scada

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scada

  1. 1. 2nd IEEE International Conference on Power and Energy (PECon 08), December 1-3, 2008, Johor Baharu, Malaysia Supervisory Control and Data Acquisition System (SCADA) Based Customized Remote Terminal Unit (RTU) for Distribution Automation System * M. M. Ahmed, Member, IEEE and ** W. L. Soo * Universiti Teknikal Malaysia Melaka (UTeM), Melaka, Malaysia. Email: musse@utem.edu.my ** Universiti Teknikal Malaysia Melaka (UTeM), Melaka, Malaysia. invy2004@hotmail.com Abstract—This paper presents the development of a Supervisory Control and Data Acquisition (SCADA) based Remote Terminal Unit (RTU) for customer side distribution automation system (DAS). It is to apply automation technique for operating and controlling low voltage (LV) down stream of 415/240V. The SCADA system developed provides fault isolation operation, monitoring and controlling functions for the operators and data collection for future analysis. An embedded Ethernet controller is used as RTU to act as converter for Human Machine Interface (HMI) and to interact with digital input and output modules. RTU is the master and digital input and output modules are the slaves. RTU will initiate the transaction with the digital input and output modules. Two proprietary software systems are used are to develop algorithm for the controller and to develop HMI for monitoring and controlling functions for the operator. Index Terms-- SCADA system, RTU, RS-485, Serial Modules, Mod-bus, TCP/IP, Master-Slave. I. INTRODUCTION Control systems designed to monitor processes are referred to as data acquisition systems. If the system allows also remote control to function based upon the acquired data, it is referred to as a SCADA system [1]. Modern SCADA provides proper monitoring of equipment to maintain operations at an optimal level by identifying and correcting problems before they turn into significant system failures. A SCADA system consists of a number of remote terminal units (RTUs) collecting field data and sending that data back to a master station via a communications system. The RTU provides an interface to the field analog and digital sensors situated at each remote site. The master station displays the acquired data and also allows the operator to perform remote control tasks. The RTU provides an interface to the field analog and digital sensors situated at each remote site. 1-4244-2405-4/08/$20.00 ©2008 IEEE In this paper, system architecture, system design requirement, RTU specification, SCADA system interface, I/O modules, panel block diagram, communication device setting, transaction using mod-bus protocol, read and write to HMI and results are presented. SYSTEM DESIGN REQUIREMENT II. TABLE 1 describes the system design requirement in this research. The RTU and I/O Modules are required to operate in the range of 0VDC to 30VDC. However for the loads in the customer panel which represent the loads use 240VAC. In the service substation panel, 11 channels of DO module and 1 channel of DI module are required. In the customer service substation panel, 8 channels of DO module and 1 channel of DI module are required. For the communication part, the RTU needs to provide two ports of RS485 communication protocol and one TCP/IP port with 10Mbps speed. Equipment is needed to measure two parameters which are the phase voltage and phase current. The RTU communicates with personal computer that runs under Windows XP operating system with minimum hard disk space of 500MB. TABLE 1 SYSTEM DESIGN REQUIREMENT No. Item 1 Operating Voltage 2 Digital Channels 1655 Output Parameters Specification 30VDC (RTU & I/O Modules), 240VAC (Loads) Service Substation Panel: 11 channels Customer Service
  2. 2. 2nd IEEE International Conference on Power and Energy (PECon 08), December 1-3, 2008, Johor Baharu, Malaysia 3 Digital Channels Input 4 equipped with a Self Tuner ASIC for all RS-485 ports. The Self-Tuner ASIC will auto detects and controls the send and receive directions of the RS485 network. The general feature of the RTU is illustrated in Fig. 2. This RTU provides one on-board 10BaseT port that is equipped with a RJ-45 connector. Substation Panel: 8 channels Service Substation Panel: 1 channel Customer Service Substation Panel: 1 channel Communication Interface Communication Ports: Com1, Com2, Com3 Baud Rate:9600 RS485 TCP/IP 5 6 PC-based SCADA Controller-RTU LAN Configuration 7 Sensor/Transducer Devices 8 Measurement Parameters Personal Computer 9 III. Speed: 10Mbps or 100Mbps Power supply: 10 to 30VDC Operating System: Window NT/XP/CE Speed: 40MHz Memory: 512Kbytes Ethernet port: 10 BaseT Serial Port: Com 1, Com 2, Com 3 Protocol:Modbus serial protocol, Modbus TCP/IP protocol Hub: Four-port of 10Mbps or 100Mbps Speed: 10 Mbps or 100Mbps CT 60/5A 24VDC Relay 3-Phase Contactor Phase Voltage Phase Current Operating System: Windows NT/2000/XP/CE Memory: Minimum of 256MB Hard disk space: Minimum of 500MB Processor: Compatible with Intel Pentium IV or higher Fig. 2. General Controller Block Diagram The communication between HMI and RTU is using TCP/IP protocol. A socket is a combination of port number and IP address. HMI will always listen for any request from the RTU. RTU will request a connection to the HMI and HMI will accept the connection before data can be sent or received. IV. I/O MODULES The series modules, including D/I, D/O, A/D, D/A, Timer/Counter and MMI modules, will be directly connected to RS-485. These series modules can connect a maximum of 256 modules to the RS-485 network. The module address can be changed from 00 to FF, a total of 256 maximum. The series modules can be programmed to 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200, a total of 8 different speeds. The I/O modules used in this research are DI/DO module which is an 8 channel digital output and 4 channel digital input module, DI module which is a 16 channel digital input and DO module which is a 13 channel digital output These modules can be remotely controlled by a set of commands. The PC will send out a command string to the RTU either by TCP/IP protocol or RS232 protocol. RTU converts this command into a RS-485 before it sends to RS-485 network. RTU SPECIFICATION Embedded Ethernet RTU is used in this research project. The RTU is designed as embedded RTU. This RTU is powered by an 80188-40 processor with 512K bytes of static RAM and 512K bytes of Flash memory. The EEPROM is designed to store the data which is not changed very frequently. The 2-wire RS-485 port is designed to directly drive the series modules. The RTU is 1656
  3. 3. 2nd IEEE International Conference on Power and Energy (PECon 08), December 1-3, 2008, Johor Baharu, Malaysia Fig. 5. : Communication Wiring Diagram Between the RTU & the Slaves Fig. 3. Service Substation System Block Diagram V. PANEL BLOCK DIAGRAM In Fig.3, the service substation block diagram consists of power line and control line. The power line shows the electricity supply to all the components in the service substation panel. The controller and I/O modules are supplied with dc power supply. Relay module receives power supply from the digital output module. The control line shows the communication line between the controller and I/O modules. In Fig.4, the customer service substation block diagram also consists of power line and control line. The power line starts from MCCB1 from the service substation panel. Digital input/output module is supplied with direct current power supply. The contactor module is connected to the ac power supply. Relay module receives the power supply from the digital input/output module. The control line shows that the digital input/output module is connected with the controller in the service substation panel. Fig. 5 shows the communication wiring diagram between RTU and the slaves. VI. Fig. 4. Service Substation System Block Diagram TRANSACTIONS USING MOD-BUS PROTOCOL Mod-bus is the protocol commonly used for SCADA applications. The Mod-bus transmission protocol was developed by Gould Modicon for process control systems [2]. A recent survey in the well-known American Control Engineering magazine indicated that over 40% of industrial communication applications use the Mod-bus protocol for interfacing. [3] Mod-bus protocol can be broken down into five sections which are message format, synchronization, memory location, function codes and exception responses. A transaction consists of a single request from the host to a specific secondary device and a single response from that device back to the host. Both of these messages are formatted as mod-bus message frames [4]. Each such message frame consists of a series of bytes grouped into four fields as described in Fig. 6. Fig. 6. Format of Mod-bus message frame 1657
  4. 4. 2nd IEEE International Conference on Power and Energy (PECon 08), December 1-3, 2008, Johor Baharu, Malaysia VIII. RESULTS Fig. 7 shows an example of message frame used in this research to read two words value of variable V1 by using mod-bus function 3. Fig. 7. Read long word by Modbus Fig. 8 shows an example of message frame used in this research to write two words value of variable V1 by using mod-bus function 16. Fig. 9. HMI and SCADA Applications for Service Substation Panel Fig. 8. Write long word by mod-bus VII. COMMAND FORMAT OF DI/DO MODULE Command format can be used to send and receive data from HMI to DI/DO modules. The command format consists of leading, address, command and checksum. The response format consists of leading, address, data and checksum. For example to change module address from 01 to 02 a command “%0102400600” is written in the HMI. RTU will send “!02” to HMI if the new configuration is successful. Tables 3 elaborates the command and receive syntaxes. Fig. 9 shows the HMI and SCADA applications for service substation panel developed by using the proprietary software. The operator can operate manually the MCCBs by pressing the Manual Button. Fig.10 shows the status of the Main MCCB, other MCBs and the outputs. If fault occurs, the MCB and the outputs will change to red colors pattern showing that the MCB is off status. In this case, alarms will be triggered and displayed on the screen. Fig. 11 shows the alarm messages. In the alarm list, the blue color text indicates that the output has changed to healthy status and the red color text indicates that the output is still remained unhealthy. Once the fault points have been checked and repaired, the “Reset” button from the control button in Fig. 13 is pressed to restore the power supply to all the outputs. TABLE 3 SET MODULE CONFIGURATION Command Syntax %AANNTTCCFF[CHK](cr) Response Syntax !AA[CHK](cr) ?AA[CHK](cr) Description %- a delimiter character AA - address of setting module (00 to FF) NN – new address for setting module (00 to FF) TT – type 40 for DIO module CC – new baudrate for setting module FF- new data format for setting module Description Valid Command Invalid Command Fig. 10. MCCBs - Service Substation Fig. 11. Alarm Messages 1658
  5. 5. 2nd IEEE International Conference on Power and Energy (PECon 08), December 1-3, 2008, Johor Baharu, Malaysia TABLE 4 RESTORATION TIME FOR CUSTOMER SERVICE SUBSTATION Panel Minimum Restoration Time (Second) 0.7 Customer Service Substation Service Substation 50 BASED ON DELAY TIMER SETTING TABLE 5 MINIMUM TOTAL OF RESTORATION TIME Fig. 12. Phase Current Reading from Power Analyzer (Customer Service Substation Panel) Delay Timer (Second) Duration Time 1 (Second) Duration Time 2 (Second) Outage Time (Second) Reset Time (Second) 6 3 1 0.5 0.1 24 12 4 2 - 30 15 5 2.5 - 54 33 15 10.5 - 42 21 7 3.5 0.7 The readings from the power analyzer are captured from both panels. Fig.12 shows the example of the graph displayed in HMI application. The reading from this graph is plotted again using Excel as shown in Fig. 13 for details analysis. Table 5 shows the minimum total restoration time for the customer service substation panel and the service substation panel. The ELCB minimum operation time is fifty milliseconds. In this case, the delay timer has to be set higher than fifty milliseconds. The minimum delay timer for the customer service substation panel is one hundred milliseconds. For the service substation, the delay timer is set to 5 seconds for proper operation of switching the MCBs to on and off. These figures can only be applied for the MCCB and MCBs used in this research. The system developed in this research is excellent to save the time needed to restore back the electricity supply after fault occurs. The restoration time definitely cannot be achieved by manual isolation done by the technicians at the remote substation site. Fig. 13. Phase Current Reading from Power Analyzer (Customer Service Substation Panel) Based on the graph in Fig.13, the outage time, duration time 1, duration time 2 and reset time are obtained. Table 4 shows the details of the duration time 1, duration time 2, outage time and reset time when the delay timer in the customer service substation is set to six seconds, three seconds, one second, five hundred milliseconds and one hundred milliseconds. The duration time 1 is the time period that is needed by the system to identify which load is the fault load. In this experiment, fixed fault points were chosen. Duration time 2 is the time period that is needed by the system to isolate the faulted load and restore electricity supply to the rest of the healthy loads. Outage time is the duration time that the customer experiences electricity supply disruption. Reset time is the total time needed to restore electricity supply to all the loads including the faulted load that has already been repaired. IX. CONCLUSIONS In this research project, a Customized SCADA based RTU for service substation and customer service substation is developed by using the open loop concept for the distribution networks. In this research, a Customized SCADA is built to provide automatic fault isolation for low voltage distribution system. The HMI can be monitored at different sites as the controller equipped with TCP/IP features. Whenever the system detects fault, an alarm message will be displayed at the HMI side to acknowledge the operator. The status of communication between the controller, digital I/O modules, power analyzer with the HMI helps to acknowledge the operator if there is a communication breakdown. The SCADA system provides GUI, alarm system, data logging and report management facilities for the operator to interact with the equipment in the service substation and the customer service substation. 1659
  6. 6. 2nd IEEE International Conference on Power and Energy (PECon 08), December 1-3, 2008, Johor Baharu, Malaysia REFERENCES [1] [2] [3] [4] [5] [6] [7] A.Daneels and W.Salter, “What is Scada?”, International Conference on Accelerator and Large Experimental Physics Control System, Trieste, Italy, 1999, pp.1 Hugh Jack, “Automating Manufacturing Systems with PLCs”, Version 4.7, April 14,2005, pp.643 John Uffenbeck,Microcomputers and Microprocessors, 2000,1991,1985 by Prentice Hall, ISBN 0-13-209198-4,pp 509 Gordon Clarke, Practical Modern SCADA protocols: DNP3, 60870.5 and Related Systems, 2004, ISBN 07506 7995, pp.45 ICP DAS, 7188E/843X/844X/883X/884X TCP/IP Library User’s Manual, Ver. 1.0 Copyright 2002 [Online] Available: www.icpdas.com Customized Non-interruptible Distribution Automation System, Short Term Project No. PJP/2006/FKE (1) , UTeM, 2005-2006 Intelligent Distribution Automation System: Customized SCADA Based Rtu For Distribution Automation System, M.Sc. Research Project, UTeM, 2005-2007. Soo Wai Lian was born in Malacca, Malaysia, on June 3, 1978. She received her B.S degree in electrical engineering from the University Technology Malaysia. She is with Universiti Teknikal Malaysia Melaka (UTeM) pursuing her PhD degree. She is specializing in electrical power distribution system. BIOGRAPHIES Dr. Musse Mohamud Ahmed is a associate professor at the Faculty of electrical Engineering, UTeM. He graduated from Universiti Teknologi Malaysia (UTM) in 2000 and got his Ph.D. He worked Multimedia University (MMU), as lecturer at the Faculty of Engineering & Technology in Malacca campus from 2000 to 2002. He joined UTeM in March 2002 as a lecturer. In October 2002, he was appointed as deputy dean, postgraduate, research & development at the Faculty of Electrical Engineering, UTeM, a position he held till March 2007. Since then he has been working in UTeM. Dr. Musse has been IEEE-PES member for eleven years and Executive Committee Member for the last five years. His research interests include: Distribution Automation System, Power System Operation and Control Simulation & Modeling of Large Scale Power Systems, Intelligent Power Systems, Energy & Renewable Energy and Risk Assessment of Electricity Supply 1660 I.

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