Renewable Energy and Sustainable Development (RESD) Volume 3 Issue 1, Special Issue, March 2017 - ISSN 2356-8569
http://dx.doi.org/10.21622/RESD.2017.03.1.019
This Paper has been Accepted and Presented in the (First International Conference on New Trends for Sustainable Energy)
1-3 October, 2016 at Pharos University, Alexandria, Egypt
19
Development of Reliability Indices for Electric Distribution
Network in Egypt
Eman Ahmed, Sherein Abdualla, Kamelia Youssef and Hatem Waheed
Egyptian Electric Utility and Consumer Protection Regulatory Agency
sharino@hotmail.com, white_storm100@yahoo.com
Abstract - Reliability indices (RIs) are the elemental
benchmark used by Egyptian Electricity Holding
Company (EEHC), and the Electric Utility and
Consumer Protection Regulatory Agency (Egypt ERA)
to evaluate the continuity and compliance of supply,
which surpasses the customer's requirements and
satisfaction.
The power system is very complex, mixing huge
different types of generating resources and clusters to
supply electric power through transmission and
distribution system to a number of customers with
varying requirements.
The main function of electric system is to supply
customers with electric energy that has an acceptable
degree of reliability and quality. The power system
continuity of supply level is controlled through system
indices. The most widely used reliability indices are
SAIFI, SAIDI and CAIDI (IEEE std. 1366-2000).
Historical electrical indices, reliability indices threshold
and satisfaction index are used as guide for electric
network performance, which measure the adequate
and secure power supply.
The paper presents the reliability indices, relation
between indices and satisfaction area to highlight the
appropriate guideline values for electric systems, also
presents the development of indices since 2011 to
now for distribution network in Egypt.
Keywords - Reliability; Power System; Benchmark;
Continuity; Indicators.
I. INTRODUCTION
The Egyptian Electricity Holding Company (EEHC)
mission towards the society is to supply electricity to
all types of consumers according to international
performance standards taking into consideration all
environmental, social and economic determinates
and also the terms and conditions set by The
Egyptian Electric Utility and Consumer Protection
Regulatory Agency (EGYPTERA).
EEHC has sixteen affiliated companies as shown in
“Fig. 1” (six generations (EPC), nine distributions and
the Egyptian Electricity Transmission Company
(ETC)).
Fig. 1. the relation between EEHC and Egypt ERA
The main objectives of electricity Distribution
Company
(EDC) are:
Distributing and selling to consumers on medium
and low voltages.
Managing, operating and maintaining medium
and low voltages grids in the company.
Ensuring high level of quality, availability and
continuity of supply to distribution customers.
http://dx.doi.org/10.21622/RESD.2017.03.1.019
Renewable Energy and Sustainable Development (RESD) Volume 3 Issue 1, Special Issue, March 2017 - ISSN 2356-8569
http://dx.doi.org/10.21622/RESD.2017.03.1.019
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The following procedures have been taken to
improve
Continuity of supply indices:
Analysis of the causes in case of increased
unplanned interruptions and relate it to network
renovation and Rehabilitation plans.
Follow up the implementation of maintenance
programs to insure optimizations of interruption
of supply time and at the same time
implementation of the maintenance procedures
with high quality.
Intensive field inspections and data collection for
interruptions.
Each EDC consists of number of geographical
sectors, Have number of districts. The district network
consists of MV distributors, distribution transformers
(MV/LV), and MV, LV lines, as shown in “Fig.2”.
EEHC and EGYPTERA use RIs to trace the
Performance of EDCs. EGYPTERA most commonly
uses KPIs: SAIFI, SAIDI, CAIDI, ENS and CENS.
II. PERFORMANCE INDICES (PIS)
Recommended interruption indices or key
performance indices (PIs) are those defined in both
IEEE 1366[1] and the CIGRE study committee C2 [2]:
SAIFI (System Average Interruption Frequency
Index): the average number of sustained
interruptions per customer during the year.
SAIDI (System Average Interruption Duration
Index): the average time for which customers
power supply is interrupted in a year.
CAIDI (Customer Average Interruption Duration
Index): the average time required to restore
service to the average customer per sustained
interruption.
ENS (Energy Not Supplied): the summation of
energy not supplied due to supply interruptions
over a year Period. Its cost is CENS (cost of
energy not supplied).
Fig. 2. Part of geographical area of an EDC
III. SYSTEM RELIABILITY INDICES (RIS)
A. System Average Interruption Frequency Index
(SAIFI)
It measures the average number of interruptions
experienced by each customer. All planned and
unplanned interruptions are used in calculating the
index. SAIFI can be calculated as follows:
SAIFI = (No. of interruptions during one year)/ (No. of
customers).
B. System Average Interruption Duration Index
(SAIDI)
It measures the yearly average interruptions duration
per customer. It can be calculated as follows:
SAIDI = (Σduration of interruption in min)/ (No. of
customers).
C. Customer Average Interruption Duration Index
(CAIDI)
It measures the average time required to restore
service to the average customer per interruption. The
following formula is employed for calculating CAIDI:
CAIDI = (SAIDI)/ (SAIFI). [4], [5]
IV. CONTINUITY OF POWER SUPPLY
The main aspects of quality for electric network
operation are continuity of supply, safety, technical
quality of the commodity, end user service and
environmental impact. Continuity of supply measures
the electric networks ability to supply the end users
with electricity. It is generally characterized as the
frequency and duration of interruptions in supply.
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Renewable Energy and Sustainable Development (RESD) Volume 3 Issue 1, Special Issue, March 2017 - ISSN 2356-8569
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Continuity of power supply or sustained outage –
an outage that lasts longer than a specified
amount of time .SAIDI, SAIFI and CAIDI are all
based on sustained outage .The duration of a
sustained outage varies from state to state.
IEEE -1366 defines the duration of sustained
outage to be 5 minutes.
Power quality – measure of the purity of the
electric waveform on power lines. A power
quality event, which is not the same as an
outage, occurs when one of the waveforms
differs from a pure sinusoidal waveform or one
or two phases of power are lost. [10]
Measurements that can quantify power quality are
harmonic distortion and peak to peak voltage. Power
quality events can last from few cycles to a few
seconds and can be caused by lightning strikes,
falling trees, utility operations and operations from
other customers such as disturbances from starting a
large motor.
A. International example
A review of some countries revealed the SAIDI and
SAIFI performance shown in “Table I”. These
countries also put greater emphasis on power quality
[3], [11]
B. Variables affecting reliability indices
1. Longer circuits lead to more interruptions. It is
easier to provide higher reliability in urban areas;
line lengths are shorter.
2. The distribution supply configuration greatly
impacts reliability. Long radial lines provide the
poorest service; grid networks are exceptionally
reliable.
3. Higher primary voltages tend to be more
unreliable, mainly because of longer lines.
Table 1. EUROPEAN RELIABILITY PERFORMANCE, WITH MAJOR EVENTS
Country SAIDI SAIFI
Austria 72 0.9
Denmark 24 0.5
France 62 1.0
Germany 23 0.5
Italy 58 2.2
Nerthlands 33 0.3
Spain 104 2.2
UK 90 0.8
*Source: council of European energy regulator ASBL (2008) 4th
benchmarking report on the quality of electricity supply .Brussel
CEER.
Faults and interruptions have significant year-to-year
variation because weather conditions vary
significantly, age of electrical equipment, or
performance of protective systems. These factor
variations are translated into variations in the number
of faults and in reliability indices.
C. Relation between SAIFI & CAIDI
The envelope of “acceptable supply” for relation
between frequency of interruptions and longest
duration per interruption is shown in “Fig.3”.
Find optimum and customer satisfied: “A” area,
represents the area of biggest reliability, move
towards the origin, the performance will be better.
Customer dissatisfied: Balanced area represents
the lower reliability, divided to:
Region “B” indicates for the excess number of
interruptions but for short time durations.
Region “C” indicates for little number of
interruptions but for long time durations.
Vertical axis “X” and horizontal axis “Y” give the
reliability indices threshold.
D. Performance indicators for EDC
“Table 2” and “Table 3” represent the development of
SAIFI and CAIDI during 2011:2014 for EDCs. If
indicators through the three years are abnormal, (as
CAIDI for EDC3 & EDC5), the stray number must be
dropped out.
Fig.3. Relation between SAIFI and CAIDI
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Renewable Energy and Sustainable Development (RESD) Volume 3 Issue 1, Special Issue, March 2017 - ISSN 2356-8569
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Table 2. DEVELOPMENT OF CAIDI FOR EDCS
CAIDI
Company 2011 2012 2013 2014 average
EDC1 102.4 117.761 107.852 97.062 106.269
EDC2 31.768 27.12 24.118 21.758 26.191
EDC3 54.851 18.483 18.906 9.509 25.437
EDC4 143.577 2.094 7.576 67.048 55.074
EDC5 40.071 40.416 41.76 36.177 39.606
EDC6 67.841 48.567 27.377 28.104 42.972
EDC7 23.879 24.474 88.877 106.13 60.84
EDC8 152.413 106.931 103.703 108.7 117.937
EDC9 77.801 83.167 130.727 171.301 115.749
Table 3. DEVELOPMENT OF SAIFI FOR EDCS
SAIFI
Company 2011 2012 2013 2014 average
EDC1 0.435 0.495 0.423 0.341 0.4235
EDC2 0.192 0.169 0.134 0.131 0.1565
EDC3 0.149 0.934 0.958 0.764 0.70125
EDC4 0.452 0.405 0.442 0.445 0.436
EDC5 0.66 0.533 1.01 1.009 0.803
EDC6 3.01 2.145 0.095 0.081 1.3328
EDC7 0.121 0.117 1.388 0.559 0.5463
EDC8 0.289 0.169 0.464 0.225 0.287
EDC9 1.59 2.237 0.221 0.179 1.0568
The relation between SAIFI and CAIDI for 9 EDCs
during 2011:2014 is presented in “fig. 4”.
Fig.4. relation between SAIFI&CAIDI for EDCs (data 2011-2012-
2013-2014)
Fig.5 Relation between SAIFI and CAIDI fir EDCs in 2014
“Fig.5” represents the envelope of “acceptable supply
“for relation between SAIFI and CAIDI for EDCs in
2014.
According to IEEE1366, 2001 the target of SAIFI and
CAIDI are 1.0 and 90 minute respectively, they are
close to the calculated threshold values
Notes:
1. SAIFI and CAIDI are improved in 2014 for most
EDCs.
2. EDC2 and EDC3 are in optimum area
V. CONCLUSION
There is increasing demand from consumers for more
reliable and economical electric power. Many factors
share to evaluate the reliability of a power network:
design, planning, operation and maintenance and
faults; which have their contributed input to all power
network reliability.
The main measures to improve reliability: adequate
maintenance, adoption of preventive maintenance
rather than break down maintenance, improving
power quality and ensuring coordination protection
settings.
The reliability indicators for electric network in Egypt
are used by EEHC and Egypt Era to benchmark
performance and scenariotize investments in
generation, transmission and distribution network, to
improve performance. Also, these indicators are used
by system planners and operators as a channel to
improve the level of customer service.
Reliability level for its delivery facilities and, where
appropriate to improve performance.
The results are the reliability performance objectives
for EDCs, ETC, and EPCs shall have threshold
objective designed to help maintain the acceptable
envelop.
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Renewable Energy and Sustainable Development (RESD) Volume 3 Issue 1, Special Issue, March 2017 - ISSN 2356-8569
http://dx.doi.org/10.21622/RESD.2017.03.1.019
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RESD © 2017
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