# Some features of possible solutions of installing telecontrolled ... Some features of possible...

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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