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CONTENTS

1.Abstract2. Introduction

2.1 What is Zigbee?

3. Study on relative model3.1 Preambles of Conductor Capacity Ratings3.2 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 softwares

6.1 Functions of Expert Software

6.2 Figure below shows the flow chart of monitoring and

Communication unit

7.Temperature sensor LM 357.1 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 SignalConditioned, Temperature Compensated and

Calibrated MPX5700SERIES8.1 Features MPX5700SERIES

8.2 On chip Temperature compensation ,calibration and signal

Condition

9. Laboratory Bench-Testing

10.Example Calculations

11.Pressure Altitude Calculator12.Conclusions & Future Scope

13. References


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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).


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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 powerworkers. 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 linesincreased. 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 70 to 80or even 90. 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, theimpact 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.


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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 instrumentmounted 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 methodinclude 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 usingsmall, 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.
http://en.wikipedia.org/wiki/Specification_%28technical_standard%29http://en.wikipedia.org/wiki/Digital_radiohttp://en.wikipedia.org/wiki/IEEE_802.15.4-2003http://en.wikipedia.org/wiki/Standardizationhttp://en.wikipedia.org/w/index.php?title=Wireless_home_area_network&action=edit&redlink=1http://en.wikipedia.org/wiki/ZigBee_specificationhttp://en.wikipedia.org/wiki/Wireless_personal_area_networkhttp://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Bluetoothhttp://en.wikipedia.org/wiki/Wireless_personal_area_networkhttp://en.wikipedia.org/wiki/ZigBee_specificationhttp://en.wikipedia.org/w/index.php?title=Wireless_home_area_network&action=edit&redlink=1http://en.wikipedia.org/wiki/Standardizationhttp://en.wikipedia.org/wiki/IEEE_802.15.4-2003http://en.wikipedia.org/wiki/Digital_radiohttp://en.wikipedia.org/wiki/Specification_%28technical_standard%29


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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 RatingsTransmission 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
http://en.wikipedia.org/wiki/Radio_frequencyhttp://en.wikipedia.org/wiki/Radio_frequency


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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 90C, France

85C, Germany, 80C, India 75 C, the Soviet Union 70C, Britain 50C. When

the allowable temperature of conductor increases from 70 to 80C 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 operatingtemperature of +70C

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 +70C), but increasing the maximum

allowable temperature to +80C or +90C, 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 hasbeen 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


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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 giventransmission 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 basedon 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 ofanemometer. 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


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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 withboth 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. Allthe 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 communicationunit, 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


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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 importantparameter 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,


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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


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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.


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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 afterconversion 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 70C 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


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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 andalso send information to communication unit by ZIGBEE module

.Figure 6: Flow Chart for Monitoring Unit:


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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. ZIGBEEs

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 link is uncorrupted.


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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 14C at room

temperature and 34C over a full 55 to +150C temperature range. Low cost is

assured by trimming and calibration at the wafer level. The LM35s low outputimpedance, 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 A from its supply,

it has very low self-heating, less than 0.1C in still air. The LM35 is rated to

operate over a 55 to +150C temperature range, while the LM35C is rated for a

40 to +110C range (10 with improved accuracy). The LM35 series isavailable 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

* 0.5C accuracy guarantee able (at +25C)

*Rated for full 55 to +150C range* Suitable for remote applications

* Low cost due to wafer-level trimming* Operates from 4 to 30 volts

* Less than 60 A current drain* Low self-heating, 0.08C in still air

*Nonlinearity only 14C typical* Low impedance output, 0.1 W for 1 mA load


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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 affectedadversely 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 F from output to ground are often useful. These are

shown in Figure 10,


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

FIGURE 11. Temperature To Digital Converter (Parallel TRI-STATE Outputs for

Standard Data Bus to P Interface) (128C Full Scale)

6.2 Block Diagram of LM 35

FIGURE 12


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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%

. 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


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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 85C 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


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

Figure 15. Recommended Power Supply Decoupling and Output Filtering (Foradditional 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 85C

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


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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


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11. Pressure Altitude Calculator:

This calculator is designed to give a value for a calculated pressure altitude, basedon 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 conductors sag value.

Figure 17: Pressure Altitude Calculation


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12. Conclusions & Future Scope

The main contribution of this paper is the design, construction, field testing andanalysis 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 noneed 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 affectthe 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


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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 forOperational Real Time Ratings, IEEE Transactions on

Power Delivery, Vol. 10, No. 3, July 1995.[5] R. F. Chu, On Selecting Transmission Lines for Dynamic Thermal LineRating System Implementation, Transactions on Power

Systems, Vol. 7, No. 2, May 1992.

[6] U. K. Fernndez, C. Mensah-Bonsu, J. S. Wells, G. T. Heydt, Calculation ofthe Maximum Steady State Transmission Capacity of a

System, Proceedings of the 30th North American PowerSymposium, Cleveland,

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