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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
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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.
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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.
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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
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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
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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.
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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
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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
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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
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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
57
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
60
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
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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.