Generalized optimal placement of PMUs considering power system observability, communication infrastructure, and quality of service requirements

International Journal of Electrical and Computer Engineering (IJECE)
Vol. 10, No. 3, June 2020, pp. 2824~2841
ISSN: 2088-8708, DOI: 10.11591/ijece.v10i3.pp2824-2841  2824
Journal homepage: http://ijece.iaescore.com/index.php/IJECE
Generalized optimal placement of PMUs considering power
system observability, communication infrastructure, and
quality of service requirements
M. M. H. Elroby1
, S. F. Mekhamer2
, H. E. A. Talaat3
, M. A. Moustafa. Hassan4
1
Electrical Engineering Department, Faculty of Engineering, Ain Shams University, Egypt
2,3
Electrical Engineering Department, Future University, Egypt
4
Electrical Engineering Department, Cairo University, Egypt
Article Info ABSTRACT
Article history:
Received Mar 22, 2019
Revised Des 2, 2019
Accepted Des 10, 2019
This paper presents a generalized optimal placement of Phasor Measurement
Units (PMUs) considering power system observability, reliability,
Communication Infrastructure (CI), and latency time associated with this CI.
Moreover, the economic study for additional new data transmission paths is
considered as well as the availability of predefined locations of some PMUs
and the preexisting communication devices (CDs) in some buses. Two cases
for the location of the Control Center Base Station (CCBS) are considered;
predefined case and free selected case. The PMUs placement and their
required communication network topology and channel capacity are
co-optimized simultaneously. In this study, two different approaches are
applied to optimize the objective function; the first approach is combined
from Binary Particle Swarm Optimization-Gravitational Search Algorithm
(BPSOGSA) and the Minimum Spanning Tree (MST) algorithm, while
the second approach is based only on BPSOGSA. The feasibility of
the proposed approaches are examined by applying it to IEEE 14-bus and
IEEE 118-bus systems.
Keywords:
Binary particle swarm
optimization
Communication infrastructure
Economic study for the addition
new data transmission paths
Gravitational search algorithm
Latency time
Minimum spanning tree
Observability
Phasor measurement unit
Reliability
Copyright © 2020 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
M. M. H. Elroby,
Electrical Engineering Department, Faculty of Engineering,
Ain Shams University, Egypt.
Email: mousaelroby@yahoo.com
1. INTRODUCTION
The Phasor Measurement Units has the ability to provide synchronized phasor measurements of
voltage and currents, that distinguishing it from all other metering devices. It has been perceived that PMUs
hold the capability of revolutionizing the way of power system monitoring and control [1]. In contrary to
Remote Terminal Unit (RTU), the output sample rate of PMUs is high and may vary from 1 to 120 samples
per second with synchronization accuracy less than 1 μs and maximum total vector error of about 1% [2].
Because of this high sampling rate, PMUs provide large amounts of data; and consequently, they need
modern communication systems with medium to high bandwidth in order to transmit their data. Mainly,
the communication media of the power grid has been divided into two groups; owned and unowned ones.
The first group is a part of power system elements, i.e., power line communication, Optical Power Ground
wire (OPGW), and microwave communication media. While, the later didn’t depend on the power system
and may be of the type available to all users as an open access media or those owned by data service
providing companies (such as leased line, dedicated data links, and satellites) [3]. CI should be established in
the entire system for the purpose of high bandwidth data delivery and transmission. The transmission

Int J Elec & Comp Eng ISSN: 2088-8708 
Generalized optimal placement of PMUs considering power system observability … (M. M. H. Elroby)
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medium should satisfy the purpose of high bandwidth data and other requirement of Quality of Service
(QoS). However, high per unit cost and challenges related to its communication system have made its judicial
placement in an electric grid significant [4]. The data generated by PMUs needs a reliable and stable
communication network. The OPGW is selected to be the media of the case study based on the high channel
capacity, low latency time, and immunity to electromagnetic interference [5-8]. With limited annual
investments, it would be desirable to add a limited number of PMUs until a final goal is achieved. Initially,
there will not be enough PMUs to have a linear estimator. The attempt is to place the PMUs so that at each
stage the selection satisfies some design criteria [9]. In order to obtain a sufficient amount of observability of
a power system PMUs, installation sites are dispersed over a wide area. In recent years, many investigators
presented different methods for finding the minimum number and optimal placement of PMUs with different
degree of observability [10]. The actual subproblem is the issue of sequentially adding PMUs to a system
starting with a low degree of observability and ending with complete observability with redundancy.
Generally, observability analysis can be done using either a numerical approach or a topological
approach [11]. In numerical observability analysis, for specific application, a network is observable if - and
only if - its measurement gain matrix is of full column rank [12]. In this approach the observability usually is
derived from Energy Management System (EMS) applications [13, 14]. However, for a large-scale system,
the computational burden of this approach is heavy, and it sucks in the identification of the real zero diagonal
elements of the matrix due to the possible errors in rounding numbers. Most papers, as a result, have gone
through using the topological approaches to verify the system full observability [15]. On the other hand,
the topological observability approach determines network observability strictly based on the type and
location of measurements in the entire system. The topological observability analysis uses graph concepts.
The network is observable topologically if - and only if - a spanning tree can be found in the graph. Readers
may refer to [10, 16, 17] for more details about topological observability analysis. Since in the power
systems, measuring and its application lie within the power system studies, power system engineers mainly
focus on these observability problems in their researches. On the other hand, in some researches,
telecommunication engineers have paid more attention to communication systems. As a result,
few researches have considered the whole domains of the observability and CI comprehensively [18].
A number of limitations while designing a communication system gives rise to need for an optimal solution
that takes into account the QoS requirements such as reliability, data loads, latency time, and congestion of
the communication network [19]. Many researchers considered the PMUs optimization problem as
a minimization of the PMUs number. The mainly used optimization techniques are conventional such as
linear integer programing [15, 20–23] or meta-heuristic such as Genetic Algorithms (GA) [24, 25], simulated
annealing [4, 11, 26], tabu search [27], and binary particle swarm optimization [28]. In [14], the author
assumed a pre-known installed communication infrastructure for the system and assigned a penalty factor for
the case when a PMU is placed at a bus lacking CI. In other words, in this approach, communication
infrastructure is also considered as a constraint. In [18], the measurement and communication infrastructures
were optimally designed using the GA. They formulated and optimized this problem with a GA model in
both simultaneous and independent approaches. The results indicate that while the total number of
measurement devices for system observability may increase (and therefore, the observability is improved),
the total cost is reduced. However, they did not introduce any specific method to evaluate the location of
the CCBS. In addition, the meter placement has been carried out only for PMUs as measurement devices.
Also, the authors considered that the cost of the network depends on the accumulative length of the OPGW
only, and did not consider the allocation of the link capacity. Moreover, the authors did not take into
account the quality of service such as latency time of the communication network, reliability, and the degree
of the observability. Therefore, in the proposed approaches, the power system observability, CI requirements,
system reliability, and the latency time are considered in the objective functions. We take into account
the predesign requirements such as predefined locations of some PMUs and any existing CDs in some buses
and CCBS location. For this study, two different approaches are used. The first approach uses BPSOGSA to
search the best location of the PMUs and the channel capacity of the Communication Links (CLs) while
the connection topology is done using MST algorithm. The second approach uses BPSOGSA to search
the best location of the PMUs, the channel capacity of CLs, and the connection topology.
The rest of the paper is organized as follows: Section 2 describes the observability constraint.
Section 3 introduce BPSOGSA. Section 4 describe Minimum Spanning Tree. Section 5 presents the quality
of service. Section 6 presents the total cost calculation. Section 7 presents problem formulation and
implementation, also this section discuss the systems variables and cost factors. Section 8 discuss the two
approaches results. Finally, conclusions are extracted in Section 9.

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2. OBSERVABILITY CONSTRAINT
In general, given a PMU with unlimited number of channels at a bus, bus voltage phasor and all
current phasors along lines connected to that bus will be available. As shown in (1) presents observability
constraint in general form as introduced in [10, 16] for complete observability with a required degree of
redundancy (Without Conventional Measurements - With Conventional Measurements), one depth of
unobservability (Without Zero Injection Measurement - With Zero Injection Measurements)and,two depth of
unobservability (Without Zero Injection Measurement - With Zero Injection Measurement ).
Observability constraint: TX ≥ B (1)
T and B are a matrix and vector depend on each case [10, 16].
X is the PMUs placement variables X = [x1 x2 … xn],
xi = {
1 if PMU at bus i,
0 if No PMU at bus i,
The minimum number of PMUs (PMUSmin) can be formulated as a problem of Integer Linear
Programming [29] as shown in the following equation.
PMUSmin = {
min ∑ xk
N
k=1
Subject to: Observability constraint
(2)
where
N is the number of buses
3. BINARY OPTIMIZATION USING HYBRID PSO AND GSA
The PSOGSA is a hybrid optimization algorithm, combining strengths of both PSO and GSA.
This algorithm performs both PSO and GSA in terms of improved exploration and exploitation [30].
This technique has the nature of meta-heuristic optimization techniques. One of the main advantage of these
techniques is that they do not need a function formulation, but rather need a fitness function only or any other
way for distinguishing the results. As a result, the black box problem can be solved using these techniques.
The BPSOGSA algorithm is a binary version of hybrid PSOGSA. Readers may refer to [31] for more
detailsabout this algorithm. For the above-mentioned reasons, this version will be used in this study.
4. MINIMUM SPANNING TREE
The vertices (nodes) of the CI in a power grid correspond to PMUs, CDs, and CCBS, while
the edges correspond to high-voltage lines [32] or a new data transmission paths. Dijkstra's algorithm,
conceived by Dutch computer scientist Edsger Dijkstra in 1959 [33] is a graph search algorithm that solves
the shortest path problem for a graph with nonnegative edge [34]. The Dijkstra’s algorithm is used to search
the short path in the MST algorithm. The complete pseudocode for MST algorithm is shown in Figure 1 Step
3 in this algorithm could be modified to start with a highest short path and end with the lowest short path.
This modification is preferable when small propagation time delay is required, where this modification
shrinks the network and reduces the maximum propagation time delay of the farthest site. In step 4, the node
is connected with tree through switch.
Figure 1. MST Pseudocode

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5. QUALITY OF SERVICE
The Wide Area Measurement System (WAMS) is a distributed communication network. The QoS in
the WAMS depends on the latency time, data losses and reliability of the system. The latency time
performance is very important especially in protection and dynamic control applications [35]. The tree
network is a common methodology in order to design the networks [36, 37]. The network architecture
consists of several PMUs, CDs, and Phasor Data Concentrators (PDCs) as shown in Figure 2. PDC collects
the data generated by these PMUs over a shared communication network. Additionally, it performs quality
checks on phasor data and interprets and inserts the missing data at their appropriate position [38, 39].
Typically, many PMUs located at various substations gather data and send it in real time to a PDC.
Many PDCs can be connected to a common central PDC, in order to provide an interconnection wide
snapshot of the power grid measurements. In large systems, they may contain more than one PDC, where
each PDC is placed in a subarea. For simplicity in this study, the power system is assumed as one area, and
only one PDC is used in the control center. The measurements are made at specific time instances and
physical distant locations. They are then transmitted to a common location for use by wide area applications.
The latency time experienced by data between PMU and the destination node (CCBS) is
a combination of PMU reporting delay, the network propagation delays, queuing, routing delays, and PDCs
delay [40]. A representative latency time of the data network is shown in Figure 3. PMU reporting delay
𝑡 𝑝𝑚𝑢 is defined as the maximum time interval between the data report time as indicated by the data
timestamp, and the time when the data becomes available at the PMU output. This delay includes many
factors, such as the window over which data is gathered to make a measurement, measurement filtering, and
the PMU processing time. PDC delay 𝑡 𝑝𝑑𝑐 is defined as the maximum time interval between
the data input time as indicated by the data timestamp, and the time when the data becomes available at
the PDC output. This delay includes many factors such as processing, and alignment received data from
PMUs/PDCs. The PDC aligns received data and places that data in a packet. In addition, the PDC data
processing may include filtering, reporting rate conversion, interpolation, extrapolation, phase and magnitude
adjustment, etc. Most of the time the data frame is transmitted continuously from the PMU or PDC at
the designated reporting rate.
Figure 2. CDs and PMUs network
Figure 3. Latency time

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Queuing and transitions delays (𝑇𝑞𝑢) are caused by the amount of data that has to be transported
across the medium and the data rate of the medium. Considering an M/M/1 model, 𝑇𝑞𝑢 can be expressed as
follows [41]:
Tqu =
𝜇
𝐶 𝑙 −𝑓 𝑙
(3)
C𝑙 > f𝑙
where μ is the average packet length in bits, 𝐶𝑙 and 𝑓𝑙, respectively, represent the capacity and the flow of
the link l in bps.
The propagation delay (𝑡 𝑝) is dependent on the medium and thus is a function of both the medium
and the physical distance separating the individual components of WAMS. In the fiber optic, the propagation
delay can be considered as in the following equation [42].
tp =
NL
S
(4)
where
S is the speed of the light in a vacuum.
L is the length of the communication link
N is the group index of the material≈1.5
Consider the network is connected using backbone switches. We can conclude the above-mentioned
facts and summarize the total communication latency time as in the following equation:
T = tpmu + ∑ tpi
𝑙n
i=1 + ∑ tqu i
SWn
i=1 + tpdcpdc (5)
where
T is the total latency,
𝑙 𝑛 is the number of links between PMU and CCBS
SWn is the number of switches between PMU and CCBS
tpdc is PDC delay
Based on the typical values shown in Table C.2 in [43], and with assuming PDC uses direct forward
mode tpdc ≈ 2ms, and tpmu ≈ 25ms. The (5) will be as follows:
T ≈ 25 + ∑ tpi
𝑙n
i=1 + ∑ tqu
SWn
i=1 + 2 (6)
Queuing packet losses mostly occur because of the finite queue capacity of packet switching
networks. To compute the average loss rate at each switch, each node is modeled with the M/M/1/k queuing
system. On the topic of [44], the total number of packet losses is estimated as a function of the link flow and
the capacity of buffers and links. The form of average packet loss will be:
Average packet loss =
1
∑ hdd
∑
1−ρe
1−ρe
be+1e ρe
be
(7)
where
ρe =
fe
ye
hd = Traffic volume for all PMUs and CDs
be = Buffer capacity of link e ,
ye = Capacity of link e ,
fe = Traffic flow of link e.
For a system, which contains 500 PMUs and 500 CDs with each data flow 128 kbps and 500 links
with flow link ratio 𝜌 𝑒 equal to 0.8, if we use a buffer memory equal to one mega, average packet loss ≈ 0.
Therefore, the buffer memory can be assumed with enough value and the cost of this memory relative to
other component in CI can be neglected. This leads to reducing variables in the optimization problem and
reducing the run time.
The reliability of the WAMS depend on the reliability of media channel and nodes elements. Based
on the concept in [45] we can describe the relation which assess the reliability of connection between any
Required-node (Rnode) and CCBS as follows:

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RS = ∏ Ris (8)
Rp = 1– ∏ [1 – Ri ]p (9)
where
Rs=series element reliability,
Rp=parallel element reliability,
s = Number of series elements in a path
p = Number of parallel elements in a paths.
For each bus reliability calculation, there are two cases: Case1) Complete observability without
redundancy. In this case, there is only one path. If the PMU is located at Rnode the series components are
only communication components (i.e. switches, communication links (cl), and PDCs) as shown in
Figure 4(a). If the PMU is located at Neighbor-node (Nnode), the series components are communication
components plus the transmission line (T.L.) as shown in Figure 4(b) (Case2) Complete observability with
redundancy. In this case, there are series path and parallel paths as shown in Figure 5 and Figure 6 (for two
degree of redundancy). If the PMUs are located at Rnode, the path contain Rnode has only communication
components and the other paths have communication components plus T.Ls. If the PMUs are located at
Nnodes, all paths contain communication components plus T.Ls.
Figure 4. Complete observability
Figure 5. Redundancy with PMU at Rnode and Nnode

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Figure 6. Redundancy with PMUs at Nnodes
In this study, the reliability of each switch is assumed as 0.99 and the reliability of OPGW and
transmission lines is calculated as follows:
Reliabilitycl or T.L. = RL/BL
(10)
where
L is the length per km of the OPGW link or transmission line
BL is the base length
R is the reliability of the base length
In this study, the base length and the reliability of the base length is assumed 20 km, and 0.99 respectively
6. COST CALCULATION
The WAMS cost depends on CI cost, PMUs cost, and CCBs cost. The cost of a CI is mainly
composed of two major costs including the cost of passive components and the cost of active devices. In fiber
optic networks, the price of passive components mainly depends on OPGW length and capacity. On the other
hand, the cost of active devices mainly depends on the number of switches, which are installed at backbone
nodes [46]. As a result, the cost of CI correspond directly to the number of switches, and data transmission
medium (i.e. OPGW) price and installation cost as in the following equation
CostCI = ∑ Li
𝑙
i=1 di + ∑ SWci
SWn
i=1 (11)
where
𝑙=number of the links
Li = Lcrpi
+ Lini
𝐿 𝑐𝑟𝑝=link capacity rate price factor (Depend on the link capacity)
𝐿𝑖𝑛=link installation cost factor
𝑑𝑖=length of the link
SWc i ≈ switch crpi
+ switch ini
switch crp=switch capacity rate price factor
switch in=switch installation cost
Subscript i indicate link or node i
Actually, however, the model should be such that the price of channel capacity can take only
discrete values. In addition to the CI cost, there are the cost of PMUs, which equal to the total price of
the PMUs and its installation cost.
CostPMUs = ∑pmu
i=1 pmuci (12)

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where
pmu=number of the PMUs
pmuci = PMUpchni
+ PMUini
PMUpchni
= PMU price factor (depend on the number of channal of the PMU)
PMUini
= PMU installation cost (depend on site location)
In the case of adding new data transmission paths between buses, the economic study has considered
the establishment of new towers; the cost of the total new towers will depend on the link length. The total
link cost can be calculated as follows:
cdi = (Lavcrp + Lini
)di + tc = Lavi di + αidi = Lavidvi (13)
dvi =
di(Lavi+α)
Lavi
= di (1 +
αi
Lavi
) = di(1 + β) (14)
where
𝑐𝑑𝑖=cost for direct link i
Lavcrp=Capacity rate price factor of the new data transmission paths
𝐿𝑖𝑛 =link installation cost factor
𝑡𝑐=towers cost=𝛼𝑑𝑖
α=tower cost factor
𝐿 𝑎𝑣𝑖 = 𝐿𝑎𝑣𝑐𝑟𝑝 + 𝐿𝑖𝑛 𝑖
𝑑𝑖=actual distance for link i
𝑑 𝑣𝑖= virtual direct distance for link i
β=direct connection factor
The minimum number of the PMUs required could be calculated using (2). In addition, the number
of CDs (Ncds) are known, so that the capacity of the new data transmission line Cav) could be approximated
as follows:
Cav ≈ (
PMUSmin
2
) PMUdata flow + (
Ncds
2
) CDdata flow (15)
where
PMUdataflow is rate of the pmu data flow (kbps)
CDdataflow is rate of the CD data flow (kbps)
For each existing economic study between two buses, calculate virtual distance from (14) for all
possible new data transmission paths. After calculating virtual distance there are two-distance matrices:
distance matrix corresponding to transmission lines distance matrix (𝐷 𝑝𝑜𝑤𝑒𝑟) and distance matrix from
virtual calculating (𝐷𝑣𝑖𝑟𝑡𝑢𝑎𝑙). Merge the two matrixes in one matrix 𝐷 𝑚𝑒𝑟𝑔𝑒𝑑 as follows:
- For direct connected buses, compare the link distance in Dpower with 𝐷𝑣𝑖𝑟𝑡𝑢𝑎𝑙 and take the 𝑑 𝑣𝑖 as link
distance if it is less than 𝑑𝑖 in Dpower. 𝑑 𝑣𝑖
- For not direct connected buses, take the virtual length as link distance.
- Then modify (11) as follows:
CostCI = ∑ Li
𝑙𝑝
i=1 di + ∑ (Li
𝑙
i=𝑙𝑝+1 di + α di) + ∑ SWci
SWn
i=1 (16)
where
from 1 to lp are the links from power system network
from 𝑙 𝑝+1 to 𝑙 are the links from new added paths
Finally, the total cost will be as following
Total Cost = CostCI + CostPMUs + CostCCBi (17)
where
CostCCBi is the cost of CCBS (Include CCBS site and PDC cost)

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7. PROBLEM FORMULATION AND IMPLEMENTATION
The PMUs optimal placement problem can be considered as nondeterministic polynomial complete
problem [47]. For a system with N buses, the search space is 2 𝑁
without considering CI topology, channel
capacity allocation, and number of PMU channels. Therefore, the PMUs optimal problem is considered as
a combinatorial optimization problem [48]. Meta heuristic algorithm population based methods, such as
BPSOGSA, are candidate for solving such problems. In the following, two approaches are presented to
minimize the total cost with considering the observability and CI. In these approaches, the optimization
problem is defined as follows:
Prob. ∶
{
Min: (Total Cost = CostCI + CostPMUs + +CostCCBi)
variable:PMUs locations, the network
topolgy, link capcity, and buffer memory
Subject to:
{
i) Observability constraint
ii) Connection constraint (
All PMUs, CDs, and
CCB are connected
)
iii) Latency time constraint
V) Reliability constraint
(18)
The following considerations are made in these approaches:
- Some CDs are existed, and will be connected with the communication network.
- Two Cases are considered for location of the CCBS; predefined and free selected.
- Some PMUs locations are predefined and included in the cost calculation.
- Conventional measurements and ZIB with a required degree of observability and required redundancy are
considered in the observability constraint such as in Section 2
- The buffer to store the packet in the switching node has a fixed enough value and not considered in
the optimization problem.
- Based on fairness grade of service, the link capacity is allocated to minimize the maximum latency time.
The maximum Latency time for any PMU(𝐭 𝐫𝐞𝐪) is less than 0.04 Sec.
- PMU and CD dataflow are assumed 128 kbps.
- The reliability of the observability for any node (rreq) is greater than 0.8
In the following sections, the IEEE 14 and IEEE 118 systems with given data in below is
investigated for full observability condition using PC with Intel Core i5-430M @ 2.27 GHz and Matlab 2016.
In addition, the results of these approaches are compared with the method, which was presented in [18] with
fixed channel capacity (ten times actual data flow) and without adding new data transmission paths. Distance
matrix of each IEEE test network, we have assumed that all transmission lines have the same conductors.
Thus, the relative distances between system buses can be extracted from system admittance matrix.
In addition, the distances of the new data transmission paths are assumed as listed in Table 1 and Table 2 for
IEEE 118 bus and for IEEE 14 bus. Table 3 and Table 4 show CCBS per unit cost at each bus for IEEE 14
bus and IEEE 118 bus systems respectively. Table 5 shows the rate of the data flow for PMU and CD.
Table 6 presents cost factors values, which are used to calculate the total cost.
Table 1. distances of the new data transmission paths for IEEE 118 bus
Bus To Bus Distance (k M)
24 17 16
24 31 24
24 39 32
24 49 28
24 96 20
5 27 33
37 47 16
32 43 18
45 80 31
Table 2. distances of the new data transmission paths for IEEE 14 bus
Bus To Bus Distance (k M)
5 10 28.5 2
6 10 23.2
4 14 26.2
7 14 20.2

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Table 3. CCBS per unit cost for IEEE 14 bus
Bus No. CCBS cost Bus No. CCBS cost
1 2 8 2.6
2 2.2 9 2.6
3 2.3 10 2
4 2 11 2.7
5 2.4 12 2.1
6 2.1 13 2.3
7 2.5 14 2.4
Table 4. CCBS per unit cost for IEEE 118 bus
Bus No. CCBS Cost Bus No. CCBS Cost Bus No. CCBS Cost Bus No. CCBS Cost
1 3.719 60 3.3434 31 3.1984 91 2.9697
2 2.3641 61 1533 32 2.9213 92 3.3111
3 1.9626 62 2.2164 33 3.9567 93 2.1998
4 2.2863 63 2.9469 34 2.542 94 2.6452
5 3.4149 64 3.2891 35 2.542 94 2.6452
6 1.7678 65 3.8697 36 3.1778 95 2.5281
7 3.5341 66 3.0082 37 3.1812 96 3.0965
8 3.8472 67 2.6127 38 2.485 97 3.422
9 1.9138 68 2.9791 39 3.3338 98 3.1374
10 2.0987 69 3.4924 40 2.1127 99 1.7917
11 2.7317 70 3.1871 41 2.2335 100 3.8055
12 2.0737 71 1.524 42 2.4873 101 2.228
13 3.681 72 3.331 43 2.1265 102 2.9907
14 3.6215 73 3.2627 44 2.5577 103 3.0714
15 1.659 74 1.8533 45 2.5245 104 2.1432
16 2.1787 75 3.3286 46 2.8445 105 3.3132
17 3.7605 76 2.3377 47 3.1605 106 3.9032
18 2.5059 78 3.4523 48 3.9543 107 3.3752
19 2.2869 79 1.5871 49 1.9412 108 2.8049
20 3.1107 80 3.9971 50 3.2633 109 1.9165
Table 5. Flow data
PMU and CD data flow 128 kbps
PMU and CD frame length 1 Kb
Table 6. Cost factors values
Factor Rate value Cost Per unit cost
𝐿 𝑐𝑟𝑝 ( IEEE 14 bus) 0.3 Mbit/s
0.7 Mbit/s
1.3 Mbit/s
2.7 Mbit/s
6 Mbit/s
200 Mbit/s
14 $/km
40 $/km
60 $/km
100 $/km
200 $/km
50000 $/km
0.00014
0.0004
0.0006
0.001
0.002
0.5
𝐿 𝑐𝑟𝑝 ( IEEE 118 bus) 0.3 Mbit/s
1.3 Mbit/s
6 Mbit/s
12 Mbit/s
24 Mbit/s
48 Mbit/s
96 Mbit/s
600 Mbit/s
1200 Mbit/s
14 $/km
60 $/km
200 $/km
400 $/km
800 $/km
1600 $/km
3200 $/km
18000 $/km
36000 $/km
0.00014
0.0006
0.002
0.004
0.008
0.016
0.032
0.18
0.36
switch 𝑐𝑟𝑝 ( IEEE 14 bus) 100 Mbit/s
250 Mbit/s
500 Mbit/s
10,000 $/node
20,000 $/node
40,000 $/node
0.1
0.2
0.4
switch 𝑐𝑟𝑝 ( IEEE 118 bus) 100 Mbit/s
250 Mbit/s
600 Mbit/s
1200 Mbit/s
10,000 $/node
20,000 $/node
40,000 $/node
80,000 $/node
0.1
0.2
0.4
0.8
𝑃𝑀𝑈𝑐ℎ𝑝 2 channel
4 channel
6 channel
8 channel
10 channel
12 channel
14 channel
20,000 $/node
50,000 $/node
60,000 $/node
70,000 $/node
80,000 $/node
90,000 $/node
100,000[1*] $/node
0.2
0.5
0.6
0.7
0.8
0.9
1
𝑃𝑀𝑈𝑖𝑛 20000 $/node 0.2
α (tower cost) 1000 $/km 0.01[2*]
𝐿𝑖𝑛 1000 $/km 0.01[2*]
switch 𝑖𝑛 100 $/node 0.001[3*]
[1*] This value is used as base for the per unit cost
[2*] This value is used for all links unless otherwise stated
[3*] This value is used for all nodes unless otherwise stated

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7.1. Using BPSOGSA Combined with MST
In this approach, the optimization is divided into three loops as shown in Figure 7. The first loop,
the main loop, the BPSOGSA in Section 3 is tseb uh secrao uoe desu location of the CCBS and PMUs that
achieve the observability constraint as shown in Section 2. If the observability condition is not met, the inner
loops are not required. Therefore, the following equation is used as the cost function in the outer loop.
Total Cost = C1 + OBS_Penalty (19)
where
OBSPenalty = C2 ∗ ineqdsum
𝐶1, 𝐶2 are constants with large value
ineqdsum = summation of all postive elements in OBSd vector
OBSd = observability right hand side − observability left hand side
Based on Dmerged, the MST or MMST in Section 4 to connect all PMUs, CDs, and CCBS is used in
the second loop. The third loop, BPSOGSA is used to allocate the links capacity of the connected network.
Cost of the connected network according to (17 This loop return the total) with considering the (20) and (21)
as a weighted penalty.
max (Tpmu) < treq (20)
min (RNode) < rreq (21)
where
Tpmu is a vector of latency time for all PMUs according to (6)
RNode is a vector of latency time for all nodes according to (9), (10).
Figure 7. Flow chart of BPSOGSA and MST

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7.1.1. IEEE 14 bus Case study
a. Free selection of the CCBS
Table 7 lists the predefined locations of the PMUs and CDs. In addition, Table 8 shows the results
of the proposed approach, and the network topology is shown in Figure 8. The results of the used method
in [18] for this case are: cost= 33.048 per unit, maximum latency 0.027844 Sec., and minimum
reliability =0.87146.
b. Predefined selection of the CCBS (CCBS=14)
Table 9 lists the Predefined locations of the PMUs, CDs, and CCBS. In addition, Table 10 shows
the results of the proposed approach, and the network topology is shown in Figure 9. The results of the used
method in [18] for this case are: cost= 47.561 per unit, maximum latency 0.02826 Sec., and minimum
reliability =0.83678.
Table 7. Predefined locations
PMUs locations 2,8
CDs locations 3,10
Table 8. Results of the proposed approach
CCBS location 10
All PMUs locations 2, 6, 8, 9
Total cost (per unit) 9.212
Maximum latency time (Sec) 0.028169
Minimum reliability 0.90821
Runtime (minute) 40
Figure 8. Network topology (14 bus free selection case)
Table 9. Predefined locations
PMUs locations 2,8
CDs locations 3,10
CCBS location 14
All PMUs locations 2 ,6 ,8, 9
Total cost (per unit) 10.228
Runtime (minute) 35
Figure 9. Network topology (14 bus predefined selection case)

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7.1.2. IEEE 118 bus Case study (Free selection of the CCB)
The Predefined locations of the PMUs, CDs, and the results of the proposed approach are listed in
Table 11. In addition, the network topology is shown in Figure 10. The results of the used method in [18] for
this case are: cost= 54 per unit, maximum latency 0.029074 Sec., and minimum reliability =0.76225.
Table 11. Predefined locations and optimization results
Predefined locations
PMUs locations 2, 5, 10, 12, 14, 21, 32, 34, 37, 41, 94
CDs locations 91, 92, 96, 100, 105
Results of the proposed approach
CCBS location 30
All PMUs locations 2, 5, 10, 11, 12, 14, 17, 21, 25, 29, 32, 34, 37, 41, 45, 49, 53, 56, 62. 64, 72, 73, 75,77, 80,85, 87,
91, 92, 94 ,96, 97, 100, 105, 106 ,110, 114, 116
Total cost 49 (Per unit) + penalty of the reliability constraint
Minimum reliability 0.79868 <0.8
Runtime (minute) 230
7.2. Using BPSOGSA
In this approach, the optimization is divided into three loops.
- The first loop, the main loop, is treated as explained in the Section 7.1
- The second loop, the BPSOGSA with particles dimension equal length of 𝐷 𝑚𝑒𝑟𝑔𝑒𝑑 is used to search
the low cost network connection topology, which connect all CCBS, PMUs, and CDs. The value of
the fitness function for this loop is evaluated using the connectivity algorithm, which is shown in
Figure 11.
Figure 11. Connectivity algorithm

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- The third loop is treated as explained in the Section 7.1 complete the flowchart of the approach is shown
in Figure 12.
The main difference between the approach in this section and the approach in Section 1.7 is that
the connection topology is not depend on the length of the network, but the topology connection is depend on
the CI cost.
Figure 12. Flow chart of BPSOGSA
7.2.1. IEEE 14 bus Case study
a. Free selection of the CCBS
Table 7 lists the Predefined locations of the PMUs and CDs. In addition, Table 12 shows the results
of the proposed approach, and the network topology is shown in Figure 13.

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CCBS location 10
All PMUs locations 2, 6, 8, 9
Total cost (Per unit) 9.1316
b. Predefined selection of the CCBS (CCBS=14)
All PMUs locations 2,6,8, 9
Figure 14. Network topology (118 bus predefined selection case)
7.2.2. IEEE 118 bus Case study (Free selection of the CCBS)
CCBS location 26
All PMUs locations 2, 5, 10, 12, 14, 15, 17, 21, 25, 29, 32, 34, 37, 41, 45, 49,
53, 56, 62, 64, 72, 73, 75, 77, 80, 85, 87, 91, 92, 94, 100,
105, 110, 114, 116

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8. RESULTS DISCUSSION
The following results were observed from simulation results.
- The run time of second approach is longer than the first approach
- The second approach is more efficient than the first approach, especially if the difference in price
resulting from the change in channel capacity is significant.
- Indeed, the methods presented in [18] was unsuccessful to achieve the global solution. Since it used MST
algorithm to find the network topology and did not take into account the channel capacity allocation.
Also due to, the multi-loop is not used in this method, the runtime is large.
9. CONCLUSION
In this study, optimal placement of PMUs and their required CI for power systems are co-optimally
designed. Two approaches have been presented. The first approach (i.e. BPSOGSA Combined with MST)
and the second approach (i.e. BPSOGSA) to find the optimum placement of PMUs and their CI are
investigated using IEEE 14 buses and IEEE 118 buses. The simulation results indicate that the second
approach is cost effective. Moreover, the second approach, due to using BPSOGSA in all loops, may succeed
converge to the global solution. In contrast, the first approach due to using MST for links topology can take
less run time but it may not converge to the global solution. The cost of the CI in this study is not depend on
the accumulative length of the OPGW only. However, it considered the switches and the link capacity in
the objective function. In addition, the quality of service such as latency time and the reliability of
the communication network and the degree of the observability are considered. Also, the partially
optimization problem (predefined locations of some PMUs and CDs), and the economic study for additional
new data paths are considered in the proposed approaches.
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