A Proposed Secure Network Model for Implementing Smart Grid Applications in Ghana with WiMAX Technology

Full text

International Journal of Computer Science and Telecommunications [Volume 4, Issue 10, October 2013] 14
Journal Homepage: www.ijcst.org
E. T. Tchao, K. Diawuo, W. K. Ofosu and I. Ghansah
Abstract— Advocates of Smart Grid networks implementation
in Ghana believe that Smart Grids will deliver a more secure,
sustainable and affordable energy for future generations of
Ghanaian consumers. It is also believed that Smart Grids would
underlie much of the infrastructure which makes everyday life
possible. In order to realize this dream, an Ultra High Frequency
(UHF) telemetry system has been used to deploy pilot
Supervisory Control and Data Acquisition (SCADA) networks in
the urban centres of Accra and Tema as a starting point in
implementing a full nationwide Smart Grid Network for the
energy generation and distribution sectors of the country.
Evaluation of the deployed pilot network showed that the limited
coverage range of the UHF system inhibits a full nationwide
deployment. The evaluation also found serious security
vulnerabilities in the deployed SCADA model. In order to achieve
the aim of deploying a secure and ubiquitous intelligent SCADA
network which serves as the data processing and collection
infrastructure in a Smart Grid network, this paper has proposed
a secure SCADA model using WiMAX technology to help
improve the efficiency of current energy production,
management and distribution sectors of the economy.
Index Terms— Smart Grid, SCADA, WiFi, Security
Vulnerabilities and WiMAX
I. INTRODUCTION
MART Grid could be referred to as the modernization of
the electric power grid for the purpose of enabling
bidirectional flows of information and electricity in order
to optimize energy production, management, distribution and
consumption [1]. Electrical distribution networks are
becoming increasingly complex systems. The addition of
embedded generation, sustainable energy projects, demand
side participation schemes and smart metering require the
system operator to gather an unprecedented level of
information in real-time from their network [2]. Information
E. T. Tchao and K. Diawuo are with the Dept. of Electrical and Electronic
Eng., Kwame Nkrumah University of Science and Technology, Ghana
W. K. Ofosu is with the Department of Electrical Engineering
Technology, Penn State Wilkes-Barre, USA
I. Ghansah is with the Dept. of Computer Science, California State
University, Sacramento, USA
Communication Technology (ICT), which is the basis of
autonomic and intelligent systems, is being used in the energy
sector to deploy Smart Grid networks. Smart Grids are
intelligent systems and networks which effectively improve
the efficiency of current energy production and also integrate
a growing number of renewable sources [1]. Smart Grids
provide consumers with diverse choices on how, when, and
how much electricity they use [3].
Additionally, Smart Grids aim at providing better power
quality and efficient distribution of electricity. Indeed, all
these goals cannot be achieved and realized without a
communication technology infrastructure that will gather,
assemble, and synthesize data provided by smart meters,
electrical vehicles, sensors and ICT systems.
SCADA systems, which form the data collection and
processing infrastructure of these complex and intelligent
networks, are used to control geographically dispersed assets,
often scattered over thousands of square kilometers, where
centralized data acquisition and control are critical to system
operation [4]. In electrical power grids, a SCADA control
center performs centralized monitoring and control for field
sites over long-distance communications networks, including
monitoring alarms and processing status data. Based on
information received from remote stations, automated or
operator-driven supervisory commands can be pushed to
remote station control devices, which are often referred to as
field devices. Field devices control local operations such as
opening and closing valves and breakers, collecting data from
sensor systems, and monitoring the local environment for
alarm conditions.
In Ghana, The energy distribution network is undergoing
changes to take advantage of the numerous benefits Smart
Grids offer. Pilot SCADA networks have been incorporated in
the power distribution systems in Accra and Tema, and have
been generally successful in providing wide area situational
awareness to the distribution company. These networks are
gradually altering the distribution network landscape. Where
previously, the distribution network could have reasonably
been considered a simple unidirectional system delivering
power from substation to consumer, now a typical distribution
network in the Accra and Tema Municipality is a complex
entity with intricate power flows as shown in Fig. 1 and Fig. 2.
S
A Proposed Secure Network Model for Implementing
Smart Grid Applications in Ghana with WiMAX
Technology
ISSN 2047-3338

E. T. Tchao et al. 15
In order to extend the success of these pilot networks
nationwide in line with the Government’s agenda of building a
robust economy powered by an efficient energy sector, this
paper seeks to evaluate the deployed SCADA network by
looking at the vulnerabilities in the network and the realistic
chance of extending the current SCADA model nationwide in
a bid to implement a full smart grid network. The sources of
vulnerabilities in the network, the limitations of the network
model and the proposed solutions have been discussed.
II. DEPLOYED SCADA NETWORK MODEL
Electricity distribution companies around the world are at
different points in the Smart Grids network life cycle. Some
utility companies have begun pragmatically planning holistic
networks by applying new enterprise architectures to handle
the demands Smart Grid applications will make on their
networks [3].
In Ghana however, Smart Grid is a relatively new concept
but is believed to be the solution to creating a more efficient
and vibrant energy sector. As such, pilot SCADA networks
have been deployed in selected cities as a starting point in
deploying a nationwide Smart Grid infrastructure to help
improve electricity generation, management and distribution.
The deployed SCADA networks under evaluation cover the
urban centres of Accra and Tema. The electricity generation
and distribution companies, thus Volta River Authority (VRA)
and Electricity Company of Ghana (ECG) respectively, are
owned by the Government of Ghana. They have a number of
primary and secondary substations and power distribution
lines interconnecting these stations which supply power to
homes and industries within Accra and Tema as shown in
Figures 1 and 2 respectively. The benefits of the SCADA
network have been enormous. The major benefit of the
SCADA network implemented in the Accra and Tema power
grids is the network’s ability to provide wide area situational
awareness to the power generation and distribution
companies. This has helped in preventing major power
outages in the two cities and has also helped in providing a
more reliable energy distribution network.
The deployed SCADA system serves as a monitoring
mechanism which makes available in real-time, the current
and voltages on each process (transformers and feeders).
It also serves as a control mechanisms which safely and
remotely control circuit breakers, relays and isolators in the
network.
The implemented SCADA systems hardware can be broken
down into the following five major categories as shown in
Fig. 3. These categories are:
• Field level instrumentation and control devices
• Remote Terminal Units (RTUs)
• Communications system
• Master stations
• Data processing computer system
A Professional Mobile Radio (PMR) system, which is a
dedicated mobile communications system, is used by the
Fig. 1: Accra Power Grid
Fig. 2: Tema Power Grid
Fig. 3: Deployed SCADA hardware Architecture

International Journal of Computer Science and Telecommunications [Volume 4, Issue 10, October 2013] 16
utility company to provide wireless connectivity to the field
devices from the Base Station. This UHF scanning telemetry
system typically offers 9.6 - 19.2 kbps throughput.
When the Government extends the success of the pilot
SCADA networks to other cities and towns in the country,
devices will become more dispersed in wide areas.
Compliance of requirements to meet standards will become
increasingly challenging. Interdependencies between
computer communication systems and the physical
infrastructure will also become more complex as information
technologies are further integrated into other devices and
networks as seen in Smart grids deployment in other
countries [5]-[7].
Moreover, in assessing the feasibility of any wireless
system, the range of coverage from a Base Station and the
individual and aggregate throughputs are critical parameters.
Although UHF scanning telemetry systems can be established
without line of sight, experience in the pilot SCADA network
suggests that adequate performance in range and throughput
can only be achieved with line of site (LOS) of the field
devices with the Base Station.
Latency of the UHF Telemetry system is of the order of
seconds. Smart Grid network design parameters are specified
in Table 1. In the implemented SCADA model, devices are
polled in series and taking into consideration the specified
parameters in Table 1, the UHF scanning telemetry system
may be too slow for real-time control applications when the
network size grows exponentially.
From Table 1, the UHF system cannot provide the required
bandwidth to support vital Smart Grid applications and as
such an alternative microwave access technology which offer
greater bandwidth, reliability and extended coverage range is
needed for a successful nationwide deployment.
Field trial measurements of WiFi and 3G systems carried
out in outdoor locations within the pilot network showed these
two systems do not have the capacity and range to help deploy
these complex systems [9]. Fortunately, the Government of
Ghana has successfully deployed a Fourth Generation World
Wide Interoperability for Microwave Access (4G-WiMAX)
network in Accra and Tema for implementing Electronic
Governance applications. These WiMAX networks have been
extended to other cities in the country as shown in Figure 4
with the aim of providing ubiquitous coverage to enable
Electronic Governance applications reach remote parts of the
country.
Performance evaluation of these deployed networks
measured 1Mbps at 5km away from the Base Stations [10].
Fortunately, the deployed WiMAX networks are widely being
underutilized [11]. This makes WiMAX the best microwave
access technology for deploying a nationwide Smart Grid
system since Long Term Evolution (LTE) systems have not
been deployed in the country yet.
WiMAX has the reliability, capacity and coverage range to
provide ubiquitous coverage to the increasing number of
devices which will be located in wide and remote areas. This
will drastically reduce the initial cost of Smart Grids
deployment since there will be no need to set up new PMRs in
various cities and towns.
III. VULNERABILITY ASSESSMENT OF THE
DEPLOYED WIMAX NETWORK
Security for control and data acquisition systems is a
significant and current concern [12]. Best practices for secure
control system design [13]-[17] generally call for a control
system network to be logically separated from the corporate
network devices.
However, data and control traffic in the deployed model as
shown in Fig. 5 is carried by the same networking
infrastructure that carries other corporate traffic. As such,
direct applications of traditional best practices for these
control systems’ security have not been adhered to.
Vulnerability assessment of the deployed network found no
Virtual Local Area Network (VLAN) segregating the SCADA
network from the corporate network. There was no logical or
Use Case
DL
(kbit/s)
UL
(kbit/s)
Latency
(ms)
Wide Area Situational
Awareness (WASA)
1.0
5.0
1000
Monitoring
10
300
100
Control
1.0
5.0
100
Protection
150
150
20
Metering Regional Collector
5.0
64
1000
Remote Site Communications
500
500
100
Direct 4G Smart Metering
(AMI)
0.5
1.0
5000
Table 1: Smart Grid network design parameters [8]
Fig. 4: Major Cities and Towns on the Electronic Government
WiMAX network

E. T. Tchao et al. 17
physical separation and this exposes the main SCADA Servers
to the corporate TCP/IP network.
Moreover, administrator credentials of the SCADA servers
are commonly known to most of the workers at the Network
Operation Center. Passwords being used for administrative
accounts on the SCADA servers, databases and network
devices were easily guessable and very weak.
There is also the issue of one-way authentication in the
deployed UHF network where only the Base Station
authenticates the field equipment. This makes the field devices
vulnerable to rogue Base Stations. Moreover, UHF
communication systems are vulnerable to traffic analysis, a
technique that allows the attacker to determine the load on the
communication medium by monitoring and analyzing the
number and size of packets being transmitted.
Because UHF communication systems are susceptible to
passive and active eavesdropping, an attacker can listen to the
wireless connections in the SCADA network as well as
actively inject messages into the communication medium.
In addition, threats in wireless systems in general focus on
compromising the radio links. Hence, these systems are also
vulnerable to radio frequency (RF) jamming. It implies, the
UHF system is susceptible to scrambling attacks, where an
attacker injects RF interference while transmitting specific
management data. RF interference affects proper network
ranging and bandwidth sharing capabilities of wireless
systems [18]. The effect of the limited coverage range, which
is a denial of service caused by RF interference in the UHF
system has been illustrated in the coverage simulation in
Fig. 6.
SCADA devices which will be in the coverage range of the
rogue Base Station will be denied access and this could be
very disastrous.
These identified security vulnerabilities in the SCADA
network could seriously affect a full Smart Grid integration of
the electric power grid. Millions of dollars have been spent on
deploying these networks but apathy which could be attributed
to the false notion that the SCADA networks are physically
isolated from the corporate offices makes this critical national
infrastructure vulnerable. These major security issues need to
be addressed as there are plans to put more critical national
infrastructure on the grid.
IV. PROPOSED SECURE NETWORK MODEL
The Government of Ghana has a major objective of
improving the existing energy generation, transmission and
distribution grids through the introduction of smart devices
and a communication network, deployed on top of the
electrical infrastructure which will enable real-time
interactions among the devices, systems and operators. The
aim of providing high quality energy in Ghana in the context
of increased variability and complexity of the electric system
requires a suitable control infrastructure based on more
pervasive and secure ICT solutions into the whole electrical
generation and supply chain as specified by the NIST Smart
Grid conceptual model shown in Fig. 7.
Fig. 5: Deployed SCADA Communication model
Fig. 7: NIST Smart Grid conceptual Model
Fig. 6: UHF RF Jamming Scenario Simulation

International Journal of Computer Science and Telecommunications [Volume 4, Issue 10, October 2013] 18
A logical isolation is proposed between the SCADA and
corporate TCP/IP networks by using a securely configured
bridge acting as a control network perimeter security as
proposed in [13], [19].
Role based access control is also recommended among the
staff at the Network Operation Center of the utility company.
The bridge must be securely configured and at least a 12
character password consisting of upper cases, lower cases,
numbers and special characters is also recommended
WiMAX has been used as the microwave access technology
for the proposed SCADA model in Figure 8 because it enables
mutual authentication by both Subscriber Stations and Base
Stations. This will help significantly in solving the threat of an
attacker setting up rogue Base Stations and transmitting
information to the field devices.
WiMAX also has extended coverage and greater Bandwidth
capacity as compared to the UHF telemetry system. Eleven
WiMAX Bases Stations have been used to provide ubiquitous
coverage for the urban centres of Accra and Tema as shown
by the coverage simulation in Figure 9 using an adaptive 4x4
Multi-Input Multi- Output (MIMO) antenna configuration.
The existence of these WiMAX networks deployed by the
Government in major cities and towns provide both technical
and economic advantages. This makes such a proposal very
feasibly. The distribution company can operate a Virtual
Private network (VPN) over the WiMAX networks all over
the country. It is possible for the utility companies to emulate
a LAN over the open connections of the WiMAX network,
creating virtual circuits.
The VPN eliminates the need for an expensive region by
region roll-out and also allows for tunneling over other media.
This makes the network communications fully transparent to
the SCADA application. This will also help provide a logical
separation of the communication system from the corporate
TCP/IP network.
The use of inverse multiplexing or network striping is
proposed in the case of RF jamming. This technique will
allow the construction of a high bandwidth virtual channel
from a collection of multiple low bandwidth network
channels. Control and data information could be sent via
alternate channels with the applications on the alternate
channels being oblivious of the way in which data and control
information are routed to specific network channels. This is
very appropriate for the SCADA applications in case the
specified operating frequency of the WiMAX network is
jammed.
Because the locations of some of the field devices are
isolated, it is recommended that these Remote Terminal Units
are physically protected.
V. CONCLUSION
Community benefits of a nationwide Smart Grid
implementation in Ghana will be enormous. A journey of a
thousand miles begins with a step and as such, the utility
companies in Ghana have started with pilot implementation of
SCADA networks in the energy generation and distribution
sectors. Vulnerability assessment of the pilot networks has
shown immediate concerns revolving around the security of
this critical infrastructure.
UHF systems which are currently been used have serious
security vulnerabilities, low throughput and limited coverage
range and would be overwhelmed given the task of providing
communication service to the volume of devices needing
connections which will be installed on the power system in the
medium to long term.
WiMAX technology has been proposed as the microwave
access system for deploying the nationwide Smart Grid
network because of its extensive coverage, reliability and
capacity. WiMAX networks have already been deployed by
the Government and this eliminates the tendency of deploying
new PMRs in cities and towns to achieve the nationwide
Fig. 8: Proposed Communication model for the deployed SCADA
network
Fig. 9: Coverage Simulation of the Accra and Tema WiMAX sites [9]

E. T. Tchao et al. 19
Smart Grid deployment objective. A Virtual Private Network
(VPN) operating over the WiMAX network has been
proposed to provide the logical isolation the network needs.
REFERENCES
[1]. Christine Hertzog, Liz Ude, and Douglas Stuart, “Smart Grid
Dictionary” 2nd Edition, 16 June, 2010.
[2]. Securing an Integrated SCADA System; Network Security &
SCADA Systems Whitepaper, Published April 2007
[3]. Andrew K. Wright, Paul Kalv and Rodrick Sibery:
“Interoperability and Security for Converged Smart Grid
Networks”; Grid-Interop Forum proceedings, published 2010
[4]. Pertti Järventausta, Sami Repo, Antti Rautiainen, Jarmo
Partanen: “Smart grid power system control in distributed
generation environment”, Annual Reviews in Control, Volume
34, Issue 2, December 2010, pp. 277-286
[5]. Gurlin Singh Lamba:” Smart Grid and its Development
Prospects in the Asia-Pacific Region”, Journal of Emerging
Trends in Computing and Information Sciences, Vol.2, No. 1,
pp. 62-66, January, 2011.
[6]. ISO New England, “Overview of the Smart grid – Policies,
Initiatives and Needs”, February 17, 2009.
[7]. Leonardo Meeus, Marcelo Saguan, (2011) “Innovating grid
regulation to regulate grid innovation:From the Orkney Isles to
Kriegers Flak via Italy”, Renewable Energy, Volume 36, Issue
6, June 2011, pp.1761-1765.
[8]. Requirements for Smart Grids, “WiMAX Forum System
Profile Requirements for Smart Grid Applications”, WMF-
T31-002-R010v01; WMF Approved (2013-02-05)
[9]. E.T. Tchao, W. K. Ofosu and K. Diawuo; “Radio Planning
and Field Trial Measurement of a Deployed 4G WiMAX in
an Urban Sub-Saharan African Environment ”, conference
proceeding, IEEE Wireless Telecommunications symposium,
17-19 April, 2013, Phoenix, Arizona
[10]. E.T Tchao, W.K. Ofosu and K. Diawuo; “On the Comparison
Analysis of Two 4G-WiMAX Base Stations in an Urban Sub-
Saharan African Environment”, Journal of Communication
and Computer, Vol. 10, No. 7, July, 2013
[11]. E.T Tchao, W.K. Ofosu and K. Diawuo; “A Performance Case
Study of Electronic Governance Implementation in Ghana
with WiMAX Technology”, International Journal of Computer
Applications Volume 71-No. 14, June 2013.
[12]. Stouffer, Falco, Scarfone, Guide to Industrial Control Systems
(ICS) Security, Draft, National Institute of Science and
Technology SP800-82, Sept. 2008.
[13]. The Smart Grid Interoperability Panel, Cyber Security
Working Group, Guidelines for Smart Grid Cyber Security,
Volumes 3, National Institute of Science and Technology
NISTIR 7628, Sept. 2010.
[14]. Idaho National Laboratory, Control Systems Cyber Security:
Defense in Depth Strategies, Homeland Security External
Report No: INL/EXT-06-11478, May 2006.
[15]. NISCC Good Practice Guide on Firewall Deployment for
SCADA and Process Control Networks, National
Infrastructure Security Coordination Center, London, 2005.
[16]. TR99.00.01: Security Technologies for Industrial Automation
and Control Systems, ISA, 2007.
[17]. David Laverty, D. John Morrow, John O’Raw and Peter A.
Crossley: “Wireless Telecoms for Distribution Networks
Based on WiMAX”; 20th International Conference on
Electricity Distribution, Prague, 8-11 June 2009, Paper 0856.
[18]. Gee Rittenhouse: “A 1000X of data - Technology Directions
in the Wireless market”, Conference proceeding, IEEE
Wireless Telecommunications symposium, Phoenix, Arizona,
17-19th April 2013.
[19]. Guide to Security for Worldwide Interoperability for
Microwave Access (WiMAX) Technologies, NIST SP800-
127.