uniten arsepe 08 l16

7/30/2019 UNITEN ARSEPE 08 L16

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MV Switchgear

2008-02-18 ARSEPE 2008 Malaysia 1

Basic Requirements for

Developing a Condition BasedMaintenance (CBM) Plan.Hardanjit S. Gosal [email protected]


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Why do we need to maintain aswitchgear?

To preserve its primary functionsTo improve its availability

ARSEPE 2008 Malaysia 22008-02-18

next failureTo reduce the frequency of service

interruptions and the undesirableconsequences


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Maintenance has a majorimpact on -

Component and System ReliabilityIf too little is done

Hi her number of failures


Poor system reliability

If done regularly at fixed time intervalsReliability will improveCost will increase sharply


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Maintenance of SwitchgearsDeserves Special Consideration

Importance for routine switchingProtection of other primary equipment &


May remain idle in either OPEN orCLOSED positions for long periods of time


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Examples of switchgear failures



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What is Condition BasedMaintenance?

Also known as Predictive MaintenanceIt relies on knowing the condition ofindividual pieces of equipment


It includes:

monitoring equipment parameterstesting on a periodic basis and/or whenproblems are suspectedData analysis and data management


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What is Condition BasedMaintenance?

Results in knowledgeable maintenancedecisions which would reduce overallcosts b focusin onl on e ui ment that


really needs attention


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Drawbacks:

Some parameters are very difficult andexpensive to monitor


analysis to be effectiveCondition monitoring equipment and

systems need to be maintained andcalibrated


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In summary, CBM is:A cost-effective maintenance scheme whereSystem Reliability and Maintenance Cost are

balanced.A methodology that comes under the broadera roach of RCM


In RCM approach, various alternative maintenancepolicies are compared and the most cost-effectivefor sustaining equipment reliability is selected.

It is nearly impossible to apply a condition basedmaintenance program to the entire distributionnetwork.


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Asset Maintenance Strategy

TNB Distribution Division strategy is apractical approach. It is a hybrid i.e. acombination of Condition Based Maintenance


.CBM will be applied to key and critical primaryequipment that has an impact on systemreliability such as:

1. Power Transformers2. Switchgears3. MV UG Cable Feeders


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Asset Maintenance Strategy

PM will continued to be applied to:1. LV UG Cable Feeders2. LV Equipment


3. LV OH Line Feeders4. MV OH Line Feeders5. DC Battery Banks


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How to initiate a CBM Program?

The migration from a purely PM program to CBMis not an easy one. Listed below are some basicsteps that are required to initiate a CBM program:


1. Develop a master list of all primary equipment in yournetwork

2. Prioritize the primary equipment based on theirimportance to system reliability

3. Group them according to voltage rating, type,manufacturer, age, etc


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4. Determine the type & number ofmaintenance activities required andfre uenc usin :


a. Manufacturer technical manualsb. Maintenance historyc. Root cause analysis findings - Why did it fail?d. Good engineering judgment


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5. Assess the size of your maintenance staff.6. Identify tasks that may be performed by your

operations maintenance personnel and those


that can be outsourced to service providers.7. Analyze equipment failure modes and effects

(FMECA).

8. Identify effective maintenance tasks ormitigation strategies.


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FMECAThe FMECA (Failure mode, Effects and CriticalityAnalysis methodology is employed in TNB Distribution toidentify potential failures. For the switchgear or system,assess the risk associated with those failure modes, rankthe issues in terms of importance and identify and carryout corrective actions to address the most serious


concerns:All potential failure modes of the various components ofa systemThe effects these failures may have on the system

How to avoid and/or mitigate the effects of the failures onthe system


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Standards Related to FMECA

FMECA standards are:MIL-STD 1629 Procedures for erformin a


failure mode and effect analysisIEC 60812 Procedures for failure mode andeffect analysis (FMEA)

BS 5760-5 Guide to failure modes, effects andcriticality analysis (FMEA and FMECA)


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Pre-requisites of FMECA

1. Defining the system to be analyzed and dividing it intomanageable units called functional elements.2. Collecting available information that describes the

system to be analyzed; including-drawings,


specifications, schematics, component lists, interfaceinformation and functional descriptions.3. Collecting information about previous and similar

designs through interviews with design personnel,

operations and maintenance personnel and componentsuppliers.


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Limitations of FMECA

In spite of being so popular FMECA alsohas downsides and they are:


, -expensive process.It is not suitable for multiple failures.


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Sample of FMECA

From FMECA:We identified the test techniques andtechnologies to be adopted for CBM of


switchgearsDeveloped Acceptance CriteriaDeveloped a Switchgear Maintenance Manual

Developed a Frequency & Maintenance Matrix


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What is in the manual?

Maintenance ManagementCategorisation of AssetsSafety Procedures


-Commissioning ProceduresMaintenance Servicing ProceduresPost-breakdown ProceduresTest Equipment RequirementsData Analysis & Trending


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Application

Air Insulated Switchgear (AIS) VCB,OCB, GCB.


Ring Main Units (RMU) Oil , SF6.Outdoor Switchgear OCB, VCB.


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Servicing MatrixNo. Test Classification

Routine Diagnostic AdvanceDiagnostic

In-house Out-sourced

1 Physical Audit

2 IR Thermography

3 Ultrasound


4 PD Measurement

5 Gas Purity TNBR Lab

6 Gas Dew-point

7 Gas Leakage

8 Contact resistance


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9 Timing & Travelinclusive of first trip

10 Vacuum Check

11 Contact Erosion & Ad ustment


12 Oil Dielectric

13 HV Dielectric Test

14 Insulation Resistance

15 Tan Delta (DDF)

16 CT & VT Test


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17 Mechanical Functional Check


18 Electrical Functional Check

19 Interlocks

20 Gas Pressure

21 Temperature Scan


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CMMSA computerized maintenance management system(CMMS) is a type of management software that performsfunctions in support of management and tracking ofO&M activities.


CMMS systems automate most of the logistical functionsperformed by maintenance staff and management.CMMS systems come with many options and have manyadvantages over manual maintenance tracking systems.

A CMMS is being developed by TNB Research for TNB-Distribution Divisions CBM Program.


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tnb distribution division : condition based maintenance program

1


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MaintenanceAction

MaintenanceManual

Module 1

Module 2Repository of all maintenance procedures,manuals, guidelines etc.

Tracking and recording of all maintenance actionson each equipment

TNB Research Involve to Solve

Test Results

Decision Support

Maintenance

Planning

Module 3

Module 4

Module 5

Collation of all maintenance test results of all equipments

CBM actions, determining maintenance intervals

Levels of authority2


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Maintenance work orders (generated thruERMS)Date / Time start / endResponsible person


maintenance actions (maintenance testsheets)

FindingsClosing of maintenance work orders

3


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Related PSI documentsEquipment ManualsProceduresGuidelines


Distribution DivisionStored in a central server and available on

demandLinked to Maintenance Action Module

4


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Similar to Patients Medical RecordLinked to Maintenance Action moduleAble to list categories, tabulate resultsGenerate charts and graphs, look for


Used for technical analysis

5


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High level prognostic and diagnostic capabilityEvaluate what next scenariosIncorporate risk-based analysis


Expert system capabilityPrioritise maintenance actionsMake use of database of maintenanceexperience, previous test results, previousfailures, maintenance costs etc.

6


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Linked to current ERMS SAP-PM ModuleList of possible maintenance actionsAccept / Reject output from Decision Support


ModuleAdd maintenance actions (if required)Prioritise Maintenance Action

Generate work order via ERMS

7


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TNB Research Involve to Solve 8


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[email protected]

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