The use of Cloud Computing in AMI System Architecture (PDF ...

The use of Cloud Computing in AMI System Architecture K. Billewicz Senior Member, IEEE Department of Electrical Engineering Wroclaw University of Technology, Poland e-mail: [email protected] Abstract-- The article describes a new concept of Advanced Metering Infrastructure (AMI) system architecture with a cloud computing technology. Each smart meter will be equipped with a Wi-Fi module and a power-line communication (PLC) module. The PLC technology will be used to send control and configuration signals and for administrative purposes. This is a completely new approach in a relation to the currently implemented in Poland and in many European countries solutions in AMI systems. This AMI system architecture can be used in cities.

The world however changes and other new technologies are available. One of the most promising technology is cloud computing (CC), which also would change the approach to the realization of data acquisition from smart electric meters.

Keywords -- smart meter, smart grid, gas meter, cloud computing, Wi-Fi, power line communication, in-home display.

The idea of using electrical network for the data transmission purposes is not new. The Power-line communication (PLC) carries data on a conductor, which is used simultaneously for electric power transmission or electric power distribution to consumers. Power lines are designed for delivering power reliably to end consumers, however they may be used also to transmit the data. The PLC technology is interesting because there is no need to use additional wires to supply devices. This feature causes growth of the PLC technology In Poland, the president of the Energy Regulatory Office and managers that work in energy distribution companies promote the Power Line Communication (PLC) technology for communication with smart meters. Most of large distribution system operators prefer a PRIME (PoweRline Intelligent Metering Evolution) technology, while other one – G3-PLC technology. In Italy, more than 30 million smart meters are read by the PLC. In Sweden, the PLC technology is often replaced by GPRS.

I. INTRODUCTION In AMR (Automated Meter Reading) and AMI (Advanced Metering Infrastructure) systems a principal issue is ensuring reliable communication with electronic (smart) meters installed by the end-customers. The last part of the communication network between a data concentrator (master) and the smart meter (slave) is the most troublesome, and it is called the last mile problem. Existing solutions assume, that the distribution system operator (DSO) must take care of the measurement infrastructure. In such approach energy companies must invest in the AMI and these companies own the infrastructure. The main advantage of this approach is the freedom of use of measurement infrastructure and low cost of the data transmission. The grid operator is not dependent on external service providers, what provides him high security and reliability. The operator also will not be surprised by a sudden increase of the price of using of the communication channel. Such price increase could occur if the grid operator would use an external service provider (ESP). In which as a shareholder could be the investor from a hostile country or from a terrorist group. In case of strong downward pressure on the price of the Service, the ESP could go bankrupt, which could also cause disturbances in the energy companies. The communication between smart meters and the acquisition server can be solved in a different way. The smart meter can connect to the server in the energy company by use of Wi-Fi technology.

The cloud-based AMI systems could significantly increase the quality of the service [1]. II. THE POWER LINE COMMUNICATION AND THE WIRELESS LOCAL AREA NETWORK

On 20th November, 2013, the IEEE has approved the IEEE 1901.2™ Standard - “Standard for Low-Frequency (less than 500 kHz) Narrowband Power-Line Communications for Smart-Grid Applications”. The IEEE 1901.2™ standard intended to specify secure PLC at data rates up to 500kbps and at transmission frequencies of less than 500 kHz [2]. Wi-Fi is the name of a popular wireless networking technology that uses radio waves to provide wireless highspeed Internet and network connections. This technology can be also used to provide wireless broadband Internet access for many modern devices. The popularity of the Wi-Fi has grown steadily. An outdoor public Wi-Fi technology can be used successfully in wireless mesh networks. Some cities have constructed free citywide Wi-Fi networks. Unfortunately, on vast rural areas will appear additional

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problems related to this technology. In these areas, the installation of multiple signal repeaters is required, which sometimes is not profitable. The AMI consists of the electricity meter that records consumption of the electric energy and communicates that information to the distribution system operator and energy supplier for monitoring and billing purposes. Thanks to this information the consumers are able to directly control and manage their individual energy consumption. Moreover, the grid operators can better plan the use of the infrastructure and balance the system, e.g. in terms of integration of renewable energy sources. III. THE LAST MILE PROBLEM In Europe, the PLC transmission is used as the primary communication channel to transmit all data between the smart energy meter and the data concentrator. Then, data concentrators communicate with the acquisition servers via the Internet, GPRS, GSM or other communication technologies. Here occurs the fundamental problem in communication between the data concentrator and the smart energy meter. This problem is called the last mile problem. Words “mile” or “kilometer” are used metaphorically. The length of the last mile link may be more or less than a mile. The last mile symbolizes the section of the network between each smart meter and the data concentrator. The data concentrator communicates with smart meters, sometimes through intermediary devices such as routers, repeaters, regenerators etc. In the cities, there is a problem of reading data from smart meters. From one side there is a need to create a special measurement infrastructure and on the other hand, such smart meter is in the range of several wireless Wi-Fi networks. IV. NEW APPROACH Two questions can be asked: • do these networks can be used to communicate with the smart meters? • how to agree with owners of such wireless networks the possibility of using their networks for the communication with meters? There are several advantages and disadvantages of using wireless Internet provided by local suppliers. The power grid operator would have to sign many contracts with many Internet Service Providers (ISPs). In this case, the operator will not be dependent on one large ISP, which can dictate terms and inflate the price. However, in the case of large Internet Service Provider costs may be lower/smaller. In addition, the DSO can agree terms with large ISPs, that ISP will be responsible for transmitters in areas where there is little chance of success of such a venture business and return of the invested money. The DSO will need the Wi-Fi network in such area.

In many places in the cities there are tens of Wi-Fi networks and DSOs are wondering, what kind of communications technology (ICT) can be used to send signals and data from/to such measurement devices. The PLC is the transmission technology which is characterized by low data rate and in addition is quite unreliable. The Wi-Fi is the wireless communication, faster and very popular and also has much higher bandwidth than the PLC. The radical attitude of using only the Wi-Fi for reading data from all of the smart meters is not desired. Sometimes there may occur problems with access to (range of) Wi-Fi networks in some rural areas. In this case, the basic/primary technology should be the PLC and as a backup transmission channel the, GPRS transmission could be implemented. Therefore, in some rural areas, the reading of meters using the Wi-Fi or the PLC is not economically justified. For example, sometimes there is a need to install the PLC repeater for single smart meters in some households. This technology requires regenerators or repeaters to ensure the quality of transmission (QoT). V. TWO (OR MORE) SEPARATE COMMUNICATION CHANNELS Currently, two (or more) separate communication channels are used to communicate with the smart meters in AMI systems. The primary transmission channel usually is the PLC and as the backup is usually GPRS where transmission costs are higher, but more reliable than the PLC. However another approach can be applied. The primary transmission channel for smart meters can be the Wi-Fi and as the backup transmission channel - the PLC. The Wi-Fi technology is faster and more popular than the PLC. VI. THE COMMUNICATION TECHNOLOGY AND QUANTITY OF DATA TRANSMISSION

Smart meters have the ability to provide meter read data at smaller intervals, such as every 15, 30 or 60 minutes. The interval depends on the features/function that will be implemented in the AMI system. If the data read from meters will be used only for billing purposes, the read e.g. once a month or once every two months is enough. If the data acquisition will be used for more efficient use of the power network, such as load management, the reading should be performed more frequently, e.g. once per hour or once per 15 minutes. The required time interval between readings determines the selection of appropriate communication technology. The PLC technology is viable in the situation that the reading of the measurement data occurs on a regular basis, not just once a month when the data is needed for billing. The PLC is incomparably lower in operating costs comparing to transmission such as the GPRS, in case of continuous monitoring of the energy consumption at different points of the low voltage grid. Another issue is whether there is really a

need of continuous monitoring of the low voltage grid elements and the energy consumption of individual households?

• Resource pooling;

If the AMI system performs the functions of the remote upgrade firmware, the communication technology should enable the smooth transmission of large data packets/packages and the efficient management of the firmware upgrade in smart meters. Technologies for low-bandwidth impede the efficient process management of the remote firmware upgrade for the hundreds of thousands of energy meters.

• Measured service.

In the case of wireless communication technology, two parameters should be taken into consideration: a range of transmission and an effective transmission rate. For example, the GPRS modem allows to set the baud/speed rate at 115200 bps. However, when taking into account the speed limit and the fact that broadband use by other users with the same mobile operator, it turns out that the final speed will be comparable to landline and will be 19200 bps. The actual speed depends on the particular mobile operator in the particular country. In case of the wireless technology, the important parameter is the frequency. Lower frequencies (several hundred 433.92 MHz) are characterized by a lower bandwidth, however the wave is longer and less dumped. Lower frequencies allow to penetrate walls, windows, doors and other substances that could be barriers for technologies operating at frequencies of the order of GHz. VII. COMMUNICATION TECHNOLOGIES AND OPPORTUNITIES TO FURTHER DEVELOP THE AMI SYSTEM After few years of the beginning of the AMI implementation by the energy companies, the new smart meters may appear on the market. The meters will have much more memory, faster processors and greater functionality than the currently available energy meters. For example, the meters will be able to collect data of energy consumption not only in fifteen-minute intervals, but for example in five-minute or one minute. Technical limitations of the communication technology may prevent the use of some advanced functionality, thus limiting the technical possibilities of extending the system and showing the necessity of the implementation, after a few years, the entire system from scratch, using other communication technology characterized by the higher rate. VIII. THE DEFINITION OF CLOUD COMPUTING Cloud computing (CC) is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g., servers, storage, networks, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction [3]. Essential characteristics [3] are: • On-demand self-service; • Broad network access;

• Rapid elasticity; Cloud computing has five key attributes that give it an advantage over similar technologies: • shared resources; • high scalability; • flexibility; • pay only for resources used (pay as you go); • users determine what resources they need by themselves. CC has emerged as a novel technology, in the paradigm shift from the traditional “desktop-as-a-platform” to “internetas-a-platform” model. To achieve the infinite scalability, guaranteed performance and nearly “always-on” availability demands, these computing platforms are typically deployed in clusters of massive number of servers hosted in dedicated data centers [4]. Using a cloud computing environment generally requires sending data over the Internet and storing it on third-party systems – on the provider cloud services system. Over the past few years fast development of services based on cloud computing has been observed, together with slow evolution of thinking of computer and mobile devices users. The cloud computing has already become the new standard, and the cloud is the default piece of infrastructure. IX. THE SMART METER AND CLOUD COMPUTING Cloud computing is especially beneficial for companies that collect information from multiple sources. For example, global oil and fuel companies receive data using sensors or other automated devices and send them to the cloud on a virtual disk. As a result, the data is available in a very short time, from anywhere in the world. Similarly, the smart meters could connect via Wi-Fi to the cloud and send the data to the virtual storage data. This considerably increases the bandwidth of the communication channel between the energy company and the smart energy meter. A communication with the smart meter can be divided as follows: • reading the energy and events of the smart meter; the reading is made periodically, in accordance with the schedule; in case of any problem, the data concentrator will try to read a data from a meter in future; • remote upgrade firmware; • smart meter sends messages about events: physical opening of the meter, loss of power - the last gap communication etc.

• sending control signals to the smart meter: the tariff change, the change of accounting credit for prepayment, disconnection of the power at the customer's side, limiting the power level in case of emergency in the power system. • In the AMI system there can be distinguished the following communication channels [5]: • slow – the mass reading of energy consumption profiles and events from meters, transfer of measurement data from all meters to the acquisition server, the transmission require the relatively low level of certainty; • fast – transfer of relatively few messages and information between the acquisition server and meters, during several minutes or without delay, depending on the status of the message. The use of cloud computing technology for the purposes of communication between energy companies and smart meters could be done in the following way: • The smart meter would connect regularly (e.g. once a day or once an hour) with a cloud-based service (cloud computing) or the meter would be constantly in an online mode and communicate with a cloud-based application. Then the meter would send the data file: a profile of the measurement data, events, etc. After this operation, the meter would verify whether the application in the cloud does not have any requests related to the change in its configuration. The configuration commands, such as the tariff change, the accounting method change for prepaid/credit, are not signals that need to reach the meter immediately. Therefore, in this case, a delay associated with time to wait until the meter connects to the cloud-based service is acceptable. Uploading the data to the cloud, in realtime, increases safety and availability of such data by both the energy company, as well as by the customer who has access to company’s applications e.g. via smartphone, www, in-home display (IHD). • In the same way, the smart meter would verify whether in a cloud-based service is the new firmware version and if it was, then the meter download it and upgrade. The meter would send information to the cloud-based application/service about the fact of successful firmware upgrade. The meter would record the events: the information about new firmware version, the successful download from the cloud, successful or unsuccessful upgrade of new firmware. In case of the firmware upgrade, the main limitations are the communication channel bandwidth and the memory capacity of the meter. In case of the registration of many physical quantities or measurement time interval increase the memory fills up quickly. Then new data is overwriting a part of the old data, even if the old data was not read from the meter. In case of cooperation with cloud, these two limitations do not play an important role.

Fig. 1. An AMI system architecture with a cloud computing technology

In the new system architecture (see Figure 1), instead of regular data reading from devices through the data concentrator using the PLC, smart meters would connect according to the schedule with cloud (cloud-based service) via Wi-Fi network and exchange the data. This considerably would increase the communication channel bandwidth between the energy company and the smart energy meter. Once the data would be send to the cloud-based service, it would be available for the energy company practically from anywhere in the world. In the cloud there will be also the application, which will process the uploaded data and prepare the data for billing invoices. We can go even further. Assuming that every time when the smart meter reboots, it automatically starts the application available in the cloud. In this case, the availability of the firmware new version would only need to restart the device. Of course, the smart meter would store in the memory the latest version of the firmware and would run it, if at the time of relaunching for some reason would be off-line. The cooperation with the cloud will cause that the data concentrators will not store the measurement data from multiple meters. Therefore data concentrators will not have to be protected against the possibility of reading the measurement data gathered there, which is considered as a personal data. Sending to smart meter the control signals, such as remote disconnection of the power at the customer’s side or the last gap communication would be performed by the PLC. The PLC technology would also be used for the administrative and emergency communication. This technology would not be used for firmware upgrade. The profile of data reading or events would take place only incidentally. The use of the technology would guarantee the safety because the owner of the entire measurement infrastructure would be the DSO. In this case, the grid operator would not be in any way dependent on external suppliers of ICT. The PLC transmission would be also used to configure Wi-Fi parameters - the access to the cloud computing services in the smart meter. As a result, the DSO will not depend on a single external supplier of Wi-Fi and cloud-based services and

periodically could change the suppliers, thus remotely reconfigure communication modules in the smart meter. X.

THE CONSTRUCTION OF THE SMART METER

A smart meter which measures the end user power consumption in a low voltage, comprises: an analog-digital converter, a Digital Signal Processor, a CPU (central processing unit), an Ethernet interface, a memory, a display, an emergency battery supply, a PLC module [a preferred standards are IEEE 1901.2™, PoweRline Intelligent Metering Evolution (PRIME, Iberdrola), Echelon PLC and Interoperable Device Interface Specification (IDIS, Landis+Gyr)] and a Wi-Fi module. The Wi-Fi technology will be used as the primary transmission channel and PLC or GPRS technologies will be used as a backup transmission channel. The PLC will be also used to transmit control signals and to administrate and reconfigure smart meters. The smart meter will exchange data with application/service cloud computing according to schedule.

the the

The main advantage of the smart meter using the technology of cloud computing would be enhanced data security. It is possible that new threats will appear, however, the smart meter will store only small amount of the data. The meter could work in such way that all the currently data would send to the cloud, instead of saving in in its local memory. The two options would be possible: if the smart meter would be in the on-line state, the measurement data would be recorded immediately in the cloud, while if the meter were off-line, it would write the data to its memory, and would send it to the cloud immediately, as soon as the meter would connect to the Wi-Fi network (on-line state). The physical exchange of the smart energy meter at the customer side would not cause a loss of continuity of measurement data. The new meter could read from the cloud the final reading of the meter which has been exchanged. Such measurement data would be immune to physical attacks, together with its complete destruction, burning, flooding or stealing. Many other advantages of smart energy meters using the technology of the cloud computing has been described in the patent/paper [6]. XI. SMART GAS METERS AND SMART WATER METERS In United Kingdom, together with the implementation of smart energy meters, gas smart meters and in-home displays are installed. The communication with heat meters, water meters and gas smart meters is a principal challenge in AMI systems. These meters do not have a guaranteed power supply, as it is in case of smart energy meters. They must have a battery power supply. In order to ensure effective communication with these meters, the meters have to have suitable external or

built-in communication modules. Such module is supplied by the battery. In AMR systems the data from gas meters or water meters is read remotely. Usually, reading is done in such a way that the meters (gas, water or heat) send data by themselves to the acquisition server. The communication module installed in the meter usually is in the standby mode. The module “wakes” up from time to time e.g. once a month or once a day and sends the required data to the server. After successful sending of such data goes back to standby mode. In this case, the water meter, the gas meter and the smart energy meter should be equipped with other communication module e.g. which uses Zig-Bee technology. The module in the gas or water meter would send the data to the smart energy meter. The energy meter would send the measurement data to the cloud. Measurement data is not the sensitive data but it is a personal data. Energy companies (gas, water or energy) will store files and data online in “the cloud”. By using this approach, there would be only one infrastructure for meters measuring the different media. It would be very desirable from the point of view of multi-utility companies. XII. THE IN-HOME DISPLAY The guidelines of the British energy regulator for smart metering systems are such that the household should have one in-home display (IHD), showing the data from smart gas meters and smart energy meters. Several IHDs in one house could distract the customer. The vision presented here assumes the use of a single In-home display for 3 smart meters: gas, water and electricity. Such IHD would also connect with the cloud-based application and display the data available in the cloud. The data available in the cloud would be transferred by both: the network operator (e.g., energy consumption, exceeding the power factor, the rates in the tariff of the distribution) as well as by the energy supplier (e.g. about energy prices in particular hours, available tariffs for the client, the last bill, payment dates) The measurement data of the current power consumption would be issued on demand - by clicking the appropriate options on the display. In a similar way, the data would be available in the app on the smartphone. The average client sleeps 8 hours, works at least 8 hours, furthermore shopping outside the house, watches TV, works on the computer, sometimes works in the garden or outside the home. The effective impact of the information presented by the in-home display is very short. Therefore, there is no need to send information about the power consumption by the smart meter to the cloud, in real-time, because such data would be in most cases ignored by the client. Such data should be available on the customer's request. XIII. MEASURING DATA REPOSITORIES Sending measurement data to the cloud would cause that soon afterwards they would be accessible from anywhere in

the world. Additionally, it is worth considering whether there is a need to create one large central repository of the measurement data for the DSO, which would be a critical resource vulnerable to attack by cyber criminals. It seems that it is better to create several smaller repositories which will correspond to the territorial divisions of the distribution company. XIV. CONCLUSION The new approach has many advantages. It radically changes the use of the AMI architecture, which in the traditional sense will serve only as a reserve transmission channel and is used for the rapid transmission of signals and messages. Polish experiences show that radical attachment to one communication technology used as the elementary one is not justified, because many very different situations can occur. Therefore there is a need of more flexible approach. The described technology can be successfully applied in the cities. Some cities have free citywide Wi-Fi networks. Sometimes the coverage of free Wi-Fi network also includes the suburbs, or villages near the city. On the other hand, on the vast rural areas, far from the cities, it may be necessary to use other solutions. The interesting idea is to use the wireless

Wi-Fi network at the customer's side for communication with the smart meter, after signing the agreement with the client. The use of cloud-based technology will revolutionize the AMI systems and approach to the transmission and processing of data in these systems. REFERENCES [1]

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