Journal of Applied Science and Engineering, Vol. 20, No. 1, pp. 21-30 (2017)
DOI: 10.6180/jase.2017.20.1.03
Energy Loss Reduction in a 20-kV Distribution
Network Considering Available Budget
Mehdi Izadi1* and Farzad Razavi2
1
Young Researchers and Elite Club, Qazvin Branch,
Islamic Azad University, Qazvin, Iran
2
Faculty of Electrical and Biomedical Engineering Qazvin Branch,
Islamic Azad University, Qazvin, Iran
Abstract
The present paper is a report on a study which tried to determine the best way of allocating the
budget available to the Qazvin Electric Distribution Company in Iran in order to optimally decrease
energy loss in an affiliated distribution network. Five methods of loss reduction were compared in
terms of the degree of loss reduction and cost-effectiveness. The budget to be assigned to each method
was determined. The results show that the budget should only be appropriated to capacitor placement,
replacement of dilapidated conductors, and load imbalance adjustment, in that order.
Key Words: Available Budget, Loss Reduction, Load Imbalance Adjustment, Capacitor Placement,
Dilapidated Conductors
1. Introduction
Preservation of energy is very important from the
point of view of environmental issues, high fossil fuel
prices, formation of private power utilities, and the cost
of developing power plants. It follows that loss of electrical energy generated for sale would mean many charges
on power utilities and the industry. This has led many
governments to considerably invest in reducing energy
loss.
Various approaches have been used in the past few
decades for reducing loss. Study [1] summarizes a list of
such methods at the distribution level:
+ Reconductoring in primary and secondary feeders
+ Reconfiguring feeders
+ Using high-efficiency distribution transformers
+ Reducing secondary network length by adding and
optimally placing distribution transformers
+ Using distributed generation
+ Placing subtransmission substations near load centers
+ Load balancing
*Corresponding author. E-mail: [email protected]
+ Improving load factor
+ Improving voltage profile.
Loss stems from, among other things, load imbalance,
reactive power, dilapidated transformers, dilapidated conductors, and weak connections. Adjusting load imbalance will decrease loss in the lines and transformers. Optimally placing a capacitor in a network improves power
factor and reduces reactive power. Replacing overworked
and dilapidated transformers reduces copper and iron
loss. Dilapidated cables and conductors should be replaced as their increased resistance results in energy loss.
And finally, correcting the connections weakened over
time will reduce line resistance and energy loss.
A review of previous studies on loss reduction follows.
Study [2] tried to reduce loss by removing load imbalance.
Study [3] used evolutionary fuzzy programming algorithm and dynamic information structure to optimally
place capacitors in a 69-bus radial distribution system.
Genetic Algorithm (GA) was used by [1] for capacitor
placement in a 69-bus system. Study [4] placed capacitors
using the particle swarm optimization (PSO) algorithm.
22
Mehdi Izadi and Farzad Razavi
Study [5] found that loss in a transformer decreases
if the transformer works at half the nominal load and if
harmonics filters are installed. The algorithm proposed
in [6] for reducing network loss and determining the optimum conductor for a radial distribution network drew
upon a new load flow. Study [7] studied the impact of
fixing weak connections on loss reduction in Hormozgan power network in Iran regarding the relevant operating costs.
This study is innovative in the following ways; first
of all determining the efficiency of different methods of
loss reduction in Sharif-Abad’s 20-kV feeder will be
considered and then tries to evaluate methods of loss reduction on the basis of the available budget.
However, these studies that were mentioned in advance did not pay serious, if any, attention to the expenses
involved in the method they employed. The present research attempts to evaluate several ways of reducing
energy loss in the 20-kV distribution network of SharifAbad, which is part of the Qazvin Electrical Distribution Company in Iran, in terms of the operating costs involved, method efficiency, and the available budget. For
this purpose, we first measured energy loss at the peak
hour of the period spanning annual. Then, energy loss
for the period under study was calculated. Having the
data for power loss and energy loss, we obtained the loss
factor of the network for the year-long period. The objective functions used in the research was then minimized
using the Genetic Algorithm.
2. Model Formulation
It is worth noting that the authors of [8] did not have
any idea about power loss at peak and the energy loss in
the year under study and thus did not know the loss factor. For this reason, they considered the loss factor in
the feeder under investigation to be 0.52 on the basis of
the loss factor in the adjacent feeders in Qazvin Electrical Distribution Company. However, in the present research, the loss factor was calculated to be 0.4047. Another point that makes the current work different from [8]
is that the main objective here is budget allocation.
2.1 Fixing Load Imbalance
Fixing load imbalance requires that the current of
each phase be close to the average current of the three
phases.
Load imbalance was adjusted as described below [8]:
+ The percentage of imbalance was determined for each
phase (Eq. (1)).
+ A certain percentage (from 0 to 100) was randomly
assigned to each load by means of GA.
+ The cost of imbalance adjustment for each phase
equals the integral of the area under the curve of the
A/x graph in the interval [anew, aold].
+ The cost of imbalance adjustment for each load is
equal to the sum of the costs related to imbalance adjustment for the three phases.
The total cost of imbalance adjustment is equal to the
sum of the costs associated with imbalance adjustment
for all the loads in the feeder at issue (Eq. (2)).
(1)
where Ip (A) is the phase current, and Iave (A) is the average of the three phase currents.
(2)
where Cimbalance is the cost of adjusting imbalance ($). A
is a constant set at $70 according to our empirical work.
aold-p-i is the old percentage of load imbalance for the
pth phase of the ith load. anew-i is the new percentage of
load imbalance for the ith load.
The cost of reducing load imbalance from 60% to
50% is less than the cost associated with decreasing imbalance from 30% to 20% (Figure 1).
Figure 2 is the flowchart related to fixing load imbalance.
2.2 Capacitor Placement
Capacitors were placed considering the following [8]:
+ Capacitors were only placed where loads were.
+ Loads were adjusted before capacitor placement.
+ Use was made of 12.5-kvar capacitors. GA determined the number of capacitors.
+ A gene was considered for each load.
+ The total number of capacitors multiplied by the price
Energy Loss Reduction in a 20-kV Distribution Network Considering Available Budget
23
phase angle between the current and voltage after the
installing capacitor.
Given that the transformer operates at its nominal
apparent power, then Pmax = 504 kW, cos f1 = 0.8, and
tan f1 = 0.75.
As this work aims to increase the power factor from
0.8 to 0.955, the capacitor to be installed in the feeder
will have a maximum capacity of 222 kvar.
The cost of capacitor placement for the whole network is obtained from Eq. (4). Additionally, the cost of
capacitor placement for each bus and the variable cost of
placing capacitors for each bus are calculated from Eqs.
(5) and (6), respectively.
Figure 1. The A/x diagram.
(4)
where Ccap: the cost of capacitor placement ($). Ccap-i:
cost of placing capacitors on the ith bus ($).
(5)
where Ccap-fixd-i fixed cost of placing capacitors on the
ith bus ($). Ccap-variable-i variable cost of placing capacitors on the ith bus ($).
(6)
th
where ncap: number of capacitors on the i bus. pcap:
price of each capacitor ($/unit).
Figure 2. The flowchart of fixing load imbalance.
of each capacitor and the fixed costs related to capacitor placement were added up in the objective function.
+ Fixed costs in this study were of three types: (a) 1-6
steps; (b) 7-12 steps; and (c) 13-18 steps.
The maximum number of steps was determined by
the transformer with the highest capacity (Eq. (3)).
(3)
where Qc: is the capacity of the installed capacitor (kvar).
Q1: reactive power before installing the capacitor (kvar).
Q2: reactive power after installing the capacitor (kvar).
P: active power (kW). f1: phase angle between the
current and voltage before the installing capacitor. f2:
2.3 Replacing Dilapidated Transformers
Dilapidated transformers were replaced with the following in mind [8]:
+ The transformers used in the feeder under study had
the apparent power values of 25, 50, 100, 200, 250,
315, 500, and 630 kVA.
+ A gene was considered for each transformer.
+ If a transformer is replaced, its copper and iron losses
decrease by 20%, according to Qazvin Electrical Distribution Company.
+ The costs involved in replacing all transformers were
added up to obtain the total cost of transformer replacement.
The cost of transformer replacement is the sum of all
the expenses associated with replacing the transformers,
as determined by GA.
24
Mehdi Izadi and Farzad Razavi
2.4 Replacing Dilapidated Lines
Dilapidated lines were replaced on the basis of the
following [8]:
+ A gene was considered for each line.
+ If a line is replaced, its resistance decreases by 10%,
according to Qazvin Electrical Distribution Company.
+ The costs associated with replacing all dilapidated
lines were added up to obtain the total cost of line replacement.
The cost of conductor replacement is the sum of all
the expenses associated with replacing the conductors,
as determined by GA.
2.5 Correcting Weak Connections
Weak connections in the network were corrected in
the following way [8]:
+ The length of the lines connecting buses was calculated using computer software.
+ It was assumed that there was a connection at each
end of each line.
+ A connection was added if the line connecting every
two buses was longer than 480 m.
+ A gene was considered for each connection.
+ The assumed number of connections is for singlewire lines only. For three-wire lines, the number should
be multiplied by three.
+ If a weak connection is corrected, line resistance decreases by 0.001 ohms, according to Qazvin Electrical Distribution Company.
+ In order to calculate the total cost of correcting weak
connections, the operating costs associated with correcting each connection was multiplied by the total
number of connections (Eq. (7)).
(7)
where Cconnection: the cost of correcting weak connections ($). nconnection: the total number of weak connections. pconnection: the cost of fixing each weak connection
($/unit).
2.6 The Benefit Obtained from Loss Reduction
The benefit to be obtained from reducing power loss
is calculated using Eq. (8).
(8)
where Bloss_reduction : the benefit resulting from loss reduction ($). Ploss-after: loss after the application of the
methods (kW). Ploss-before : loss before the application of
the methods (kW). T: the period, in hours, for which
energy loss was calculated. This covered the full length
of a year (8760 hours). LSF: loss factor. penerge: price of
energy ($/unit) [8].
2.7 Objective Function without Considering the
Budget
The objective function without considering the budget was calculated from Eq. (9):
(9)
where OF1: objective function regardless of the budget
($). Cimbalance: the cost of adjusting imbalance ($). Ccap:
the cost of placing capacitors ($). Ctrans: the cost of replacing transformers ($). Cline: the cost of replacing conductors ($). Cconnection: the cost of correcting weak connections ($). Bloss_reduction : the benefit resulting from loss
reduction ($) [8].
The flowchart of OF1 is portrayed in Figure 3.
3. New Method: Budget Allocation
The objective function defined above (OF1) can be
rewritten as Eq. (10) below:
OF1 = a + b
(10)
where OF1: objective function regardless of the budget
($). a: The total cost associated with employing loss reduction methods ($). b: The benefit resulting from loss
reduction ($). Since loss before the reduction methods
were employed is less than post-reduction loss, b is always a negative value.
However, this objective function needs to be modified because the present research aims to determine how
much of the budget available to the company under study
should be allocated to each method of reducing loss and
also because the entire budget considered for loss reduc-
Energy Loss Reduction in a 20-kV Distribution Network Considering Available Budget
Figure 3. The flowchart of the OF1 for each iteration.
tion is expected to be spent.
The procedure used to reduce loss considering available budget is as follows:
First, the amount of the budget considered for loss
reduction is given to the software, which calculates the
total cost associated with each method of reducing. The
objective function is optimized when the cost is equal to
the available budget. The proposed objective function is
presented as Eq. (11) below.
25
Figure 4. This Feeder is radial and it fed from 63 to 20
substation. Type of loads of this feeder are: agricultural,
domestic and commercial. Figure 5 is the expanding of
marked area in Figure 4. In Figure 5 electrical tower and
lines are clarified and information mentioned.
Information and description of equipment of this feeder given in Tables 1 to 5 are as following:
+ Information about transformers (apparent power and
number)
+ Information about lines (length and types of conductors, resistance, reactance and weight)
+ Operating costs of equipment and services
Table 1 presents different levels of apparent power
as used in the network under study and the number of
transformers or each level.
There are nine agricultural transformers in this feeder.
Table 2 gives the number of transformers associated
with different levels of apparent power used in the network.
The specifications of this feeder can be seen in Tables 3 and 4.
(11)
where n: available budget. a: all the costs associated
with power loss. b: the benefit to be obtained from loss
reduction. b: a very large constant (e.g., 1010). OF2: the
objective function for the available budget.
An important consideration in this objective function is that the available budget must be less than the total cost of fully implementing all the methods of loss reduction (n £ a).
Figure 4. The schematic representation of Sharif-Abad Feeder.
4. Simulation
4.1 Case Study
The distribution network studied in this research was
the 20-kV Feeder of Sharif-Abad in northwestern Iran.
The schematic represenation of this feeder is given in
Figure 5. The enlargement of the area marked in Figure 4.
26
Mehdi Izadi and Farzad Razavi
Table 5 summarizes the operating costs of the methods applied to the network under discussion.
4.2 Software
DIgSILENT Power Factory 13.2 was used to develop the proposed algorithm for the objective functions
and to analyze the system. This application can calculate
load flow, short-circuit level, active losses of the netTable 1. Levels of apparent power and the number of
associated transformers
Apparent power (kVA)
25
50
100
200
250
315
500
630
Number of associated
transformers
1
1
8
6
6
4
1
1
Table 2. The number of agricultural transformers
associated with levels of apparent power
Level of apparent power
(kVA)
100
200
Number of associated
transformers
6
3
Table 3. A sample of the length of line between every
two terminals
Terminals i - j
T59-T60
T60-T61
T62-T63
T64-T65
T65-T66
T66-T67
T67-T68
T68-T69
T69-T70
T70-T71
T71-T72
T72-T73
T73-T74
T74-T75
T75-T76
T76-T77
Length (km)
0.046580
0.042101
0.081154
0.052930
0.054265
0.058357
0.068757
0.073169
0.062034
0.036182
0.034367
0.063003
0.024233
0.061842
0.073207
0.065371
work, and the network parameters. The main feature of
DIgSILENT is DPL (DIgSILENT Programming Language), which simplifies the application of the proposed
method. The objective functions were optimized using
GA on MATLAB R2008a Software. A text file connected the two applications.
4.3 Proposed Algorithm
In the proposed algorithm, GA determines the following for each load:
+ The percentage of imbalance, which is a number from
0 to 100.
+ The quantity of 12.5-kvar capacitors, which is a number from 0 to 18.
+ In addition, each transformer, line, and loose connection is assigned a value of either 0 or 1, denoting the
necessity (1) or lack thereof (0) of fixing/replacement.
The above-mentioned are only done if constraints
are not violated. The details of the proposed method are
given below:
(1) DIgSILENT writes the zero in the text file to flag the
beginning of the initial calculation. Detecting this
flag, GA will not begin the associated program.
Table 4. Conductor types
Type
1
2
Resistance
(W/km)
Reactance
(W/km)
Weight
(kg/km)
0.2712
0.4545
0.2464
0.2664
450
255
Table 5. Operational costs
Equipment and services
Capacitor 12.5 kvar
Fixed cost 1
Fixed cost 2
Fixed cost 3
Trans 25 kVA
Trans 50 kVA
Trans 100 kVA
Trans 200 kVA
Trans 250 kVA
Trans 315 kVA
Trans 500 kVA
Trans 630 kVA
Conductor type1
Conductor type2
Energy
Cost
136.550 ($/unit)
100 ($/unit)
200 ($/unit)
300 ($/unit)
2266.938 ($/unit)
2707.938 ($/unit)
3688.177 ($/unit)
5602.810 ($/unit)
5792.808 ($/unit)
6863.947 ($/unit)
10352.565 ($/unit)
11970.326 ($/unit)
4.092 ($/kg)
4.246 ($/kg)
0.180 ($/kWh)
Energy Loss Reduction in a 20-kV Distribution Network Considering Available Budget
(2)
1
ù
é
ú
ê
nvars
ú
ê
ê nvars - imbalance ú
DIgSILENT writes the matrix ê
ú in
nvars - cap
ú
ê
ê population_ sizeú
ê Generation ú
û
ë
the text file. The first row is the flag which shows the
program must begin its operation. When the flag is
set to 1, GA must run. nvars, nvars-imbalance, and nvars-cap
respectively identify the total number of the genes
within the chromosome, those related to load imbalance, and those associate with the capacitors.
(3) GA writes the matrix [2 B1…BnC1…Cn T1…TnL1…
Lm X1…Xk] in the text file. In this matrix, B1,…, Bn
are the new percentages of imbalance for each load,
C1,…, Cn are the number of 12.5-kvar capacitors for
each load, T1,…, Tn are the values of 0 or 1 related to
each transformer, L1,…, Lm are the values of 0 or 1
associated with each line, X1…Xk are the values of 0
or 1 pertinent to the loose connections of each line,
and Flag 2 indicates that DIgSILENT must restart its
operation.
(4) Upon seeing Flag 2 at the beginning of the text file,
DIgSILENT commences operation and calculates the
OF using the chromosome given in that file. The application, then, inserts in the text file Flag 3 and the
é 3 ù
quantity of the OF in the form of a matrix ê ú,
ëOF û
where Flag 3 is an indicator of the temporary termination of the operation of DIgSILENT and the restart
of the operation of the GA.
(5) If the maximum number of iterations is not reached,
the process described above reverts to stage 3. Otherwise, the process goes on to stage 6 below.
(6) The GA is finished, so it inserts Flag 4 in the text file,
denoting the end of the process.
(7) Upon seeing Flag 4 in the text file, DIgSILENT realizes that the process is over.
gard to attendant costs:
(1) Adjusting load imbalance
(2) Placing capacitors
(3) Replacing transformers
(4) Replacing line conductors
(5) Correcting weak connections
(6) All the above carried out together without regard to
the available budget
(7) All the above carried out together with regard to the
available budget
5.1 Adjusting Load Imbalance
Table 6 summarizes the results of adjusting load imbalance in transformers.
Power loss was 129.389 kW after load imbalance
was corrected, indicating a drop of 13.14 kW, which
equals 10.16% of the total loss of the network. The cost
of balancing all the loads was obtained from Eq. (2). The
quantity of phase current R was 1.5 times as large as that
of the average current. The quantities of phase currents
S and T were respectively 0.8 and 0.7 times those of the
average current. Phase current R was 50% more than
the average current. Phase currents S and T were 20%
and 30% less than the average current, respectively.
Now, by reducing the surplus of phase current R to 30%,
we can reduce the deficit of phase currents S and T to
10% and 20%, respectively, at a cost of $112.7. The loss
reduction thus obtained will be 21 MWh, and the resultant benefit will be $3700 a year.
5.2 Placing Capacitors
Unless load imbalance had been adjusted, capacitors
could not be placed. Hence, loss should have a different
amount before capacitor placement than before the deployment of any of the other methods. The results of allocating capacitors in the network are given in Table 7.
Different capacitors were placed at different busses
Table 6. Fixing load imbalance
Item
5. Results and Discussion
In this research, loss factor was considered to be
0.4047, and the following items were calculated with re-
27
Loss after run
Loss reduction
Cost
Benefit
|OF1|
Quantity
129.389 kW
013.140 kW
$1234.419
$8453.307
$7218.888
28
Mehdi Izadi and Farzad Razavi
Table 7. Capacitor allocation
Item
Loss before run
Loss after run
Loss reduction
Cost
Benefit
|OF1|
Quantity
135.719 kW
112.783 kW
22.936 kW
$12677.8
$14755.802
$2078.002
as follows:
+ 12.5-kvar capacitors at busses T18, T28, T36.
+ 25-kvar capacitors at busses T2, T4, T10, T20, T50.
+ 37.5-kvar capacitors at busses T26, T30, T40, T46,
T48, T54.
+ 50-kvar capacitors at bus T22.
+ 62.5-kvar capacitors at bus T14.
+ 75-kvar capacitors at busses T38, T44, T56.
+ 87.5-kvar capacitors at bus T24.
+ 137.5-kvar capacitors at bus T52.
Before capacitor installation and at the peak moment,
the apparent power input was 4368.262 kVA, the reactive power input was 2143.851 kvar, and power loss was
135.719 kW. After placing capacitors and at the peak
moment, the apparent power input was 3973.889 kVA,
the reactive power input was 1216.810 kvar, and power
loss was 112.783 kW. This shows that the apparent power input was reduced by 394.373 kVA (equal to 9.03%),
the reactive power input by 927.041 kvar (or 43.24%),
and power loss by 22.936 kW (i.e., 16.90%).
The total capacity of all the capacitors added to the
network under investigation was 950 kvar at the peak
moment of the year. Capacitor installation increased the
usable capacity of the network by 394.373 kVA (equal to
9.03%) at the peak moment of the year.
5.3 Replacing Transformers
Zero transformers had to be changed. This finding
can be explained as follows:
There were 28 transformers in the feeder studied in
this research. The loss of the transformers consists of
copper and iron loss. At the peak moment of the year, the
total loss of all the transformers was 31 kW, with the total iron loss being 19 kW, and the total copper loss being
12 kW. The total loss of all the transformers was equal
to 54.82% of the total loss of the network. Iron loss
was 60.29% of the total loss of the transformers and
33.05% of the total loss of the network. Copper loss was
amounted to 39.71% of the total loss of the transformers
and 21.77% of the total loss of the network.
Replacing dilapidated transformers will reduce the
total loss of transformers by 20%. That is to say, a reduction of 55.4 MWh will bring the total loss of transformers to 221.6 MWh. It follows that the total loss of
the network will reduce by 10.96%. Given that the benefit of loss reduction resulting from replacing dilapidated
transformers will be $7523 a year, and that replacing all
the transformers will cost $152633, the benefit to be obtained from replacing dilapidated transformers will be
not be significant.
5.4 Replacing Line Conductors
The total loss of lines was 228.30 MWh, equaling
45.18% of the total loss of the network. Replacing the dilapidated conductors of a line diminishes its resistance
by 10%. This correspondingly reduces the loss of the
lines as loss is positively related to resistance. Thus, replacing all dilapidated conductors will result in a reduction of about 4.52% in the total loss of the network. Loss
will be reduced by 22.83 MWh. The benefit to be obtained will be $4109.4 a year. Replacing all the conductors will be approximately $114000 given that all the
lines in the network are about 19 km in length. In consequence, the benefit to be obtained from replacing dilapidated conductors will be insignificant.
Table 8 summarizes the results of line conductor replacement.
5.5 Correcting Weak Connections
Weak connections should not be corrected. The explanation is as follows:
As mentioned above, the resistance of a weak connection in the network under study was 0.0001 ohm. The
Table 8. Replacing line conductors
Item
Loss after run
Loss reduction
Cost
Benefit
|OF1|
Quantity
142.234 kW
0.295 kW
$166.089
$189.787
$23.698
Energy Loss Reduction in a 20-kV Distribution Network Considering Available Budget
resistance of the weak connections in a 0.480-km line
was 0.0003 ohm. The resistance of a 0.480-km line was
found to be 0.11904 ohm. The resistance emanating from
weak connections is equal to 0.08% of the total resistance of the line. Fixing weak connections in a line will
cost $1.406.
The benefit to be obtained from fixing weak connections seems trivial in comparison with the costs involved.
5.6 All the Methods Applied Simultaneously
Different capacitors were installed at different busses as follows:
+ 12.5-kvar capacitors at busses T4, T54.
+ 37.5-kvar capacitors at busses T20, T38, T40, T48.
+ 50-kvar capacitors at busses T8, T16, T26, T30, T44.
+ 62.5-kvar capacitors at busses T14, T56.
+ 75-kvar capacitors at busses T32, T50.
+ 100-kvar capacitors at buss T10.
+ 50-kvar capacitors at busses T8, T16, T26, T30, T44.
+ 112.5-kvar capacitors at bus T46.
+ 137.5-kvar capacitors at bus T52.
Table 9 presents the results of simultaneous application of all the five methods of loss reduction, only placing capacitors and fixing load imbalance seem cost-effective. More specifically, simultaneously applying all
the methods reduces power loss by 18.10%, with the ratio of benefit to cost being 47 to 40. The total capacity of
the capacitors added to the network was 1050 kvar.
5.7 Prioritizing Methods of Loss Reduction
According to the Degree of Reduction and the
Amount of Available Budget
Tables 10 and 11 summarizes the ratio of benefit to
cost and percentage of loss reduction, respectively. The
best method of loss reduction will be fixing load imbalance providing that the decision is based on the bene-
fit-cost ratio. However, if the percentage of loss reduction forms the basis of the decision, capacitor placement
will be the best method.
As the budget available to Qazvin Electrical Distribution Company (n) was $19000, running OF2 gave the
results presented in Table 12.
All the five methods were concurrently used to reduce loss in the network. According to the results, only
adjusting load imbalance, placing capacitors, and replacing dilapidated conductors are advisable considering the available budget. In addition, a comparison of
Tables 9 and 12 reveals that running OF1 showed capacitor placement and load imbalance adjustment to be
the best of the five alternative methods. Running OF2
showed that replacing dilapidated conductors can be a
good alternative as well. The difference lies in the fact
that OF2 was run with a $19,000 budget in mind. From
Table 12, it can be seen that 2.95% of the available budget should be allocated to adjusting load imbalance,
76.59% to placing capacitors, and 20.46% to replacing
dilapidated conductors.
6. Conclusions
This study proposed a way for allocating the budget
Table 10. Cost-benefit ratio
Method
Benefit-cost ratio
Fixing load imbalance
Placing capacitors
Replacing line conductors
6.85
1.16
1.14
Table 11. Percentage of loss reduction
Method
Percentage of loss reduction
Fixing load imbalance
Placing capacitors
Replacing line conductors
Table 9. All the methods applied simultaneously
Table 12. The results of running OF2
Item
Item
Loss after run
Loss reduction
Cost
Benefit
|OF1|
Cost of Fixing load imbalance
Quantity
116.734 kW
025.795 kW
$14008.043
$16460.424
$2452.3810
$437.84300
29
09.22
16.09
00.21
Loss after run
Amount of loss reduction
|OF2| = |Benefit|
Cost of adjusting load imbalance
Cost of placing capacitors
Cost of replacing dilapidated conductors
Quantity
109.622 kW
030.907 kW
$19722.453
$560.21780
$14552.950
$3886.8322
30
Mehdi Izadi and Farzad Razavi
available to the Qazvin Electric Distribution Company
to different approaches to loss reduction in an attempt to
obtain maximum loss reduction. For this purpose, an actual feeder was subjected to five methods of reducing
loss. These methods were studied in terms of the degree
of loss reduction brought about and the amount of costs
involved. Then, the budget to be assigned to each method was determined using the proposed objective function. The results showed the available budget should
be assigned to capacitor placement, replacement of dilapidated conductors, and load imbalance adjustment in
that order. This finding can help power utilities better allocate their loss reduction budget. A limitation of the
present research is that only the five methods discussed
were applicable to the network under study. Thus, it seems
advisable to evaluate some other methods. Finally, when
the model is put into operation, load imbalance adjustment should always be performed prior to capacitor
placement. No particular order is needed for the other
methods of loss reduction.
References
[1] Haghifam, M. R. and Malik, O. P., “Genetic Algorithm-based Approach for Fixed and Switchable Capacitors Placement in Distribution Systems with Uncertainty and Time Varying Loads,” IET Generation,
Transmission & Distribution, Vol. 1, pp. 244-252
(2007). doi: 10.1049/iet-gtd:20045267
[2] Lin, C.-H., Chen, C.-S., Chuang, H.-J., Huang, M.-Y.
and Huang, C.-W., “An Expert System for Threephase Balancing of Distribution Feeders,” IEEE Transactions on Power Systems, Vol. 23, pp. 1488-1496
(2008). doi: 10.1109/TPWRS.2008.926472
[3] Venkatesh, B. and Ranjan, R., “Fuzzy EP Algorithm
and Dynamic Data Structure for Optimal Capacitor
Allocation in Radial Distribution Systems,” IEE Proceedings-Generation, Transmission and Distribution,
Vol. 153, pp. 80-88 (2006). doi: 10.1049/ip-gtd:200
50054
[4] Etemadi, A. H. and Fotuhi-Firuzabad, M., “Distribution System Reliability Enhancement Using Optimal
Capacitor Placement,” IET Generation, Transmission
& Distribution, Vol. 2, pp. 621-631 (2008). doi: 10.
1049/iet-gtd:20070515
[5] Senior, A. H. A.-B., Elmoudi, A., Metwally, I., AlWahaibi, A., Al-Ajmi, H. and Bulushi, M. A., “Losses
Reduction in Distribution Transformers,” Proceedings
of International MultiConference of Engineers and
Computer Scientists, Hong Kong, pp. 948-952 (2011).
[6] Sivanagaraju, S., Sreenivasulu, N., Vijayakumar, M.
and Ramana, T., “Optimal Conductor Selection for Radial Distribution Systems,” Electric Power Systems
Research, Vol. 63, pp. 95-103 (2002). doi: 10.1016/
S0378-7796(02)00081-0
[7] Nemati, G. and Nasr, K. S., “Reducing Operation Costs
and Losses Using Thermography,” Presented at the
21st International Conference on Electricity Distribution, Frankfurt Germany (2011).
[8] Izadi, M., Razavi, F., Gandomkar, M., Najafi, A. and
Soleimani, M., “Power Loss Reduction in Distribution
Systems through an Intelligent Method Considering
Operational Costs,” J. Basic Appl. Sci. Res., pp. 67446756 (2012).
Manuscript Received: Jun. 27, 2016
Accepted: Oct. 14, 2016