Progress Report Modern Transformer Protection John Citizen Student # 12345678 26 May 2099 Supervisor: Dr Jane Public

ENS6126 Master of Engineering 1
Progress Report
Modern Transformer Protection
John Citizen
Student # 12345678
26 May 2099
Supervisor: Dr Jane Public

Abstract
The advancement in Modern Power System has gained a design of wide range of
Transformers With sizes of few KVA to several hundred of MVA. Huge Transformers
are used to step up a voltage of about 25KV to transmission level, such as 330KV.The
Transformers are availed in various sizes to step down the voltages from 330KV to
130KV and then its distributed in level of 33KV ,then its again stepped down for
domestic supply to 415V.The transformer has to be protected for reliable Power
System. The losses due to thermal stress and electrodynamics forces of the transformer
has to be decreased to make steady flow of supply. To ensure the supply magnetising
inrush current and fault current of transformer has be reduced. In this project the fault
and magnetising inrush current has been identified using wavelet transform and
continuous monitoring of the system will help to handle the fault current so it can be
reduced. The harmonics are formed by the non-linear devices placed in the power
system. These harmonics are the multiple integers of the fundamental frequency. These
Harmonics Frequencies are due to the voltage and current distortions. Distortions in
voltage and current will results problem in power quality. So approximation of
harmonics is most important for the efficiency of the system. The Quality of the system
has to be maintained as per the given standards and to protect the system from damages
due to loads. A filtering device has been used to filter the unwanted frequencies. This
device will allow only some specific frequencies and reduce the distortions. Therefore a
digital filter has been designed to reduce the harmonics and improve the quality of the
power in the system. This project is to explain the methods of protection of transformer
by reducing the fault current and magnetising inrush current using Wavelet Transform
and to reduce the harmonics in the power system using Digital Filter. There are various
types of digital filter has been used to improve the efficiency and reduce the distortions
to maintain the quality of the system. Digital Filters are basically classified in two types
depending upon the impulse response as IIR and FIR filters. The FIR filter have linear
Phase response and there won’t be any phase distortion and it will maintain the stability.
Therefore a Transformer protection methods has been given using Wavelet Transform
and FIR filter based algorithms and analysed using MATLAB.
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Table of Contents
List of Figures.......................................................................................... iii
1. Introduction............................................................................................ 1
1.1 Introduction......................................................................................... 1
1.2 Objectives............................................................................................ 2
1.3 Significance.......................................................................................... 2
1.4 Report Organisation.............................................................................. 3
2. Background............................................................................................. 5
2.1 Literature Review...................................................................................... 5
2.2 Transformer losses..................................................................................... 9
2.3 Different current losses in transformer.........................................................10
2.4 Current Transformer Issues.......................................................................14
3. Proposed Approach................................................................................. 17
3.1 Wavelet transform.................................................................................... 17
3. 2 Continuous wavelet transform...................................................................18
3.3. Wavelet based algorithm...........................................................................19
3.4 Digital filters........................................................................................... 20
3.5 Infinite impulse response (IIR) filter............................................................22
4. Preliminary Results and Discussions...........................................................29
4.1 Wavelet based Algorithm Result.............................................................29
5. Conclusion............................................................................................ 35
References................................................................................................... 37
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List of Figures
Figure 1 Magnetizing inrush current.............................................................11
Figure 2 Harmonic distortion........................................................................13
Figure 3 Basic Circuit of Relay.....................................................................15
Figure 4 Circuit to implement the Relay.......................................................16
Figure 5 Wavelet based algorithm flow chart...............................................19
Figure 6 Digital filters...................................................................................20
Figure 7 Magnitude response for the filters..................................................21
Figure 8 Infinite impulse response (IIR) filter................................................22
Figure 9 Structure of FIR Filter.....................................................................25
Figure 10 Digital Filter Design Flow Chart....................................................26
Figure 11 Magnitude Response of the Filter.................................................27
Figure 12 Simulation Diagram of Transformer for Fault...............................29
Figure 13 the output Waveform for fault current.........................................30
Figure 14 Output Waveform for inrush Current............................................30
Figure 15 Output waveform of FIR Filter......................................................33
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1. Introduction
1.1 Introduction
Generally Transformers are considered as a most reliable unit, but there is a
chance of failure because of internal fault, due to stresses from external sources. Fuse
has been used for smaller distribution Transformer. Sometimes inverse definite
minimum time or instantaneous over current and Earth fault relays has been used for
Transformer Protection. For this type of protection downstream power system co-
ordination is necessary.so this could lead to time delay. Therefore this method cannot be
used for Large Power Distribution which could lead to unstable system and generate
more power losses.
A Device where the electrical energy from one circuit is transferred to another
by a magnetic field without changing the frequency, this is done by a transformer. At
this modern times it is essential to have transformers that have reduced loss and to
transmit electric power at a greater level. The life span of a transformer is reduced due
to the effect of overload that increases the temperature of the transformer. Filters are
used for reducing the loss of electric power in the transformers. The aim of the report is
to provide a transformer protection for the purpose of steady electrical flow by using
wavelet transform algorithm and algorithm based on filter. This project also explains the
current transformer issues and their restrain characteristics. By providing a continuous
the supply magnetizing inrush current and fault current of the transformer, it has been
reduced the fault current of the transformer. The required hardware for the
implementation of the reduced electrical losses is been given in this project. The
methods to protect the transformer through minimizing the fault current by using the
wavelet transformation algorithm and to reduce the harmonics by using the digital filter
will be explained in this project. The result of this implementation of the steady flow
electric power will be given in MATLAB, which is a programming language that
includes data visualization and creating user interface, also includes developing and
running algorithms. The report will provide the harmonic distortions, different varieties
of current in the transformer and external and internal short circuits. Various types of
digital filter has been used to progress the efficiency and to reduce the distortions to
maintain the quality of the system. Digital Filters are basically classified in two types
depending upon the impulse response as IIR and FIR filters. The FIR filter have linear
Phase response and there won’t be any phase distortion and it will maintain the stability.
Digital filters will be used for reducing the electric losses and the distortion are
protected.
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1.2 Objectives
The objective of the project is to reduce the loss due to thermal stress and
electrodynamics forces of the transformer and to maintain a steady flow of electric
current, to maintain the quality of the system and to protect the reliable power system of
the transformer. It also aims at reducing problems related to power quality by
decreasing the distortions in the current. To reduces the higher voltage electricity into
lower voltage systems that is used by the end users.
1.3 Significance
1. In a distribution system a better regulation of voltage is been produced by the
transformer that acts as a booster to it. The transmission of power occur in
higher rate that is not economical, the voltage level is been enhanced by the
transformers by producing a voltage with greater level at a very low loss. The
power transformers assist in maintaining the power quality and control and
simplifies the electrical networks.
2. The transformer that is generated in electrical power is a cost effective
transformer with a low voltage level, if this low voltage power is transmitted in
in the receiving end it results in a greater linear circuit that causes the line losses.
The increase in the voltage power causes the reduction in the ohmic.
3. Power transformer can electrically segregate the circuits.
4. Power transformer can decrease or increase the capacitor’s value, a resistance or
an inductor in an AC circuit. Power transformer thus perform as an impedance
transferring device.
5. Power transformer can also be used to avoid DC current passing starting from
one circuit to another circuit.
6. Each single show gadget or recording gadget can be perused in the wire lengths
between the distinctive channels for get to, not caused by wire length going
between accuracy.4mA to zero level, to decide the open circuit or sensor is
harmed (0mA state) is extremely helpful, in the simple expansion of two-line
outlet surge and lightning assurance gadgets, is helpful for safe mine blast.
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7. The capacitive protection of the beneficiary causes obstruction on the blunder,
both for 4 ~ 20mA wire circle, the recipient protection is normally 250
(specimen Uout = 1 ~ 5V) that protection sufficiently little to create huge
mistakes, in this manner, can permit the link length longer than the voltage
telemetry framework further
8. In the present source yield protection is sufficiently expansive, the attractive
field sensor coupled to the wire the voltage circle won't have a huge effect, on
the grounds that the obstruction caused by the current is little, as a rule utilizing
turned combine can decrease the impedance resistance. Less defenseless to
parasitic thermocouples and weight drop along the wire protection and
temperature float of the transmission line can be extremely economical contorted
match wire better.
1.4 Report Organisation
This report contains five topics namely introduction, Background of the project,
proposed approach, preliminary results and discussions and conclusion, which are
arranged as below
Introduction provides a general description about the Power transformers the
magnetic field that is changed by the transformers is given. The objective of the report
and its significance of implementation of the transformer is been explained. The
objective is gives as to provide a steady flow of electric power. The aim of the report is
given as to provide a transformer protection for the purpose of steady electrical flow by
using wavelet transform algorithm and algorithm based on filter. The main theme of the
project is given in the introduction part. A description about the MATLAB and the
definition of the filters is given.
The Background topics presents the clear vision about the project background. This
explains about the transformer losses, different current losses in the transformer and
current transformer issues. This topic also includes the literature review related to the
journals Modern Protection of Three-Phase and Spare Transformer Banks by Michael
Thompson, Faridul Katha Basha, and Craig Holt, article about Transformers Fault
Detection Using Wavelet Transform by Y. Najafi Sarem, E. Hashemzadeh, and M.A.
Layegh , a journal about Simulation Of Transformer For Fault Discrimination Using
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Wavelet Transform & neural Network by Laxminarayan Sonwani, Dr. Dharmendra
Kumar Singh and Durga Sharma and journal about A Review Of Design Digital Filter For
Harmonics Reduction In Power System by Prashant Nagare, Dr. Sachin Pable, Dr. A.K.
Kureshi. In transformer losses explanation is given about Copper loss, Dielectric loss
and Radiation and induction loss. The Different current losses in transformer topic
explains about the hysteresis loss eddy current loss and a graph that shows the inrush
current is caused when application of source voltage to a reenergized transformer gives
rise to sudden increase in current is been explained. The hardware that are required to
implement the relay is been given and a figure of basic circuit of the relay is given and a
figure Circuit to implement the Relay is also provided
The topic Proposed Approach addresses the wavelet transform, continuous wavelet
transform, wavelet based algorithm, digital filters and Infinite impulse response filter.
Preliminary Results and Discussions describe the Wavelet based Algorithm Result and
figures of Simulation Diagram of Transformer for Fault, the output Waveform for fault
current, Output Waveform for inrush Current and Output waveform of FIR Filter. FIR
Based Algorithm is also been explained
Conclusion gives the summary of the project.
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