avaoid more expensive maintenance laterTo extend the life of the equipmentTo avoid unsafe situationsTo repair failed componentsTo avoid legal and financial penalties

11 Maintenance strategies (1)
According to a CIGRE questionnaire comparing maintenance on switchgear, transformers, lines and cables, cables have the lowest expenditure on predictive maintenance and the highest expenditure on corrective maintenancePossible explanation:Cables are usually invisibleCables do not have moving partsCables have low risk of explosion

12 Maintenance strategy (2)
The available budget is at present obviously not assigned according to the contribution to the overall system reliabilityCables should have a higher maintenance priority as cables and accessories are subject to failure and outage.A CBM approach appears to offer opportunities to detect potential failures and to reduce the probability of failures in service

13 Survey of presently used maintenance programs
To avoid 3 rd party damage:Inspections of cable routesAdministrative procedures to provide cable route information to other parties (using a central ofice to coordinate)

14 Survey of maintenance programs (2)
Extruded cables:Serving testVisual inspection of terminationsThermal monitoringInspection of alarm equipment (if installed in tunnel)

15 Survey of maintenance programs (3)
FF cables:Serving testInspection of terminationsInspection of fluid equipment (pressure, tank)Inspection of fluid alarm equipmentDGA

16 Survey of maintenance programs (4)
Test on specially bonded systemsInspection of link boxInspection of surge arrestorCurrent measurementTo collect statistical dataInnovative actionsTan delta measurementPD measurementAdvanced failure analysis

17 Survey of maintenance programs (5)
Conclusions:Preventive maintenance rather than predictive maintenanceFrequency of maintenance actions decided by the utility involvedCBM not well appliedFailure analysisInvestigation of “coincidental” samplesCollecting information in data base

18 Failure modes / detection methods / maintenance actions
The following cable types are considered:Low pressure self contained fluid filledHigh pressure fluid filledGas compression cablesExtruded cables

19 Failuremodes/detection methods /maintenance actions (2)
A standard list has been compiled according to the following headings:Item: identifies the component in the system involvedEvent/cause: describes the event that has occured to cause failure, damage or degradationConsequence: describes the effect of the eventProbability of occurence: high, medium low

20 Failure modes/detection modes /maintenance actions (3)
Impact: categorised into: Health & Safety, Environment, SystemDiagnostic indicator: the measurable property that changes as a result of the eventMaintenance action: to reduce the probability of the occurrence of the eventEffectiveness: well established/under developmentOn-line / off-line

21 Failure Mode Analysis Tabel
Table headings ExampleEvent Damaged outer sheathConsequence of the event Corrosion sheathProbability of occurrence (H/L) HighImpact (S, H&S, E) SystemDiagnostic indicator Loss of insulationMaintenance action Serving test+repairEffectiveness (WE/UD) Well establishedOn-line/off-line Off line

22 Failure modes of SCFF cables
Damaged cable / oversheath / metal sheath by 3rd partyDamaged metal sheath by corrosion or fatigueIngress of water in cable / accessory or link boxesExternal mechanical stress due to ground changes, thermal expansion / contraction and improper clampingAssembly errorsThermal ageing of insulationFailure of fluid pressure gauges / transducers or gauge contactsMovement of cable due to poor clamping

23 Failure modes of HPFF cables
Damaged cable by 3rd partyLeaking or damaged steel pipe due to corrosionAssembly errorsLeakage of fluid from terminationFailure of fluid feeding and pressurisation system due to fluid leaks in pipework / tank, fluid pump failure, faulty gauges

24 Failure modes of Gas Pressure cables
Damaged cable by 3rd partyLeaking or damaged steel pipe due to corrosionAssembly errorsLeakage of internal fluid from terminationFailure of gas pressure system due to gas leaks, in associated pip work, gas leak from canister and faulty gauges

25 Failure modes of Extruded cables
Damaged cable, oversheath, metal sheath by 3rd partyDamaged metal sheath due to corrosion or fatigueIngress of water in cable accessory of link boxExternal mechanical stress due to ground changes, thermal expansion / contraction (snaking) and improper clampingThermal ageing of insulationAssembly errorsMovement of cable due to thermal cycling or poor clamping

26 Available diagnostic tools
A list of available diagnostic tools has been compiled under the following headings:Tool: identifies the available diagnostic toolDescription of method: summarizes basic principlesEvent/cause detected: describes the event/cause that has occurred to cause the system failure which are detectable with the diagnostic toolComment: regarding the toolOn-line / off-line

27 Available Diagnostic Methods
Table headings ExampleTool Serving testDescription of method DC test 5 minApplication Damaged outer sheathEffectiveness EffectiveOn-line/off-line Off-line

28 Available tools for SCFF cables
Cable route inspectionsIndications of falling oil pressureServing testTemperature measurementThermal backfill surveyPD measurementChemical / physical analysis of fluidX-ray of accessoriesInspection of cable systemRegular gauge maintenance,calibration, alarmSVL test

29 Available tools for HPFF/GP cables
Cable route inspectionInspection of falling fluid pressureElectrical test on pipe coatingInspection of CP systemTemperature measurementThermal backfill surveyChemical / physical analysis of paper and fluidX-ray of accessoriesInspection of cable systemInspection of pumping systemRegular gauge maintenance, calibration, pressure alarm

30 Available tools for Extruded cables
Cable route inspectionServing testTan delta measurementTemperature measurementThermal backfill surveyPD measurementChemical / physical analysis of fluid in terminationX-ray of accessoriesInspection of cable systemSVL testBonding system test

31 Case studies Administr.method to avoid 3rd party damage in the NL
The serving test on 150 kV cables in the NLFluid pressure monitoring in BelgiumEarly leak detection in HPFF cable systems in CanadaLocating leaks in SCFF cables in Canada, using tracer technologyExperiences with CBM on MV power cable systems using PD diagnostics in the NL and ItalyCondition assessment with PD measurementsProbalistic optimisation for external cable damage in France

32 Adminisitr. method to avoid 3rd p.d.
Planned work in the soil at a certain site has to be reported to central office KLICKLIC registers request and send messages to all underground services, who have underground systems in the vicinity of the siteThe owner is asked to provide maps and to give permission to start workThe owner makes a staff member available to attend and to guide workFor each particular activity in the soil specific instructions are given

33 Serving test procedure
Purpose of the oversheath:To protect the cable against mechanical forces during installationTo protect the metallic sheath against corrosionTo isolate the metallic sheath from earth potential for cross bondingTo protect the insulation against ingress of water

34 Procedure of the serving test (4kV/mm-10kV,5min)
Voltage between sheath and earthIf there is a defect, a high leakage current will flow (>10mA)The fault is pinpointed using fault localisation techniquesAfter repair the test will be repeated

35 Fluid pressure monitoring in Belgium
Pressure must be between bar (8 bar for transient pressure)Pressure loss can indicate defect in metal sheath, causing water ingress+ environmental impactPreferably loss of fluid pressure should be detected prior to alarm activation (fluid pressure within safe limits)Visual inspection of termination and fluid tanksPressure gauge readings are taken at each injection point and are compared with previous measurements

36 Fluid pressure monitoring (2)
The urgency of leak location is determined by:Circuit criticalityLeakage rateProximity to waterEnvironmental legislationPublic perception

37 Fluid pressure monitoring (3)
Cost comparison:Preventive maintenance (without fluid loss)Hours of operator to checkCorrective maintenance (with fluid loss)Hours of operatorLocalisationRepair of sheathDecontamination of the soil

38 Fluid pressure monitoring (4)
Correct maintenance (loss of fluid + electric failure)LocalisationRepairDecontamination of soilAll costs related to an electric failure:Repair of cableIngress of waterDamage to other equipmentPower interruption

39 Advanced leak detection methods
Early leak detection using artificial neural networks:In case of small leaks monitoring of fluid level is interfered by fluid movement because of load fluctuationsInput parameters are: load current, cable fluid pressure, cable fluid temperature, soil temperatureOutput from the ELD system, includes the instantaneous leak rate in l/h

40 Advanced leak location methods
Tracer technology:After detection of leak injection of a harmless tracer gas (perfuorinated chemical) in the fluid reservoirThe leaked tracer evaporates from the fluid, moves up through the soil and can be detected in the air above the cable routeAccuracy 0.001%

41 Probabilistic maintenance optimalisation for 3rd party damage
Application of economic modeling to a maintenance policyThe method expresses the links between the failure and the maintenance tasksThe knowledge of an expert will be combined with statistical data, resulting in the optimal maintenance solution:32% preventive maintenance (route inspection, serving test68% corrective maintenance costFrequency cable route inspec. 1m; serving test 3-6 y

42 CBM on MV power cables in the NL
Maintenance strategy is developed to detect potential failures by diagnostic testing (lfpdd)Cost/benefit analysis confirms the economical feasibility:Cost BenefitDiagnostics Outage costsPersonnel Follow up failuresEarly replacement ClaimsEngineering PenaltiesBad reputation

43 CBM on MV power cables in the NL(2)
Selection ctiteria for cable circuits to be diagnosed are based on the following issues:Expected outage timeType of regionCurrent loadingLoad patternNumber of jointsType of soilFailure dataCircuits are excluded from testing, if there are no joints and if they meet n-1 criterion

44 CBM on MV power cables in the NL(3)
Each selection criteria is given a value between 1-4First selection: circuits with total value > 26Second selection: values 23-26Circuits with values < 21 are not selectedConclusions:Cost / benefit ratio <1Reliabilty is increased

45 Remaining Life Management
Maintenance can be performed to extend lifeMaintenance will not be performed on a component of which the RL is expected to be relatively shortCan the result of diagnostic testing, part of CBM, in terms of “risk of failure” be converted into a RLM?

46 Remaining Life Management (2)
Criteria for end of life:High risk of failureHigh cost of operationHigh cost of maintenance

47 An approach for RLM To collect data concerning ageing
To collect data concerning failure statisticsTo develop a methodology for RLMTo prepare practical guide lines for RLMCIGRE WG B1-09 prepares a report on RLM by August2007.

48 General recommendations
Cary out cable maintenance with a clear strategyUse a statistical approach in formulating maintenance policyKeep maintenance strategy under reviewDevelop and maintain a data base of cable system failuresFully investigate failuresPay attention to control 3rd party damageImplement preventive actions appropriate to the cable type

49 Recommendations for SCFF cables
Basic Maintenance:Ensure that cable route information is available and procedures are in place to exchange informationContinuous measurement of fluid pressure and pressure alarmPeriodic serving testPeriodic inspection of outdoor terminationsRegular gauge maintenance and calibration

50 Recommendations for SCFF cables (2)
Regular testing of gauge/transducer alarm functionalityPeriodic visual inspection of link boxesData base including failure events and causesAdditional recommendations:Continuous measurement of gas pressure in terminations and /or low pressure alarmPeriodic inspection of cooling system

51 Recommendations HPFF/GP cables
Ensure that cable route information is available and procedures are in place to exchange informationPeriodic inspections along the cable routeContinuous measurement of pipe fluid pressure and pressure alarmsPeriodic inspection of outdoor terminationsPeriodic inspection program covering the entire fluid feeding systemData base including failure events and causes

52 Addition. Recommend. HPFF/GP (2)
Periodic pipe coating surveyMonitoring of pipe to soil potential (where CP is fitted)Continuous measurement of gas pressure in terminations and/or low pressure alarms

53 Recommendations for extruded cables
Ensure that cable rout information is available and procedures are in place to exchange informationPeriodic inspections along the cable route to check 3rd party activitiesPeriodic serving testPeriodic inspection of out door terminationsPeriodic visual inspection of link boxesData base including failure events and causes

54 Additonal recommendations for extruded cables
Continuous measurements of pressure in terminations and/or low pressure alarmsPeriodic inspection of forced cooling system

55 Future developments Improved hardware and software
Characterisation of extruded insulationImproved non-destructive tetsLinking field tests to laboratory tests

56 Improved hardware and software
On site PDD with enhanced sensitivityNoise cancelationLF dissipation factor measurementsEarly oil-leak detection

In the following section you see how different bibtex styles look in the resulting PDF. The style is defined in the \bibliographystyle{style} command where style is to be replaced with one of the following styles (e.g. alpha, etc.). The following bibliography inputs were used to generate the result:

@article{article, author = {Peter Adams}, title = {The title of the work}, journal = {The name of the journal}, year = 1993, number = 2, pages = {201-213}, month = 7, note = {An optional note}, volume = 4 } @book{book, author = {Peter Babington}, title = {The title of the work}, publisher = {The name of the publisher}, year = 1993, volume = 4, series = 10, address = {The address}, edition = 3, month = 7, note = {An optional note}, isbn = {3257227892} } @booklet{booklet, title = {The title of the work}, author = {Peter Caxton}, howpublished = {How it was published}, address = {The address of the publisher}, month = 7, year = 1993, note = {An optional note} } @conference{conference, author = {Peter Draper}, title = {The title of the work}, booktitle = {The title of the book}, year = 1993, editor = {The editor}, volume = 4, series = 5, pages = 213, address = {The address of the publisher}, month = 7, organization = {The organization}, publisher = {The publisher}, note = {An optional note} } @inbook{inbook, author = {Peter Eston}, title = {The title of the work}, chapter = 8, pages = {201-213}, publisher = {The name of the publisher}, year = 1993, volume = 4, series = 5, address = {The address of the publisher}, edition = 3, month = 7, note = {An optional note} } @incollection{incollection, author = {Peter Farindon}, title = {The title of the work}, booktitle = {The title of the book}, publisher = {The name of the publisher}, year = 1993, editor = {The editor}, volume = 4, series = 5, chapter = 8, pages = {201-213}, address = {The address of the publisher}, edition = 3, month = 7, note = {An optional note} }
@manual{manual, title = {The title of the work}, author = {Peter Gainsford}, organization = {The organization}, address = {The address of the publisher}, edition = 3, month = 7, year = 1993, note = {An optional note} } @mastersthesis{mastersthesis, author = {Peter Harwood}, title = {The title of the work}, school = {The school of the thesis}, year = 1993, address = {The address of the publisher}, month = 7, note = {An optional note} } @misc{misc, author = {Peter Isley}, title = {The title of the work}, howpublished = {How it was published}, month = 7, year = 1993, note = {An optional note} } @phdthesis{phdthesis, author = {Peter Joslin}, title = {The title of the work}, school = {The school of the thesis}, year = 1993, address = {The address of the publisher}, month = 7, note = {An optional note} } @proceedings{proceedings, title = {The title of the work}, year = 1993, editor = {Peter Kidwelly}, volume = 4, series = 5, address = {The address of the publisher}, month = 7, organization = {The organization}, publisher = {The name of the publisher}, note = {An optional note} } @techreport{techreport, author = {Peter Lambert}, title = {The title of the work}, institution = {The institution that published}, year = 1993, number = 2, address = {The address of the publisher}, month = 7, note = {An optional note} } @unpublished{unpublished, author = {Peter Marcheford}, title = {The title of the work}, note = {An optional note}, month = 7, year = 1993 }

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