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  • Reliability Centered Maintenance - use in

    practice

    VB-TU OstravaFaculty of electrical engineering

    and informatics

    Stanislav Rusek,Vladimr Krl,Radomr Go o

    and others

    pindler v Mln 2017

  • The objective of RCM is to create such amaintenance strategy as to minimize thetotal operating costs while maintaining thenecessary level of reliability, safety andenvironmental friendliness of the operatedfacilities.

    RCMReliability Centered Maintenance

  • simple, over dimensioned facilities low level mechanization

    corrective maintenance

    Maintenance history

    up to the 1950s

    1950s - 1970s

    post-war period industrial development, more complicated

    facilitiespreventive maintenance

  • development of metering and diagnostics methods

    subordination of maintenance to the real needs of the facilitiesmaintenance according to condition

    Maintenance history

    1980s

    1990s

    effort to achieve the highestmaintenance efficiency

    consideration of the, so-called,importance of the facilityreliability focused maintenance

  • Types of maintenance

    corrective maintenance

    TS (%)

    t1 t2 t3 t4time t

    t1, t2, const., TS1 = TS2 == 0

    100 %

    preventive maintenance

    TS (%)

    t1 t2 t3 t4time t

    t1 = t2 = onst., TS1, TS2, const.

    100 %

  • Types of maintenance

    maintenance according to condition

    reliability focused maintenance

    TS (%)

    t1 t2 t3 t4time t

    t1, t2, onst., TS1 = TS2 == const.

    100 %

    maintenance

    TS (%)

    t1 t2 t3 t4time t

    t1, t2, const., TS1, TS2 , const.

    100 %

  • Criteria, which reflect the importance of the elements for the given power distribution company.

    The criteria in this category must express the completeness and adequate number of input data for establishment of the RCM system.

    The third group of criteria must consider the nature of recoverability, i.e. the fact that perhaps the existing maintenance system shall not be changed for some elements.

    Criteria for selection of elements for RCM

  • Determination of all devices that will be subject to maintenance and shall thus be applied in the actual RCM process.

    Definition of the functions of these devices.

    Determination of the resultant device aging model.

    Definition of the importance of the device.

    Identification of the device failures and their consequences.

    Construction of an equation of total operating costs for the device and identification of the best forms of maintenance.

    RCM procedure

  • Importance of an element

    Transformer 22/0.4 kV

    household industrial plant

    importance

    Transformer 22/0.4 kV

  • Possible approaches to RCMDetermination of the optimal

    maintenance intervalDetermination of the order of

    elements for maintenanceThe number of elements of a given type is large.

    The number of elements of a given type is not large.

    The importance of the element is generally low. The importance of the element is high.

    It is not possible to ascertain the costs relating to a specific element.

    It is necessary to define the limit from which maintenance must commence.

    When analyzing an incident (outage, failure), it is not possible to ascertain a specific element.

    When analyzing an incident (outage, failure), it is possible to ascertain a specific element.Monitoring of the device is possible(on-line, off-line, diagnostics).We must be capable of determining the condition and importance of the device.

  • Block diagram

    RCMProgram

    Importance

    TIS FIS

    Regulations

    RCMProgramCriteria

    Importance

    TIS FIS

    Regulation

    Coordinatesof the equipment

    optimal maintenancecycle

  • Optimization of maintenance cycle

    Cost curve

    VOUC NNNN

    U1UU NNMaintenance costs Repair costs

    PKO1O NN

    U

    P

    PPK e - 1

    Corrected failure rate Outage costs

    PNVPKV NPTN

  • NMMO number of retail households connected to the given DTS

    NMOP number of retailers connected to the given DTS

    NVO number of wholesalers connected to the given DTS

    kMMO coefficient of retail households with value 1

    kMOP coefficient of retailers with value 5

    kVO coefficient of wholesalers with value 50

    T DTS type - 2 for containerized and brick walled, 1 for the rest

    P DTS load (kW)

    kp weight coefficient of load

    Division of the DTS according to credits

    PVOVOMOPMOPMOOMOO )( kPTkNkNkNKredit

  • Application to the DTSCost dependence graph - 2002

    (DTS with maintenance downtime)

    0

    500

    1000

    1500

    2000

    2500

    3000

    3500

    4000

    4500

    5000

    5500

    6000

    0 0,05 0,1 0,15 0,2 0,25Maintenance rate

    Cos

    ts [

    CZK

    ]

    Total. costs.Maintenance costs.Breaker costsMaintenance downtimecostsRepair costs.

  • Categorization of DTS into groups

    1989

    4966

    1333

    0

    765

    184

    3368

    43257

    71607

    34278

    349788

    408507

    0%

    10%

    20%

    30%

    40%

    50%

    60%

    70%

    80%

    90%

    100%

    Number of DTS Total VO Total MOP Total MOO

    A

    B

    C

  • Optimization of DTS maintenance cycle

    Comparative graph of the maintenance cycls of individual DTS groups( Pro: kned = 500 ) s .p.

    0

    1000

    2000

    3000

    4000

    5000

    6000

    7000

    8000

    9000

    10000

    0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4

    Optimal maintenance rate

    Cos

    ts (C

    ZK)

    C

    B

    A

  • Optimization of DTS maintenance cycle

    Total number of DTS - 8,613.

    Till 2004 standard maintenance in a cycle of 4 years.

    Division into 3 groups according to RCM: A - 1,606 units, period of 4 years

    A - 4,940 units, period of 6 years

    A - 2,067 units, period of 8 years

    Reduction of dust nuisance by 31% per year.

    Given an average standard maintenance cost of CZK 3,022 for one DTS, this represents a total maintenance cost saving for all DTS in the DS, Moravia Region in the amount of CZK 2 millionper year.

  • 22 kV linesDivision of the lines into sections

  • NMMO number of retail households connected to the given sectionNMOP number of retailers connected to the given sectionNVO number of wholesalers connected to the given sectionkMMO coefficient of retail households with value 1kMOP coefficient of retailers with value 5kVO coefficient of wholesalers with value 50kk weight coefficient of clientsI element load - current (A) kI weight coefficient of element load - currentV line section type - trunk V=5, main branch Vho=1, secondary branch Vpo=0.1Z possibility for output reserve for customers - without a reserve possibility Z = 1, remote controlled element Z=0.1, manually controlled element Z=0.5

    Evaluation of the importance of the line

    ZVkIkkNkNkNKredit I ))(( kVOVOMOPMOPMOOMOO

  • The importance of individual groups of line sections isdeterminant for enumeration of the costs upon unplannedoutage (failure to supply power) and has a direct impact onthe line section maintenance cycle.Using the mean values of the credit intervals of the individualline groups, determination of the importance multiples - VX isdone for the individual line section groups.

    Credit intervals in groups

    Group A max. > credits >= 50,000Group B 50,000 > credits >= 15,000Group C 15,000 > credits >= 2,000Group D 2,000 > credits >= 0

  • According to the limits given inthe previous table, the numberof sections in the individualgroups were determined.

    Group A 289Group B 855Group C 224Group D 56

    Due to the fact that the failure rateand financial flow data are related toa kilometer of the line, it isnecessary to determine the averagelength of the line per section andsubsequently the length of the line inthe individual groups.

    Group A 1,637Group B 4,843Group C 1,269Group D 317

    Determination of the number of sections

  • Cost function in the individual categories according to significance for faults, which can be impacted by

    maintenance

    0

    1000

    2000

    3000

    4000

    5000

    6000

    7000

    8000

    9000

    10000

    11000

    12000

    0 0,05 0,1 0,15 0,2 0,25

    Optimln intenzita drby

    Nkl

    ady

    (K)

    D

    C

    BA

    kned = 1

  • Cost function in the individual categories according to significance for faults, which can be impacted by

    maintenance

    kned = 24

    0

    2000

    4000

    6000

    8000

    10000

    12000

    14000

    16000

    18000

    20000

    22000

    24000

    26000

    28000

    30000

    0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4

    Optimln intenzita drby

    Nkl

    ady

    (K)

    D

    C

    B

    A

    Optimln cyklus drby: 4 roky

    7 rok Skupina C a D maj optimln cyklus drby do poruchy

  • Cost function in the individual

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