Improved Web-based Power Quality Monitoring Instrument

Sensors & Transducers Volume 132, Issue 9, September 2011

www.sensorsportal.com

ISSN 1726-5479

Editors-in-Chief: professor Sergey Y. Yurish, tel.: +34 696067716, e-mail: [email protected] Editors for Western Europe Meijer, Gerard C.M., Delft University of Technology, The Netherlands Ferrari, Vittorio, Universitá di Brescia, Italy Editor South America Costa-Felix, Rodrigo, Inmetro, Brazil

Editors for North America Datskos, Panos G., Oak Ridge National Laboratory, USA Fabien, J. Josse, Marquette University, USA Katz, Evgeny, Clarkson University, USA Editor for Asia Ohyama, Shinji, Tokyo Institute of Technology, Japan

Editor for Eastern Europe Sachenko, Anatoly, Ternopil State Economic University, Ukraine

Editor for Asia-Pacific Mukhopadhyay, Subhas, Massey University, New Zealand

Editorial Advisory Board Abdul Rahim, Ruzairi, Universiti Teknologi, Malaysia Ahmad, Mohd Noor, Nothern University of Engineering, Malaysia Annamalai, Karthigeyan, National Institute of Advanced Industrial Science and Technology, Japan Arcega, Francisco, University of Zaragoza, Spain Arguel, Philippe, CNRS, France Ahn, Jae-Pyoung, Korea Institute of Science and Technology, Korea Arndt, Michael, Robert Bosch GmbH, Germany Ascoli, Giorgio, George Mason University, USA Atalay, Selcuk, Inonu University, Turkey Atghiaee, Ahmad, University of Tehran, Iran Augutis, Vygantas, Kaunas University of Technology, Lithuania Avachit, Patil Lalchand, North Maharashtra University, India Ayesh, Aladdin, De Montfort University, UK Azamimi, Azian binti Abdullah, Universiti Malaysia Perlis, Malaysia Bahreyni, Behraad, University of Manitoba, Canada Baliga, Shankar, B., General Monitors Transnational, USA Baoxian, Ye, Zhengzhou University, China Barford, Lee, Agilent Laboratories, USA Barlingay, Ravindra, RF Arrays Systems, India Basu, Sukumar, Jadavpur University, India Beck, Stephen, University of Sheffield, UK Ben Bouzid, Sihem, Institut National de Recherche Scientifique, Tunisia Benachaiba, Chellali, Universitaire de Bechar, Algeria Binnie, T. David, Napier University, UK Bischoff, Gerlinde, Inst. Analytical Chemistry, Germany Bodas, Dhananjay, IMTEK, Germany Borges Carval, Nuno, Universidade de Aveiro, Portugal Bousbia-Salah, Mounir, University of Annaba, Algeria Bouvet, Marcel, CNRS – UPMC, France Brudzewski, Kazimierz, Warsaw University of Technology, Poland Cai, Chenxin, Nanjing Normal University, China Cai, Qingyun, Hunan University, China Campanella, Luigi, University La Sapienza, Italy Carvalho, Vitor, Minho University, Portugal Cecelja, Franjo, Brunel University, London, UK Cerda Belmonte, Judith, Imperial College London, UK Chakrabarty, Chandan Kumar, Universiti Tenaga Nasional, Malaysia Chakravorty, Dipankar, Association for the Cultivation of Science, India Changhai, Ru, Harbin Engineering University, China Chaudhari, Gajanan, Shri Shivaji Science College, India Chavali, Murthy, N.I. Center for Higher Education, (N.I. University), India Chen, Jiming, Zhejiang University, China Chen, Rongshun, National Tsing Hua University, Taiwan Cheng, Kuo-Sheng, National Cheng Kung University, Taiwan Chiang, Jeffrey (Cheng-Ta), Industrial Technol. Research Institute, Taiwan Chiriac, Horia, National Institute of Research and Development, Romania Chowdhuri, Arijit, University of Delhi, India Chung, Wen-Yaw, Chung Yuan Christian University, Taiwan Corres, Jesus, Universidad Publica de Navarra, Spain Cortes, Camilo A., Universidad Nacional de Colombia, Colombia Courtois, Christian, Universite de Valenciennes, France Cusano, Andrea, University of Sannio, Italy D'Amico, Arnaldo, Università di Tor Vergata, Italy De Stefano, Luca, Institute for Microelectronics and Microsystem, Italy Deshmukh, Kiran, Shri Shivaji Mahavidyalaya, Barshi, India Dickert, Franz L., Vienna University, Austria Dieguez, Angel, University of Barcelona, Spain Dighavkar, C. G., M.G. Vidyamandir’s L. V.H. College, India Dimitropoulos, Panos, University of Thessaly, Greece Ding, Jianning, Jiangsu Polytechnic University, China Djordjevich, Alexandar, City University of Hong Kong, Hong Kong

Donato, Nicola, University of Messina, Italy Donato, Patricio, Universidad de Mar del Plata, Argentina Dong, Feng, Tianjin University, China Drljaca, Predrag, Instersema Sensoric SA, Switzerland Dubey, Venketesh, Bournemouth University, UK Enderle, Stefan, Univ.of Ulm and KTB Mechatronics GmbH, Germany Erdem, Gursan K. Arzum, Ege University, Turkey Erkmen, Aydan M., Middle East Technical University, Turkey Estelle, Patrice, Insa Rennes, France Estrada, Horacio, University of North Carolina, USA Faiz, Adil, INSA Lyon, France Fericean, Sorin, Balluff GmbH, Germany Fernandes, Joana M., University of Porto, Portugal Francioso, Luca, CNR-IMM Institute for Microelectronics and Microsystems, Italy Francis, Laurent, University Catholique de Louvain, Belgium Fu, Weiling, South-Western Hospital, Chongqing, China Gaura, Elena, Coventry University, UK Geng, Yanfeng, China University of Petroleum, China Gole, James, Georgia Institute of Technology, USA Gong, Hao, National University of Singapore, Singapore Gonzalez de la Rosa, Juan Jose, University of Cadiz, Spain Granel, Annette, Goteborg University, Sweden Graff, Mason, The University of Texas at Arlington, USA Guan, Shan, Eastman Kodak, USA Guillet, Bruno, University of Caen, France Guo, Zhen, New Jersey Institute of Technology, USA Gupta, Narendra Kumar, Napier University, UK Habib, Maki K., American University in Cairo, Egypt Hadjiloucas, Sillas, The University of Reading, UK Haider, Mohammad R., Sonoma State University, USA Hashsham, Syed, Michigan State University, USA Hasni, Abdelhafid, Bechar University, Algeria Hernandez, Alvaro, University of Alcala, Spain Hernandez, Wilmar, Universidad Politecnica de Madrid, Spain Homentcovschi, Dorel, SUNY Binghamton, USA Horstman, Tom, U.S. Automation Group, LLC, USA Hsiai, Tzung (John), University of Southern California, USA Huang, Jeng-Sheng, Chung Yuan Christian University, Taiwan Huang, Star, National Tsing Hua University, Taiwan Huang, Wei, PSG Design Center, USA Hui, David, University of New Orleans, USA Jaffrezic-Renault, Nicole, Ecole Centrale de Lyon, France Jaime Calvo-Galleg, Jaime, Universidad de Salamanca, Spain James, Daniel, Griffith University, Australia Janting, Jakob, DELTA Danish Electronics, Denmark Jiang, Liudi, University of Southampton, UK Jiang, Wei, University of Virginia, USA Jiao, Zheng, Shanghai University, China John, Joachim, IMEC, Belgium Kalach, Andrew, Voronezh Institute of Ministry of Interior, Russia Kang, Moonho, Sunmoon University, Korea South Kaniusas, Eugenijus, Vienna University of Technology, Austria Katake, Anup, Texas A&M University, USA Kausel, Wilfried, University of Music, Vienna, Austria Kavasoglu, Nese, Mugla University, Turkey Ke, Cathy, Tyndall National Institute, Ireland Khelfaoui, Rachid, Université de Bechar, Algeria Khan, Asif, Aligarh Muslim University, Aligarh, India Kim, Min Young, Kyungpook National University, Korea South Ko, Sang Choon, Electronics. and Telecom. Research Inst., Korea South Kotulska, Malgorzata, Wroclaw University of Technology, Poland Kockar, Hakan, Balikesir University, Turkey

Kong, Ing, RMIT University, Australia Kratz, Henrik, Uppsala University, Sweden Krishnamoorthy, Ganesh, University of Texas at Austin, USA Kumar, Arun, University of South Florida, USA Kumar, Subodh, National Physical Laboratory, India Kung, Chih-Hsien, Chang-Jung Christian University, Taiwan Lacnjevac, Caslav, University of Belgrade, Serbia Lay-Ekuakille, Aime, University of Lecce, Italy Lee, Jang Myung, Pusan National University, Korea South Lee, Jun Su, Amkor Technology, Inc. South Korea Lei, Hua, National Starch and Chemical Company, USA Li, Genxi, Nanjing University, China Li, Hui, Shanghai Jiaotong University, China Li, Xian-Fang, Central South University, China Li, Yuefa, Wayne State University, USA Liang, Yuanchang, University of Washington, USA Liawruangrath, Saisunee, Chiang Mai University, Thailand Liew, Kim Meow, City University of Hong Kong, Hong Kong Lin, Hermann, National Kaohsiung University, Taiwan Lin, Paul, Cleveland State University, USA Linderholm, Pontus, EPFL - Microsystems Laboratory, Switzerland Liu, Aihua, University of Oklahoma, USA Liu Changgeng, Louisiana State University, USA Liu, Cheng-Hsien, National Tsing Hua University, Taiwan Liu, Songqin, Southeast University, China Lodeiro, Carlos, University of Vigo, Spain Lorenzo, Maria Encarnacio, Universidad Autonoma de Madrid, Spain Lukaszewicz, Jerzy Pawel, Nicholas Copernicus University, Poland Ma, Zhanfang, Northeast Normal University, China Majstorovic, Vidosav, University of Belgrade, Serbia Malyshev, V.V., National Research Centre ‘Kurchatov Institute’, Russia Marquez, Alfredo, Centro de Investigacion en Materiales Avanzados, Mexico Matay, Ladislav, Slovak Academy of Sciences, Slovakia Mathur, Prafull, National Physical Laboratory, India Maurya, D.K., Institute of Materials Research and Engineering, Singapore Mekid, Samir, University of Manchester, UK Melnyk, Ivan, Photon Control Inc., Canada Mendes, Paulo, University of Minho, Portugal Mennell, Julie, Northumbria University, UK Mi, Bin, Boston Scientific Corporation, USA Minas, Graca, University of Minho, Portugal Moghavvemi, Mahmoud, University of Malaya, Malaysia Mohammadi, Mohammad-Reza, University of Cambridge, UK Molina Flores, Esteban, Benemérita Universidad Autónoma de Puebla, Mexico Moradi, Majid, University of Kerman, Iran Morello, Rosario, University "Mediterranea" of Reggio Calabria, Italy Mounir, Ben Ali, University of Sousse, Tunisia Mulla, Imtiaz Sirajuddin, National Chemical Laboratory, Pune, India Nabok, Aleksey, Sheffield Hallam University, UK Neelamegam, Periasamy, Sastra Deemed University, India Neshkova, Milka, Bulgarian Academy of Sciences, Bulgaria Oberhammer, Joachim, Royal Institute of Technology, Sweden Ould Lahoucine, Cherif, University of Guelma, Algeria Pamidighanta, Sayanu, Bharat Electronics Limited (BEL), India Pan, Jisheng, Institute of Materials Research & Engineering, Singapore Park, Joon-Shik, Korea Electronics Technology Institute, Korea South Penza, Michele, ENEA C.R., Italy Pereira, Jose Miguel, Instituto Politecnico de Setebal, Portugal Petsev, Dimiter, University of New Mexico, USA Pogacnik, Lea, University of Ljubljana, Slovenia Post, Michael, National Research Council, Canada Prance, Robert, University of Sussex, UK Prasad, Ambika, Gulbarga University, India Prateepasen, Asa, Kingmoungut's University of Technology, Thailand Pullini, Daniele, Centro Ricerche FIAT, Italy Pumera, Martin, National Institute for Materials Science, Japan Radhakrishnan, S. National Chemical Laboratory, Pune, India Rajanna, K., Indian Institute of Science, India Ramadan, Qasem, Institute of Microelectronics, Singapore Rao, Basuthkar, Tata Inst. of Fundamental Research, India Raoof, Kosai, Joseph Fourier University of Grenoble, France Rastogi Shiva, K. University of Idaho, USA Reig, Candid, University of Valencia, Spain Restivo, Maria Teresa, University of Porto, Portugal Robert, Michel, University Henri Poincare, France Rezazadeh, Ghader, Urmia University, Iran Royo, Santiago, Universitat Politecnica de Catalunya, Spain Rodriguez, Angel, Universidad Politecnica de Cataluna, Spain Rothberg, Steve, Loughborough University, UK Sadana, Ajit, University of Mississippi, USA Sadeghian Marnani, Hamed, TU Delft, The Netherlands Sandacci, Serghei, Sensor Technology Ltd., UK Sapozhnikova, Ksenia, D.I.Mendeleyev Institute for Metrology, Russia Saxena, Vibha, Bhbha Atomic Research Centre, Mumbai, India

Schneider, John K., Ultra-Scan Corporation, USA Sengupta, Deepak, Advance Bio-Photonics, India Seif, Selemani, Alabama A & M University, USA Seifter, Achim, Los Alamos National Laboratory, USA Shah, Kriyang, La Trobe University, Australia Silva Girao, Pedro, Technical University of Lisbon, Portugal Singh, V. R., National Physical Laboratory, India Slomovitz, Daniel, UTE, Uruguay Smith, Martin, Open University, UK Soleymanpour, Ahmad, Damghan Basic Science University, Iran Somani, Prakash R., Centre for Materials for Electronics Technol., India Srinivas, Talabattula, Indian Institute of Science, Bangalore, India Srivastava, Arvind K., NanoSonix Inc., USA Stefan-van Staden, Raluca-Ioana, University of Pretoria, South Africa Stefanescu, Dan Mihai, Romanian Measurement Society, Romania Sumriddetchka, Sarun, National Electronics and Computer Technology Center, Thailand Sun, Chengliang, Polytechnic University, Hong-Kong Sun, Dongming, Jilin University, China Sun, Junhua, Beijing University of Aeronautics and Astronautics, China Sun, Zhiqiang, Central South University, China Suri, C. Raman, Institute of Microbial Technology, India Sysoev, Victor, Saratov State Technical University, Russia Szewczyk, Roman, Industrial Research Inst. for Automation and Measurement, Poland Tan, Ooi Kiang, Nanyang Technological University, Singapore, Tang, Dianping, Southwest University, China Tang, Jaw-Luen, National Chung Cheng University, Taiwan Teker, Kasif, Frostburg State University, USA Thirunavukkarasu, I., Manipal University Karnataka, India Thumbavanam Pad, Kartik, Carnegie Mellon University, USA Tian, Gui Yun, University of Newcastle, UK Tsiantos, Vassilios, Technological Educational Institute of Kaval, Greece Tsigara, Anna, National Hellenic Research Foundation, Greece Twomey, Karen, University College Cork, Ireland Valente, Antonio, University, Vila Real, - U.T.A.D., Portugal Vanga, Raghav Rao, Summit Technology Services, Inc., USA Vaseashta, Ashok, Marshall University, USA Vazquez, Carmen, Carlos III University in Madrid, Spain Vieira, Manuela, Instituto Superior de Engenharia de Lisboa, Portugal Vigna, Benedetto, STMicroelectronics, Italy Vrba, Radimir, Brno University of Technology, Czech Republic Wandelt, Barbara, Technical University of Lodz, Poland Wang, Jiangping, Xi'an Shiyou University, China Wang, Kedong, Beihang University, China Wang, Liang, Pacific Northwest National Laboratory, USA Wang, Mi, University of Leeds, UK Wang, Shinn-Fwu, Ching Yun University, Taiwan Wang, Wei-Chih, University of Washington, USA Wang, Wensheng, University of Pennsylvania, USA Watson, Steven, Center for NanoSpace Technologies Inc., USA Weiping, Yan, Dalian University of Technology, China Wells, Stephen, Southern Company Services, USA Wolkenberg, Andrzej, Institute of Electron Technology, Poland Woods, R. Clive, Louisiana State University, USA Wu, DerHo, National Pingtung Univ. of Science and Technology, Taiwan Wu, Zhaoyang, Hunan University, China Xiu Tao, Ge, Chuzhou University, China Xu, Lisheng, The Chinese University of Hong Kong, Hong Kong Xu, Sen, Drexel University, USA Xu, Tao, University of California, Irvine, USA Yang, Dongfang, National Research Council, Canada Yang, Shuang-Hua, Loughborough University, UK Yang, Wuqiang, The University of Manchester, UK Yang, Xiaoling, University of Georgia, Athens, GA, USA Yaping Dan, Harvard University, USA Ymeti, Aurel, University of Twente, Netherland Yong Zhao, Northeastern University, China Yu, Haihu, Wuhan University of Technology, China Yuan, Yong, Massey University, New Zealand Yufera Garcia, Alberto, Seville University, Spain Zakaria, Zulkarnay, University Malaysia Perlis, Malaysia Zagnoni, Michele, University of Southampton, UK Zamani, Cyrus, Universitat de Barcelona, Spain Zeni, Luigi, Second University of Naples, Italy Zhang, Minglong, Shanghai University, China Zhang, Qintao, University of California at Berkeley, USA Zhang, Weiping, Shanghai Jiao Tong University, China Zhang, Wenming, Shanghai Jiao Tong University, China Zhang, Xueji, World Precision Instruments, Inc., USA Zhong, Haoxiang, Henan Normal University, China Zhu, Qing, Fujifilm Dimatix, Inc., USA Zorzano, Luis, Universidad de La Rioja, Spain Zourob, Mohammed, University of Cambridge, UK

Sensors & Transducers Journal (ISSN 1726-5479) is a peer review international journal published monthly online by International Frequency Sensor Association (IFSA). Available in electronic and on CD. Copyright © 2011 by International Frequency Sensor Association. All rights reserved.

Sensors & Transducers Journal

Contents Volume 132 Issue 9 September 2011

www.sensorsportal.com

ISSN 1726-5479

Research Articles Gas Sensors Based on Inorganic Materials: An Overview K. R. Nemade .....................................................................................................................................

1

Control Valve Stiction Identification, Modelling, Quantification and Control - A Review Srinivasan Arumugam and Rames C. Panda.....................................................................................

14

Numerical Prediction of a Bi-Directional Micro Thermal Flow Sensors M. Al-Amayrah, A. Al-Salaymeh, M. Kilani, A. Delgado .....................................................................

25

The Linearity of Optical Tomography: Sensor Model and Experimental Verification Siti Zarina Mohd. Muji, Ruzairi Abdul Rahim, Mohd Hafiz Fazalul Rahiman, Zulkarnay Zakaria, Elmy Johana Mohamad, Mohd Safirin Karis ......................................................................................

40

Structure Improvement and Simulation Research of a Three-dimensional Force Flexible Tactile Sensor Based on Conductive Rubber Shanhong Li, Xuekun Zhuang, Fei Xu, Junxiang Ding, Feng Shuang, Yunjian Ge ...........................

47

Modeling and Simulation of Wet Gas Flow in Venturi Flow Meter Hossein Seraj, Mohd Fuaad Rahmat, Marzuki Khaled, Rubiyah Yusof and Iliya Tizhe Thuku .........

57

Improvement Study of Wet Nitrocellulose Membranes Using Optical Reflectometry Hariyadi Soetedjo ...............................................................................................................................

69

Use of Balance Calibration Certificate to Calculate the Errors of Indication and Measurement Uncertainty in Mass Determinations Performed in Medical Laboratories Adriana Vâlcu .....................................................................................................................................

76

Improved Web-based Power Quality Monitoring Instrument I. Adam, A. Mohamed and H. Sanusi .................................................................................................

89

Design and Fabrication of a Soil Moisture Meter Using Thermal Conductivity Properties of Soil Subir Das, Biplab Bag, T. S. Sarkar, Nisher Ahmed, B. Chakrabrty ..................................................

100

Numerical Study of Mechanical Stirring in Case of Yield Stress Fluid with Circular Anchor Impeller Brahim Mebarki, Belkacem Draoui, Lakhdar Rahmani, Mohamed Bouanini, Mebrouk Rebhi, El hadj Benachour ..............................................................................................................................

108

Computer Vision Based Smart Lane Departure warning System for Vehicle Dynamics Control Ambarish G. Mohapatra .....................................................................................................................

122

Simple Implementation of an Electronic Tongue for Taste Assessments of Food and Beverage Products Abdul Hallis Abdul Aziz, Ali Yeon Md. Shakaff, Rohani Farook, Abdul Hamid Adom, Mohd Noor Ahmad and Nor Idayu Mahat...........................................................................................

136

Aluminum-Selective Electrode Based on (1E,2E)-N1,N2- dihydroxy )-N1,N2- bis (4-hydroxy phenyl) Oxalimidamide as a Neutral Carrier Aghaie M., Esfandyar Baghdar, Fekri Lari F., Ali Kakanejadifard, Aghaie H. ....................................

151

Authors are encouraged to submit article in MS Word (doc) and Acrobat (pdf) formats by e-mail: [email protected] Please visit journal’s webpage with preparation instructions: http://www.sensorsportal.com/HTML/DIGEST/Submition.htm International Frequency Sensor Association (IFSA).

Sensors & Transducers Journal, Vol. 132, Issue 9, September 2011, pp. 89-99

Sensors & Transducers ISSN 1726-5479 © 2011 by IFSA http://www.sensorsportal.com

Improved Web-based Power Quality Monitoring Instrument I. Adam, *A. Mohamed and *H. Sanusi Electronics Section, UniKL-BMI, Bt. 8, Jln. Sg. Pusu, 53100, Gombak, Selangor, Malaysia Tel.: +603-61841000, fax: +603-61864040 * Department of Electrical, Electronics and System Engineering, Faculty of Engineering & Built Environment, 43000, UKM Bangi, Selangor, Malaysia Tel.: +603-89216006, fax: +603-89202314 E-mail: [email protected], [email protected], [email protected]

Received: 1 August 2011 /Accepted: 19 September 2011 /Published: 27 September 2011

Abstract: Presently, the need for power quality (PQ) monitoring instrument to characterize the performance of power system is becoming more important. Advancement in the embedded web based technology has enabled PQ data to be monitored and captured remotely via the web browser. This paper presents the development of a web-based PQ monitoring instrument for single phase power measurements. The embedded web based technology is applied and this contributes to the reduction in the development and operational cost of the PQ instrument. The PQ data is processed at the receiving end so as to eliminate dependency in processing the PQ data at customer sites. The results on real–time monitoring and downloading of the PQ data via the web browser are also described. The novelty of the developed PQ monitoring instrument is in the simplicity of the design and cost of developing the instrument. Copyright © 2011 IFSA. Keywords: Power quality, Real-time, Web-based.

1. Introduction Modern power system has shifted far from the traditional power system in terms of generation, distribution and customer applications. Moreover, the requirement of the electricity customers has changed tremendously over the years [1, 2]. The application of machines and power electronic components that are usually non-linear contribute to large amount of harmonic currents which pollute the electricity supply. To some extent, the polluted electricity supply may damage or disrupt the 89

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operation of electronic equipments [3]. As the quality of power supply is deteriorating in modern power systems, there is an increasing need for power quality monitoring instrument to characterize the performance of the power system. In addition, the increased requirement on supervision and control of modern power systems makes power quality monitoring a common practice for utilities. Furthermore the use of equipment sensitive to power disturbances and the related economic aspects, the increasing awareness of power quality issues and deregulation, have created the need for extensive monitoring of power system operation. However, power quality problem cannot be realized unless power quality monitoring instruments are installed at the sites [3]. There are several objectives for performing power quality monitoring; to characterize system performance, to characterize specific problems and to enhance power quality service. Characterizing system performance is considered a proactive approach to power quality monitoring. By understanding the power quality performance of a system, a utility can quickly identify problems and offer information to its customers to help them match their sensitive equipment’s characteristics with realistic power quality characteristics. To characterize specific problems, short-term monitoring is usually performed at specific customer sites or at difficult loads. This is a reactive mode of power quality monitoring, but it frequently identifies the cause of equipment incompatibility which is the first step to a solution. Currently, many utilities are providing power quality monitoring services so as to offer customers with differentiated levels of power quality to match the needs of specific customers. Instruments used to monitor electromagnetic phenomena can range from a simple analog voltmeter to a sophisticated multiple-site, permanently installed monitoring sites. The selection and use of the correct type of monitor requires a user to understand the capabilities and limitations of the instrument, its responses to power variations, and the specific objectives of the analysis. IEEE 1159 is a recommended practice for monitoring electric power quality which states that power quality monitoring instruments must have the capability of generating voltage and current data over a period of time. In processing the sampled data, application software is developed to process the data for specific power quality parameters. Many research works have been carried out in developing power quality monitoring instruments. The newly developed instruments have the capability of processing data internally in embedded systems and can support power system predictive maintenance, energy management, cost management and quality control. Unfortunately, such power quality monitoring instruments are expensive in which the price depends on the type of monitoring performed, the number of power quality parameters to analyze and the size of data that it can save [4]. This paper presents the development of a low cost web based power quality monitoring instrument with Ethernet connectivity based on the Embedded Web Server (EWS) configuration embedded system. The EWS configuration is selected because of several advantages such as; it is easy to use and inexpensive graphical user interface for remote control and monitoring that can be easily developed by embedding a tiny website in the firmware.

2. Instrument Design The conceptual design of the developed instrument for the purpose of real-time and remote power quality monitoring of the electric supply networks is shown in Fig. 1. The instrument which is denoted by ‘i’ can be remotely accessed through a web browser. Independent of the network (internet), it samples and processes a single phase power line voltage and current. The processed data which are the rms and THD of the voltage and current are relayed in the form of graph into the user terminal. Upon request, the saved raw data is downloaded into the user terminal. The block diagram in Fig. 2 simplifies the conceptual design of the instrument. As shown, the power line current and power line voltage is fed to the system via the signal conditioning circuit. The signal conditioning circuit is bring in to condition the huge power line voltage and current to the level which suits the microcontroller input level. Two microcontrollers are used to sample, save, process and 90

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publish the PQ data. As depicted in Fig. 2, the processor handles the sampling, processing and saving of the PQ data. The PQ data is saved in the SD/MMC card which is attached to the microcontroller through the SPI connection. The publisher is equipped with Ethernet connectivity and handles the publishing of PQ data.

Fig. 1. Conceptual design of the proposed power quality monitoring instrument.

Fig. 2. Block diagram of the web-based PQ monitoring instrument.

The processor is integrated to the publisher through the RS-232 connection. Upon request, the PQ data which in the SD/MMC card is transferred into the RAM of the processor. The data is conveyed to the publisher via the RS-232 and published by the publisher. For that purpose, a simple handshaking protocol is developed to govern the transferring of PQ data between the processor and publisher. The protocol establishes the connection of the processor and publisher; manages the data transfer and reports to publisher in the failure or absent of SD/MMC card. In addition to that special protocol, the speed of transferring data between the two microcontrollers is improved by revising the common technique used in transferring data between two microcontrollers through the RS-232. The proposed data transferring technique through the RS-232 is based on the shifting property of the microcontroller as discussed in [5] and proven to improve the downloading speed of the web-based PQ monitoring instrument. 91

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In processing the PQ data, the Fast Hartley Transform (FHT) technique is used because it has faster processing speed compared to the Fast Fourier Transform (FFT). In reducing the data to be saved, the pre-processing block is added to preprocess each of the complete sampled voltage and current. Fig. 3 shows the addition and operation of the pre-processing block to the system. The operation of the preprocessing block is such that at all times, the instrument samples power line voltage and current and keep them in a separate input buffer. Whenever the input buffers are full, the sampled voltage and current are compared with the previous sampled voltage and current. If the sampled voltage and current data are different from the previous data, the sampled data will be passed to the SD/MMC card and then processed by the microcontroller for determining the power quality parameters such as THD. This method reduces the data by saving and processing only the sampled data that is different from the previous sampled data.

Previous data

Processing block

SD/MMC

not equal

Input buffer

Present data

Sampled data

full Pre-processing block

Fig. 3. Additional pre-processing block.

2.1. Voltage Measurement The line voltage is much greater than the low voltage analog to digital converter (ADC) and therefore the line voltage signal is attenuated to about half of the maximum ADC input to ensure no clipping on the signal under measurement [6]. For instance, if the voltage to be measured is 400 Vp-p and the maximum input of the ADC is 5 VP-P, the selected attenuation ratio is 160:1. The high line voltage is attenuated by using the voltage divider method due to its better frequency response, cheaper and simpler. The drawback is that it has high output impedance [6]. The high output impedance is rectified by introducing an impedance buffer between the attenuator and filter. The attenuated signal is filtered to ensure that the sampled signal consists of frequency below the Nyquist frequency [7]. In ensuring that the signal amplitude is within the Vref+ and Vref- of the ADC, the filtered signal is shifted to the middle of Vref+ and Vref- of the ADC. The process of conditioning the high line voltage to accommodate the system is depicted in Fig. 4. As shown, the power line voltage is attenuated, filtered and shifted prior to voltage conversion by the ADC. The complete schematic diagram of the voltage conditioning circuit is shown in Fig. 5.

Fig. 4. Voltage measurement. 92

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VCC

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2.2. Current Measurement As shown in Fig. 6, the initial stage in the current conditioning circuit is the inverting amplifier. It is required due to the voltage emitted by the current sensor relative to the current in the power line is practically insignificant to be processed. As the sensitivity of the current sensor is 1mV/A, the voltage is amplified by a factor of twenty (20) prior to filtering and clamping. With this gain factor, if the line current is at 60 Amps, the conditioned current will be around 1.2 Vp. If the current is clamped at 1.6 V, then the current swing from 0.2 V to 2.8 V, which is within the capability of the ADC.

Fig. 6. Current measurement.

The complete schematic diagram of the current conditioning circuit is shown in Fig. 7. It is apparent that the difference between these circuits to the voltage conditioning circuit shown in Fig. 5, is in the initial stage.

2.3. Saving and Publishing of the Data via the Internet Saving of the raw data (sampled voltage or current) is done upon completion of one cycle sampling. In this case, the present sampled data is analyzed for similarity with the previous sampled data. If the data is different from the previous sampled data, it will be kept in the SD/MMC card. The voltage and current data is kept in the SD/MMC by stacking the 16-word of voltage with the 16-word of current 93

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data in a block of 256-word block. Publishing of data over the internet is made possible by the Microchip’s TCP/IP stack. The code is developed based on the HTTP2 web server module provided by Microchip®. The publishing of data is improved by using the AJAX Command through JavaScript object XMLHttpRequest. This technique allows the individual data to be updated instead of the whole web page. Basically as shown in Fig. 8, the data to be published is combined with the web page and transmitted over the internet to the recipient through the web browser. The web page which is situated in the EEPROM is combined with the data to be published and pushed into the internet. Remotely, the combined data and web page could be accessed by a user via the web browser.

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Fig. 7. Complete schematic of the current conditioning circuit.

Fig. 8. Publishing of combined data and web page via the internet.

2.4. Power Factor Measurement In ensuring that the overall cost of the instrument is fairly low, the power factor is not measured in hardware but a software technique is exploited to measure the power factor. The technique analyzes the exact zero crossing of the sampled signals. Upon localization of the exact zero crossing of the 94

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sampled signals, the phase angle is calculated. Its simplicity lies in its simple working principle in which it works on the simple interpolation technique [8].

3. Experimental Set Up The developed power quality monitoring instrument was tested to monitor the quality of the power supply at the Powerlab, University Kebangsaan Malaysia (UKM). As shown in Fig. 9, the current sensor is used to capture the current in the distribution board and the voltage sensor is tapped to the outlet socket. The voltage and current at the corresponding points are measured and compared to the voltage and current published by the instrument. The performance of the system to download the saved data is tested for the download speed. In addition, the downloaded data is plotted by using the MATLAB® package and the plotted graph is compared with the voltage and current measured by the oscilloscope.

Fig. 9. Experimental set up.

The PQ data can be downloaded at a speed of 3.6 kb/s which is reasonable for downloading medium size data through the web browser. It is achieved by a slight modification in the way the data is transferred from the processor to the publisher. The PQ data which is sampled and saved in the SD/MMC of the processor is retrieved to the publisher and propagate through the web browser to a remote end, when it is requested. It is noted that the bottleneck during downloading of data is at converting and reconverting data into a string form. This is due to the built-in C function which takes some processing time for string conversion. In addition, the processing time is directly proportional to size of string generated. The bigger the size of data, the greater will be the processing time and this causes a delay. As stated in [5], by exploiting the shifting property of the microcontroller for data downloading, the overall downloading speed can be made faster by a factor of 1: 23.47. A Web-based Power Quality Application Software (WPQAS) is also developed to publish the downloaded data graphically and dynamically. The chart constructor/visualization which works on a number of methods or Application Programming Interface (API) is added to the WPQAS. The inclusion of chart constructor/visualization in the system has increased the size of the web page. This results in reduction of the refresh rate for the WPQAS. To improve the refresh rate for publishing of data, the AJAX Command through the JavaScript object XMLHttpRequest is introduced. The AJAX 95

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Command allows only the requested data to be updated individually rather than the whole web page. The refresh rate of the WPQAS is greater than the refresh rate required which is 20 ms. In general, the WPQAS is formed by a number of files which are arranged and managed by the Microchip File System Application software (MPFS2). The MPFS supports the downloading of the MPFS image into an external serial EEPROM. The WPQAS supports the transferring of data from the instrument remotely to data server and provides a number of web-based PQ processing options such as power factor calculation. This software tool has the ability to display voltage and current input signals, analyze the signals using the FHT and display the calculated PQ parameters in terms of THD of voltage and current.

4. Experimental Results The web-based PQ instrument has been successfully developed to display the power quality parameters graphically and dynamically as shown in Fig. 10. There are five different colours used to identify the different power quality parameters which are Vrms, Irms, Vthd, Ithd and phase angle.

Fig. 10. The outlook of monitoring the processed data.

In downloading of the sampled data, there are four files which are user selectable. Upon power up, the PQ data is sampled and save into FILE 1, FILE 2, FILE 3 and FILE 4 continuously. A close observation on Fig. 11 shows that the data is downloaded through the web browser at a speed of 3.6 kb/s once the appropriate file is selected. The speed is acceptable for downloading of small size data. Upon downloading, the desktop notepad application is used to unwrap the file. Fig. 12 shows the data that resides in the file magic1.dat. As shown, the 16 sampled current and voltage data is arranged in a row. The current resides in the odd column and the voltage resides in the even column as shown in Fig. 12. 96

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Fig. 11. The outlook of downloading raw data

Fig. 12. The downloaded raw data.

To validate the downloaded data by the instrument, the MATLAB GUI is used to retrieve, reconstruct, plot and process the original data. In Fig. 13, the original sampled voltage is plotted on the left upper row, and the original sampled current is plotted in the left bottom row. Thus, the developed MATLAB GUI is used to verify the capability of the developed PQ instrument in sampling, saving and downloading of the PQ data. From Fig. 13, it is apparent that the reconstructed voltage and current are identical to the voltage and current signals measured by the oscilloscope shown in Fig. 14. This indicates that the developed PQ monitoring instrument successfully sampled, saved and transferred the PQ data remotely via the web browser. 97

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Fig. 13. The plot of downloaded raw data using the Matlab package.

Fig. 14. The measured voltage and current data.

5. Conclusions A low cost web-based PQ monitoring instrument for remote monitoring of distribution feeders in real time has been developed. The development of the low cost web-based PQ monitoring instrument is accomplished by considering the microcontroller, EWS embedded system application and a simple signal processing technique based on FHT. The FHT technique is implemented in a microcontroller for the purpose of calculating the values of individual harmonic, THD and rms values of voltage and current signals in real-time. FHT is applied because it gives faster computing speed compared to its counterpart FFT. The application of the EWS embedded web system allows real-time sampling, processing, saving and relaying of data through the web browser. The system’s flow control and protocol is also developed in ensuring that the prototype instrument processes, saves and transfers data accordingly in true real-time. As a result, the PQ instrument with Ethernet connectivity for accessing of PQ data remotely is developed. 98

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Acknowledgements This work was carried out with the financial support from the Malaysian Ministry of Science, Technology and Innovation under the Science Fund research grant 03-01-02-SF0071. The technical supports by colleagues and laboratory staff of UKM are gratefully acknowledged.

References [1]. A. So, N. Tse, W. L. Chan & L. L. Lai, A Low-Cost Power Quality Meter for Utility and Consumer Assessments, in Proc. of the International Conference on Electricity Utility Deregulation and Restructuring and Power Technologies, 2000. [2]. V. Kuhlmann, C. P. Arnold, M. B. Dewe, System Requirements of Real Time Continuous Data Acquisition for Power Quality Monitoring, in Proc. of the 41st International Universities Power Engineering Conference (UPEC’06), 2006, pp. 1031 – 1035. [3]. R. C. Duccan, M. F. McGranagahn, S. Santoso & H. W. Beaty, Electrical Power System Quality. McGrawHill, 2004. [4]. A. McEachern, A New, Ultra-low-cost Power Quality Measurement Technology, in Proc. of the Asia Pacific Conference on Power Quality, 2007. [5]. I. Adam, A. Mohamed, H. Sanusi, Modified Controller to Controller Communication Through USART”, in Proc. of the International Conference of Engineering Technology (ICET’ 2009), Kuala Lumpur, Malaysia, 08-11 December 2009. [6]. IOtech, Signal Conditioning & PC-based Data Acquisition-Handbook, IOtech Inc, 1998. [7]. P. Denbigh, System Analysis and Signal Processing: With emphasize on the use of Matlab, Prentice Hall, 1998. [8]. I. Adam, A. Mohamed, Hilmi Sanusi, Simple Phase Angle Measurement of Two Periodic Signals, in Proceeding of the Student Conference on Research and Development (SCORED’ 2009), 16-18 November 2009. [9]. A. Mureno-Munoz and J. J. G. de la Rosa, Use of Smart Sensors in the Measurement of Power Quality, Sensor & Transducers, 89, 3, 2008. ___________________ 2011 Copyright ©, International Frequency Sensor Association (IFSA). All rights reserved. (http://www.sensorsportal.com)

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