This research paper examines the reliability of Haramaya University's power distribution system and suggests improvement techniques. The existing system has serious reliability issues, with root causes including overload, tree contact, wind, aging of poles and equipment, cable failure, and maintenance and operational practices. The study modeled Haramaya University's existing and future distribution systems using ETAP 19.0.1 software and simulated six cases. The results showed that the reliability indices of the existing system are beyond Ethiopian standards. The reliability indices were significantly enhanced in Case 5 (underground ring distribution network), with reduced interruptions per customer per year, shorter interruption durations, and an increased service availability index. The study suggests installing fuses and reclosers in distribution lines, integrating solar distributed generators, and converting an overhead radial network to an underground ring network to improve distribution system reliability.
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reliability assessment of power distribution system.pptx
1. Reliability Assessment of Power
Distribution System
Haramaya University, HiT, SECE
2/16/2024
M.Sc. Thesis Defense Presentation
By: Abdulaziz Adem
Program: Electrical Power Engineering
Major Advisor: Dr. Ramesh Kumar
Co-Advisor: Mr. Wehib Abubeker
3. 1. Introduction
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The purpose of power systems is to provide an
economic and reliable network for electricity.
The role of electric utility is to provide reliable electric
power to the customers.
However, reliability problems in power systems usually
occurs at DS.
Historical and predictive assessment two methods of RA.
SAIFI,SAIDI,,CAIDI, ASAI, ASUI, EENS are commonly used
standard reliability metrics.
4. Statement of the problem
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In Ethiopia, delivering reliable electric power is the role of
EEU, however, power interruptions are becoming a critical
problems.
Particularly, HU DS usually experiences power interruption.
The university is using the diesel generators as a backup
supply.
However, due to high price of fuel, the operating cost of
diesel generator is more.
Considering the problem an assessment of HU DS reliability
was conducted.
5. Objectives
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General objective
To assess the reliability of HU DS and propose improvement
technique.
Specific Objectives
To identify the major causes of power interruptions
To model and simulate existing and under construction HU
DS
To compare existing and under construction DS
To propose improvement technique
To perform cost analysis
6. 2. Literature Review
6
Power System Reliability
Reliability
The probability a system/component performing its
function adequately for a given period time.
Adequacy
Sufficient facilities within the power system to satisfy
customer demand.
Security
The ability of the system to respond to disturbances
arising within the system.
RA :- Generation, composite generation&transmission,
Distribution system ,substation
7. Component Model
7
• Failure rate (λ)
• 𝑀𝑇𝑇𝑅 =
total repair time
total no.of int.s
(2.1)
• µ =
8760
𝑀𝑇𝑇𝑅
(2.2)
• MTTF =
1
λ
(2.3)
• MTBF= MTTF +
MTTR
8760
(2.4)
• U =
MTTR
MTTF×8760
(2.5)
Fig.2.12 :Two-state space
diagram
Fig.2.13 : Mean time
Two-state model
8. Series & Parallel Systems
For n components in series
λs = i
n
λi (2.6)
Us = i
n
λi ri (2.7)
rs =
Us
λs
(2.8)
For 3 components in parallel
λp = λ1 λ2λ3 r1r2 + r2r3 +
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9. Reliability Indices
SAIFI = i λiNi
i Nt
f/yr (2.12)
SAIDI= i riNi
i Nt
hr/yr (2.13)
CAIDI =
SAIDI
SAIFI
hr/int (2.14)
CAIFI = i λiNi
Cn
f/yr (2.15)
ASAI =
Nt∗8760)− i riNi
Nt∗8760)
(2.16)
ASUI= 1−𝐴𝑆𝐴𝐼
(2.17)
EENS = i La i Ui (2.18)
AENS = i La i)Ui
i Nt
(2.20)
9
11. 3. Materials and Methods
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Haramaya substation
Fig.3.1: One-line diagram of Haramaya distribution
substation
12. Calculation of Reliability Indices
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The load point reliability indices have been calculated
using equation (2.6) to (2.8).
The overall system reliability indices have been
calculated using equations (2.11) to (2.20).
Table 3.11: Calculated system reliability indices of HU DS
SAIFI SAIDI CAIDI ASAI ASUI EENS AENS
198.15 275.39 1.4 0.968
6
0.031
4
2167.4
3
103.21
13. Comparison Reliability Indices
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Table 3.12: Comparison of HU DS reliability indices with
benchmarks
Countries SAIFI
(int./cust.yr)
SAIDI
(hrs./cust.yr)
CAIDI
(hrs./int)
ASAI
(%)
USA 1.5 4 2.05 99.91
Denmark 0.5 0.4 1.67 99.981
France 1 1.03 0.97 99.97
Spain 2.2 1.73 1.9 99.968
Germany 0.5 0.38 0.83 99.999
UK 0.8 1.5 1.67 99.964
Canada 3.4 6.9 2.03 99.95
Netherland 0.3 0.55 1.25 99.97
Italy 2.2 0.97 1.77 99.999
Australia 0.9 1.2 1.87 99.97
Ethiopia 20 25 2.23 99.71
HU 198.15 275.39 1.4 96.86
14. Power Interruption Cost
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The outage costs have seen by the utility and the
customers.
Utility side
Loss of revenue
Customer side
Cost of alternative supply
15. Sizing of Solar DG for HU
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PV Syst 7.2 software has been used to size the system.
Data required:-
Load data
Meteorological data
16. 4. Results and Discussions
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The simulation was performed for the following cases.
Reliability
indices
Base
case
Case 1 Case
2
Case
3
Case 4 Case 5
SAIFI 196.38 196.50 1.18 176.8
0
168.53 80.57
SAIDI 277.78 191.98 20.77 123.5
7
118.64 78.44
CAIDI 1.41 0.98 17.60 0.69 0.70 0.97
ASAI (%) 96.83 97.81 99.76 98.59 98.65 99.1
ASUI (%) 3.17 2.19 0.24 1.41 1.35 0.9
EENS 2186.5
7
1509.2
0
290.1
9
981.4
2
958.81 671.33
AENS 104.12 71.87 13.82 46.73 45.66 31.97
17. Cost Analysis
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The reliability of a system can be increased by increasing
investment cost.
Payback Period =
Investment Cost
Annual Revenue Saved
(4.1)
18. …Cost Analysis
18
Table 4.8: Summary of cost analysis for all cases
Case (3)and (4) are profitable for both utility and HU.
Case 5 and 2 are profitable only for HU.
Study
Utility side HU side
Revenue
saved (ETB/yr)
Payback
period
(yr)
Money
saved
(ETB/yr)
Payback
period
(yr)
Case 3 1,414,909.93 1.11 3,297,306 0.48
Case 4 1,141,883.66 2.05 3,423,349.
3
0.7
Case 5 1,784,847.3 34.38 4,328,113.
6
14.17
Case 2 2,239,549.9 77.7 5,762,746.
4
30.2
19. 5. Summary and Conclusion
19
Conclusion:
HU DS is out of service due to unplanned and planned
interruptions.
There are serious reliability problems in HU DS.
The reliability problem in existing system has a negative
impact on economy of utility and customers.
Fuses, reclosers, solar DG, and UG ring network can all
improve DS reliability.
UG ring HU DS has improved system reliability indices.
HU can save 5,762,746.38ETB/yr by constructing an UG
ring DS and the payback period will be 30.2 yr.
20. Recommendations/Future Work
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The next researcher will work on power quality issues
raised when DG is connected to grid.
Case 3&4 are recommended for the utility to implement
(in terms cost).
UG ring DS is recommended for HU to get improved
reliability performance.
Preventive maintenance of existing distribution line are
required on a regular basis.
I recommend Haramaya substation and EEU to enhance
data record experiences.
21. References
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