ZIGBEE and GSM-SMS Based Conductor Temperature and Sag Monitoring
#1

ZIGBEE and GSM-SMS Based Conductor Temperature and Sag Monitoring
Presented By
ANEESH P
Roll No. 203
Electrical and electronics engg.
College of engineering, Trivandrum


contents

Introduction
Study on Relative Models
Preambles of Conductor Capacity Ratings
Dynamic Thermal Line Ratings (DTLR)
Traditional Methods for DTLR
The Structure of the Monitoring System
The Topology of System
Structure and Design of Monitoring Unit
The structure of temperature monitoring device
The structure of temperature monitoring unit
The structure of the communication unit
The Block diagram of Monitoring System
Flow charts
Example Calculations
Conclusions & Future Scope
References

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Introduction
Why this monitoring system is needed?

What is ZIGBEE GSM-SMS Method of monitoring system?

The principle of GSM-SMS and ZIGBEE system

Software hardware design

Study on Relative Models
Preambles of Conductor Capacity Ratings
Dynamic Thermal Line Ratings (DTLR)
Traditional Methods for DTLR

2.1 Preambles of Conductor Capacity Ratings
Key factors driving the changes in the way of utilities operate their transmission systems
Conductor thermal limits relates to conductor temperature and sag
Preset system accordance with environment, different boundary conditions in diifferent countries( india-75,usa-90,france-85)

2.2 Dynamic Thermal Line Ratings (DTLR)
Benefits of DTLR system

2.3,Traditional Methods for DTLR
Three traditional methods can be identified in industry practices for DTLR based on the measured parameters. These
are:
(1) weather-based models,
(2) Conductor temperature-based model, and
(3) The conductor tension-based model.

3. The Structure of the Monitoring System
The monitoring system of temperature of conductors and fittings and conductor sag based on GSM SMS and ZIGBEE is mainly composed of the provincial monitoring center, the municipal monitoring center, the communication unit, the temperature and pressure monitoring unit and the expert software



The Topology of System
4. Structure and Design of Monitoring Unit
The temperature of environment, conductor, and the crossing, Altitude values can be measured by the monitoring unit, which is composed of power module, MCU (Micro Control Unit), ZIGBEE communication module,
temperature sensors, Barometric pressure sensors and so on
LM35 is selected as the temperature sensor
MPXAZ6115A selected as pressures sensor

The structure of temperature monitoring device
The structure of temperature monitoring unit
The structure of the communication unit
The Block diagram of Monitoring System
Design of Software
Functions of monitoring unit
How its works?
Working based on sampling time base or cyclic mode alarm


5.1 Functions of Expert Software:
Functions of expert software
How it is functioning?
Use of ZIGBEE
Figure 8: Flow Chart for Monitoring Unit:
Figure 9: Flow Chart for Communication Unit


5.2 Laboratory Bench-Testing
Objectives of the bench-testing….
Where it is performed
Is it possible in real life…









5.3 Example Calculations
5.4 Pressure Altitude Calculator:
6. Conclusions & Future Scope
The main contribution of this paper is the design, construction, field testing and analysis of a GSM SMS and ZIGBEE based instrument for the real time direct measurement of overhead HV conductor temperature and sag. It is a direct technique It also presents a potential source for cost reduction and better accuracy in the conductor sag measurement . The real time direct measurement of overhead conductor temperature and sag is a clear advantage. The measured sensor temperature is not equal to the conductor temperature because the sensor is a heat sink in this complex thermal system. So the conductor temperature must be computed by using the measured temperatures of the sensor. For this purpose a
calibration of the sensor and conductor must be made in the laboratory.
References
[1]M.V. Vijaya Saradhi et al. / International Journal of Engineering Science and Technology Vol. 2(4), 2010, 372-381
[2] T. O. Seppa, “Accurate Ampacity Determination: Temperature-Sag Model for Operational Real Time Ratings,” IEEE Transactions on Power Delivery, Vol. 10, No. 3, July 1995.
[3] Zhao Chen,HE Bo, Wang Rui. A Design for ZigBee Wireless Communication Based on CC2420 RF transceiver. Micro-Computer Information, 2007.
[4] Zhang Xuezhe,Li Xiaoqing,Liu Changqing,and so on.Discussing on Measurement of Improving Conductor Transmission Capacity - Improving Conductor Allowable Temperature[J]. For electricity, 2005.


[attachment=4157]
Full report:
http://ijest.info/docs/IJEST10-02-04-06.pdf
Reply
#2
Development of a Low-Cost ZIGBEE and
GSM SMS-Based Conductor Temperature
and Sag Monitoring System
Presented by,
Aneesh p
College Of Engineering ,Trivandrum
2007-11 batch


[attachment=6781]
Guys, If you liked this report, say hi to the author: aneeshpunnapra.p[at]gmail.com
CONTENTS
1. Abstract
2. Introduction
2.1 What is Zigbee?
3. Study on relative model
3.1 Preambles of Conductor Capacity Ratings
3.2 Dynamic Thermal Line Ratings (DTLR)
3.3 Traditional Methods for DTLR
4. The structure of monitoring unit
5. Structure and design of monitoring unit
6. Design of software’s
6.1 Functions of Expert Software
6.2 Figure below shows the flow chart of monitoring and
Communication unit
7. Temperature sensor LM 35
7.1 Features Of LM 35
7.2 Typical application of LM 35
7.3 Block Diagram of LM 35
8.Integrated Silicon Pressure Sensor On-Chip Signal
Conditioned, Temperature Compensated and
Calibrated MPX5700SERIES
8.1 Features MPX5700SERIES
8.2 On chip Temperature compensation ,calibration and signal
Condition
9. Laboratory Bench-Testing
10. Example Calculations
11. Pressure Altitude Calculator
12. Conclusions & Future Scope
13. References






1. ABSTRACT

This paper deals with the design, construction, instrumentation and testing of a GSM and ZIGBEE based monitoring system for the measurement of Overhead High Voltage (HV) Conductor Temperature and Sag. The main advantage of this concept is the real time direct measurement of the parameters (i.e., conductor sag and temperature) needed for the operation of the transmission system without intermediate measurement of conductor tension and ambient weather conditions, by which the temperature controlling of transmission lines conductors is realized the stoppage caused by raised temperature can be avoided and some accidents caused by the increased temperature can be avoided. The principle and the feature of GSM SMS and ZIGBEE communication are analyzed. The construction of this system is outlined, and the force modal of calculating the variety of the sag due to the increased temperature of conductors is built. Finally, the software and hardware design of the online temperature monitoring unit of conductors and fittings are outlined. In this paper, a self-designed industrial GSM module is selected to finish the transmission and the decoding of the monitoring data through AT command and coding of short message PDU (Protocol Data Unit).

















2. INTRODUCTION

With fast development of economy in India, the demand of electricity is higher and higher, and the problem between lag of construction of network and inadequacy of transmission capacity becomes increasingly prominent, which exacerbates the unharmonious contradictions of development between power grids and power generation structure. Some provinces and cities have begun to take power limited policies to alleviate contradiction of the current electricity supply-demand, how to resolve this problem has become imperative responsibility for many power workers. Recently, in order to prevent overloading of transmission lines [1,9,10], domestic power system usually adopts the static, conservative transmission capacity value in design, which is a conservative static value based on the severest weather conditions. However, such severe weather conditions rarely occurred, and it has resulted in the inefficient use of potential transmission capacities in most time.

Now, according to the traditional technology, the transmission capacity [3,10] can be increased only by adding transmission lines. However, it is becoming more and more difficult to build new transmission lines with the transmission lines increased. From the perspective of sustainable development and environmental protection, we should pay more attention from power grids expansion to increase the potential transmission capacity of available transmission lines, and enhance the transmission capacity of power grids, so as to resolve the problems between high requirement of electricity and difficulty of new transmission line. At present, some areas adopt the allowable temperature value of 70º to 80ºor even 90º. Properly increasing the allowable temperature of existing conductors can increase stable carrying capacity of transmission lines; thereby the normal transmission capacity is improved. The method is a breakthrough of current technical regulations, the impact caused by improving conductor temperature on conductors, the mechanical strength and the lifespan of matched fittings, the increase in sag and so on should be studied. In addition, if the conductor temperature and the sag can be real-timely monitored, the dynamic regulation of the transmission capacity, such as day and night, cloudy and sunny, summer and winter under the different environmental conditions can be realized to improve the transmission capacity.
In order to meet these demands, the monitoring system of temperature of conductors and fittings conductor sag [2,3] based on GSM SMS and ZIGBEE [11,12] is studied and developed in this paper. In any interconnected HV transmission system, there is the need to define in quantitative terms the maximum amount of power that may be transferred without violating the system safety, reliability and security criteria that are in place. Hence, real time ratings of circuits are critical to system capacity utilization. The current carrying capability of many transmission circuits is limited by the conductor temperature (thermal limits) and sag. For this reason, real time conductor temperature and sag measurements and real time current rating hold promise for the improvement of system transfer capability. Traditionally, overhead conductor sag has been considered for line rating by using indirect measurements. Recent commercialized techniques include the physical measurement of conductor surface temperature using an instrument mounted directly on the line, and the measurement of conductor tension at the insulator supports. These measured parameters can be used to estimate conductor sag. The pertinence of conductor sag to circuit operation relates to the calculation of Dynamic Thermal Line Rating (DTLR).

A new direct method for the measurement of overhead conductor temperature and sag factors based on GSM SMS and ZIGBEE has been proposed in this dissertation work for the purpose of DTLR. This temperature and sag monitoring device responds to the weather conditions. The main advantages of the method include the accurate measurement of conductor sag and temperature values without recourse to simplified assumptions that could otherwise affect its accuracy. With this method, errors caused by insulator swings could be eliminated. To be able to directly monitor and display the conductor temperature and sag values in real time will enable prospective engineers to physically capture the conductor behavior, and to take judicious steps towards a reliable system loading.

2.1 WHAT IS ZIGBEE ?

ZigBee is a specification for a suite of high level communication protocols using small, low-power digital radios based on the IEEE 802.15.4-2003 standard for wireless home area networks (WHANs), such as wireless light switches with lamps, electrical meters with in-home-displays, consumer electronics equipment via short-range radio. The technology defined by the ZigBee specification is intended to be simpler and less expensive than other WPANs, such as Bluetooth. ZigBee is targeted at radio-frequency (RF) applications that require a low data rate, long battery life, and secure networking.



3. STUDY ON RELATIVE MODEL

3.1 Preambles of Conductor Capacity Ratings
Transmission lines across the country are recently being operated at higher temperatures. Two key factors driving the changes in the way utilities operate their transmission systems can be attributed to the increased population growth, and the necessity to maximize equitable return on investment in the electricity deregulation era. The population growth has not only increased power demand, but also reduced the available rights-of-way for new transmission lines. For the purpose of curtailing investments, a probable option for increasing power transfer capability is to operate lines at significantly higher loading levels than ever before. It is very important for electric power utility companies to know the power level that can be transmitted over their power transmission lines at any given time. This enables them to serve load reliably and to secure adequate and equitable financial gains without compromising system-wide reliability during normal operating conditions. For this reason, both the conductor thermal and mandated sag limits must be evaluated. The conductor thermal limit relates to conductor temperature and sag, and it is often a main concern especially for circuits that are heavily loaded. The thermal capacity of overhead conductors depends on conductor temperature due to ambient air temperature, Ohmic heating, incident solar radiation, local wind speed and wind direction, limiting physical conductor characteristics, conductor configuration and geometry. For purposes of DTLR (Dynamic Thermal Line Ratings) [4,5,6,7], these parameters must be accurately determined since operating conductors at higher temperatures for longer duration of time could cause irreversible aging phenomena, referred to as annealing and creep. This could lead to a total loss of conductor life. In order to better utilize existing transmission circuits therefore, utility companies must also strive to match closely the conductor thermal ratings by taking into consideration actual weather conditions. The conventional steady state thermal ratings of certain overhead conductors have been based on the 1971 standard worst case conditions such as wind speed of 2 ft/s, summer ambient temperature of 40oC and maximum allowable conductor temperature of 95oC. The conservative nature of these assumptions is due to the lack of actual knowledge of the conductor operating conditions. The utilization of the extra capacity of the system by operating conductors at higher load levels in real time could serve as an option for an improvement in power wheeling. This is a potential source of reduction in capital and operating costs. At present, in accordance with different natural environment, different countries adopt different boundary conditions to calculate the transmission capacity of conductors such as wind speed, sunlight, temperature and conductor temperature, which has a large impact on the calculation results. Different countries have different allowable temperature [9] value about the ACSR, Japan and the United States 90°C, France 85°C, Germany, 80°C, India 75 °C, the Soviet Union 70°C, Britain 50°C. When the allowable temperature of conductor increases from 70° to 80°C in short time, its cumulative loss of mechanical strength for 30 years fall in the permitted scope of 7% to 10%. If the allowable temperature of conductor exceeds current operating temperature of +70°C
It will bring the following questions:
(1) It does not comply with current design standards (in the current standards the maximum temperature of conductor is +70°C), but increasing the maximum allowable temperature to +80°C or +90°C, it does not affect its safety operation of conductor itself;
(2) It brings some impacts on conductors, mechanical strength and lifespan of fittings. When the temperature of linear linking tube of conductor and the combination fittings of tension resistible clinch is below the temperature of the conductor, the grasp strength after the thermal cycling tests is also in compliance with the international standard;

3.2 Dynamic Thermal Line Ratings (DTLR)

Deregulation has opened the doors of power industries to a more competitive electricity market. This raises the levelof interest on the thermal capability of overhead conductors for the maximum power transfer capacity from one point of a transmission circuit to another. The recognition of the limitations of the conservative steady state ratings and the potential benefits of a DTLR system has been an interesting issue in recent years. Real time thermal rating methods have been given various names including DTLR. DTLR is a method described by the process of favourably adjusting the thermal ratings of power equipment for actual weather conditions and load patterns. This is the case,particularly if an overload which causes a small conductor loss of life or strength but never violates the code
mandated clearance is to be applied for an acceptable period of time. There appears to be no firm industry standard for DTLR methods.

3.3 Traditional Methods for DTLR

In recent years, many authors including and EPRI have intensified research and proposal of various DTLR methods as a strategic option for transmission system operators. Most of the proposed methods measure some related parameters, which are then used to indirectly compute the overhead conductor sag. Although the existing DTLR systems have not been thoroughly assessed, there seems to exist a potential source of weakness in terms of measurement precision and cost since they do not measure the overhead conductor sag directly. The GSM and ZIGBEE based sag instrument is likely to require installation of fewer units for a given transmission network compared to existing systems.

The overhead conductor temperature and sag information can be used to:

(1) Determine the load carrying capabilities of overhead conductors,
(2) ensure that conductors do not violate their code mandated clearances,
(3) For estimating the conductor loss of strength caused by annealing, and
(4) To limit the elevated temperature creep of conductors.
Three traditional methods can be identified in industry practices for DTLR based on the measured parameters.
These are:
(1) weather-based models,
(2) Conductor temperature-based model, and
(3) The conductor tension-based model.
All the three models have some advantages and some disadvantages, for example, the monitoring method based on weather-based is simple and less calculation, but at a certain interval of time the anemometer should be corrected. In the model based on conductor temperature and meteorological environment, a method of directly detecting the temperature of conductor avoids the influence of anemometer. But because the temperature detection equipments directly contact with the high-voltage conductors, the high voltage magnetic field has a certain impact on measurement accuracy, some methods should be adopted to reduce or avoid the impact of the magnetic field. The model based on pulling force need monitor some effective factors of meteorological environment, but pulling force
sensors can only be installed when conductors is unloading, that is to say, they can only be installed in maintenance period. In addition, the reliability of pulling sensor also should be higher. In the present industry DTLR methods, the sag information is a calculated output, whereas in this new proposed approach (i.e., GSM and ZIGBE based instrument); the sag information is a measured input.

4. THE STRUCTURE OF MONITORING UNIT

The monitoring system of temperature of conductors and fittings and conductor sag based on GSM SMS and ZIGBEE is mainly composed of the provincial monitoring center, the municipal monitoring center, the communication unit, the temperature and pressure monitoring unit and the expert software, the topology of system is shown in Figure.3. The communication unit is installed on the tower with both GSM and ZIGBEE communication modules, and the temperature and pressure monitoring unit on the corresponding conductors with the same potential.
According to the sampling interval time set up remotely by the monitoring center, the communication unit can regularly or real-timely call the temperature and pressure monitoring units controlled by the communication unit in turn by ZIGBEE communication. The monitoring unit, installed on the conductor can measures the actual operating temperature of conductor and pressure values under local weather conditions, sends the pressure and temperature of conductor to the communication unit by ZIGBEE communication whose frequency is 2.4 GHz. All the temperatures of conductors and pressure values coming from various monitoring points will be packed as GSM SMS to send to the municipal monitoring centre by GSM communication module. All the information of the temperature and altitudes of various points can be managed by the expert software, and the current capacities can be real-timely stored into the database. Then the expected temperature of conductors, the current capacities, the expected time, the real-time sag, the expected sag of conductors and so on can be calculated according to the computing model. When the measured or calculated temperature or the safe distance exceeds the allowable value, an alarm message can be send by GSM SMS to some managers. The operating parameters of the communication unit, such as time interval, system time of unit and requests of real-time data etc.,
can be remotely modified by GSM communication. The municipal monitoring centres are connected to the provincial monitoring centres by LAN, and the provincial monitoring centre can directly browse the monitoring data of all measured conductors and fittings. By comparing with allowable temperature and analyzing, the transmission capacity will be enhanced with no break of the available technical regulations. Of course, the operating temperature of conductors can also be monitored by this system when the transmission capacity is increased.


Figure 1: The Topology of System



5. STRUCTURE AND DESIGN OF THE MONITORING UNIT

In order to improve the transmission capacity of conductors with no break of the available technology, the of the conductor temperature is very important. However, the traditional wireless temperature measurement methods cannot meet requirements; for example, using infrared to measure temperature should keep
the distance close (within 5m) and the accuracy of measurement is low. Using fibre temperature measurement will not be able to meet the requirements of insulation for the high-voltage and long-distance transmission lines. Using radio to transmit data directly will be difficult to organize an effective star network with multi-points to one. The temperature of conductor is the most direct and important parameter during the operation of transmission lines, how to real-timely and accurately monitor the temperature of conductor is the key technique to solve this problem.
The temperature of environment, conductor, and the crossing, Altitude values can be measured by the monitoring unit, which is composed of power module, MCU (Micro Control Unit), ZIGBEE communication module, temperature sensors, Barometric pressure sensors and so on, as shown in Figure.7. Here, LM35 is selected as the temperature sensor which is a single-bus digital sensor and MPXAZ6115A selected as pressures sensor which is Integrated Silicon Pressure Sensor Altimeter/Barometer Pressure Sensor On-Chip Signal Conditioned, Temperature Compensated and Calibrated. Using single-bus (1- wire) technology, LM35 and MPXAZ6115A are blends with address bus, data bus and control bus for a bidirectional serial signal wire, which provides a simple structure, the convenient bus expansion and maintenance. Zigbee modules are developed independently by authors to achieve the short-distance communication. The specific structure is shown as Figure.2.




Figure 2: The structure of temperature monitoring device








Figure 3: The structure of temperature monitoring unit





Figure 4: The structure of the communication unit


The block diagram of monitoring system consists of power supply unit, microcontroller, temperature and pressure sensors, ZIGBEE module, and GSM module.







Figure 5: the Block diagram of Monitoring System

6. DESIGN OF SOFTWARES

The main function of the monitoring unit is to monitor temperature of conductors and the pressure station value. On one hand, monitoring unit works in interrupted mode, which starts to convert the temperature and pressure values when the sampling time is coming, then sends data to the communication unit after conversion by Zigbee module.The interrupted program flowchart is shown as Figure.8. On the other hand, monitoring unit works in a cyclic mode for an alarm (the upper limit temperature of LM35 can be set to 70°C or other values), which will ignore the limitation of sampling interval time and send signals to communication unit by ZIGBEE module when the temperature beyond the limit, and the communication unit sends the messages to workers to take measures timely.

6.1 Functions of Expert Software:

All the information of the monitoring systems of various points can be managed by the expert software. Then the expected temperature of conductors, the expected current capacities, the expected time, the real-time sag, the expected sag of conductors and so on can be calculated according to the computing model, and shown in graphic. When the measured or calculated temperature or the safe distance exceeds the allowable value, an alarm message can be send by GSM SMS to some managers. The operating parameters of the communication unit, such as time interval, system time of unit and requests of real-time data etc., can be remotely modified by GSM communication.

6.2 Figure below shows the flow chart of monitoring and communication unit.

Initialize RS 232 and LCD & ports. Check whether there is any LM35 and MPXHZ 6115A.if it is present initialize it. The processor sends order to monitor temperature and pressure. Send analogue values to microcontroller for ADC conversion after that it send digital values to EEPROM using protocol .the microcontroller read values from memory send the values to LCD to display and also send information to communication unit by ZIGBEE module

. Figure 6: Flow Chart for Monitoring Unit:


Figure 7: Flow Chart for Communication Unit

The ZIGBEE transceiver is used for the communication between the monitoring and communication units, in the present work. The AVR Microcontroller takes data and decides where it should be sent. This involves looking at the data type and the destination to determine whether the data should be sent over the serial port. The ZIGBEE module is responsible for encapsulating the data in the required packet format for sending it to another ZIGBEE, or to the serial port. ZIGBEE’s SPI protocol performs tasks, such as timing and parity checking, that are needed for data communications. The data enters the DO buffer and is sent out the serial port to a host device. It has been seen that the data transmitted over the communication page link is uncorrupted.



7. Temperature sensor LM 35

The LM35 series are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1⁄4°C at room temperature and ±3⁄4°C over a full −55 to +150°C temperature range. Low cost is assured by trimming and calibration at the wafer level. The LM35’s low output impedance, linear output, and precise inherent calibration make interfacing to readout or control circuitry especially easy. It can be used with single power supplies, or with plus and minus supplies. As it draws only 60 μA from its supply, it has very low self-heating, less than 0.1°C in still air. The LM35 is rated to operate over a −55° to +150°C temperature range, while the LM35C is rated for a −40° to +110°C range (−10° with improved accuracy). The LM35 series is available packaged in hermetic TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface mount small outline package and a plastic TO-220 package.

7.1 Features Of LM 35

* Calibrated directly in ° Celsius (Centigrade)
* Linear + 10.0 mV/°C scale factor
* 0.5°C accuracy guarantee able (at +25°C)
*Rated for full −55° to +150°C range
* Suitable for remote applications
* Low cost due to wafer-level trimming
* Operates from 4 to 30 volts
* Less than 60 μA current drain
* Low self-heating, 0.08°C in still air
* Nonlinearity only ±1⁄4°C typical
* Low impedance output, 0.1 W for 1 mA load

7.2 TYPICAL APPLICATION OF LM 35



FIGURE 8. LM35 with Decoupling from Capacitive Load



FIGURE 9. LM35 with R-C Damper


CAPACITIVE LOADS


Like most micro power circuits, the LM35 has a limited ability to drive heavy capacitive loads. The LM35 by itself is able to drive 50 pf without special precautions. If heavier loads are anticipated, it is easy to isolate or decouple the load with a resistor; see Figure 3. Or you can improve the tolerance of capacitance with a series R-C damper from output to ground; see Figure 4.When the LM35 is applied with a 200W load resistor as shown in Figure 5, Figure 6 or Figure 8 it is relatively immune to wiring capacitance because the capacitance forms a bypass from ground to input, not on the output. However, as with any linear circuit connected to wires in a hostile environment, its performance can be affected adversely by intense electromagnetic sources such as relays, radio transmitters, motors with arcing brushes, SCR transients, etc, as its wiring can act as a receiving antenna and its internal junctions can act as rectifiers. For best results in such cases, a bypass capacitor from VIN to ground and a series R-C damper such as 75W in series with 0.2 or 1 μF from output to ground are often useful. These are shown in Figure 10,


FIGURE 10. Temperature To Digital Converter (Serial Output) (+128°C Full Scale)


FIGURE 11. Temperature To Digital Converter (Parallel TRI-STATE™ Outputs for
Standard Data Bus to μP Interface) (128°C Full Scale)

6.2 Block Diagram of LM 35

FIGURE 12
8.Integrated Silicon Pressure Sensor On-Chip Signal Conditioned, Temperature Compensated and
Calibrated MPX5700SERIES

The MPX5700 series piezoresistive transducer is a state-of-the-art monolithic silicon pressure sensor designed for a wide range of applications, but particularly those employing a microcontroller or microprocessor with A/D inputs. This patented, single element transducer combines advanced micromachining techniques, thin-film metallization, and bipolar processing to provide an accurate, high level analog output signal that is proportional to the applied pressure.

8.1 Features MPX5700SERIES

. 2.5% Maximum Error over 0to 85C
. Ideally Suited for Microprocessor or Microcontroller-Based Systems
. Available in Absolute, Differential and Gauge Configurations
. Patented Silicon Shear Stress Strain Gauge
. Durable Epoxy Unibody Element



7.2 ON-CHIP TEMPERATURE COMPENSATION, CALIBRATION AND SIGNAL CONDITIONING

Figure 3 illustrates both the Differential/Gauge and the Absolute Sensing Chip in the basic chip carrier (Case 867). A fluorosilicate gel isolates the die surface and wire bonds from the environment, while allowing the pressure signal to be transmitted to the sensor diaphragm. (For use of the MPX5700D in a high-pressure cyclic application, consult the factory.) The MPX5700 series pressure sensor operating characteristics, and internal reliability and qualification tests are based on use of dry air as the pressure media. Media, other than dry air, may have adverse effects on sensor performance and long-term reliability. Contact the factory for
information regarding media compatibility in your application.
Figure 2 shows the sensor output signal relative to pressure input. Typical, minimum, and maximum output curves are shown for operation over a temperature range of 0° to 85°C using the decoupling circuit shown in
Figure 4. The output will saturate outside of the specified pressure range.
Figure 4 shows the recommended decoupling circuit for interfacing the output of the integrated sensor to the A/D input of a microprocessor or microcontroller. Proper decoupling of the power supply is recommended.

FIGURE 14






Figure 14. Cross-Sectional Diagrams (not to scale)


Figure 15. Recommended Power Supply Decoupling and Output Filtering (For additional output filtering, please refer to Application Note AN1646)

This Figure.2 shows the sensor output signal relative to pressure input. Typical minimum and maximum outputcurves are shown for operation over 0 to 85°C temperature range. The output will saturate outside of the ratedpressure range. A gel die coat isolates the die surface and wire bonds from the environment, while allowing thepressure signal to be transmitted to the sensor diaphragm. The gel die coat and durable polymer package provide amedia resistant barrier that allows the sensor to operate reliably in high humidity conditions as well as environments
containing common automotive media.
Transfer Function:
Volt = VS x (0.009 x P - 0.095) ± (Pressure Error x Temp. Factor x 0.009 x VS)
VS = 5.0 ± 0.25 Vdc Temp.Factor =1 Pressure Error = ± 1.5 kPa




9. Laboratory Bench-Testing

A selected number of experiments were performed on the GSM and ZIGBEE based overhead conductor temperature and sag measuring instrument at different environmental conditions. The main objectives of the bench-testing experiments were to evaluate the proper functioning of the radio communication links. In this case the experiments GSM and ZIGBEE based conductor sag instrument was not directly mounted on an energized overhead HV conductor due to lack of logistics and high cost in terms of the availability of necessary facility. To be able to perform such an experiment in a real life application is beyond the capability of the university research resource at this time.

10. Example Calculations:

The received Monitoring System values from GSM Module are shown in the below figure




Figure 16: Received Monitoring System Values from GSM Module as SMS
11. Pressure Altitude Calculator:

This calculator is designed to give a value for a calculated pressure altitude, based on data entered. The term station is the designation for the vertical point that you take your measurements; vertical meaning above (or below) sea level. The absolute air pressure is the calculated air pressure, but not corrected for altitude. In our calculator, enter the station pressure (absolute); be sure to click on the proper designation if using measurements. Click on Calculate and the calculated pressure altitude will be returned in both feet and meters. Based on this Pressure Altitude
Calculation, we can calculate the conductor’s sag value.



Figure 17: Pressure Altitude Calculation






12. Conclusions & Future Scope

The main contribution of this paper is the design, construction, field testing and analysis of a GSM SMS and ZIGBEE based instrument for the real time direct measurement of overhead HV conductor temperature and sag. The resulting conductor sag information can be used to enhance the operation of electric power systems, particularly the DTLR. The proposed GSM and ZIBBEE based measurement of overhead HV conductor sag is a more direct technique in some ways as compared to similar alternative methods. This is concluded because the direct measurement of overhead conductor position involves no intermediate calculations and measurements of conductor tension, ambient weather conditions, or makes any assumptions to that effect. It also presents a potential source for cost reduction and better accuracy in the conductor sag measurement, since there is no need to directly measure conductor tension, and weather conditions. The real time direct measurement of overhead conductor temperature and sag is a clear advantage. With the power grids gradually increasing and the new lines building difficult, improving allowable temperature of conductors can fully exploit massive transmission capacity of existing transmission lines, and the number of new lines or the cost of investment in new lines can be deduced, the economic and social benefits brought by it is very large. The measuring unit measures the temperature of the sensor and pressure station values. The conductor temperature is the result of the flowing to and effluent thermal power. The ambient conditions, which affect the conductor temperature, are the current, the wind velocity, the angle between the conductor and the wind direction, the global radiation, the solar radiation and fluent cooling mechanism. These components have different influences on the conductor and the sensors, but both are influenced by the same factors. In general the measured sensor temperature is not equal to the conductor temperature because the sensor is a heat sink in this complex thermal system. So the conductor temperature must be computed by using the measured temperatures of the sensor. For this purpose a calibration of the sensor and conductor must be made in the laboratory






12.References
[1]Development of a Low-Cost ZIGBEE and GSM SMS-Based Conductor Temperature and Sag Monitoring System, M.V. Vijaya Saradhi et al. / International Journal of Engineering Science and Technology
Vol. 2(4), 2010, 372-381
[2] IEEE std 738-1993, IEEE Standard for Calculating the Current-Temperature Relationship of Bare Overhead Conductors, New York,s1993.
[3] T. O. Seppa, “Factors Influencing the Accuracy of High Temperature Sag Calculations,” IEEE Transactions on Power Delivery, Vol.
9, No. 2, April 1994,
[4] T. O. Seppa, “Accurate Ampacity Determination: Temperature-Sag Model for Operational Real Time Ratings,” IEEE Transactions on
Power Delivery, Vol. 10, No. 3, July 1995.
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