The electric power is operating near capacity and need of the electric power is increasing, to compromise this, there is needs for critical improvements in distribution and mixing of electric generated from different energy resources. Additionally, the grid has got to shore up efforts to cut carbon emissions and use of renewable energy resources more ingeniously through revolutionizes in energy use pattern. This demand and management of the electric power is possible through the smart grid technology.
The Smart Grid is the upgrading of the electricity grid by means of communication technology for achieving primary goals as
reduce energy consumption and hence production so as to limit environmental impact
reduce energy costs for consumers
encourage customers to produce energy through clean sources like solar panels and grant them credit for it
set up a level of automation, including Automated Meter Reading (AMR)
Smart grids organize the requirements and ability of all generators, end-users, grid operators and electrical energy market stakeholders to operate all parts of the system as efficiently as possible, reduce costs and environmental impacts while maximising system reliability, security, precision, connectivity and interoperability.
The move towards Smart Grid initiatives is varied across utilities. Selected applications, priorities, requirements and preferences differ, driven by geography, funding availability and services offered. In nearly all cases, applications are rolled out in phases as resources become available and as utilities become ready to integrate them within the organization. By gradually adding new applications, utilities can incrementally extract more benefits from the Smart Grid. The different implementation paths are still on research for the best working capabilities and what type of application should be given highest priority.
The success of Smart Grid working rely on telecommunications networks which are scalable and future-proof aiming easy adjustment for addition of new applications and improvement to existing ones. This technology allows utilities to deploy new applications without facing expensive overlay network deployments.
Smart grids roadmap consists of electrical energy networks and communication interfaces with production, storage and end-users. Figure 1 demonstrates the evolutionary character of smart grids.
A comparision of the present and smart grid is disscused on Table 1.
Characteristic
Today's Grid
Smart Grid
Facilitates active involvement by consumers
Consumers are unaware and not involve with power system
Consumers up to date, concerned, and active involvement about demand and circulated energy resources
Accommodates all production and storage options
Dominated by central generation- a lot of obstructions exist for different energy resources interconnection.
Various energy resources available in plug-and-play connection and are focus on renewable energy.
Recent products, services and markets availability.
Restricted wholesale markets, not well-integrated few opportunities for consumers
Established, well-integrated wholesale markets, development of new electrical energy markets for consumers
Power quality for the digital market
Centre on outages and deliberate reaction to power quality issues
Power quality is a prime concern with a selection of quality/price selection and rapid resolution of issues
Optimization of resources & operation efficiency
Small inclusion of functioning data with asset management and silos business process
Significantly extended data acquisition of grid factors aimed for preventing and minimizing impact to consumers
Anticipation and response to system disorder (self-heals)
React to prevent further damage but focusing on protecting assets
Automatically discover and take action to troubleshoot it and focusing on prevention, reducing impact to consumer
System architecture
The smart grid is the meeting point of information technology, digital communications and power system to present a further robust and well-organized electric energy system [7]. Smart grids consist of sensing system, digital communication, control and actuation systems that facilitate persistent supervising and control of the electrical power grid [8]. These characteristics allow accurate prediction, management and control of the electricity flows all over the grid. They provide the bi-directional power grid so that customers can receive electricity and supply electricity produced by some renewable electricity production system. Hence, smart grids convert the power grid into a distributed power generation system [10].
General architecture of the Smart grid is shown in the Figure 2 [8].
Power System Layer: The base of this construction is the power system infrastructure (Actuators) which consists of power conversion, transportation, and consumption and actuation devices. Actuators comprise power plants, transmission lines, transformers, smart meters, capacitor banks, reclosers and various devices. Smart meters allow bidirectional power flows so that customers consume and supply energy to the grid. During the utility power outage the smart meter allows alternative power source to supply the electricity to the grid, hence add the reliability to the power system. This also enhances electricity system effectiveness by eliminating the electric energy losses due to long distance transmission. Because of these capabilities, use of the smart grid will promote better merging of renewable energy sources like wind and solar power into the grid. As a result there will be reduction of dependence on fossil-fuel energy and reducing greenhouse gas emissions.
Control Layer: Control layer of the smart grid architecture consist of devices like SCADA, sensors, etc. The sensors are the devices that are usually embedded on the nodes of power system. These sensors allow real-time fault discovery and isolation by the use of bidirectional digital communication links. These sensors are capable of providing rough data of the system health which can be used for system analysis, fault pre-emption and trending. At this layer the real-time consumption of power are recorded which can be accessed by the utilities and consumers. Smart meters allow remote monitoring and controlling of home appliances and building loads.
Communication Layer: The communications layer is the bond that connects all these different layers together. The Communications Layer is further divided into three sub divisions. They are:
Home Area Network [HAN]: HAN involves the communication between various devices in a apartment. In case of the smart grid technology the HAN provide communication between devices installed and the Smart Meters at costumer premises.
Neighbourhood Area Network [NAN]: NAN provides the communication between the utility companies and customers premise Smart Meters.
Wide Area Network [WAN]: WAN provides the backhaul communications. Backhaul communication make available the link to the network operating centre (NOC), to be more specific, to the nearest or most cost-effective fiber connection.
The communication technologies like 802.16, 802.15.4/Zigbee, 802.11 WiFi, WiMAX and optical fiber are the backbone for providing the interface for communication. Figure ... shows the hierarchical organization for efficient use of communication technology in term of coverage area and bandwidth utilization for such coverage. The analysis is done for the cost effectiveness.
Application Layer: Decision intelligence is the final layer at the top of the smart grid architecture. This layer cover substation automation, load distribution, fault-management and other control plans which assure power system constancy and balance power requirement and supply.
For the wireless infrastructure component, 4G technologies like WiMAX can host the entire set of Smart Grid applications that utilities want to implement. Other technologies, such as narrowband proprietary wireless networks, second generation (2G) or third generation (3G) cellular networks, or Wi-Fi networks can support some applications, but not all.
Home Area Network (HAN)
In Smart Grid technology HAN provide the communication between the customers premise and the Smart Devices. This network is set up by the utility company and is connected to the backhaul network for communication with the utility company headquarters. Figure shows a typical HAN communication.
For such network use of the Zigbee wireless technology is one of the good options. Zigbee is a low cost, low data rate, low power and short range communication technology built on the IEEE 802.15.4 standard. The Zigbee devices operate on 2.4-GHz radio band which is licence-free radio signal in most of the countries. United States National Institute for Standards and Technology (NIST) has defined ZigBee smart energy profile (SEP) as one of the communication standards to be used on smart grid in the customer premise network domain [4]. But due to the limited transmission range of Zigbee for long-range communication, technologies like IEEE802.11 is used to provide communication between utilities and customer premises. The protocol stack of Zigbee is shown below
The extra feature that are added on Zigbee at application Layer that make suitable for HAN are describe bellow
Application profile: An Application Profile is the framework that defines a set of devices that are rationally used together in implementing an application. Zigbee has defined framework differently according to different use. For instance, the ZigBee Alliance has defined the application profile as Home Automation (HA) profile, HA is used to control appliances and systems in the home, such as a heating system. It also defines the number of 'devices' to be used along with function to control them. For heating system the function defined might be the time to on/off the heater, control the temperature, etc.
Devices, Clusters and Attributes: Zigbee defines 'device' as a software entity that defines the functionalities and properties for application that are to be connected to network node. An attribute is a data entity like temperature, intensity, etc exchange between the different applications in the network. Cluster in Zigbee is the communicating attribute which consist of a set of related attributes along with set of commands. A cluster has two commands send and receive used to communicate between Input cluster and Output cluster as shown in Figure
ZigBee Cluster Library (ZCL): Even though clusters are defined in an Application Profile but due to certain clusters being common to all Application Profiles, Zigbee define ZCL which contain all the standard clusters. For instance, the Smart Energy profile utilizes the Time cluster from the ZCL for synchronizing the different nodes in HAN.
Neighborhood Area Networks
NAN is the communication network that aids the communications connecting the utilities and the Smart Meters installed at the customer premises. For Neighborhood Area Networks, the protocols/standards IEEE 802.11 [Wi-Fi] and Cellular technology [GSM] well in terms of security, coverage range, accessibility and ease of implementation. Figure-2 shows scenario to implement Neighborhood Area mesh-Networks in the smart grid. The data are collected from smart meters of customer premises by the 2.4/5 GHZ.
Smart Grid Security
For better management like real-time billing cost, system load prediction and customer energy management, Smart Grid needs complete information of energy usage by the customers. The accessibility of such usage data from customer premises every 5 - 15 minutes has serious security threat [49]. From Smart meter data analysis it is easy to find out which appliances are being uses at certain time period. People are feared that by use of the smart meter they might be spied, hece producing negative impact on smart meter deployment [50]. Furthermore, use of smart meters for networking with electricity grid might raises the presence of smart meter cheating and also adds chances of malicious attacks such as Denial of service (DoS) due to the exposure of these devices.
A. Privacy Issues:
As the information are all recorded in the smart meter. The use of "appliance load profile" that is detection of the appliances used by mean appliance unique fingerprint, the identification of the appliances being used or has been used can be easily decided. [51-53]. This also make available access to information including the variety of appliances a resident owns, at what time and for how long the particular appliance being used each day, even they knows they cook food or use microwave meal. This raises the privacy issue as they might be monitored. Additionally, inappropriate use to such data can lead to breaches of privacy or even make one open to security issue.
B. Smart Meter Fraud:
The want for lower electricity bills might give a compelling encouragement for smart meter fraud. Some people who want to show their ability might release the software or toolkits for hacking the smart meter. By use of such tools one can send the false data to the utility and pay the bill for less electricity then used. [54].
C. Malicious Attacks:
The internetworking of smart meters makes them especially vulnerable to denial of service attacks in which several meters are hijacked in order to flood the network with data in order to shut down portions of the power grid, or report false information which can result in grid failures.
D. Smart Grid Security Solutions
Smart grid security problems can be resolved via a mix of regulatory and technological solutions. A rigid structure is essential to indicate who has right to use the smart meter data and under which circumstances, in addition to this, penalties for data misuse should be enforced [54]. Two technological solutions have been proffered. The first is to combined HAM data at the neighbourhood transformer and then sending it by stripping off its source address before transmitting it to the utility [49]. Kalogridis et al [55] suggest the utilize of a third party escrow facility that receives the detailed meter data, anonymizes it by stripping off any information that could be used to identify a specific household, and then sends the utility the aggregate data required for billing and monthly energy usage for each customer.
We propose a digital rights management system (DRMS) based scheme which extends that proposed in [56]. Users license permission to the utility to access their data at varying levels of granularity. By default the utility would have access to monthly usage and billing data, but customers have to grant the utility permission to access their data at higher levels of granularity in exchange for rebates or other incentives. Such a system eliminates the need for an intermediary between the utility and the consumer, but requires a means of guaranteeing that the utility cannot access restricted customer data.
For instance, narrowband or cellular networks provide good coverage and sufficient throughput to transport metering data, but are insufficient for remote surveillance, because their uplink capacity is severely constrained. Wi-Fi networks can support remote surveillance in some environments, but typically lack the ubiquitous coverage needed to support metering or mobile workforce access and have limited quality of service (QoS) functionality.
Common to both the rural islanding and urban meshed distribution scenarios is the potential need for a communications infrastructure with exceptionally tight latency characteristics. The extreme time-sensitivity of these factors results in a tolerance for a maximum latency of 6 cycles, or 100 ms. The communications network supporting these scenarios must therefore strictly respect this latency constraint. It is conceivable the grid operator has access to fiber optic facilities, either owned directly or leased. Latency is exceptionally low with fiber optic - the rule of thumb being just under 5 μs latency per kilometer length of strand. Where fiber is not available to the system operator, or where fiber is available to some, but not all points in the system, the use of wireless technology is very attractive. One wireless network technology exhibiting very good latency characteristics is WiMAX (Worldwide Interoperability for Microwave Access).
Because they combine high throughput, low latency, and wider coverage, 4G technologies can host and integrate all Smart Grid applications, and also act as the unifying platform that provides backhaul connectivity for other wireless networks using BPL, ZigBee (Institute of Electrical and Electronics Engineers [IEEE] 802.15.4), Wi-Fi (IEEE 802.11), or license-exempt wireless technologies. For utilities, a single wireless technology like WiMAX that is widely deployed within their territory means lower costs, less complexity, improved control over applications, and better overall performance.
4G as smart grid communicator
One of the challenges-but also a main benefit-of the Smart Grid is that energy generation, distribution, and consumption are managed throughout it, using different tools in different locations but within a unified network core. To do this, multiple applications must run in parallel and coexist on the same network (Figure 1), and each must be assigned to the appropriate priority level.
For instance, metering data can receive lower priority than emergency communications or, in most cases, surveillance data. A voice over Internet Protocol (VoIP) call from a field engineer trying to fix a problem can have priority over the download of a blueprint or a map that another engineer will need later in the day. The ability to control and actively manage traffic enables utilities to cope with a complex mix of requirements driven by multiple applications by operational requirements.
Utilities are increasingly moving to deploy and manage their wireless networks in ways that meet the challenging demands of Smart Grid traffic. As they do so, they need to choose technologies that give them the flexibility to use their wireless network capacity effectively-advanced traffic management tools such as QoS, traffic prioritization, and policy management.
These tools are available in 4G networks, but they are typically not supported in cellular and Wi-Fi networks, which provide best-efforts data connections with high levels of contention.
If using a shared network, the cellular operator or service provider may use sophisticated traffic management tools, but utilities might have little or no visibility into or control of how this is done-or how it affects them. They certainly cannot dictate their own conditions on how to manage traffic.
The lack of control becomes a particularly sensitive issue during emergencies. Competition for network resources is likely to be highest at these times, and although not all traffic is equally crucial to resolving the emergency, in today's cellular networks, it is treated equally. In shared, best-efforts networks, utilities are not able to secure priority over other network customers-or even to have a guaranteed bandwidth-and end up competing for bandwidth with subscribers who are calling family and friends to let them know they are safe.
Ecosystem. Utilities have long operated proprietary networks, and know well that they often carry a hefty price tag, limit their ability to innovate and upgrade, and keep them tied to a vendor. WiMAX is not a technology specifically developed for utilities. It has wide appeal among network operators that provide services within public networks (e.g., Clear in the US, Yota in Russia, or P1 in Malaysia) or within enterprise or vertical networks (e.g., for utilities, transportation, or health care). WiMAX also has support from many infrastructure and terminal device vendors.
With WiMAX, utilities can rely on a standards-based (IEEE 802.16) technology that keeps evolving, with the next major release, IEEE 802.16m-also referred to as WiMAX 2-promising higher throughput and better support for mobility and voice applications.
Because WiMAX equipment is interoperable, utilities can source it from multiple vendors, and select the best-of-breed gear for each application. For instance, utilities may choose one vendor for base stations and others for the terminal devices for meters and for the wireless units for cameras-or they may keep their current vendors while adding new ones for new equipment. In either case, they will be able to choose from multiple infrastructure and device vendors, which means more competitive pricing and wider selection.
WiMAX as a smart grid enabler
WiMAX is the first commercially available 4G technology. It is ideally suited to meeting both the requirements of Smart Grid applications and the needs of utilities to keep complexity under control without sacrificing security or reliability.
Environment. Utilities have a presence throughout their territory. They need to reach every business and household, and they have assets in both urban and remote areas. The connectivity requirements-and challenges-differ wildly depending on location. In rural areas, coverage and backhaul availability are main issues. In urban areas, the more prominent issues are availability of spectrum and access point locations, the need for interference management, and the requirement for higher capacity. WiMAX, with its support for both multiple input, multiple output (MIMO) A and MIMO B, can operate in all environments, providing wide-area coverage in rural areas and high capacity in urban areas.
Performance. WiMAX has the right mix of features to support Smart Grid applications within a manageable carrier-class network:
Uplink and downlink throughput is sufficient to host even the most demanding video surveillance applications. Uplink gain can be optimized with maximal-ratio receiver combining (MRRC).
Low latency (< 100 ms round trip) enables support for real-time applications with video and voice components.
Mobile workforce access and in-vehicle applications benefit from handover support.
Utilities that are not interested in mobile access can deploy a streamlined version of WiMAX that supports only fixed applications, in which the terminal is at a fixed location, and nomadic applications, in which the terminal can be moved but needs to reconnect to the network after its location changes.
As an IP-based technology, WiMAX supports QoS, traffic prioritization, policy management, and additional traffic management tools. With these, utilities can actively manage bandwidth and optimize the use of network resources.
Security. Security is a paramount concern for utilities, and it is likely to become an even more prominent one within a Smart Grid environment, where information on the entire grid is shared throughout the network. WiMAX provides secure communications and provides support for multiple security standards, including:
128-bit Advanced Encryption Standard (AES)
Centralized authentication, authorization, and accounting (AAA)
Access service network (ASN) gateway authentication
EAP Tunneled Transport Layer Security (EAP-TTLS)
The role of WiMAX within the smart grid
The role of WiMAX within different Smart Grid implementations will vary depending on the utility's requirements and existing infrastructure, the availability of wireline connectivity, and the overall environment in which the utility operates. WiMAX is a versatile technology that can be deployed in multiple roles:
Backhaul. WiMAX can provide the backhaul link to the network operating center (NOC) or, more commonly, to the nearest or most cost-effective fiber connection. In this scenario, 1WiMAX can transport application data from and to terminal devices that use an intermediary wireline or wireless interface, such as BPL, ZigBee or Wi-Fi. This is likely to be the case for many smart meter applications, at least initially, with meters transmitting data to concentrators that in turn are connected with WiMAX base stations.
Last-mile connectivity. WiMAX can also be directly connected to terminal devices. This is the most likely scenario for surveillance and remote monitoring of assets, especially for applications that require significant uplink bandwidth. As volumes grow and prices decrease, WiMAX will become widely used as a module to connect smart meters directly to the WiMAX network. This approach will enable the deployment of more-advanced applications that require real-time control and wider bandwidth channels. Initially, smart meters with WiMAX modules are more likely to be employed in rural, low-density areas, where WiMAX base stations can cover wide areas and may result in cost savings over the concentrator model.
Mobility. A WiMAX network can also provide connectivity to the mobile workforce and to service vehicles, using the same network infrastructure that supports connectivity to fixed terminals and backhaul.
Emergency. Mobile base stations and terminal devices can be moved to emergency areas to create temporary networks, which may use WiMAX, satellite, or other technologies for backhaul. In this case, the same devices used by the mobile workforce and in service vehicles and fixed locations (e.g., modules embedded in cameras or sensors) can be used to connect to the temporary base station.
