37

CHAPTER-3

ON-LINE MONITORING OF TRANSMISSION LINE USING GSM

TECHNOLOGY

3.1 INTRODUCTION

Power sector is facing severe energy losses right from Generation to

distribution, The technical losses in generation can be well defined and innovations

are on to scale down these losses. The severe losses on account of Transmission and

Distribution are indefinable but cannot be quantified with the sending end parameters.

This illustrates the involvement of non-technical parameters in T&D of electrical

energy. T & D losses are of greater concern for the Indian Electrical Industry (IEI)

since their magnitude is huge when compared to other developed countries. The

present T & D losses which include unaccounted energy loss are between 18 to 32%

amounting to a financial loss of Rs 1,000,000 Cr PA. These losses are on account of

improper handling of transmission and distribution system. If we can save even 1%

out of the above losses it will be a definite help to the power sector in specific and the

environment at large.

As per The Energy and Resources Institute (TERI) [59], energy losses occur

during the process of supplying electricity to consumers. The total T & D losses are

combination of technical and non-technical losses. The technical losses are due to

energy dissipated in the conductors and equipment used for transmission,

transformation, sub-transmission and distribution of power. These losses are inherent

in a system and can be reduced to a best level. The non-technical (commercial) losses

are caused by pilferage, defective meters, and errors in meter reading and in

estimating unmetered supply of energy.

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Reduction of losses will have healthy economics and also a positive step to

preserve environment, however it is often expensive and difficult to reduce technical

losses. Replacement of old equipment with the latest is one way to reduce technical

losses. The Life of system components can be increased substantially if the faults are

sensed through an effective, speedy and highly sensitive wireless communication

System. Current method being used to assess the damage on the transmission grid is

by visual inspection. Due to dispersion of transmission lines over hundreds of miles, it

is difficult to sense the fault by visual inspection or by using traditional methods. In

order to acquire different parameters and deliver them to the control centers, it is

required to install data acquisition systems (DAS) and various sensors in

predetermined towers and communicate via wireless network. For efficient

monitoring and control, a robust and fast communication system is required [60]. This

chapter discusses how the different data is acquired and delivered to the control center

for loss analysis and to initiate corrective measures by using different sensors and

wireless communication. The proposed method is highly useful for the future

deregulated power system and smart grid applications.

There are many ways to collect the information i.e., SCADA, PLC, optical

fiber, etc. However, it is impossible to use these systems in many places in the power

system (remote places) and also costly. A wireless solution is thus sought. There are

wide smart grid applications [41] using wireless communication. The GSM SMS and

ZigBee communication are proposed [61] for monitoring over head conductors. The

concept of using wireless sensors has proposed [62] for substation automation .The

Y.Yang, F.Lambert and D.Divan were first proposed the use of sensor networks to

monitor overhead transmission lines [63, 64]. R. A. Leon, V. Vittal, Y. Yang et al [65,

66] introduced the importance and implementation of sensors in power grid

39

monitoring. The proposed model consists of sensors like; voltage sensing transformer

is used for acquiring change in voltage, Thermister for change in temperature and

Accelerometer for cable sag & tilt due to overloading and climatic conditions.

Wireless GSM is used to deliver and collect the data. Fig.3.1 shows the single line

diagram of power system network using wireless communication.

Fig.3.1. Single line diagram

3.2 LINEAR NETWORK MODEL

This section explains the proposed linear network model. Fig.3.2 shows an

example of long overhead transmission line where the number of towers in-between.

The distance between two primary substations can be 50 kilometers. On the other

hand distance between two towers can be 0.25 to 0.5 kilometer depending on actual

needs and geographical constraints.

To monitor the transmission line and acquire the changes in the power system

line with respect to time, different sensors listed in Table 3.1 are used. In general all

sensors are analog in nature and deliver output in the form of voltage, current,

resistance, etc. All the signals will be fed for conversion to achieve signals which can

be perfectly suitable for computing using state of art embedded technology.

40

Fig.3.2. Power system network with sensors

The embedded technology collects data and converts it for soft computing.

Appropriate software can compute these signals and creates control, information, data

logging and communicating signals.

The primary parameter which can change during all the conditions is voltage

and it determines the energy loss. The change in voltage is directly proportional to

losses to certain extent. The second parameter is current which gives information

about real usage. Once, if the current goes high beyond the set limit, it creates sag

(voltage sag) and power becomes infinite. So, entire thing will be considered as loss.

Unless we have a proper tool to monitor, this cannot be identified and solved. A real

relationship of usage verses loss can be arrived only from the magnitude of current.

The change in temperature occurs on transmission line due to various reasons;

it starts from simple overloading, continuous overloading, and climate changes. All

this creates skin effect and makes them to elongate from its original length and

thereby forms physical sag between two poles (Towers) [67, 68]. The proportional

increment of cable length will increase I2R loss and voltage drops in the transmission

lines.

41

To analyze the parameter called sag, created because of frequent change in

temperature and it is essential to overcome on long term basis. Sag will not be created

at the time of installation. During the course of time with the changes in temperature

and climate sag will be created automatically and increase the loss. More sag can

create tilting of transmission line during climatic turbulences. The effect of sag can be

reduced by maintaining the temperature within the limit.

The model is designed by considering voltage sensing transformers,

accelerometers and temperature sensors. These are placed at 25% and 75% of the total

distance and close to the poles/towers. Each sensor sends data at regular intervals

[65]. Data acquisition system also placed on the poles / towers to collect the data from

the sensors. The data obtained on transmission lines are sent through GSM lines to the

control centre in the substation.

At the receiving point (control centre) all GSM data will be received from

various parts of transmission line and fed to a single computer. Analysis is made

regarding the losses at various points and will be displayed. All the collected data will

be logged safely for future or present comparison of utilization factor (UF).

The UF based demand management will reduce various burdens on

transmission line and keeps devices perfect. The proposed scheme presents data like

power handled by tower, losses between tower to tower, loss percentages at each

tower, overall efficiency of transmission line. As a decision making system, the

scheme will deliver control outputs in the form of digital and will be converted into

RS-232 standard. The RS-232 data will be converted into GSM signals and passed to

distribution end. Thus, wireless communication provides a major contribution to

reliable network operation and efficient energy management.

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Table 3.1.Types of sensors for monitoring

Monitoring parameters Type of sensor

Cable tilt Accelerometers

Inclination Accelerometers

Temperature Temperature sensor

Extension & Strain Strain sensor

Cable position Accelerometers

Current Magnetic field Sensors

Magnetic field Magnetic field Sensors

Power Quality Graph Magnetic field Sensors

3.3. STRUCTURE OF LABORATORY MODEL

The structure of the proposed laboratory model for on-line analysis of

transmission line is shown in Fig.3.3. The model is a scaled down version of the

original system using low voltages. The change in voltage, current, temperature and

angle are scale down values of real variables. The same circuits can be employed for

higher version installation at the field areas. There are no changes required except

enclosures for the DAS circuit. The proposed technology consists of the following

seven major categories to meet on-line challenges and acquiring transmission line

data:

� Instrument Transformers

� Signal conditioning circuits (SC)

� Accelerometers

� Temperature Sensors

� Embedded microcontroller (EMC)

� Software required

� Communication network

43

Fig.3.3.Block diagram representation of the laboratory model

3.3.1 Instrument Transformers

Instrument transformers are used in the measurement and control of

alternating current circuits [10]. These are essential to step down the high voltage /

current into measurable low voltage / current for measuring purpose. Isolation with

ratio metric reduction will be done by these types of transformers.

There are two distinct classes of instrument transformers:

(1) Potential transformer

(2) Current transformer

Potential Transformers

The potential transformer operates on the same principle as that of a power or

distribution transformer. The main difference is that the capacity of a potential

transformer has ratings from 100 to 500 volt amperes (VA). The low voltage side is

usually wound for 110 V. The high voltage primary winding of a PT has the same

voltage rating as that of the primary circuit. Assume that it is necessary to measure the

voltage of a 3.3kV, single phase line. The primary of the PT is rated at 3.3kV and the

44

low voltage secondary is rated at 110V. The ratio between the primary and the

secondary winding is: 3300/110 or 30/1.

Current Transformers

Current transformers are used so that ammeters and the current coils of other

instruments and relays need not be connected directly to high voltage lines. In other

words, these instruments and relays are isolated from high voltages. CTs also step

down the current in a known ratio. The use of CT allows using relatively small and

accurate instruments, relays and control devices of standardized design in the

measuring circuits.

The existing transmission line need not be modified or reconfigured, because

the CT is noncontact primary (Clamp type or tong type) type. The secondary winding

has the standard current rating of 5A; therefore the ratio between the primary and

secondary current is xxx/5A.

3.3.2 Signal Conditioners

These devices are made up of semiconductor operational amplifiers. Signal

conditioners are more reliable. The output of secondary isolation system will be AC in

nature, must be rectified, conditioned and calibrated as per the requirement of

conversion circuits. These circuits are Op-Amp based full wave precision rectifiers

(or) absolute rectifiers. These circuits meet overall standards of measurements. The

prime objectives of these devices are to rectify, filter, setting up the calibration limits,

protecting the high voltage hazards, protecting the inputs and outputs. Output of these

circuits will be pure DC in nature.

3.3.2.1 Voltage Sensing

Voltage sensing circuit is shown in Fig.3.4. It consists of bridge rectifier; it

can be used to convert AC to DC. A1 is an inverting unity gain amplifier. A2 is

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inverting summing mixed gain amplifier. During positive half cycle the Op-Amp A1

produces an output of 0.454V. Op-Amp A2 produces an output of 0.908V across the

path having gain of –2 and an output of –0.454V across the path having a gain of –1.

Thus, the resultant output voltage is 0.454V. It can be amplified to require voltage by

varying the trim pot. The 500K trim pot is adjusted so that a full scale output voltage

of 5V is produced. A capacitor is connected to A2 so that it acts as an integrator.

Hence output voltage is a pure DC voltage it is then given to ADC.

Fig.3.4 Voltage sensing circuit diagram

3.3.2.2 Current Sensing

Current sensing circuit diagram is shown in Fig.3.5. Current sensing is very

similar to the voltage sensing, instead of potential divider a shunt to be used to

convert current into voltage. Once current is converted into voltage, Full wave

precision rectifier (FWPR) can be directly used and output will be 0-5V

corresponding to the minimum to maximum CT value of 0-5Amps.

46

Fig.3.5 current sensing circuit diagram

3.3.3 MEMS Accelerometer

MEMS Technology is a well known abbreviation for Microelectromechanical

systems even though; there exist various names for MEMS technology such as micro

machines etc. MEMS Accelerometer accurately detects and measures acceleration,

tilt, shock and vibration in performance-driven applications. In industry it detects the

power, noise, bandwidth and temperature specifications and earthquake detection in

geotechnical engineering (Bernstein, 1999). Since there are various types of sensors

for various applications, there is a need to select the right sensors which fit to the

intended applications. In our work we have used MEMS Accelerometer to measure

transmission line tilt and sag.

We have used three axes MEMS accelerometer which provide voltage output

for the change in X, Y, Z axes. No need to connect signal conditioner because it

produces 0 to 5V for the change in physical directional changes.

3.3.4 Temperature Sensors

Transmission lines are heated due to over load and climatic conditions. When

line current increases, the conductor heats up, elongates, and the line sag increase. If

the line is operated beyond its maximum design temperature, the line sags may violate

47

design clearances. Use of the Transmission Line Monitoring System for dynamic

ratings allows utilities and transmission operators to develop and apply line ratings in

real time, based on actual weather conditions instead of fixed, conservative

assumptions. By using temperature sensors and wireless communication, over-head

lines and cables are monitored, analyzed, and visualized with one system. In the

proposed model Thermister is used as a temperature sensor which is inexpensive, easy

to use and adaptable. Temperature is the most important parameter during high

current flow on the cables, possibility of losses will be very high and can be detected

using temperature sensor and appropriate tripping action can be performed to save

energy.

3.3.5 Embedded Microcontroller

Generally A/D converters are interfaced with the microprocessor using a

separate interfacing IC namely programmable peripheral device. This requires large

hardware circuit. But in the proposed design, state of art embedded system technology

is used to reduce lot of hardware. These devices consist of packed hardware inside;

any devices can be brought down to the front end and can be used. Output from signal

conditioning circuits is connected to this circuit for A/D application. Simultaneously

all analog data are fed and digitized data are sent to computer as RS-232 signals. The

digitized data is to be decoded for real values. The expected speed of this device is

9600 baud rate. It proposes middle end embedded microcontroller like pic16F877A,

which consists of 8 channel 10bit ADC with lots of additional features. These devices

require very minimum supporting hardware’s like clock and reset circuits externally.

The embedded circuit diagram is shown in Fig.3.6. The circuit consists of

1) Power supply

2) Clock circuit

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3) PIC16F877A

4) Reset circuit

5) RS232 circuit

Fig.3.6 Embedded circuit diagram

3.3.5.1 Power Supply Circuit

Irrespective of the technological growth one must construct a reliable power

source for embedded controller. A 230V/12V step down transformer and bridge

rectifiers are used to convert into DC. A constant voltage regulator LM7805 with

necessary filters is used to produce constant 5V given to embedded circuit.

Irrespective of the change in voltage and current, output voltage will be kept constant

at 5V.

49

3.3.5.2 Clock Circuit

10 MHz crystal as a resonator made up of Quartz is used in this work to meet the

requirements. Generally crystal oscillator is made up of quartz whose crystalline

structure will not be changed under any circumstances on physical changes. 10 MHz

crystal oscillator is used to produce constant frequency. Further, it can be divided

inside the microcontroller as per the requirement of the operation to achieve exact

timing. The general disadvantage of the crystal, it may produce abnormal clocking at

some conditions, which can be eliminated using appropriate low pass filter coupled

across crystal and connected to ground. Crystal is connected across 13 and 14 pins.

3.3.5.3 PIC16F877A Microcontroller

Microprocessors brought the concept of programmable devices and made

many applications of intelligent equipment. Most applications which don’t need large

amount of data and program are tended to be costly and consist of a lot of peripherals.

These drawbacks lead to the use of microcontroller, which is a true computer on a

chip. This is heart of the work, which collects the data, passes to the computer and

takes control action. To perform various operations and conversions required to

switch, control and monitor the devices a processor is needed. In this research a

PIC16F877A Microcontroller is used. The pin-Diagram of the Microcontroller is

shown in Fig.3.7. The features and external requirements are discussed below.

Features

• High-performance RISC (Reduced Instruction Set Controller) CPU

• Only 35 single word instructions to learn

• All single cycle instructions except for program branches which are two cycle

• Operating speed: DC - 20 MHz clock input and DC - 200 ns instruction cycle

• 4K x 14 words of Program Memory (EPROM)

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• 256 x 8 bytes of Data Memory (RAM)

• Interrupt capability (up to 14 internal/external interrupt sources)

• Eight level deep hardware stack

• Direct, indirect, and relative addressing modes

• 12-bit multi-channel Analog-to-Digital converter On-chip absolute band gap

voltage reference generator

• Universal Synchronous Asynchronous Receiver Transmitter, supports

high/low speeds and 9-bit address mode (USART/SCI)

Industrial Features

• Built in ADC of multi channel with 10 bit accuracy- used to acquire voltage,

current, temperature, power.

• Built in reference facility and external reference provision- to fix a bandwidth

of reference voltage.

• Built - in ports-to drive the relays and getting feedback from the relays.

Requirements of PIC16F877A

• A separate power supply for digital and analog supplies must be provided to

prevent affecting the quality of analog measurement due to digital current

fluctuations.

• Double regulated completely filtered analog reference supply.

• Needs external power on reset and CPU synchronization switch.

• External quartz crystal to be used for frequency stability.

• 10 MHz for 9600 baud rate

• 20 MHz for 19200 baud rate

• RS-232 converter is used to link it with the computer.

• For all the analog inputs voltage should not exceed 5V.

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• For digital outputs we should not consume current beyond 25mA.

• All the logical inputs must reach PIC16F877A as a perfect square wave form.

Software Advantages

• Reduced Instruction set computing “RISC” orientation.

• Only 35 single word instructions to learn. Reduces design and learning time.

• RS-232 interface is possible for COMPORT serial port.

• This embedded can be interfaced with all old and latest computing languages.

• Basic, C, VB.

• Host CPU can be varieties of operating frequency as well as different bits.

Pin Diagram

Fig.3.7 Pin Diagram of PIC16F877A

3.3.5.4 Reset Circuit

In Fig.3.6 the capacitor C1 is in the OFF condition when power is switched

OFF. When the power is switched ON or Reset then this capacitor gets charged

through the resistor R2 and then through R1 this appears at the MCLR pin of the PIC.

This is the memory clear pin and thus the memory is cleared and is ready for use as

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soon as power is switched ON. S1 is the synchronous switch which is also used for

the same operation and for PC and PIC synchronous operation.

3.3.5.5 RS-232

In personal computer, data transfer takes place serially. RS-232 standard is

used for serial communication. PIC Microcontroller is linked to PC through the RS-

232 port. The most common communication interface for short distance is RS-232.

RS-232 defines a serial communication for one device to one computer

communication port, with speeds up to 19,200 baud. Typically 7 or 8 bit (on/off)

signal is transmitted to represent a character or digit. The 9-pin connector with pin

detail is shown in Fig.3.8.

Fig.3.8 RS-232 Pin connector

Interface

Analog values like voltage, current, temperature, etc will be connected on port

A and E. Digital output like relays and input like switch gear positions can be

connected to digital port like port B,C,D. Port C upper two lines is used as TXD and

RXD for serial communications. The process will be started as soon as the EMC is

powered and acquires the data for display, control and for data logging.

The general electrical data like voltage, current, frequency is more traditional

than new sensor devices like accelerometer and temperature sensors on transmission

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line. The concept of all electrical and non electrical parameter processing will be done

using Op-Amp based electronic circuits. Output of the signal conditioner will be fed

to EMC for analog to digital conversion, digital to serial. EMC device has lot of built

in features like A/D, USART, RAM, EEPROM etc. The most important concept of

programming is more essential i.e, current conversion takes more than 70% of time

and rest goes to all other parameters, because, current is the most crucial parameter in

decision making on substations/grids. The conversion ratio is to be altered as per the

priority of measurement.

The Table 3.2 shows 85% of time is allocated for current sensing because it is

most fluctuating parameter of the transmission line and rest goes to all other

parameters. Non-electrical parameters will not change offen, so acquiring them

doesn’t solve any problem. So least priority given to acquire non electrical

parameters.

Table 3.2: Conversion ratio for different parameters

Parameter % of Time Conversion Ratio (% of Time*9600bd)

Current 85 8160

Voltage 10 960

Sag 2.5 240

Temperature 2.5 240

The analog input given to MUX inside the EMC and selects as per the priority

given in Table 3.3. MUX accepts many analog data and sends one at a time to ADC

as per the control inputs given to it. MUX must be analog MUX, and output of the

MUX must be connected to 10 bit ADC which is a built in option of EMC. The

conversion rate is very high, and given data will be fractioned to 210. The converted

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analog data and MUX input data combinely can represent digital equivalent of the

concern input.

Table 3.3:Chanel selection

MUX input ADC output Channel

000 1023 Ch 0 5V

001 512 Ch 1 2.5V

. . .

. . .

111 256 Ch 7 2.5V

The Table 3.3. shows, how the multiple inputs enters to the EMC and works.

The above data must be decoded to get real value. The data of the ADC will be stored

on to the RAM for short time and fed to USART (or) UART (Universal Synchronous

Asynchronous Receiver Transmitter). USART is device, converts parallel data into

serial data and serial into parallel and works in synchronous with the counter part of

CPU. It works at a speed of 9600 baud rate, without this networking is absolutely not

possible. Even higher baud rate could be achieved for very high speed applications.

Output of the USART will be fed to GSM transmitter. In the substation, GSM

receives data from different GSM transmitters at different locations and deployed in

the control centre PC for further analysis and future comparison.

3.3.6 Communication Network

To transmit on-line acquired data to substations, wireless communication is

the most advanced and cost-effective in terms of the equipment, installation cost and

installation time [11]. Communication standards are categorized based on their

communication range, maximum throughput, power consumption, etc. Larger the

communication range, lower the maximum throughput and larger the power

55

consumption. For long distance transmission a dedicated channel is required. Most

devices are onsite equipments used to acquire the data at one end supports to

communication equipments and passed through leased lines, often the quality of

communication is kept under leased line owners. The leased lines are not dedicated to

one single application. Decoding the necessary data is much complex because of

many servers were introduced in between and causes slow down the data transfer rate.

There are many communication techniques like Unidirectional RF, carrier

communication, ZigBee, GSM, Internet, CDMA, Blue tooth, Fiber-optic cable, Bi-

directional RF, etc. Out of which many of the communication systems are leased

lines and dependency goes to service providers. Few of them are suitable for long

distance communication. Now a days carrier power line communication and

Supervisory Control and Data Acquiring Systems are the powerful methods widely

used for transmission lines. But these methods have some drawbacks. Whenever there

is disconnection between two ends of the transmission line, the communication can’t

be possible, which leads to reduction of utility factor & energy loss. For remotely-

located transmission lines, PLC & SCADA connection cannot found benefit.

Therefore, wireless GSM is best suitable for online data acquisition of long and

remote lines.

3.3.6.1 GSM Technology

GSM (Global System for Mobile Communications) was developed in 1990.

Popular cellular phone operates in India use GSM or the CDMA technology to

provide voice and data services. GSM uses a combination of TDMA (time division

multiplexing) and FDMA (frequency division multiplexing). This means that users A

and B are not only sharing the channel in time but also frequency. This means that

user A is ON the channel 890MHz for 2 seconds, then jumps to 900Mhz channel for

56

the next two seconds, then jumps to 910MHz for the next 2 seconds and so on. Thus,

each user uses a different frequency at different time slots. This is called Frequency

Hopping. There is GSM 900, 1200, 1800, 2100etc these days. 900 is the operational

frequency of the GSM in MHz. The key characteristic of a cellular network is the

ability to re-use frequencies to increase both coverage and capacity. The re-use

distance, D is calculated by using equation 3.1.

N3RD = 3.1

Where R is the cell radius and N is the number of cells per cluster. Cells may vary in

radius in the ranges (1 km to 30 km). Cell Coverage comparison of different

frequencies are given in Table 3.4. The boundaries of the cells can also overlap

between adjacent cells; large cells can be divided into smaller cells.

Table.3.4: Coverage comparison of different frequencies

3.4 RESULT ANALYSIS

The Results for different faults created on transmission line for the analysis

purpose are shown in Fig.3.9. The results shown in Fig.3.10 are the real-time data

received from different GSM receivers at different places of transmission line. This

data sheet consists of date, time, GSM transmitter code, voltages of all phases, cable

tilt angle and temperature of the cable.

Frequency (MHz) Cell Radius (km) Cell Area (km2) Relative Cell

450 48.9 7521 1

950 26.9 2269 3.3

1800 14 618 12.2

2100 12 449 16.2

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Fig.3.9 (a) Normal condition

Fig.3.9(a) shows results at normal condition (without fault). At this condition

all phase currents and voltages are almost equal. There is no loss and the data

obtained on real time shows perfect working of the system.

Fig. 3.9 (b) Single line to ground fault

The currents and voltages in Fig.3.9(b) shows that, there is a single line to

ground fault in R-phase. Abnormal rise in current make voltage falling and finally

collapses the grid. The design is not for tripping the relays during switching

58

conditions of the circuit breaker because overloads are possible during instantaneous

switching of circuit breaker. If the fault retains for more than two and half-cycles the

trip command will be fed to the relays thereby huge power can be saved during

abnormalities. The circuit consists of sensing system with fast acting relay to trip the

circuit breaker and to avoid losses during short circuit. The tripping graph is shown in

the next chapter.

Fig.3.10(a) normal condition

The results shown in Fig.3.10(a) are the real-time on-line data obtained from

GSM transmitters at 25% and 75% of the total distance at normal condition. Initially

the values for all phases are considered to have voltage 48v, line tilt angle is 90° and

temperature is 30°c.

Results of Fig.3.10 (b) gives change in voltage levels in Y-phase due to fault,

other phase voltages, tilt angle and temperature sent by GSM transmitter placed at

59

25% of the total line distance. During this condition an automated command will be

sent by the EMC to trip the circuit breaker and save energy with in shortest time

period may be four cycles.

Fig.3.10 (b) Fault at 25% of distance

Results of Fig.3.10 (c) gives change in voltage levels in Y-phase due to fault,

other phase voltages, tilt angle and temperature sent by GSM transmitter placed at

75% of the total line distance. During this condition an automated command will be

sent by the EMC to trip the circuit breaker and save the energy with in shortest time

period may be four cycles.

Fig.3.10 (c) Fault at 75% of distance

Fig.3.10(d) shows the change in cable tilt and temperature sent by GSM

transmitters at 25% and 75% of the total line distance. These are the non-electrical

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parameters obtained through GSM from the field and will be used to take effective

decision. This will be useful to the engineers to take preventive steps (includes the

safety tripping to save energy from thermal effects, and cable elongation due to over

load and climate) to avoid damage to the cables. Based on these results partial load

shedding or load diversion should be effected to save power.

Fig.3.10 (d). Temperature & cable sag angle at 25% and 75%

3.5 HARDWARE FIGURES

Photographs of hardware models are shown in Fig.3.11.

Fig.3.11(a) Sending end model

61

Fig.3.11(b) Receiving end model

Fig.3.11(C) Transmission line

62

Fig.3.11 (d) Resistive load

Fig.3.11 (e) Fault sensing at 25% of total distance

63

Fig.3.11 (f) Temperature sensor

Fig.3.11 (g) Accelerometer

64

Fig.3.11 (h) Receiving centre

3.6. CASE STUDY

Line diagram of 220/132/33kV substation Renigunta, Chittor district, Andhra

Pradesh, India is shown in Fig.3.12. It consists of 6 numbers of 220kV, 13 numbers of

132 kV and 7 numbers 3kV feeders. The loss analyses of each, 220kV feeder is

carried out for two periods i.e. one month & one year and is tabulated in Tables 3.5

and 3.6 respectively. The graphical representation of percentage losses are shown in

Fig.3.13.

65

AMARARAJA

GRINDWELL NORTON

RAILWAYS - I

PUTTUR -II

RAILWAYS - II

TIRUPATHI

CHANDRAGIRI -II

CHANDRAGIRI -I

220KV/110VBUS II - PT

MANUBOLU - II MANUBOLU - I

132KV/110VBUS PT - I

132KV/110VBUS PT - II

AREA OF THE SS :20.18AcresSURVEY NO: 29-1A:29-2:30-1

DATE OF CHARGING :1961/1971/1980/1982/1995CAPACITY: (3 X 100 MVA)+(31.5+2X16)MVA

REACTIVE POWER COMPESATION:(1X 7.2+2X5) MVARBATTTERIES: 200 AH AMARA RAJA (M.F)

BATTERY CHARGER: DUBAS& HEE

220/132/33 KV SS RENIGUNTASRIKALAHASTI

C.K.PALLI

220KV/110V BUS I - PT

ALSTOMFXT 14F600242

M.MAGALAM I

BUS COUPLER

M.MAGALAM II

ALSTOMFXT 14F600243

ALSTOMFXT 14F600643

ALSTOMFXT 14F60064

ABBELF SL-4-1IB 106243

ABBELF SL-4-1IB 109018

PTR III100 MVACGLBH-8849/2

PTR I100 MVACGLT -8449/2

PTR II100 MVACGLT - 8462/5

ALSTOMFXT 14F60062

ABBELF - SF 2-1IB 109280

ABBELF SL-4-1IB 106238

BUS - II

BUS - I

CONTROL ROOM

SIEMENS3 AP 1 FGIND/05/7462

BHELHLD 2/145304895

BHELHLD 2/145304890

BHEL3ARI EG400123

PUTTUR -I

CGL120 SFM - 32 B32267 C

SIEMENS3 AP 1 FGIND/05/1290

ABBELF SL-2-19600544022

ABBELF SL-2-19600544021

PTR I31.5 MVAAPEXT - 371/45329

PTR II16 MVANGEF2800048623

PTR III16 MVANGEF

ALSTOMFX 1130933

CGL120 SFM - 32 B23861 C

SIEMENS3AF 014236S/1960

SIEMENS3AF 014236SN/68

CAP. .BANK - III5 MVARBHEL110 KVAR

CAP. .BANK - II5 MVARBHEL110 KVAR

CAP. .BANK - I7.2 MVARBHEL/SHREEM200 KVAR

STN. TRANS. - I33KV/440V100 KVA

33KV/110V PT

THUKIVAKAM - I

THUKIVAKAM - II

KARAKAMBADI

STN. TRANS. - II33KV/440V100 KVA

YERPEDU

GAJULAMANDYAM - II

GAJULAMANDYAM - I

LANCO

SIEMENS3 AP 1 FGIND/07/3848

KODURU

ALSTOMFXT 14F600244

BHEL3ARS400451

ALSTOMFXT 14F30900

CGL200-SFM4014169

CGL120 SFM - 32 B32257 C

33 KV

INDEX

BREAKER

P.T

C.T

LA

CVT

ISO LATORSTN. TRANSFO RMER

132 KV

CAP. BANK

220 KV

AUTO TRANSFO RMER

PO WER TRANSFO RMER

Fig. 3.12.Line diagram of 220/132/33KV substation Renigunta

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Table 3.5: 220kV feeder wise loss calculations for the month of Jan 2011 in O S D of

Renigunta

S. No Name of the Feeder Loss( kW) % Loss

1 Manubolu-I 1345400 0. 35

2 Manubolu-II 339000 0.39

3 Mahadeva Mangalam-I 506896 0.74

4 Mahadeva Mangalam-II 220400 0.31

5 C .K.Palli 506000 0.33

6 Kodur 346000 0.4

Table 3.6: 220kv feeder wise loss calculations from Jan 2011 to Dec 2011 in O S D of

Renigunta

S.No Name of the Feeder Loss(KW) %Loss

1 Manubolu-I 1393800 4

2 Manubolu-II 2516000 7.46

3 Mahadeva Mangalam-I 7990872 8.94

4 Mahadeva Mangalam-II 1818600 5.46

5 C.K.Palli 9286990 10.85

6 Kodur 4789300 8.82

Total 27795562 45.53

Feeder line losses are calculated by using the equation 3.2 and percentage of line

losses are calculated by the equation 3.3.

Sample calculations of feeder loss:

( ) ( )1 2 2 1L i n e l o s s e s E I E I= − + − 3.2

= (956800-933000) – (384432000-383110400)

= 1345400kW

( ) ( )( )

1 2 2 1

1 2

1 0 0 %P e r c e n ta g e o f l in e lo s s e s E I E IE E

− + −= ×

+ 3.3

67

= ( )956800 933000) – 384432000 383110400

100%956800 384432000

− −×

+

= 0.35%

Where

E1= Sending end export units

E2= Receiving end export units

I1= Sending end import units

I2= Receiving end import units

Fig.3.13. Loss analysis of the feeders

3.7. CONCLUSIONS

A laboratory model of the transmission line on-line monitoring and real-time

data acquisition by deploying sensors is developed and its operation is demonstrated.

They acquire the required data and transmit it to the control centre by using wireless

GSM communication. In the control centre, analysis is made and corrective action to

be taken will be advised for maintaining the UF and reducing the energy losses. Case

study of Renigunta substation is considered. The loss analysis for 220kV feeder has

68

been carried out for a period of one month and also for one year. By observation it is

clear that, losses are high. With the effort detailed above, if we can reduce even a

small amount of these losses, we will be saving huge natural resources and money.

Conserving natural resources will be a big boost in conservation of environment.

Sensors and Wireless GSM communication is suggested for on-line monitoring and

reducing energy loss. The wireless communication network offers advantages over

conventional techniques such as faster response, lower cost, always connected and

two-way communication.