Energy Monitoring System Dr. P. S. N. De Silva, Mrs. J. V. U. P. Jayatunga, Mr. H. R. G. Nadeesha, Miss. P. M. C. D. Navodanie, Mr. M. P. Palihawadana, Mr. B. C. Pasindu Department of Electrical Engineering, University of Moratuwa, Moratuwa, Sri Lanka. [email protected] [email protected] [email protected] [email protected] [email protected] [email protected]

Main features of the design can be described as follows. a. No need of a specifically intended energy meter: The energy measuring instrument of the design is an ordinary energy meter which is already available in the market. Therefore the system can be easily implemented for the factories where these meters had been installed already. Also the users of the product can easily buy the meters hence they need not to buy a product intended meters along with the product.

Abstract - Energy management (EM) is a continuous process which includes energy monitoring, communicating and processing obtained energy data. For an effective EM, energy consumption standards should be introduced first. This product facilitates an easy, quick and accurate method to perform EM. It measures energy using an ordinary energy meter. Then the measured data is converted to Ethernet data and transmit through powerline carrier to a central unit. The processing unit of the product manipulates the collected data in a way that the user is able to have an idea about the energy consumption of the selected premises.

b. Communication is done through power lines: Since the communication is done via Power Line Communication (PLC), extra communication wires are not necessary. Since the communication is done using TCP/IP protocol the energy data can be exported to the World Wide Web very easily. Therefore the energy data can be remotely accessed from any location where internet access is available.

I. INTRODUCTION Cost for electrical energy is increasing drastically. Therefore to have a profitable production, industrial sector should concern about energy management process. Typically, the purpose of electricity management is to promote and support the factories for electricity bill reduction through consulting to use electricity efficiently and effectively without negatively affecting the output(s).Before providing guidance it is necessary to obtain clear and accurate information about the factory electricity consumption. This system is capable of modeling each section of the factory along with energy data such as maximum demand, power factor, total energy consumption etc. Therefore designers can model the entire factory graphically to get a better understanding. First, it is necessary to set up energy standards. A standard describes the allowable ranges of energy consumption of each section. With continuous monitoring of power consumption of the factory, standards and actual values are compared. Then corrective actions should be taken to meet the standards [1]. Data acquisition unit of the system continuously receive the data from energy meters. These data is collected in definite time intervals. Received energy data of the entire factory, is transmitted through power line carrier to a central unit (basically a Personal Computer). JAVA based software has been installed in the PC to compare and contrast the energy data with the standards.

c. Bi directional communication and remote access: The full duplex communication in TCP/IP is used for the communication between the energy meter and the central control unit enabling the user to control the energy usage of the factory remotely. d. Scalability: JAVA which is a platform independent language has been used to develop the software. It can be incorporated to user’s existing software. Therefore the buyer need not to buy any other manufacture’s extra supporting software to run the system. Also the user can change the program and enhance it in order to meet his requirements making this product fully scalable.

II. METHODOLOGY A. Overall function of the system The functional block diagram is depicted in Figure 1. The block diagram of Remote unit is illustrated in Figure 2.

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Branch 1

Remote unit

Ethernet – Powerline adapter

P o w e r

l i n e

Energy meter

Branch 2

Remote unit

Data Acquisition Unit

Serial – Ethernet converter

(Xport) Ethernet – Powerline adapter

Branch 3

Figure 2: Remote Unit d. Power Supply Units: Data acquisition unit needs a 5V power supply, whereas the Serial to Ethernet converter needs a 3.3V power supply. Regulator circuits were used to fulfill this requirement. For 5V power supply, the IC 7805 was used and for 3.3V power supply, the IC 78R33 was used.

Remote unit BaseStation (PC)

Figure 1: Overall function of the System Branch 1, Branch 2 and Branch 3 carries power to different sections. Remote units measure the parameters (Active/Reactive power, Power factor, Current, Voltage, etc.) in each branch and send them to the PC through a powerline carrier.

e. Powerline Ethernet Adapter/Modem (PEA): The data is transferred to the central controlling unit through the power line. Therefore a powerline – Ethernet adopter must be used. The designers selected Corinex AV200 Powerline Ethernet Adapter for this function. This device uses 2 – 34 MHz frequency range for powerline carrier with OFDM technology in setting up a duplex TCP/IP based Ethernet communication network [6].

B. Components and Tools Selection a. Energy meter: This system is implemented such that it can accept the inputs that come from any kind of energy meter. The system can communicate with meters using protocols. Also it can identify pulse outputs (The meter constant) of energy meters.

C. Network Set up A PEA can be configured as a Master or as a Slave. In the PEA network there is one Master and all the others are Slaves. The Master modem is connected to the base station and the others are connected to Remote units (Xport). (Figure 3) The Ethernet to powerline modem is a Layer two device. [6] Therefore it unbundles IP packets (Datagrams) up to the Datalink Layer. Therefore it does not mess with the IP address of the datagrams that comes in or goes out of it. After setting up the network by Powerline Ethernet Adapters, the network can be considered as a simple Local Area Network. (Figure 4) The bidirectional communication can be acquired in this network [6] Initially, Remote Unit (Xport) acts as the server and the PC (Base Station) acts as the client. Therefore to setup the network the Base Staion sends requests to Xports. When the Xports accept that request the network can be set up. However after setting up the connection, the PC acts as the controller of the network and the server program which is implemented in the PC takes the control of the system. The Local Area Network that formed ultimately is easy to handle with JAVA. Every Xport is assigned with a unique static IP address. In this case all the IP addresses should have the same subnet mask. (Since they are in the same LAN) This IP address is used for identification of Xports and the PC can distinguish them all using that unique IP address.

b. Data acquisition unit: Main functions of Data acquisition unit are given below.  Accepts the output from the Energy meter.  Stores the data such as active power, reactive power, power factor, voltage, current, etc.  Accepts the user and PC commands.  Send requested data to PC.  Output data is sent using serial communication. To meet all these requirements and for further developments designers selected the microcontroller PIC18F452 from Microchip as the Data acquisition unit. c. Serial to Ethernet converter: The Data processing unit communicates with serial protocol and the power line modems work with TCP/ IP protocol. So these to protocols should be interfaced. This function is done by a serial to Ethernet converter. The designers selected the device “Lantronix Xport”, which is a compact, integrated solution available to web-enable any device with a serial interface.

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Slave 1

RU 1

Slave 3

RU 3

Ethernet

Server

Slave 2

RU 2

Slave 2

RU 4

Controller Master User Interface

Powerline

(PC)

Data Processing Unit

Figure 5: Software Design Figure 3: Network set up by Powerline Ethernet Adapters.

RU 1

To implement the server the designers have used socket connection, a core library in JAVA language (JAVA.net). The Server sends the request to Xport to set up the connection with its specified IP address through a specified port. After accepting the request, the Server creates a data input stream and a data output stream for bidirectional communication.

RU 3 RU 4

b. Controller: The Controller controls the system as per the user requirement. The controller handles the Man-Machine interface; the data transfer and function co-ordination between server, data processor and the user. The controller is coded in JAVA.

RU 2

Switch

(PC)

c. Data processing unit: Data processing unit manipulates data according to the requirement of the user. It stores data that comes from all the meters that are connected to various branches in the system. Here are some important functions of this unit.  Displays a descriptive real-time picture about the power flow in each branch. (Using Graphs, Tables, etc.)  Provides an informative history about the energy consumption in all the branches of the system. (Active power, Reactive power, Power factor, etc.)  Changes its settings according to user’s requirement and provide requested information to user. Most of the parts of Data processing unit has been done by core JAVA libraries. However, Plotting Graphs has been done with external JAVA libraries.

Figure 4: The resulting network after successful network set up by PEAs.

D. Software Design The software implementation, (Figure 5) includes the controlling and processing of the system and it is done using JAVA. The software consists of four sub platforms namely “Server”, “Controller”, “Data Processing unit” and “User interface”. a. Server: The main function of the Server is setting up the connections with all the Data acquisition units in the system and communicating with them. It interfaces all the Data acquisition units with the Data processing unit. Designers selected TCP/IP protocol (Transmission Control Protocol / Internet Protocol) for communication due to following advantages.  Reliability of TCP/IP protocol.  Easy to add further enhancements to the system.  There are so many devices in the market that supports that supports TCP/IP.

d. User Interface: This is a Graphical User Interface, which acts as the access point of the user to the system. The user can change the settings according to his requirement and give commands to the system through the Controller. Implementation of the User Interface has been done with core JAVA libraries.

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E. Design Considerations a. Data Acquisition: Data acquisition is done by communicating with the energy meter. The communication procedure is different from meter to meter. (Pulse out puts / Protocols) Therefore pre-implemented programs are saved inside the Micro controller. Before using the system the user has to load the suitable program to the memory of the Data acquisition unit. Loading the program is done according to the instruction of the controller. This can be easily done through the user interface.

2. User interface is run by a separate thread. Therefore the user can deal with the system disregarding the current operating condition of the system. 3. Data processing unit is run by a separate thread. Therefore the functions (plotting, saving, displaying) of the Data processing unit can be done parallel with all other functions. The designers have used separate threads wherever it can be applied, to enhance the efficiency and fast operation of the software.

b. Data Communication: Data communication is done using the Ethernet protocol. Each metering unit (Unit A) is given a unique static IP address, with the same Sub net mask. The Serial to Ethernet Converter can be assigned with an IP address. Therefore this system will be identical to a Local Area Network. The Server can access all the metering units uniquely using their IP address and also the Server can identify the source of the incoming data [4].

d. Fast operation: The Designers have acquired fast operation through multithreading, a major facility provided by JAVA language. Because of that, so many functions of the system can be done concurrently, ultimately providing fast operation. e. Reliability: Reliable data communication is essential in this system. Therefore the designers have used TCP/IP protocol, which is a well known protocol for reliable data communication.

c. Error handling and Exceptions: In soft ware design errors runtime errors should be taken into consideration. The ideal time to catch an error is at compile-time. However, not all errors can be detected at compile-time. The rest of the problems must be handled at run-time. [3] The designers have identified a wide range of origins of runtime errors that should be taken into consideration in the design. Examples:  Problems in Xport configuration.  Problems in Microcontroller (Remote Unit)  Network traffic. (This will be vital when the communication is done via World Wide Web.)  Problems in Ethernet to powerline network.  Problems in setting up the network.  Problems in communication. The other runtime errors are very common in software design. JAVA offers exception handling facility to overcome such problems that occur as runtime errors.

f. Memory Management: Memory management is important for the remote unit, since the Micro controller memory is limited. More than 70% of RAM and ROM are saved after the current programs are written in to the Micro controller. This is particularly useful for future expansions. Also it improves the efficiency and reduces runtime errors. However memory management is not an issue for the computer.

III. RESULTS AND DISCUSSION The Designers could successfully obtain results with the Design. Figure 6 is a graph which was plotted by connecting the system to a particular power line. In this instant the designers have used an ordinary Energy meter which produces pulses as its meter constant. The total amount of energy consumption is graphically represented in the graph. Figure 1 shows the historical data for the energy consumption for a particular constant test load that was observed by the system. Also it is possible to obtain graphs that represent real time power flow in the particular power line. All the history values too can be examined and compare with standards by means of tables.

d. Multithreading: Multithreading enables programs to perform operations in parallel [2]. It is a very important feature in the software design. Some examples for threads that have been used in the software design are as follows. 1. A separate thread is run by the software to communicate with each Xport. (To setup the socket connection) This enables the Server to set up connection with all the Xports concurrently and independently. Therefore the time consumption has been minimized. i. In each connection there are two threads running for data input stream and for data output stream. This feature enables concurrent data sending and receiving, reducing the time consumption.

IV.

CONCLUSION AND FURTHER DEVELOPMENTS The product developed is successful in establishing full duplex communication via Broadband over Power Line modems operating in 32 MHz range under OFDM technology using TCP/IP protocol to extract online data

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Figure 6: the Graphical representation of the Energy consumption of a particular section obtained by the Energy Monitoring System Figure 1: A part of the historical data for the energy consumption for a particular test load that was observed by the system. The column at the right side shows the consumed energy in kWh.

from distributed energy meter agents located in a finite space such as a factory premise. Further the product is capable of entertaining any energy meter despite its interface technology ranging from IEC 62056-21, DLMS or simple pulse output.

Set up the network

A. Remote Access Since the product is capable of full duplex communication, it can be used to send signals to remote units to control the power flow, in fact to disconnect the line, if the power flow exceeds certain predetermined values (standards). The designers have successfully designed a manual system which is capable of Remote Access. A button is provided in the user interface for each and every connected Remote Unit. The user can monitor the energy consumption and he can detect when the energy consumption exceeds the predetermined value. Then the user can send a request to the Remote Unit (by clicking a button) to disconnect the power. The relay which is connected to the remote unit will operate and the breaker will be switched off. However, this function can be automatically developed. Figure 7 shows the corresponding flowchart that describes the functionality of such design.

Request data from the Remote unit

Remote unit send data to PC

Received data exceeds Standards No Yes Send a request to Remote unit to Switch off the breaker

B. Connecting to the World Wide Web Without connecting the system directly to the PC, It can be connected via World Wide Web. Therefore the energy monitoring system can be remotely accessed from any location where internet access is available. (Figure 8)

Switch off the breaker

Figure 7: The flowchart for the functionality of the automatic breaker operation under undesired conditions

Also the product is in the progress in developing standard temperature or pressure transducer monitoring system creating a full distributed sensor platform capacitated to be used as a commercial sensor networks used in generators, airplanes, ships, submarines, etc.

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Branch 1

Remote unit

Ethernet – Powerline adapter

P o w e r l i n e

Branch 2

Remote unit

Branch 3

Remote unit

“WWW”

BaseStation (PC)

Figure 8: Enhanced Energy Monitoring System via World Wide Web.

4. Acknowledgment The authors wish to thank Prof. J. R. Lucas, Dr Harsha Abeykoon, Mr. Channa Unagolla and Mr. Samitha Ransara for their many helpful suggestions and comments.

6. References [1] H. P. Scheepers, Honeywell, Building solutions Europe 1999, “Building Management Systems” [2] H. M. Deitel, P. J. Deitel, “JAVA How to Program 6th Edition.” [3] Bruce Eckel, “Thinking in Java” [4] Wendell Odom, “CCENT/CCNA ICND1 official exam certification guide” [5] Todd Lammie, “Cisco Certified Network Associate Study Guide” [6] Corinex AV 200 Datasheet http://www.corinex.com/product/119.html [7] Hendric C. Ferreira, Lutz Lampe, John Newbury, Theo G. Swart,“Power Line Communications: Theory and applications for Narrowband and Broadband Communications over Power Lines”

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