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  • Some features of possible solutions of installing telecontrolled section

    switches and reclosers in the MV overhead network

    Petr Skala, Vclav Dtich, Zdenk paekEG Brno, a.s.

    Martin PaarBrno University of Technology

  • Evaluation of reliability of distribution systems

    Tools applicable to reliability evaluation Aggregated indices based on average value

    Indices based on other characteristic values of the distribution

    Expressing reliability in financial terms

    Optimization tasks

    Function of damagesValuation of energy not suppliedCosts of penalty payments

    Customers standards in Czech Republic Duration of one interruption

    Limit 12 hours (MV)/ 18 hours (LV) Penalization 10% from annual distribution payment (max. 370 (MV)/185 (LV)

    Response to the fuse operation Limit 6 hours, penalization 37

    To keep the time of planned (noticed) interruption Penalization 10% from annual distribution payment (max. 370 (MV)/185 (LV)

  • Optimization of the telecontrol in MV systems

    Reliability of feederNumber of failuresCauses of failuresDurations of failures (successive restoration)

    Feeder topologyNumber and lengths of lateralsSegmentation of feederLocalization of connections to others feeders providing backup supply

    Localization of customersNumbers of customers on individual feeder sectionsSorts of customers (small-, large-scale customers), their loads and sensitivity to

    interruption (chemical industry, banks, telecommunications, city centers)

    Most important factors influencing optimal number and placement of telecontrol switches on a feeder

    Transformation of electrical diagram to reliability model

  • B

    D

    F E

    G

    A

    C

    Reliability model of the feeder

    Diagram of the feeder

    (1-phase)

    Line section with 3 and more failures(9 years)

    Line section with 1 or 2 failures(9years)

    Section switch

    Section switch(open)

    Connection to another feeder

  • Optimization of the telecontrol in MV systems

    Model of the feederconfiguration, dislocation of consumers, swithces

    Model of reliabilitynon-homogeneity of failure rate of feeder sections

    Simulation of reliabilityannual numbers of failures on the section, durations

    Generating the telecontrol caseschoice of switching points for optimization, types of switches

    Economical evaluationmeeting the standard, penalization, NPV

    Choice of best solution

  • Simulation of reliability

    Simulation of annual numbers of failures on sections (sections between switches)respecting the non-homogeneity of failure rate

    Simulation of successive supply restoration Time of supply restoration by telecontrolled manipulations Time of supply restoration by manual manipulations Time of total supply restoration in the damaged section

    0 60 120 180 240 300 360 420 480 540 6000

    0.1

    0.2

    0.3

    0.4

    0.5

    0.6

    0.7

    0.8

    0.9

    1

    tdm, trm, tuo [min]

    F(t d

    m),

    F(t rm

    ), F(

    t uo)

    [-]

    tdmtrmtuo

    Total restoration

    Restoration by manual

    manipulations

    Restoration by telecontrolled manipulations

  • Optimization of the telecontrol on the feeder

    Simplified connection diagram of the real overhead 22 kV feeder

    B

    D

    F E

    G

    A

    C

    6320 customers 70 switching points

    (beside feeder circuit breaker and switches in front of the distribution transformer stations)

    106 failures during 9 years

    TC closed

    REC closed

    section switch closed

    TC open

    section switch open

    Feeder circuit breaker closed

    Feeder circuit breaker open

  • Optimization of the telecontrol on the feeder

    Switching elements being simulated1. Manually controlled section switch

    2. Remotely controlled section switch (TC) Have remote control Dont have protection function

    3. Recloser (REC) Have remote control Have protection function = customers connected between

    HV/MV station and REC being the nearest one to the failure record long interruption (>3 min)

    Choice of switching elements for optimization Selected according to number of customers upstream and downstream the

    switching point and according to number of failures on line section All possible combinations evaluated

    7 switching points = 2187 possibilities8 switching points = 6561 possibilities

  • Economical evaluationEvaluation of variants

    Composed customers standard (with jump-like penalty) Limit of the annual number of interruptions Ln = 8 failures/year Limit of the total annual duration of interruptions Lt = 18 hours/year Penalization per 1 consumer cp = 16,66 (500 CZK)

    jpzpp CCC ,, =

    Reduction of the costs of penalty payments= penalties for base state penalties for a given variant

    Calculated economical indices Net present value NPV Index of profitability IP (NPV/Ni) Internal rate of return IRR Payback period Tn

    Optimization criterion

    Improvement of reliability in financial terms

    Economical evaluation

  • Optimal equipping of the feederOptimal solution

    Ln = 8 failures/year, Lt = 18 hours/year, cp = 16,66

    Optimal solution = to add 5 reclosersCp = 46 thous./yearNPV = 210,2 thous.IRR = 35,4 %Tn = 3,6 yearSAIDI = - 66 min/year

  • Features of variants of equipping the feederNumber of cases of applying telecontrolled switches for 7 chosen optimized switching points

    Possibilities for a given switching point: Existing sec. switch = 0 Telecontr. sec. switch = 8,3 thous. Recloser = 20 thous.

    2187 variants in total

    1TC 2TC 1REC 1REC+1TC

    Certain investment costs=

    more solutions

  • 0 20 40 60 80 100 120 140-100

    -50

    0

    50

    100

    150

    200

    250

    Investment costs Ni [thous. Euro]

    C

    p [th

    ous.

    Eur

    o/ye

    ar],

    NP

    V [t

    hous

    . Eur

    o]

    CpNPVmax.NPV

    Features of variants of equipping the feeder

    Various magnitude of investment

    Area of the flat optimum= space for considering other

    operational influences and needs

    Envelope curve of NPV= solution with the highest NPV

    for the given magnitude of investment

    Corresponding reduction of the costs of penalty

    payments

  • 0 10 20 30 40 50 60 70 80 90 1000

    25

    50

    75

    100

    125

    150

    175

    200

    225

    250

    Installation variant for Ni = 96.7 thous. Euro

    NP

    V [t

    hous

    . Eur

    o]

    0 10 20 30 40 50 60 70 80 90 1000

    75

    150

    225

    300

    375

    450

    525

    600

    675

    750

    SA

    IDI [

    min

    /yea

    r]

    0 2 4 6 8 10 12 14 16 18 20 220

    25

    50

    75

    100

    125

    150

    175

    200

    225

    250

    Installation variant for Ni = 100 thous. Euro

    NP

    V [t

    hous

    . Eur

    o]

    0 2 4 6 8 10 12 14 16 18 20 220

    75

    150

    225

    300

    375

    450

    525

    600

    675

    750

    SA

    IDI [

    min

    /yea

    r]

    Features of variants of equipping the feeder

    Ni = 100 thous.

    Ni = 96.7 thous. Ln = 8 failures/yearLt = 12 hours/yearcp = 16.66

    Solution for the same investment costs Ni

    The same investment costs=

    various economical effectsmall change of SAIDI

    At the same investment:same SAIDI but very different econom. effect

    SAIDI is not a good measure for the appropriateness of the variant

  • Features of variants of equipping the feeder

    0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200-100

    -50

    0

    50

    100

    150

    200

    250

    300

    350

    400

    Installation variant

    NP

    V [t

    hous

    . Eur

    o]

    0 200 400 600 800 1000 1200 1400 1600 1800 2000 22000

    100

    200

    300

    400

    500

    600

    700

    800

    900

    1000

    SA

    IDI [

    min

    /yea

    r]

    SAIDI and NPV for all possible cases

    A lower limit exists under which SAIDI cannot be reduced by using the measure of the given type

    Ln = 8 failures/yearLt = 12 hours/yearcp = 16.66

  • ConclusionOptimal allocation of telecontrolled elements depends on

    Topology of the feederReliability of the feeder

    It is necessary to take into account observed data for a long period of timeDistribution of customers along feeder

    With regard to ongoing regulation of supply continuity we consider appropriate to express the supply continuity in financial terms by using the customers standards

    when the regulator manifests the tendency to establish a customers standard with a limit of annual number of supply interruptions and a limit of total annual durations

    The using of customers standards may lead to different optimal solutions when compared with the costs of ENS

    Research of influences of regulation on optimal solutions in area of distribution system can bring useful results for

    distributors when looking for robust optimization techniques and decision-making procedures

    regulators bringing them to understand how their regulation could work in real systems

  • petr.skala@egubrno.cz

    Some features of possible solutions of installing telecontrolled section switches and reclosers in the MV overhead networkPetr Skala, Vclav Dtich, Zdenk paekEG Brno, a.s.Martin PaarBrno University of TechnologyEvaluation of reliability of distribution systemsOptimization of the telecontrol in MV systemsS