Proceedings of the 6th WSEAS International Conference on Instruentation, Measureent, Circuits & Systes, Hangzhou, China, April 15-17, 007 13 A Wireless Transission Technique for Reote Monitoring and Recording Syste on Power Devices by GPRS Network Cheng-Chien Kuo *Hong-Chan Chang *Fu-Hsien Chen Departent of Electrical Engineering, *Departent of Electrical Engineering, Saint John s University, National Taiwan University of Science and Technology, 499, Sec. 4, Ta King Road, Tasui, Taiwan. 43, Sec. 4, Keelung Road, Taipei, Taiwan. Abstract: - A reote onitoring and recording syste for power devices is developed in this paper. It ais at the application of the technology of wireless transission and signal processing in the transission of the signals of long-distance electric equipent to the central control station. The terinal visualizes its working states in pictorial syste and saves all the historical data into general database for the purpose of future research and exaination. Through this proposed syste, only requires a GPRS atching acquisition syste odule which enables the longdistance control center to acquire any signals of the equipent, so that overall supervision is attained. Meanwhile, the task of wire setting on rough landfor is avoided, and the tie to overhaul can be saved. In addition, by exaining the data record or analyzing the theoretically, we coe to know the perforance, life-span and operation efficiency of the equipent, so as to propose aintenance or replaceent, thus the traditional periodical aintenance progra is upgraded to a ore efficient conditional based one. When anything abnoral happened to the equipent, the syste can infor in advance the engineers concerned to repair it iediately or replace it, and reduces the occurrence of unexpected accidents. Key-Words: - Power Devices, General Packet Radio Service, Wireless Transission, Reote Monitoring. 1 Introduction Nowadays, electric power has becoe an indispensable energy source which is used so widely that it functions as a basic necessity of every walk of life. Regarding the electric facility, high profit is earned when everything works soothly, otherwise, work-line coes to a halt and results in decreasing output, in particular serious in the power industry. Provided that the power supply is cut, every sectors of the econoy will suffer huge losses. If any proble of the equipent is spotted in advance, we replace or repair it tiely, huge losses can be avoided. With technological advanceent of inforation and network, the electric supervisory syste, no longer confined to siply electric power utilization, can offer various services by onitoring the state of power consuing in an interactively way, so as to iprove the efficiency of overall power utilization. As to the current electric facilities, little tiely supervision and analysis of syste has been done. If we can ake an iediate analysis and supervision, we will get ore data, such as load curve, deand, peak load, fro which we can work out deand factor, load factor and diversity factor. Based on the data, we are able to ake an evaluation of our equipent, energy and utilizing efficiency. To ake sure the high security of electric operating syste, SCADA has been recoended by power firs across the world to acquire the data of electric working state, to control the switch device, and to supervise long-distance equipent, so that syste dispatchers are able to onitor the operating state of on-site equipent. SCADA coprises control center, on-site equipent and counication network, etc. Before the display of PC screen, the dispatcher can ake an analysis of any coing signals. When any abnoral data appears, the dispatcher does an iediate repair to avoid any ajor accidents to coe. On the basis of the highly developed obile counications era today [1,4], it is believed that the wireless transission platfor ay odify and iprove the cable transission disadvantages. The present day GPRS network syste has been established to a perfect level leading to the popular use of obile phones []. And GPRS network can have reliable way to transit data in addition to voice [3]. There already have any applications that apply the advantage of GPRS network to iprove the conventional uses [4-1]. Hence, this research designed a wireless real-tie onitoring feedback syste to connect the built-in GPRS odule, aking it possible to send back the onitoring data without aterial cabling between the onitored ends. The use of GPRS odule akes the onitoring coands and inforation observation not confined to a fixed point, enhancing the onitoring flexibility, convenience and reliability. Therefore, this
Proceedings of the 6th WSEAS International Conference on Instruentation, Measureent, Circuits & Systes, Hangzhou, China, April 15-17, 007 133 research applied GPRS in collecting electric power data to further achieve the onitoring purpose, and developed a set of GPRS reote onitoring equipent that ainly onitor the relevant electric data at the onitored ends including the three-phase voltage rs value, electric current, and electric power. In addition, inforation on the statuses of power source over voltage, under voltage, over current and power status are fed back to the far-located onitoring end by GPRS. D. Host end onitoring: Utilize Visual Basic as the onitoring progra of Host end to revert the received data to its original wavefor, and then to work out various data after calculation, so as to coe to know the state of longdistance equipent. Software and Hardware Prograing This section is to elaborate on the syste structure and the design procedures of relevant hardware and software. The syste structure is as shown in Fig. 1. Install the GPRS reote onitoring device developed in this research at the onitored station. The device collects the inforation on electric voltage and current with its power calculated. And the onitoring data collected can be sent fro the GPRS odules at the onitored end to the central station with internet of the far onitoring end by GPRS network syste. Fig.. Syste Structure Fig. 1. GPRS reote onitoring syste structure.1 Fraework of the Syste The syste is ade of four parts as describing below and shown in Fig. including: electric signal processing, signal sapling, GPRS transission and Host end onitoring. A. Electric signal processing: Utilize siple circuit to ake soe proportional processing of signals, and then copare the siulated with the actualized, after that, ake soe odification to ake sure the circuit useable. B. Signal sapling: Utilize single chip to saple the voltage, current and phase signal, and to do soe calculation of data out of the saples. C. GPRS transission: Make use of the atch of Yi Yang s GPRS Module with single chip, and utilize AT coand to control the online and data transission by RS-3 transission technique.. Function of the Syste The ain functions of this syste can be divided as two parts. The first one is to onitor the equipents and transit back the relative paraeters. The second function is to analysis the received data for further uses as stated below. A. Monitor the data of electric equipent: We can collect the voltage and current data fro onitored equipents, and transitted the data to the long-distance PC by GPRS. When receiving the data, the PC saves it into database and visualizes its wavefor. At the sae tie we can calculate the data and get the power consued by the electric equipent concerned. B. Analyze the received data: We also can collect data fro any equipents, and then ake a coparison. For instance, we can calculate out the loss in the transission, through which, if anything abnoral, we can infor in advance the engineer to do a repair and aintenance.
Proceedings of the 6th WSEAS International Conference on Instruentation, Measureent, Circuits & Systes, Hangzhou, China, April 15-17, 007 134.3 The Principiu and Method of the Design.3.1 Signal Processing A. Voltage The power voltage of equipents is an AC large signal that is not suitable for A/D converter and GPRS transission. We utilize ceent resistance divider to drop the voltage around the range about.5v. Then we use adder circuit to raise the AC voltage level for.5v, such that the V ax is around 5V and DC value, and then the signal can be sent to ADC for conversions. B. Current As to the current, through current transforer (CT we dwindles the current in proportion. Then we connect in serial the current with a resistance, and then we utilize a reverse aplifier and an adder to aplify its voltage and ake a level shift, after that send the signal to the ADC for a conversion..3. Phase Difference Let V = V cos( ω t +θ1 and I = I cos( ω t +θ Using ultiplier to set the product of V and I then : = VI = V I cos( ω t + θ1 cos( ωt + θ V = I [cos( ωt + θ1 + θ + cos( θ1 θ ] VI VI = cos(ωt + θ1 + θ + cos( θ1 θ AC ter DC ter The AC ter will only have an offset affected by DC value at this oent as shown in Fig. 6. It is very easy to find the av through ax and in : ax + in av = (1 V I av = cos( θ1 θ V We using a hardware chip (AD633 to produce the signal of ultiplication of V and I, such that the av can be find according to (1. Therefore, the phase difference between V and I can be find as below: av θ = θ = cos 1 1 θ ( VI.3.3 Saple In signal sapling, the ADC0809 cobined with 884A is utilized to convert analog to digital. In here, 884A offers 1.MHZ clock for ADC0809 so that it can work soothly. It takes about 10 clock for each saple point of ADC0809 to ake the conversion, 1 1.MHz 10 = 8.33μs, together with 30 μs, delay of progra, the sapling frequency is about 4.KHz. Therefore, sapling 60Hz power signal in such a anner also accords with Nyquist sapling theore f p f s, and this won t bring about aliasing phenoenon. ADC0809 utilize its fraework to switchover between 8 analog channels for 8bit conversion. The signal of voltage, current and phase difference is input to connector V REF ( + to +5V, and V REF ( to GND. Since V REF is 5V, and the resolution of ADC is 8bit, 56 levels is set. Its 8 step voltage = 5V ( 1 = 0. 0196V. Then the START and ALU of ADC chip are triggered, so that the conversion is activated, and after conversion, the converted data is acquired in the anner of interrupt. Surely, to ake ADC0809 work, clock should be provided. In this design, it is ADC0809 that offers the clock, aided by 7. MHZ crystal oscillator; 884A divides by 6. Finally 1.MHZ clock is obtained by PCLK. V 0V Frequency=60Hz t ax - V I av I in 0 t Frequency= 60Hz 0 Frequency=10Hz t - I Fig. 6. The wavefor after the product of voltage and current
Proceedings of the 6th WSEAS International Conference on Instruentation, Measureent, Circuits & Systes, Hangzhou, China, April 15-17, 007 135 Microprocessor is utilized here to acquire the signal of 70 sapling points, and then GPRS is applied to transit the data to long-distance supervisory syste, where linear interpolation is eployed to revert the data to its original signal..3.4 The Connection of 89C5 with GPRS Module In the application of GPRS odule and 89C5, 89C5 is utilized in this paper to give AT Coand to control GPRS odule through RS-3, so that GPRS can connect to the network to transit the data. To get GPRS Module to transit signal soothly, AT Coand is utilized here..3.5 Power Calculation After calculating the data obtained in sapling, we get V I and θ, with which we work out for the forula P = V I cosθ. Then the power is easily got. 3 Ipleentation Three parts to be discussed here: 3.1 Voltage acquisition In this part, as shown in Fig. 8, we decrease the voltage to -.5V~+.5V as shown in upper portion of Fig. 8, but the sapling scope of ADC0809 is confined to positive value (0V~5V. Therefore, we ake a slight adjustent of the voltage, which is done in the lower part of Fig. 8. In this process, we use the IC as TL084. The U1 is the buffer added to prevent the interference between the front and back voltage. The U is the noninverted adder to raise its voltage; it is designed according the following procedure. Assue the point 3 of U is V A, the output of U1 is point 6 denoted as V i, V o is the output of U placed in point 6 R=1k,R7=R8=R9=R,R5=R6=R VA 5 VA 0 VA Vi + + = 0 R R R V A 5 + VA + V A Vi = 0 4 V A = Vi + 5 1 V A = Vi + 1.5 R 1 V o = ( 1+ VA = (1 + 1 ( Vi + 1.5 = Vi +.5 R After passing U, the level of voltage V i (-.5V~+.5V rises by.5v, thus the V o scope is expanded between 0V~5V. After such adjustent, ADC0809 is well prepared for voltage value. 3. Current conversion As shown in Fig. 9 is the current conversion circuit. When collecting real signal saple of voltage and current, we connect the equipent to 110V voltage, R3(1k in serial, LOAD and CT. R3 is set to prevent excessive short-circuit current; LOAD is set to detect the state of voltage and current value for a easy exaination, which is also the purpose of our experient; CT is set for two exaination: the first one is to easure the current passing the LOAD, and the second one is to transfor the current inducted into the voltage wavefor through R4(9.9K. The voltage of R1 and R falls into 110V, close to the voltage for LOAD. For a convenient detecting, we divide the 110V so that the voltage falls into the scope (-.5V~+.5V, convenient for its analysis to coe. Fig. 9. Current transfor by CT 3.3 Current acquisition As shown in Fig. 10 is the current acquisition circuit. The current value has been inducted fro priary to secondary through CT in part. Next, the current value is transfored into the voltage through R4. Since the current is transfor to secondary, due to the turn ratio, the previous big current is converted into sall one, the value inducted in easureent is even sall. For a convenient easureent, we utilize a reverse aplifier (U3, whose rate is R11: R10 => 31.5 ties, to aplify the voltage to the scope, -.5V~+.5V. After that, by the eans of voltage acquisition, we utilize a nonreverse adder (U4 to adjust the voltage to 0V~5V, convenient for ADC0809 to receive.
Proceedings of the 6th WSEAS International Conference on Instruentation, Measureent, Circuits & Systes, Hangzhou, China, April 15-17, 007 136 Fig. 8. Voltage acquisition circuit diagra Fig. 10. Current acquisition circuit diagra 3.4 Phase Process The ultiplier circuit of voltage and current is shown in Fig. 11. Using the product of voltage and current to get the phase difference Fig. 11. ultiplier circuit of voltage and current For exaple: The input value are V =.5cos( ω t + 45, I =.5 cos( ω t + 30 Suppose the angle of voltage and current are θ 1 and θ, respectively. = VI =.5.5cos( ω t + θ1 cos( ωt + θ 6.5 = [cos(ωt + θ1 + θ + cos( θ1 θ ] = 3.15 cos(ωt + θ1 + θ + 3.15 cos( θ1 θ the angle θ can be calculated by the DC ter that is the ean value of the wavefor. av = 3.07 av = 3.15 cos( θ1 θ = 3.07 3.03 θ = θ = cos 1 1 θ = 14.16 15 3.15 Then, the phase difference of voltage and current can be found. 4. Future Developent and Application The syste can be applied in the supervision of electric equipents, which not only saves labor cost, but also obtains the signal of equipent tiely. The
Proceedings of the 6th WSEAS International Conference on Instruentation, Measureent, Circuits & Systes, Hangzhou, China, April 15-17, 007 137 syste can be established in every circuitry to onitor the state of equipents and then transit their signal for analysis. Apart fro analyzing the current state of the equipent concerned, the syste can utilize its database to copare the state of all equipents to deterine if anything needs to be iproved and coe to know the life-span of the equipent, etc. This not only axiizes the perforance of all the equipent, but also iniizes the occurrence of accidents. In addition to siple signal transission, GPRS is very convenient for the local end or the Host end, convenient for a setup and easy for aateurs to operate. The developent of long-distance electric supervisory syste, based on GPRS transission, is proising. Hence, future research shall focus on an autoatic control of the supervisory syste, which can autoatically control the state of long-distance equipent with the result obtained fro analyzing the signal. The syste is expected to coe into factory, copany and even residence for a long-distance supervision, so as to bring security and efficient supervision everywhere. 5 Conclusion The developent of wireless counications has been iproving and enhancing the reote onitoring technology. It is an iportant link of the reote onitoring technology to transit data or control coands accurately and quickly between the onitoring end and the controlled end. In this paper, a wireless transission through GPRS network for power equipents onitoring and controlling syste is ipleented. The GPRS schee is used in the proposed transission structure and shows a good perforance in the real application. The presented devices for reote onitoring and controlling are tested under Taiwan Power Copany with rather encouraging results. It shows the ability for future technique in wireless onitoring of power equipents. 6 Acknowledgent Support for this research by the National Science Council of the Republic of China under Grant No. NSC 94-6-E-19-009-CC3 is gratefully acknowledged. References [1] Scanaill C.N., Ahearne B., Lyons G.M., Long-ter Teleonitoring of Mobility Trends of Elderly People Using SMS Messaging, IEEE Transactions on Inforation Technology in Bioedicine, Vol.10, No., 006, pp.41 413. [] Jeong-Hyun Park, Wireless Internet Access of The Visited Mobile ISP Subscriber on GPRS/UMTS Network, IEEE Transactions on Consuer Electronics, Vol.49, No.1, 003, pp. 00 106. [3] Wilson, A.J., The Use of GPRS Technology for Electricity Network Tele-Control, Journal of Coputing & Control Engineering, Vol.16, No., 005, pp.40-45 [4] Salkintzis A.K., Fors C., Pazhyannur R., WLAN-GPRS Integration for Next-Generation Mobile Data Networks, IEEE Transactions on Wireless Counications, Vol.9, No.5, 00, pp.11 14. [5] Caacho G., Alducin G., Gutierrez J., Miranda J.C., Software Developent for Local Data Transfer for Mobile Applications Using GPS and GPRS Technology, The 16th International Conference on Electronics, Counications and Coputers, 006. CONIELECOMP, 006, pp. 7 10. [6] Talledo Vilela J.P., Miranda Valenzuela J.C., Wireless Sensor Network and Reote Data Acquisition Syste for Mobile Applications, The 16th International Conference on Electronics, Counications and Coputers, 006. CONIELECOMP, 006, pp. 3 7. [7] Hongliang Zhou, GPRS Based Power Quality Monitoring Syste, 005 IEEE Proceedings on Networking, Sensing and Control, 005, pp. 496 501. [8] Talledo J.P., Miranda J.C., Design of a Multiple-Point Wireless Reote Data Acquisition Syste for Mobile Applications, The 16th International Conference on Electronics, Counications and Coputers, 006. CONIELECOMP, 006, pp. 3 8. [9] Vilela, J.P.T.; Valenzuela, J.C.M.; Design and ipleentation of a wireless reote data acquisition syste for obile applications, 5th International Workshop on Design of Reliable Counication Networks, 005. (DRCN 005, 16-19 Oct. 005, pp. 8. [10] Al-Baker O., Benlari R., Al-Qayedi A., A GPRS- Based Reote Huan Face Identification Syste for Handheld Devices, International Conference on Wireless and Optical Counications Networks, 005. WOCN, 005, pp. 367 371. [11] Rashid O., Coulton P., Ahed H., Khirallah C., Live Inforation Update Services Over GPRS, International Conference on Inforation and Counication Technologies: Fro Theory to Applications, 004, 004, pp. 5 6. [1] Druea A., Svasta P., Popescu C., Reote Access Solutions for Industrial Control Systes, 7th International Spring Seinar on Electronics Technology: Meeting the Challenges of Electronics Technology Progress, 004. Vol.1, 004. pp.30 35.