RECENT ADVANCES IN SYSTEMS, COMMUNICATIONS & COMPUTERS, Selected Papers from the WSEAS Conferences in Hangzhou, China, April 6-8, 2008
Mechanical Fault Detector in Power Transmission Lines JOAQUÍN RODRÍGUEZ, CARLOS TELLO Control and Instrumentation Department Instituto de Investigaciones Eléctricas Reforma 113, Col. Palmira, 62490, Cuernavaca, Mor. MEXICO
[email protected] http://www.iie.org.mx Abstract: - This paper presents the development of a system and a device for the detection of mechanical failure in electric power transmission lines, under oscillating movement, collapse, or short circuit faults in the cable; caused by natural or induced man effects. The system has a remote module hanging on a cable and a central operation module via wireless communications. The remote module has data acquisition; a master micro controller which defines the status of the cable, the ability to add coordinates with the Global Positioning System (GPS) to determine their location, sensing temperature, electric current and acceleration, the latter is based on MEMS technology (Micro Electromechanical Systems), which detects movement in the cable. The central operation module is connected to serial port in a personal computer. With software created in LabVIEW, the user can survey the remote module, ask the historic stored data, assign an identification number and assign global positioning coordinates via wireless. Keywords: - Remote data acquisition, wireless communication, transmission lines, MEMS, GPS.
illegal commercialization of the aluminum. The fast detection of the cause and location of the failure is of grate importance to maintain the quality of service and to avoid additional damage to costumers
1. Introduction Electric AC power transmission is a process in the delivery of electricity to consumers, is the bulk transfer of electrical power. Typically, power transmission is between the power plant and a substation near a populated area. Overhead transmission lines are uninsulated wire, so design of these lines requires minimum clearances to be observed to maintain safety.Overhead conductors are not covered by insulation. The conductor material is nearly always an aluminum alloy, made into several strands and possibly reinforced with steel strands. Today, transmission-level voltages are usually considered to be 110 kV and above. Lower voltages such as 66 kV and 33 kV are usually considered sub-transmission voltages but are occasionally used on long lines with light loads. Voltages less than 33 kV are usually used for distribution. These transmission lines cross the irregular areas and they are exposed to wind, hurricanes, tornados and others nature effects, causing damages and interruption of service. Besides that, there are places where the transmission or distribution cables are stolen for
ISBN: 978-960-6766-61-9
This article shows the implementation of a system that provides new solutions using new technologies for the monitoring of transmission lines, using MEMS systems, microcontrollers, GPS, wireless communication by radio, serial communication, email notification and systemuser software, built in two modules to solve the problem.
Figure 1. 1 Power transmission lines. The sphere are the spots where the smart sensors are to be installed.
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RECENT ADVANCES IN SYSTEMS, COMMUNICATIONS & COMPUTERS, Selected Papers from the WSEAS Conferences in Hangzhou, China, April 6-8, 2008
(milivolts) per degree centigrade. Due to the signal is too low, it is amplified with an OPAM to get a better signal.
The Figure 1.2, shows a block diagram of all system.
To sense the electric current, we used a coil that captures the electromagnetic field emitted by the line. Based on the theory of Rogowski coil, the signal obtained from the coil is rectified, integrated and amplified to obtain a response voltage proportional to the electric cable current, which is on the line. To detect the oscillating movement or collapse of the cable, is used an accelerometer based on MEMS technology.
Figure 1. 2 Mechanical fault detector block diagram.
The MEMS, is the integration of mechanical, sensors, actuators and electronics elements, manufactured on a silicon substrate with microtechnology. [1]
The system does not prevent theft or mechanics faults directly, but let the companies know where the failure was, what happened in the transmission lines and the status in seconds.
The MEMS accelerometers are manufactured with this technology and are capable of measuring the acceleration occurring in some relating axis to land. There accelerometers with 1, 2 and 3 axis, better known as X, Y or Z axis.
2. Remote module The remote module has temperature, electric current and acceleration sensors, storage system coordinates from a GPS, wireless communication system for radiofrequency (RF) and a processing unit, as shown in the block diagram of the remote module in Figure 2.1.
The accelerometer MMA7261Q of Freescale Semiconductors is a 16 pin device capable of measuring the X, Y and Z axis. The analog output voltage of each axis, are measured and interpreted in the processing unit to determine whether the cable suffered some movement that is reason to send an alarm to the central operation module. 2.2. GPS The Global Positioning System (GPS) is a system of based on satellite navigation. The satellites are constantly sending encrypted information; with a GPS receiver can determine the exact position on the Earth, in terms of latitude and longitude, you also can get the height and altitude above sea level.
Figure 2. 1 Remote module block diagram.
2.1. Sensors It was used two temperature sensors (LM35), one to measure the ambient temperature and another one to measure the temperature of the cable. This sensor delivers its output value analog 10mV
ISBN: 978-960-6766-61-9
The GPS receiver LS-40mm shown in Figure 2.2, sends the location where it is, in an encrypted data.
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RECENT ADVANCES IN SYSTEMS, COMMUNICATIONS & COMPUTERS, Selected Papers from the WSEAS Conferences in Hangzhou, China, April 6-8, 2008
2.3. Radiofrequency System. A radiofrequency communication system is the transfer of information wirelessly on a determined frequency. The system RTF-DATASAW is a transceiver module operating in the band of 433.92 MHz. The RF system has an encoder and decoder in a single integrated circuit called DPC-64. It is responsible for decoding the information it receives via wireless and deliver it in 4800 baud, 8, N, 1 protocol serial communication.
Figure 2. 2 GPS Receiver
The serial communication protocol of the GPS receiver is 4800 bauds speed transmission, 8 data bits, no parity and one stop bit (4800 Bauds, 8, N,1).
The information that sends the RF system is encoded by this integrated circuit to send it by electromagnetic waves through the air. 2.4. Microcontroller
One of the advantages of the system is that the GPS receiver is not physically mounted in the remote module. The GPS module is a module with its own supply voltage and an RJ11 connection to communicate with a phone cord to the remote module, specifically to the processing unit. When you turn on the GPS and activate a magnetic switch, the GPS acquires the location where it is, while the processing unit is storing this information in the data memory.
The microcontrollers are devices with memory, a central processing unit and I/O ports. One of its main and most attractive features is that they are programmable. You can load a program in a microcontroller created in assembly language; to perform control processes and interact with devices electronically, either analog or digital signals (TTL). Each microcontroller has its own characteristics.
When this process has been completed, the GPS module could be disconnected and turned off, leaving the location stored on the remote module and ready to install on the cable (Figure 2.3). Due to this, the system is cheaper, since there is no need to have a GPS module in all remote modules.
ISBN: 978-960-6766-61-9
The PIC16F877A is a microcontroller from Microchip in a chip type of 40-pin PDIP packages. The principal characteristics by which this PIC was used are: digital I/O ports, analog inputs, analog to digital converter of 10 or 8-bit resolution, serial communication USART (Addressable Universal Synchronous Asynchronous Receiver Transmitter), memory storage EEPROM (Electrically Erasable Programmable Read-Only Memory).
Figure 2. 3 Remote Module block diagram 215
ISSN: 1790-5117
RECENT ADVANCES IN SYSTEMS, COMMUNICATIONS & COMPUTERS, Selected Papers from the WSEAS Conferences in Hangzhou, China, April 6-8, 2008
3.1. Serial Communication with de PC This PIC (Peripheral Interface Controller) is the central processing unit. In Figure 2.4, shows a block diagram of the remote module, with the PIC16F877A, sensors, GPS module and RF system integrated to remote module.
The central operation module has a serial communication protocol of 4800 baud, 8, N, 1. To adjust the TTL signal (voltage) of the electronic circuit with the voltage needed by the RS-232, was used an integrated circuit called MAX-232.
The PIC16F877A, has programmed routines process or features, such as analog to digital conversion to get the values from the sensors, storage of historic data in the internal EEPROM when an alert happened (collapse, oscillatory movement, no electric current or overheating in the cable), generates a detection range of values which can determinate whether the system suffered acceleration that cause an alert. It also has availability to be survey, assign an identification number or assign global positioning coordinates from the central operation module, in addition to having a serial communication protocol for communication between the remote module and the GPS module, is also between the remote module and the central operation module.
3.2. System-user Software. This interface is programmed in LabVIEW. It contains indicators of temperature, electric current and acceleration. It has a control panel to assign global position coordinates, assign an identification number, ask the historical data and request the remote module. This interface generates historical data of each process, saving the information in a database. When an alert is generated, the user interface displays a warning on the screen showing the number of identification of remote module which generated the problem. In turn, creates two files, which show graphically the remote module location in Google Earth and any Internet browser. The system generates two emails and they are sent to users previously assigned. The emails contain an identification number and the files previously created like an attachment. The Figure 3.2 shows the main screen of the systemuser software.
3. Central operation module The central operation module consists of a transceiver RT-DATA-SAW, an encoderdecoder DPC-64, an integrated circuit that couple TTL voltage with RS-232 port voltage and system-user software. In Figure 3.1, shows a block diagram of the central operation module. This module has the same system of radiofrequency wireless communication.
Figure 3. 2 Main screen of system-user software Figure 3. 1 Central operation module block diagram
ISBN: 978-960-6766-61-9
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RECENT ADVANCES IN SYSTEMS, COMMUNICATIONS & COMPUTERS, Selected Papers from the WSEAS Conferences in Hangzhou, China, April 6-8, 2008
4. Results .
The remote module stores mainly accelerometer data to define the threshold of detection. This part is important, because no one knows the exact position at which the module will be, once hung on the cable. The system is sensing the temperature, the electric current and the acceleration in three axis. Once an alert occurred, the system sends an identification number via radiofrequency, one start word, the data information and the end word. The central operation module, only receives the information that contains the ID number of the module, this means, the information received with other identification number is unknown data for the central operation module.
5. Conclusions A new application capable to detect faults in power transmission lines presented to This system is capable to give instantaneous notice to the user about problems in a transmission line via e-mail. The remote smart sensor is capable to detect and identify mechanical problems. The remote smart sensor can be monitored and is able to provide the state of itself and historical data stored in local memory.
Whenever the remote module maintains communication with the central operation module, based in the last terms. When the software asks the actual values or the historic stored, as well as assign an identification number or global positioning coordinates, always sends, the identification number to the remote module and a brief instruction coded so that the microcontroller respond or act to the request.
The combination of new technologies such as MEMS, micro controllers, GPS, and wireless communication permitted the integration of smart systems for sensing and monitoring electric power transmission and/or distribution lines.
6. References
The results obtained in laboratory tests and simulations, were satisfactory. The system responds effectively when is subjected to high temperatures, lack of electric current in the cable, collapse and oscillating movements on it. The Figure 4.1 shows the mechanics faults detector working.
Figure 4. 1 Mechanics fault detector whit operation central operation module, GPS module, remote module (gray) and system-user software working
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[1]
MEMS, http://www.memsnet.org/mems/whatis.html.
[2]
JOSÉ MANUEL H, RAMÓN J. MILLÁN y DAVID ROLDAN M, Technology of Telecommunications, Alfaomega Ed., México, 2006, (Spanish)
[3]
WAYNE TOMASI, Electronic Communication System Fundamental Through Advanced, Fourth Edition, Prentice Hall, United States, 2001.
[4]
LOUIS E. FRENZEL, Electronics Communications Systems, Alfaomega Ed., México, D.F., (Spanish)
[5]
New development in electric current sensors, http://www.analog.com/UploadedFiles/Te chnical_Articles/16792408482720MI_Iss
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RECENT ADVANCES IN SYSTEMS, COMMUNICATIONS & COMPUTERS, Selected Papers from the WSEAS Conferences in Hangzhou, China, April 6-8, 2008
ue3_2001_pg52-53_analog_Spanish.pdf, (Spanish). Joaquin H. RodriguezRodriguez. Graduated as a Mechanical and Electrical Engineer from University of Nuevo Leon at Monterrey, Mexico in 1974, and obtained a Masters of Science degree in Electrical Engineering from the University of Toronto, Canada in 1980. As part of his professional experience, he worked as a research engineer for Trench Electric Ltd. of Toronto, Canada from 1979 to 1981. He joined the Electrical Research Institute in Mexico as a researcher and head of the telecommunications laboratory, where he developed projects related to electronics, optical fibers and telecommunications systems for the electrical utilities in Mexico from 1982 to 1988. In the last four years, he has been working on MEMS Applications and optical fiber sensors for on-line monitoring of Power electric apparatus. He was professor at ITESM, the University of Morelos and the Center for Research and Technological Development, all in Mexico. Has published many technical papers and participated in national and international technical meetings. From 1985 to 2007 Juan Carlos Gonzalez Tello. Mechatronics and Process Control Systems Engineer from La Salle University in Cuernavaca, Mexico. With expertise in automation, programming, electronics, robotics, in addition to leadership and decision making. He has been associated with the electronics laboratory to test optical fiber electro optics links for the Control and Instrumentation group in the Instituto de Investigaciones Eléctricas (IIE) in Mexico. and develop smart sensor for the detection of mechanical failure in electric power transmission lines as a Bsc. thesis, in the MEMS design center of the IIE. .
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