Languages
Pages
Legal
Some features of possible solutions of installing telecontrolled section
switches and reclosers in the MV overhead network
Petr Skala, Václav Dětřich, Zdeněk ŠpačekEGÚ 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
Customer’s 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 dm
), F(
t rm),
F( t uo
) [-]
tdm
trmtuo
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• Don’t 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 customer’s 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 ,, −=Δ
• 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 reclosersΔCp = 46 thous.€/yearNPV = 210,2 thous.€IRR = 35,4 %Tn = 3,6 yearΔSAIDI = - 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]
ΔC
p [tho
us. E
uro/
year
], N
PV
[tho
us. E
uro]
ΔCp
NPVmax.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 customer’s standards
⇒ when the regulator manifests the tendency to establish a customer’s standard with a limit of annual number of supply interruptions and a limit of total annual durations
The using of customer’s 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
Top Related