Cost/Benefit Analysis For Circuit Breaker Maintenance .
Cost/Benefit Analysis for Circuit Breaker MaintenancePlanning and SchedulingPayman Dehghanian, Student Member, IEEE, and Mladen Kezunovic, Fellow, IEEEDepartment of Electrical and Computer Engineering, Texas A&M UniversityCollege Station, Texas, 77843, USAEmails: payman.dehghanian@tamu.edu; kezunov@ee.tamu.eduAbstract— Maintenance planning and scheduling of circuitbreakers (CBs) always involves the cost and benefit analysis.This paper introduces a new framework for cost/benefitassessments using condition-based monitoring data. The signalsmonitored at the CB control circuit are first utilized todetermine the CB deterioration status. This information is usedto decide which type of maintenance, e.g., minor, major, orreplacement, needs to be practiced for different CBs. Systemwide analysis is then performed to assess the cost benefits of themaintenance by calculating the costs imposed to the system inthe case of CB mal-operation. A new benefit to cost ratio (BCR)index is introduced to deal with the CB maintenanceprioritization process. The proposed approach is implementedon a breaker-and-a-half substation configuration and the resultsdemonstrate the applicability of the presented framework in realworld scenarios.I.INTRODUCTIONImproved power system planning and operation policy isone of the main goals in the present economic scenario ofpower industry [1]. Among the main expenditures in powersystem exploitation, maintenance is recognized as a major costfactor due to large number of power system components [1].The power system equipment has been around for a while,hence maintenance tasks need to be adapted to differentequipment ages and various aging mechanisms. Powerindustry has been considering gradually changing fromscheduled maintenance or planned maintenance tomaintenance as needed or condition-based maintenance. It iswidely recognized that it would be ideal for maintenance tobe conducted on the components needing it the most,otherwise unnecessary maintenance action is simply a wasteof time, effort, and money [2]. This requires the powersystem components to be differentiated based on theirdeterioration status on one hand and their role and impact onpower system operation on the other. The components whichhave high probability of failure and those whose failure willdeteriorate power system performance the most need morefocused and more frequent maintenance practices [3], [4].The work reported in this paper comes from a project funded by ARPA-E todevelop Robust Adaptive Topology Control (RATC) solution under GENIcontract 0473-1510.Circuit breakers (CBs) are the components that are used inpower systems in large numbers. They are assigned twomajor roles: to react to protective relay trip decisions bydisconnecting faulted power apparatus and to facilitate theoperator role in performing topology switching needed toreroute power flows or isolate components for maintenance.Hence, special attention needs to be paid to ensure that CBsare reliable and available to operate when necessary [5].Most of the research efforts on the condition monitoring ofCBs have been focused on real time automated monitoringapplications [6]-[9]. Other research direction was moreconcerned with the evaluation of CB impacts on the systemoverall performance in the context of risk analysis and triedto prioritize the maintenance schedule and resourceallocations from the system reliability [10] and security [11]perspectives. The focus was also put on the deteriorationmodeling of the component based on its conditions [12]-[14],where the use of state diagrams in deterioration, inspection,and maintenance modeling has been explored either throughthe Markov approaches or Monte Carlo Simulations.Economic analysis of CB maintenance planning andscheduling, however, has not been widely researched yet,except for recognizing some general and valuable guidelinesas given in the IEEE standard C37.10.1-2000 [15] where theselection of monitoring techniques for CBs has beenapproached through the failure mode and effect analysis andthe economics associated with each type of CB failure havebeen quantified.This paper is focused on proposing a framework for CBcost/benefit analysis to be used in the maintenance planningand scheduling. The paper is structured as follows. Section IIpresents a background on the CB control circuit monitoringsignals and how they can be related to the CB reliability.Section III is devoted to the proposed methodology for thecost/benefit analysis. Numerical analysis is conducted inSection IV, and the conclusions are offered at the end.
II.BACKGROUNDThe approach proposed in [16] has been utilized in thispaper to find the CB’s reliability index. The control circuitmonitoring data (timing signals and waveforms) for certaintime duration is first extracted via the locally installedmonitors. Then, using the signal processing techniquestogether with the expert systems, one can extract variousfeatures of the waveforms [18]. An appropriate probabilitydistribution can be fitted to each of the extracted timingsignals using the current and historical signal records. As newmonitoring data comes in, this distribution assigned to theconsidered signal is updated. The upper and lower limits(permitted values) of each timing signal are then defined. Thetiming value can be considered normal if it falls within thisspan otherwise, it is concluded that this timing value indicatessome problems needing maintenance since some CB partsassociated with the timing signal did not operate properlywithin a certain probability [16]. The CB reliabilityassociated with a timing signal can be obtained by the shadedarea in Fig.1, using (1).σ minμσ maxFig. 1. Probability distribution assigned to a timing signal available fromthe historical data of CB control circuit monitoring.t σ kmaxtkR ( Bi ) f kt ( Bi , t ) dt(1)t σ kminwhere, Rkt ( Bi ) and f kt ( Bi , t ) are, respectively, the reliabilityindex and density function of the kth monitored timing signalassociated with the ith CB in a substation at time t, and[ σ kmin ,σ kmax ] is the accepted interval of the kth timing signal.It has been concluded in [16] that five timing signals,described in Table I, need to be within the specified upperand lower limits for CB to work properly. The reliabilitystatus of each CB as a whole can be then evaluated using (2).5U t ( Bi ) 1 Rkt ( Bi )(2)k 1tthin which, U ( Bi ) is the failure probability index of the i CBtkin a substation at time t, and R ( Bi ) is calculated earlierthrough (1). Worthy to note is that in this way, the reliabilitystatus of each CB in the substation can be calculated at anytime using the available monitoring data. In other words, thereliability index for each CB can dynamically be updatedusing new monitoring data as it arrives. The implementationframework is demonstrated step-by-step in Fig. 2.TABLE ILIST OF EVENTS AND SIGNAL PARAMETERS FOR RELIABILITY INDEXEVALUATION OF SUBSTATION CBSDescription of the eventSignal ParameterTrip coil current picks upt1Trip coil current dips after saturationt2t3Trip coil current drops offB contact breaks or makes (a change oft4status from low to high or vice versa)A contact breaks or makest5Rkt ( B ij )U t ( B ij )Fig. 2. Step-by-step implementation procedure to assess CB reliability index.III.PROPOSED METHODOLOGYA. Concept DevelopmentSince the electric utilities have recently experienced asharp increase in their operating costs on one hand, and withthe recent advent of power system restructuring on the other,the pressure to reduce or control their total costs embracingthe investment, operation, and interruption costs has beenunder much scrutiny so far [3], [4], [17]. Generally speaking,maintenance cost makes a significant contribution to theoverall operating costs of a utility. Furthermore, differentCBs introduce different maintenance costs, differentconsequences on the system performance, and differentfailure costs as well [19].For the time being, although employing continuousmaintenance strategies on all the system componentstechnically improves the overall power system operation,frequent maintenance across the board does not seem to beneither affordable nor economically justifiable. Consideringonly technical parameters without any deserving attention to
the economic aspects may result in some non-optimalsolutions for the maintenance of system components. Hence,selection of the best maintenance strategy for CBs remains tobe of keen interest [11]. Consequently, there is a vital need toconcentrate on the total imposed cost and total achievedfinancial benefits due to the maintenance of CBs.An economic index, called benefit to cost ratio (BCR) isintroduced in (1) which is assigned to the ith CB formaintenance prioritization:BCR i Total Achieved BenefitsTotal Imposed Costs(3)The total imposed cost may include the inspection costs,required manpower costs, material costs, and all thepreventive maintenance associated costs applied on the ithCB. It may be different for different CBs in the system basedon the deterioration levels and aging mechanisms which callsfor different maintenance practices. This cost can be obtainedbased on the previously introduced approach in Section II todifferentiate the CBs on the basis of their component-basedreliability performance.The achieved benefit term reflects what would be theimposed cost if a proper preventive maintenance policy on acertain CB is not applied and it fails. In other words, theproposed approach considers those costs as the benefits ofmaintaining a particular CB; the costs which are imposed dueto the required system re-dispatch, utility lost revenue andcustomer interruption costs as a result of the CB maloperation are considered as the benefits of the preventivemaintenance.The first issue which should be considered in the benefitsis the cost of corrective maintenance that needs to beperformed either in the form of replacement or repair. Thiscost is entirely associated with the component and itsmaintenance plan. However, there are some costs related tothe system-wide consequence of the CB mal-operation orfailure which needs to be quantified.If a CB fails to operate properly, the adjacent CBs mayhave to be operated in response and this may lead to somepower system components being out as a result.Consequently, a system re-dispatch may be needed to avoidsystem security violations and bring the system operationback to the normal conditions. The optimal power flow redispatch cost may be considered as the system-wide impactfrom the system security perspective, which constitutes thesecond monetary term in the analysis. Re-dispatch iscommonly done once a contingency brings some threats tothe system security. The cost associated with the re-dispatchis here considered to be the most direct consequence of theCB contingency. The re-dispatch is not required once a minorcontingency occurs. In such cases, this system benefit maynot be included in the proposed analysis [6].If the mal-operation of a CB leads to a load beinginterrupted, there will be some other costs imposed from thesystem reliability perspective. If a CB failure leads to theoutage of a customer load, an interruption cost would beconsequential. This can be interpreted in two aspects: one isfrom the utility viewpoint and the other associated more withthe customers’ perspective. The former reflects the lostrevenue the utility could obtain in return for the sold energyand power while in the cases of CB mal-operations, the utilitycannot receive the benefits anymore. The later highlights thecustomer interruption costs which need to be paid to thecustomer in compensation for the interrupted service. This isyet another monetary cost which will be taken into account inthe proposed cost-benefit methodology. Quantifying the BCRindex leads to a cost-effective prioritization of CBmaintenance plans and scheduling. The CBs with the higherBCR index would be placed in the top of the prioritization listfor prompt maintenance considerations. Those CBs placing inthe end of the list are not economically attractive formaintenance in substations.B. Mathematical FormulationsThe total imposed costs are essentially considered to be thepreventive maintenance expenses incurred while maintaininga CB within a desirable limit of availability. The cost isdependent on the deterioration level of the CB under studyand hence could be different for various CBs in the system.Again, it may include the maintenance expenses associatedwith the maintenance process, required manpower (labor),and necessary materials. All the maintenance costs arereflected in:Ci (U t ( Bi )) CiPM (α β .rβ )i .WhiPMPM(4)where, the following parameters are defined.CiCost function used in the BCR index for the ith CB.mTotal preventive maintenance cost on the ith CB.CiαβrβThe CB constant cost per repair and maintenance.The CB variable cost per repair and maintenance.Average outage time per CB maintenance trial.U t ( Bi )The failure probability index assigned to the ith CB.WhiWorking hours required for maintenance on ith CB.The maintenance costs are assumed to be guided by alinear relationship. A constant amount of money is assumedto be spent for any repair or scheduled maintenance on a CB.A variable amount of money is, in addition, assumed to bespent for each hour of outage duration for preventivemaintenance. The maintenance cost is assumed to bedependent to the CB failure probability index highlighting thefact that a higher maintenance cost would be required for theCBs with higher failure probability index. In this way, thedeterioration status of different CBs can be incorporated intothe economic analysis. Maintenance cost is the only cost termconsidered in the proposed benefit/cost ratio.In terms of benefits, there would be a correctivemaintenance cost imposed as the CB fails which can beformulated as follows.
BiCM (U t ( Bi )) (α β .rβ )i .WhiCMCM(5)where, B is the monetary benefit associated with thepostponed corrective maintenance cost on the ith CB due tothe planned preventive maintenance action. The otherparameters are the same as those introduced in (4) but appliedto the corrective maintenance schedule.In order to model the probable re-dispatch cost required toturn the system back into its normal operational conditionafter a CB mal-operation or failure, the cost function below istaken into account. The objective function is simply asummation of individual polynomial cost functions f Pj andCMif Qj of real and reactive power injections, respectively foreach generator j.OPFiB ng min ( f Pj ( pgj ) f Pj ( q gj ) ) θ ,Vm , Pg , Qg j 1 θ jref ,min θ j θ jref ,max(6)j Γ ref(7.a)Vmj ,min Vmj Vmj ,maxj 1.nb(7.b)pgj ,min pgj p gj ,maxj 1.ng(7.c)q gj ,min q gj qgj ,maxj 1.ng(7.d)BiIC EENSi .VOLLkAC OPF model with the constraints introduced in (7).θ ,Vm , Pg , Qg are representing the voltage angle and magnitude,and active and reactive power of the generator j, respectively.Also, ng and nb are the number of generators and buses in thesystem, respectively.As the third item in the evaluation of a CB maintenancebenefit, one must take into account the utility lost revenuewhich will happen if a particular CB fails and some loads areinterrupted as a result, which is quantified as in (8).(8)in which, BiLR is the monetary benefit associated with theutility lost revenue when the ith CB failure leads to a loadinterruption, EENSi stands for the expected energy notsupplied due to the load interruption, and EP is the electricityprice at which the energy is sold by the utility. This benefitfor a particular CB is actually the revenue which could beobtained if proper preventive maintenance actions wereplanned on that CB and the energy could be delivered/ sold.The last term to be considered as the benefit of a CBmaintenance is the interruption costs which can beconsequential if a particular CB failure leads to a loadinterruption due to lack of proper maintenance. This factor,which reflects the CB maintenance criticality from the(9)in which, BiIC is the benefit associated with the cost incurredonce the system kth load point is interrupted due to the failureor mal-operation of the ith CB in the substation, EENSi is thesame as introduced earlier in (8), and VOLLk is the value oflost load associated with the kth load point. This is, in fact, thecustomer discomfort cost and may have to be paid to thecustomer in compensation for the interruption.As the various terms of the benefits associated with the CBmaintenance are calculated, the overall monetary benefit canbe obtained as follows.Bi BiCM BiOPF BiLR BiIC(10)The BCR index can then be calculated for each CB whichreflects the economic criticality of the particular maintenanceplan and schedule. From an economic point of view, theultimate goal here is to maximize the BCR index. As a result,the CBs can be prioritized based on the CBR index reflectingthe most economically attractive maintenance plans andschedules.IV.BiOPF is the objective function commonly approached in anBiLR EENSi .EPcustomers' viewpoint, is quantified as follows [20].PERFORMANCE EVALUATIONA. Substation under StudyThe proposed decision making framework based on thecost-benefit analysis is applied to the IEEE 24-bus testsystem. A total of 24 substations exist in the test system. Thesubstation 16 has the breaker-and-a-half configuration and itis taken as the focus of the study in this paper, as shown inFig. 3. A generator (G) of 155 MW capacity is located thereand, 8 breakers (B1-B8) and 4 transmission lines (L) areused to route power and feed the attached load of 100 MW[21]. All the required system and substation data areborrowed from [21], [22].B. Data and AssumptionsIn order to conduct the cost-benefit analysis, thedeterioration stages associated with different CBs in thesystem have to be identified so that it is possible to know themaintenance costs of each breaker. The common way toidentify the deterioration stages for a component (CB in thispaper) is by taking the past duration of its operation intoaccount, e.g. the minor deterioration stage is reached, onaverage, in three years of the CB being installed andoperated, the major one in six, and so on. This can be doneusing the historical inspection data and related monitoringsignals. The costs associated with various deterioration stagesare assumed to follow the trend introduced in Table II, wherePM and CM respectively stand for the preventive andcorrective maintenance. The PM costs are borrowed from[14] and the CM costs are assumed to be twice that of PM.The CBs are assumed here to follow the deterioration statusin Table III.
an order from the highest to the lowest. The results are shownin Fig. 4. As can be observed, CB6, CB8, and CB3 are theones with the highest BCR indices compared to the othersand, as a result, are the most critical ones for a cost-effectivemaintenance management in the substation.The point to emphasize is that CB6, although healthy, isthe most economically attractive one for preventivemaintenance actions since if it fails, a huge financialconsequence would be the outcome. So, it needs to be wiselymaintained.V.Fig. 3. Substation 16 - breaker-and-a-half configuration.The electricity price is taken to be 13 cent per kWh [23] andthe load is assumed to be an industrial one with the VOLL of5 /kWh [24]. A switching time of 1 hour is considered forthe consequence evaluation in the case of system redispatches [20] and the CB average repair time is consideredto be 3 hours.C. Numerical AnalysisProposed formulations are applied to the substation understudy and the associated cost and benefit terms for CBs arecalculated as tabulated in Table V. As an example, assumeCB3 fails to operate successfully when, either clearing a faulton L29 or a fault on BB2 or maybe as a result of failure dueto operator-initiated switching action. In the case of a need toclear the fault, the adjacent CBs, i.e., CB2, CB6, and CB8need to open and as a result, the L29, BB2, and the load therewould be out which would affect the consequence terms inthe analysis. Corrective maintenance also has to be conductedon CB3 in form of either a replacement or repair. The costsfor the maintenance, the OPF-related cost required for thesystem re-dispatch to mitigate any security violation, theinterruption cost of the load and the utility lost revenue forthe interruption will contribute to the benefit of CB3preventive maintenance policies. The cost of preventivemaintenance for CB3 has been also considered to be 2400according to Table II since its failure probability index is0.2379, which is within the 0.2 and 0.4 specified span forminor deterioration. The same explanations can be conductedfor the other CBs under consideration, too. The BCR indexwould be finally consequential for each CB, which reflectsthe cost-effectiveness criticality assigned to each of them, asdemonstrated in Table IV. As can be seen, the failure or maloperation of some CBs has not led to the load to beinterrupted (CB1, CB2, CB4, and CB5) at all since the systemis strong enough to completely recover itself by a re-dispatch,while in some other cases (CB3, CB6, and CB8), the load hasbeen fully interrupted. The load has been partially interruptedin the case of CB7 failure after a re-dispatch since thegenerator is out. This may not be the case for other systems.The CBs can then be prioritized based on the BCR indices inCONCLUSIONThe cost-benefit framework for CB maintenance proposedin this paper leads to the following conclusions: In the present economic scenario of power industry,both the imposed component maintenance costs andachieved power system operational benefits associatedwith the CB preventive maintenance practices needspecial attention. The presented approach differentiates various CBs in asubstation according to their deterioration status andconsequently affects maintenance practices andassociated costs.TABLE IICB DETERIORATION STAGE CONDITIONS AND THE ASSOCIATED PM AND CMMAINTENANCE COSTSDeteriorationFailure ProbabilityPM CostCM Cost ofStageIndexof CB ( )CB ( )HealthU t ( Bi ) 0.2200400Minor0.2 U t ( Bi ) 0.412002400Major0.4 U t ( Bi ) 0.61440028800144000144000FailuretU ( Bi ) 0.6TABLE IIIDETERIORATION STATUS OF THE SYSTEM CBS IN THE ANALYSISCBsU t ( Bi )Deterioration hMajorHealthMinorMinorBCR indexSubstation CBsFig. 4. CB maintenance prioritization based on the cost-benefit analysis.
System CBsCB1CB2CB3CB4CB5CB6CB7CB8TABLE IVCOST/BENEFIT ANALYSIS FOR THE COST-EFFECTIVE MAINTENANCE MANAGEMENT OF THE SUBSTATION CBSMaintenance Benefit IndicesTotal BenefitsTotal CostsBiCM ( )BiOPF ( )BiLR ( )BiIC ( )Bi ( )Ci ( )NormalizedBCR 763790.0423240.113173 The proposed framework recognizes maintenancebenefits associated with the impact of the CB failure onoverall power system performance including redispatch costs, customer interruption costs, utility lostrevenue and, the corrective maintenance costs. Economic attractiveness of the proposed approach isthat the maintenance planning and scheduling can bepracticed based on the Benefit-to-Cost index associatedwith the substation CBs. The offered solution gives a choice to the assetmanager to decide on the CB maintenance schedulingin an order of cost-effectiveness. CBs prioritization on the basis of the proposedapproach could also provide considerable long-termsavings since the maintenance planning and schedulingis done in an economic manner.VI.[1]REFERENCESJ. Endrenyi, et.al., "The present status of maintenance strategies and theimpact of maintenance on reliability," IEEE Transactions on PowerSystems, vol.16, no.4, pp.638-646, Nov 2001.[2] P. Dehghanian, M. Fotuhi-Firuzabad, S. Bagheri-Shouraki, and A. A.Razi Kazemi, “Critical Component Identification in Reliability CenteredAsset Management of Power Distribution Systems via Fuzzy AHP,”IEEE Systems Journal, vol. 6, no. 4, pp. 593-602, 2012.[3] P. Dehghanian, M. Fotuhi-Firuzabad, F. Aminifar, and Roy Billinton,“A comprehensive scheme for reliability centered maintenance in powerdistribution systems-Part I: methodology,” IEEE Trans. Power Del., vol.28, no. 2, pp 761-770, April 2013.[4] P. Dehghanian, M. Fotuhi-Firuzabad, F. Aminifar, and Roy Billinton,“A comprehensive scheme for reliability centered maintenance in powerdistribution systems-Part II: Numerical Analysis,” IEEE Trans. PowerDel., vol. 28, no. 2, pp 771-778, April 2013.[5] R. D. Garzon, High-Voltage Circuit Breaker; Design and Applications.Taylor& Francis, USA: Marcel Dekker, 2002.[6] J. D. McCalley, et.al., “Automated Integration of Condition MonitoringWith an Optimized Maintenance Scheduler for Circuit Breakers andPower Transformers,” 2006. [online] Available: http://www.pserc.org.[7] M. Kezunovic, et.al., “Automated monitoring and analysis of circuitbreaker operations,” IEEE Trans. Power Delivery, vol. 20, no. 3, pp.1910-1918, July 2005.[8] M. Kezunovic, et.al., “Automated Circuit Breaker Monitoring andAnalysis”, IEEE PES summer meeting, July 2002.[9] M. Kezunovic, X. Xu, and D. Wong, ‘‘Improving circuit breakermaintenance management tasks by applying mobile agent softwaretechnology,’’ Asia Pacific. IEEE/PES Transmission and DistributionConference and Exhibition, vol.2, pp. 782- 787, 6-10 Oct. 2002.[10] S. Natti and M. Kezunovic, “A Risk-Based Decision Approach forMaintenance Scheduling Strategies for Transmission [22][23][24]Equipment,” 10th International Conference on Probabilistic MethodsApplied to Power Systems, Singapore, May 2008.P. Dehghanian, M. Kezunovic, G. Gurrala, and Y. Guan, “SecurityBased Circuit Breaker Maintenance Management”, IEEE Power andEnergy Society (PES) General Meeting, July 21-25, 2013, Vancouver,British Columbia, Canada.S. K. Abeygunawardane and P. Jirutitijaroen, “New State Diagrams forProbabilistic Maintenance Models,” IEEE Trans. on Power Systems,vol.26, no.4, pp.2207-2213, Nov. 2011.T. M. Welte, ‘‘Using state diagrams for modeling maintenance ofdeteriorating systems,’’ IEEE Trans. Power Syst., vol. 24, no. 1, pp. 58--66, Feb. 2009.J. Endrenyi, G. Anders, and A. L. da Silva, ‘‘Probabilistic evaluation ofthe effect of maintenance on reliability-----An application,’’ IEEE Trans.Power Syst., vol. 13, no. 2, pp. 576---582, May 1998."IEEE Guide for the Selection of Monitoring for Circuit Breakers,"IEEE Std C37.10.1-2000 , 2001.S. Natti and M. Kezunovic, “Assessing circuit breaker performanceusing condition-based data and Bayesian approach,” Electric powerSystems Research, no. 81, pp.1796-1804, 2011.M. Tasdighi, H. Ghasemi, and A. Rahimikian, "Residential MicrogridScheduling Based on Smart Meters Data and Temperature DependentThermal Load Modeling," IEEE Trans. on Smart Grid, in Press, 2013.C.D. Nail, Automated circuit breaker analysis, M.Sc. Thesis, Dept. ofECE, Texas A&M University, College Station, TX, 2002.Y. Guan, M. Kezunovic, P. Dehghanian, and G. Gurrala, “AssessingCircuit Breaker Life Cycle using Condition-based Data”, IEEE Powerand Energy Society General Meeting, 21-25 July 2013, Vancouver,Canada.R. Billinton, R.N. Allan, Reliability evaluation of power systems. 2ndedition, New York: Plenum Press, 1996.C. Grigg, et.al., “The IEEE Reliability Test System-1996. A reportprepared by the Reliability Test System Task Force of the Application ofProbability Methods Subcommittee,” IEEE Transactions on PowerSystems, vol.14, no.3, pp.1010-1020, Aug 1999.‘‘Three-Phase, Breaker-Oriented IEEE 24-Substation Reliability TestSystem,’’ available on-line at: http://pscal.ece.gatech.edu/testsys.Available online at: http://www.eia.gov/electricity/monthly/.J. Choi, T. D.Mount, R. J. Thomas, and R. Billinton, “Probabilisticreliability criterion for planning transmission system expansions,” Proc.Inst. Elect. Eng., Gen., Transm., Distrib., vol. 153, no. 6, pp. 719–727,Nov. 2006.
maintenance as needed or condition-based maintenance. It is widely recognized that it would be ideal for maintenance to be conducted on the components needing it the most, otherwise unnecessary maintenance action is simply a waste of time, effort, and money [2]. This requires the power system components to be differentiated based on their
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Cost-benefit analysis in practice cost-benefit analysis seems thoroughly entrenched in the federal bureaucracy. (p.5, Adler and Posner, 2000.) “if government agencies should employ cost-benefit analysis, then they should do so because it is a beneficial tool, not because the sum-of-compensating-variations test or any related test has basicFile Size: 383KB
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