Major_project_b.tech_sem8_may_2018

DESIGN OF THREE PHASE FEEDER PROTECTION
SCHEME BY TWO OVERCURRENT RELAYS AND
ONE EARTH FAULT RELAY
A
Major Project Report
Submitted in partial fulfillment for the requirements of degree of
BACHELOR OF TECHNOLOGY
IN
ELECTRICAL ENGINEERING
By
DIPEN KANTARIYA (15BEE154)
HIREN PATEL (15BEE166)
Under the Guidance of
PROF. SHANKER GODWAL
DEPARTMENT OF ELECTRICAL ENGINEERING
INSTITUTE OF TECHNOLOGY
NIRMA UNIVERSITY
AHMEDABAD 382 481
MAY 2018

NIRMA UNIVERSITY
AHMEDABAD
CERTIFICATE
THIS IS TO CERTIFY THAT THE MAJOR PROJECT REPORT ENTITLED “DESIGN OF THREE
PHASE FEEDER PROTECTION SCHEME BY TWO OVERCURRENT RELAYS AND ONE EARTH
FAULT RELAY” SUBMITTED BY MR. DIPEN KANTARIYA (15BEE154) AND MR. HIREN
PATEL (15BEE166) TOWARDS THE PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR
THE AWARD OF THE DEGREE IN BACHELOR OF TECHNOLOGY IN ELECTRICAL ENGINEERING
OF NIRMA UNIVERSITY IS THE RECORD OF WORK CARRIED OUT BY THEM UNDER OUR
SUPERVISION AND GUIDANCE. THE WORK SUBMITTED HAS IN OUR OPINION REACHED A
LEVEL REQUIRED FOR BEING ACCEPTED FOR EXAMINATION. THE RESULTS EMBODIED IN
THIS MAJOR PROJECT WORK TO THE BEST OF OUR KNOWLEDGE HAVE NOT BEEN SUBMITTED
TO ANY OTHER UNIVERSITY OR INSTITUTION FOR AWARD OF ANY DEGREE OR DIPLOMA.
DATE:
GUIDE
PROF. S. GODWAL
ASST. PROFESSOR
PROF. (DR.) P. N. TEKWANI
HEAD OF DEPARTMENT
NIRMA UNIVERSITY
AHMEDABAD
PROF. (DR.) ALKA MAHAJAN
DIRECTOR
NIRMA UNIVERSITY
AHMEDABAD

UNDERTAKING FOR ORIGINALITY OF THE WORK
We, Dipen S. Kantariya (15BEE154) and Hiren B. Patel (15BEE166) give
undertaking that the Major Project entitled “Design of Three Phase Feeder
Protection Scheme by Two Overcurrent Relays and One Earth Fault Relay”
submitted by us, towards the partial fulfillment of the requirements for the
degree of Bachelor of Technology in Electrical Engineering of Nirma
University, Ahmedabad, is the original work carried out by us and we give
assurance that no attempt of plagiarism has been made. We understand that
in the event of any similarity found subsequently with any other published
work or any project report elsewhere; it will result in severe disciplinary
action.
__________________
Signature of Students
Date: _______________
Place: _______________
Endorsed by:
(Signature of Guide)

iv | I n s t i t u t e o f T e c h n o l o g y , N i r m a U n i v e r s i t y , A h m e d a b a d
ACKNOWLEDGEMENT
We must acknowledge the strength, energy and patience that almighty GOD
bestowed upon us to start & accomplish this work with the support of all concerned, a
few of them we are trying to name hereunder.
We would like to express our sincere respect and profound gratitude to our guide
Prof. S. Godwal for guiding us through-out the semester. We are also equally thankful to
Prof. P. N. Tekwani, Head of Electrical Department to provide us great opportunity to
carryout project work. We would also like to thank Prof. S. C. Vora for his valuable
suggestions and inputs. We are equally thankful to the authorities and staff of Electrical
Engineering Department for providing the department facilities.
No words are adequate to express indebtedness to parents and for their blessings
and good wishes.
- Dipen Kantariya (15BEE154)
- Hiren Patel (15BEE166)

v | I n s t i t u t e o f T e c h n o l o g y , N i r m a U n i v e r s i t y , A h m e d a b a d
ABSTRACT
Three phase feeder is frequently subjected to line to ground and line to line faults.
It is very important to isolate the faulty part or to clear the fault as quickly as possible, so
as to maintain continuity of supply to the consumers. Conventionally electromechanical
relays are being used for the feeder protection, but they are having their own
disadvantages. With the rapid development of power electronic devices,
microcontrollers, microprocessors and digital signal processors, etc., electromechanical
relays are being replaced by static relays and numerical relays because of their
advantages. This project aims to implement three phase feeder protection scheme by the
development of numerical overcurrent relay using Arduino Uno.

vi | I n s t i t u t e o f T e c h n o l o g y , N i r m a U n i v e r s i t y , A h m e d a b a d
LIST OF ACRONYMS
DC Direct Current
AC Alternating Current
RMS Root Mean Square
CT Current Transformer
PT Potential Transformer
IDMT Inverse Definite Minimum Time
USB Universal Serial Bus
VLSI Very Large Scale Integration
LCD Liquid Crystal Display
DSP Digital Signal Processor

vii | I n s t i t u t e o f T e c h n o l o g y , N i r m a U n i v e r s i t y , A h m e d a b a d
TABLE OF CONTENTS
ACKNOWLEDGEMENT IV
ABSTRACT V
LIST OF ACRONYMS VI
TABLE OF CONTENTS VII
CHAPTER 1: POWER SYSTEM PROTECTION 1
1.1 Introduction 1
1.2 Numerical Relays 1
CHAPTER 2: POTECTION OF THREE PHASE FEEDERS 3
2.1 Introduction 3
2.2 Circuit diagram 5
2.2.1 Power supply 5
2.2.2 Main circuit 6
CHAPTER 3: CONSTRUCTION OF PROTECTION SCHEME 7
3.1 Transformer 7
3.2 Diode 7
3.3 Voltage regulator IC’s 7
3.4 Capacitors 8
3.5 Three phase contactor 8
3.6 Lamp banks 8
3.7 Cube relay 8
3.8 TLP250 9
3.9 Potentiometer 10
3.10 Push button 10
3.11 Current sensor ACS712 10
3.12 Arduino UNO 11
3.13 LCD display 15
CHAPTER 4: WORKING OF PROTECTION SCHEME 16
4.1 Configuration of relay 16
4.1.1 Relay type 16
4.1.2 Plug setting phase relay 16
4.1.3 Plug setting ground relay 17
4.1.4 Operating time phase relay 17
4.1.5 Operating time ground relay 17
4.1.6 TMS phase relay 18
4.1.7 TMS ground relay 18
4.2 Sampling process 19
4.3 Calculation of operating time 19
4.4 Tripping and reclosing 21

viii | I n s t i t u t e o f T e c h n o l o g y , N i r m a U n i v e r s i t y , A h m e d a b a d
CHAPTER 5: HARDWARE IMPLEMENTATION 23
5.1 ACS712 current sensors 23
5.2 Power supply and cube relay 24
5.3 Arduino UNO and LCD display 25
5.4 Whole setup 26
CHAPTER 6: MAIN ‘C’ LANGUAGE CODE 27
CONCLUSION & FUTURE SCOPE 38
REFERENCES 39

1 | I n s t i t u t e o f T e c h n o l o g y , N i r m a U n i v e r s i t y , A h m e d a b a d
CHAPTER:-1
POWER SYSTEM PROTECTION
1.1 Introduction
Power System Protection is necessary from the point of view of equipment safety
as well as human safety. No part of the power system should left unprotected. Any
undesirable situation in the power system is consider as fault or abnormal condition. The
device which detects fault in the power system is called relay. The function of the relay is
to sense fault in the power system and issue trip command to the circuit breaker. The
circuit breaker isolates faulty part of the power system from the remaining healthy part.
The fault should be cleared rapidly to maintain continuity of the supply to the consumers
and to increase reliability of the power system.
Three phase feeder (overhead lines) are frequently subjected to faults. Majority of
these faults are short circuits or over currents. So, they are provided with over current
protection scheme. Over current protection is the most simple, reliable and efficient
method to protect three phase feeders.
Electromechanical relays are having their own disadvantages like size and weight
constraints, burden on the current transformer, etc. These disadvantages of
electromechanical relays are overcome by the Numerical Relays.
1.2 Numerical Relays
Numerical relays are the latest development in the area of power system
protection. Numerical relays have been developed because of tremendous development
in the VLSI and computer hardware technology. They are based on numerical (digital)
devices, e.g., microprocessors, microcontrollers, Digital Signal Processors (DSPs), etc. At
present microprocessor/ microcontroller based numerical relays are widely used. These
relays use different types of relaying algorithms to process the acquired information.
The present downward trend in the cost of VLSI circuits has encouraged wide
application of numerical relays for the protection of modern complex power networks.
Economical, powerful and sophisticated numerical devices are available today because of
tremendous advancement in computer hardware technology. Hence, there a growing
trend to develop and use numerical relays for the protection of the various components
of the modern complex power system. Numerical relay has become viable alternative to
the traditional relaying systems employing electromechanical and static relays.
The main features of numerical relays are their compactness, flexibility, reliability,
self-monitoring, self-checking capability, multiple functions, low burden on instrument
transformers and improved performance over conventional relays of electromechanical
and static types.

In this project, we have designed and implemented three phase feeder protection
scheme based on the numerical overcurrent relays using Arduino UNO. ACS712, 20A Hall
Effect current sensor is used to measure all three line currents. Instantaneous, definite
time, normal inverse (IDMT), very inverse and extremely inverse, etc. types of relays are
implemented in this project by ‘C’ language code in Arduino UNO.
In this project, Auto reclosing mechanism is also implemented. A four pole
contactor used in the project performs the task of the circuit breaker. After the first
tripping, the contactor is reclosed three time after interval of five seconds. If the fault is
persisting even after three reclosure, then only feeder will be tripped permanently.
In this project three lamp banks connected in star are used as load and also used
to create the fault. Each lamp bank has the current capacity of 5 Amps. Since Hall Effect
current sensor, ACS712 used in this project has the current capacity of 20A, all three
sensors are directly connected in series with three phase line. But, in actual feeder where
line current is very high, the Hall Effect current sensors should be connected in series
with the secondary of the current transformer. In that case current transformer having
secondary current rating of 5A or 1A should be selected. The burden offered by the
ACS712 current sensor to the secondary of current transformer is 1.2 milliohms only.
This project is tested in the laboratory and it is working reliably. It is following the
trip characteristics of the Instantaneous, definite time, normal inverse (IDMT), very
inverse and extremely inverse, etc. (separately in different modes) exactly.
Auto reclosing mechanism is also working very fine and if fault is cleared in
between three reclosure, then system is set back to the normal condition. If the fault is
persisting even after three reclosure, then only feeder will be tripped permanently.
This project remains stable (inoperative) during transient conditions like inrush
current, transient faults, etc. because characteristics (IDMT, very inverse and extremely
inverse) implemented by ‘C’ language code in Arduino UNO is exactly similar to the actual
electromechanical relays.
This project is able to detect, display and respond to all types of three phase faults
whether symmetrical (L-L-L or L-L-L-G) or unsymmetrical (L-G, L-L, L-L-G) reliably.

CHAPTER:-2
POTECTION OF THREE PHASE FEEDERS
2.1 Introduction
The three-phase system is subject to phase faults as well as ground faults. For
providing complete protection to a three-phase feeder, three relays are connected to
three CTs as shown in figure below.
The relays at bus A will be coordinated with those at bus B. It may be pointed out
here that fault current for a single line to ground fault depends upon the system
grounding as well as the tower footing resistance. Therefore it may happen that the fault
current for a single line to ground fault may be less than the load current. In such cases,
it will not be possible to cater to such faults if we use the scheme shown in figure above.
A little thought will show that if we connect an OC relay in the residual current path then
it will be blind to the load current (which is balanced three-phase current) and see only
the ground fault currents.

The current in residual current path will be zero or near zero during normal
balanced load conditions as well as during a three-phase fault. Thus, the setting of this
relay, which is in the residual current path, can be made independent of load current and
can indeed be much smaller than the load current. Further, it is not necessary to use all
the three relays for detection and protection against phase faults. We can get rid of any
one phase fault relay without affecting the performance of the scheme. In the above, the
relay in the phase B has been removed.
As we can see from table below, all the 11 numbers of shunt faults are catered by
the three relays.

2.2 Circuit diagram
2.2.1 Power supply

2.2.2 Main Circuit

CHAPTER:-3
CONSTRUCTION OF PROTECTION SCHEME
3.1 Transformer
 Two transformers are used in the whole setup.
1. 230/15V, 500mA
This transformer is used to provide +15V supply to the optocoupler
TLP250 as well as to energize the coil of the cube relay through the output
terminal of the optocoupler.
2. 230/12V, 1A
This transformer is used to provide +12V supply to the DC power Jack for
the Arduino UNO. Further +5V supply of the Arduino is used to provide power
supply to the ACS712 current sensors and to the 16x2 LCD display.
Both the transformers as well as coil of the main contactor are supplied 230V,
50Hz, 1-Phase, AC supply by the common Power cord.
3.2 Diode
Two bridge rectifiers are created by using the diodes 1N4007, that converts AC
output of the secondary of the transformer into pulsating DC.
3.3 Voltage Regulator IC’s
1. 7815
It provides +15V regulated DC output voltage, which is used to provide
power supply to the optocoupler TLP250, output of which will energize the
coil of the cube relay.
2. 7812
It provides +12V regulated DC output voltage, which is used as a DC power
Jack to supply power to the Arduino. Further +5V supply of the Arduino is used
to provide power supply to the ACS712 current sensors and to the 16x2 LCD
display.

3.4 Capacitors
 Capacitors of rating 1000uF, 25V and 470uF, 25V are connected to the input side
of the 7815 and 7812 respectively.
 Their main function is to reduce ripples from the pulsating DC output of the diode
bridge rectifier and to provide stable voltage on the input side of the 7815 and
7812.
 Capacitors of rating 10uF, 50V is connected to the output terminals of the 7815 as
well as 7812.
3.5 Three Phase Contactor
 In this project three phase contactor is performing the task of the circuit breaker.
 It is supplied by 415V, 50Hz, three phase AC supply through the three phase
variac.
 It is configured such that all its four poles remain Normally Closed.
 These Normally Closed four poles become Open when coil of the contactor is
supplied by the 230V, 50Hz, single phase AC supply.
 Common and NO (Normally Open) terminals of the cube relay are connected in
series with the single phase supply and the coil of the contactor, so under normal
condition coil of the contactor does not get 230V and hence contactor remains in
the closed position.
 But when fault occurs coil of the cube relay is energized and hence it closes
common and NO contacts and hence coil of the main contactor gets 230V.
 So, main contactor operates and the four Normally Closed terminals become open
and hence feeder is isolated.
3.6 Lamp Banks
 Three lamp banks, each having capacity up to 5A current, are connected in star.
 They are used as a load as well as to create fault.
3.7 Cube Relay
 12V cube relay is used to energize the coil of the main contactor under faulty
condition to isolate the feeder.

 Coil of the cube relay is connected across the ‘output’ and ‘ground’ terminals of the
optocoupler TLP250.
 Common terminal of the cube relay is connected to one of the terminals of the coil
of the main contactor.
 NO terminal of the cube relay is connected to the one of the terminal of the single
phase AC supply.
 So, under normal condition coil of the contactor does not get 230V and hence
contactor remains in the closed position.
 But when fault occurs, coil of the cube relay is energized and hence it closes
common and NO contacts and hence coil of the main contactor gets 230V.
 So, main contactor operates and the four Normally Closed terminals become open
and hence feeder is isolated.
3.8 TLP250
 TLP250 optocoupler is used to provide isolation for the pins of the Arduino to
prevent any kind of damage to the Arduino.
 Pin-9 of the Arduino is used to give command to the main contactor.
 Pin-9 is normally LOW but when contactor is required to open, pin-9 is set to HIGH
by the Arduino code.
 Pin-9 is connected to Anode of TLP250 through 470R Resistance and digital GND
of Arduino is connected to Cathode of the TLP250.
 +15V supply is connected to the VCC and GND of TLP250.
 Coil of the cube relay is connected between OUTPUT and GND terminals of the
TLP250.
 When pin-9 is LOW, voltage at OUTPUT terminal of TLP250 is zero.
 When pin-9 is High, voltage at OUTPUT terminal of TLP250 is around 14V.

3.9 Potentiometer
 Two pots are used in the setup.
1. 5k pot_1 is used to vary relay type, plug setting phase relay, plug setting ground
relay, TMS phase relay and TMS ground relay, etc. during initial configuration
of the relay. It is connected to A0 pin of the Arduino.
2. 10k pot_2 is used to vary brightness of the LCD display.
3.10 Push Button
 Push button is required to press after selecting the each settings like relay type,
plug setting phase relay, plug setting ground relay, TMS phase relay and TMS
ground relay, etc. during initial configuration of the relay.
 For ex. After the relay type (let us say Normal Inverse) is selected using
potentiometer, push botton is required to press to go to the next setting.
 It is connected between pin-12 and the digital ground of the Arduino.
3.11 Current sensor ACS712
 ACS712 is a Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1
kV RMS Isolation and a Low-Resistance Current Conductor.
 ACS712 has continuous current carrying capability of 20A in either direction.
 Its transient current capacity is five times the continuous current carrying
capacity.
 Ip+ and Ip- terminals of the sensor are connected in series with the line whose
current is to be measured.

 +5V supply is connected between VCC and GND terminals.
 Here +5V of the Arduino is used to provide power supply to the current sensor.
 When current flowing through Ip+ and Ip- is zero, voltage at the OUT terminal is
2.5V.
 As current vary from 0 to +20A (entering through Ip+ and leaving through Ip-,
instantaneous value), the voltage at the output terminal vary from 2.5V to 5V
linearly.
 As current vary from 0 to -20A (entering through Ip- and leaving through Ip+,
instantaneous value), the voltage at the output terminal vary from 2.5V to 0V
linearly.
 So, when AC sinusoidal current flows through the sensor, voltage at the OUT
terminal of the sensor also vary sinusoidal about the 2.5V axis and at the same
frequency that of the line current.
 In this project, the Hall Effect sensors are directly connected in the series with the
line since in the experiment setup, line current cannot be increased beyond 5A.
 When line current is very high as in the case of actual feeder, the sensors should
be connected across the secondary terminals of the current transformer having
secondary current rating of 5A or 1A.
 Three OUT pins of the current sensors for R, Y, and B phases are connected to the
A5, A4, A3 analog input pins of the Arduino.
3.12 Arduino UNO
 Arduino UNO is the most important part of this project.
 Numerical overcurrent relays for each phase and also for the ground is
implemented using Arduino UNO.
 It is used to decide operating time depending on the PSM and give trip command
to the contactor.

 Technical specifications:
Microcontroller ATmega328P
Operating Voltage 5V
Input Voltage (recommended) 7-12V
Input Voltage (limit) 6-20V
Digital I/O Pins 14 (of which 6 provide PWM output)
PWM Digital I/O Pins 6
Analog Input Pins 6
DC Current per I/O Pin 20 mA
DC Current for 3.3V Pin 50 mA
Flash Memory 32 KB
SRAM 2 KB
EEPROM 1 KB
Clock Speed 16 MHz
 It is also used to implement auto reclosing mechanism.
 Arduino will auto reclose the feeder three times after the first tripping of the
feeder.
 Auto reclosing interval is 5 seconds.
 If the fault is persisting even after the third reclosure, feeder is tripped
permanently.

 Following relays are implemented using Arduino UNO in this project.
1. Instantaneous Relay
 In this mode relay operates instantaneously when the line current
exceeds plug setting of the phase relay or neutral current exceeds plug
setting of the ground relay.
 Plug setting phase relay can be varied from 0 to 5A.
 Similarly Plug setting ground relay can also be varied from 0 to 5A.
2. Definite Time relay
 In this mode relay operates after set definite operating time when the
line current exceeds plug setting of the phase relay or neutral current
exceeds plug setting of the ground relay.
 Definite operating time for the phase relay and the ground relay can be
varied from 0 to 10 seconds.
3. Normal Inverse (IDMT) relay
 In this mode operating time is decided based on the following equation.
Operating Time = TMS * (
0.14
𝑃𝑆𝑀0.02− 1
)
PSM for phase relay =
𝐴𝑐𝑡𝑢𝑎𝑙 𝑙𝑖𝑛𝑒 𝑐𝑢𝑟𝑟𝑒𝑛𝑡
𝑃𝑙𝑢𝑔 𝑠𝑒𝑡𝑡𝑖𝑛𝑔 𝑝ℎ𝑎𝑠𝑒 𝑟𝑒𝑙𝑎𝑦
PSM for ground relay =
𝐴𝑐𝑡𝑢𝑎𝑙 𝑔𝑟𝑜𝑢𝑛𝑑 𝑐𝑢𝑟𝑟𝑒𝑛𝑡
𝑃𝑙𝑢𝑔 𝑠𝑒𝑡𝑡𝑖𝑛𝑔 𝑔𝑟𝑜𝑢𝑛𝑑 𝑟𝑒𝑙𝑎𝑦
 TMS for phase relay can be varied from 0 to 1.
 Similarly TMS for ground relay can also be varied from 0 to 1.
4. Normal Inverse relay
13.5
𝑃𝑆𝑀1− 1
)

5. Extreme Inverse relay
80
𝑃𝑆𝑀2− 1
)
 A LCD display is also connected with Arduino UNO to show the line and neutral
currents, type of the fault, tripping time, reclosing status and the status of the
relay.
 Pin-9 of the Arduino is normally LOW and when it is made HIGH, it sends trip
signal to the contactor through TLP250 and cube relay.
 +12V supply is used to provide power to the Arduino.
 +12V supply is connected to the DC power jack of the Arduino.
 The program is written in the ‘C’ language by the dedicated software for the
Arduino and then it is loaded in the Arduino via USB cable.

3.13 LCD Display
 A 16x2 LCD display is used to show relay type, plug seeing phase relay, plug setting
ground relay, TMS phase relay and TMS ground relay, etc. during initial
configuration of relay at the time of startup.
 It is also used to show all line currents, ground current during normal operation.
 It is used to show type of the fault, trip time, reclosing status and whether feeder
is tripped permanently or not, etc.
 It is supplied by +5V from the Arduino.
 Brightness of the LCD display can be varied by the tiny 10k potentiometer.

CHAPTER:-4
WORKING OF PROTECTION SCHEME
4.1 Configuration of relay
4.1.1 Relay type
 When the Arduino is powered up initially, relay is required to be configured.
 First of all relay type is required to be selected.
 Following relay types are available:
1. Instantaneous Relay
2. Definite Time Relay
3. Normal Inverse Relay (IDMT)
4. Very Inverse Relay
5. Extreme Inverse Relay
 Relay type can be changed by varying 5k Pot_1.
 After selecting relay type push botton is required to be pressed to enter into the
next setting.
4.1.2 Plug Setting Phase Relay
 Plug Setting Phase Relay can be changed by varying 5k pot_1.
 Plug Setting Phase Relay can be varied from 0 to 5a.
 After selecting Plug Setting Phase Relay push botton is required to be pressed to
enter into next setting.

4.1.3 Plug Setting Ground Relay
 Plug Setting Ground Relay can be changed by varying 5k Pot_1.
 Plug Setting Ground Relay can be varied from 0 to 5A.
 After selecting Plug Setting Ground Relay push botton is required to be pressed to
enter into next setting.
4.1.4 Operating Time Phase Relay
 Operating Time Phase Relay can be changed by varying 5k Pot_1.
 Operating Time Phase Relay can be varied from 0 to 10 seconds.
 This setting is available in case of Definite Time Relay only.
 After selecting Operating Time Phase Relay push botton is required to be pressed
to enter into next setting.
4.1.5 Operating Time Ground Relay
 Operating Time Ground Relay can be changed by varying 5k Pot_1.
 Operating Time Ground Relay can be varied from 0 to 10 seconds.
 This setting is available in case of Definite Time Relay only.
 After selecting Operating Time Ground Relay push botton is required to be
pressed to enter into next setting.

4.1.6 TMS Phase Relay
 TMS Phase Relay can be changed by varying 5k Pot_1.
 TMS Phase Relay can be varied from 0 to 1.
 This setting is available in case of Normal Inverse, Very Inverse and Extreme
Inverse Relay types only.
 After selecting TMS Phase Relay push botton is required to be pressed to enter
into next setting.
4.1.7 TMS Ground Relay
 TMS Ground Relay can be changed by varying 5k Pot_1.
 TMS Ground Relay can be varied from 0 to 1.
 This setting is available in case of Normal Inverse, Very Inverse and Extreme
Inverse Relay types only.
 After selecting TMS Ground Relay push botton is required to be pressed to enter
into next setting.
 Following message is shown on the LCD display after each setting.
 Following message is shown on the LCD display when relay configuration is
completed.

4.2 Sampling process
 Three OUT pins of the ACS712 current sensors for R, Y, B phases are connected to
the A5, A4, A3 analog input pins of the Arduino UNO respectively.
 Arduino takes samples of analog pins A5, A4, A3 one by one.
 It repeats this process 59 times.
 One sampling process takes 112 microseconds.
 For three samples of A5, A4, A3 it takes,
112 * 3 = 336 microseconds
 For repeating this 59 times it takes,
336 * 59 = 19824 microseconds = 20 milliseconds (1 cycle of 50 Hz)
 In this way one cycle of 50 Hz is covered for calculating the line currents.
 59 samples are available for each R, Y, and B phases for current calculation.
 Current is calculated by using the Arduino program.
 Neutral or Ground current is calculated by adding the samples of the all three R,
Y, and B phases.
 Then current is shown on the LCD display.
 Under Normal condition it shows the currents and following message.
4.3 Calculation of operating time
 After calculating all four currents PSM is calculated by following Equation.

 If PSM for any phase or ground is greater than one then it calculates operating time
of the relay by following Equations:
1. For Instantaneous Relay operating time is zero, it means it operates
instantaneously the moment PSM exceeds one.
2. For Definite Time Relay operating time is fixed during initial configuration of
the relay.
3. For Normal Inverse Relay (IDMT) operating time is calculated by following
Equation.
0.14
𝑃𝑆𝑀0.02− 1
)
4. For Very Inverse Relay operating time is calculated by following Equation.
13.5
𝑃𝑆𝑀1− 1
)
5. For Extreme Inverse Relay operating time is calculated by following
Equation.
80
𝑃𝑆𝑀2− 1
)

4.4 Tripping and Reclosing
 Following type of message is shown when PSM exceeds one and till trip command
is not issued.
 When trip command is issued and contactor is opened, following type of message
is shown on the LCD display.
 It shows type of the fault and the tripping time.
 During the first reclosure following message is shown on the LCD display.
 Then contactor is reclosed after five seconds.
 If the fault is cleared then it goes into normal condition.
 But, if the fault is still persisting then contactor is tripped again and following
message regarding second reclosure is shown on the LCD display.

 Then contactor is again reclosed after five seconds.
 But, if the fault is still persisting then contactor is tripped again and following
message regarding third reclosure is shown on the LCD display.
 Then contactor is again reclosed after five seconds.
 But, if the fault is still persisting then contactor is tripped permanently and
following type of message is shown on the LCD display.
 It shows the type of the fault on the LCD display due to which feeder is tripped
permanently.
 Now to close the contactor again and to take the system back to the normal
condition, long press is applied on the push botton (do not require relay
configuration again) or Arduino can be reset (it requires relay configuration
again).

CHAPTER:-5
HARDWARE IMPLEMENTATION
5.1 ACS712 CURRENT SENSORS

5.2 POWER SUPPLY AND CUBE RELAY

5.3 ARDUINO UNO AND LCD DISPLAY

5.4 WHOLE SETUP

CHAPTER:-6
MAIN ‘C’ LANGUAGE CODE
[/code]
#include <LiquidCrystal.h>
#define CH_A A5
#define CH_B A4
#define CH_C A3
#define CH_SET A0
const unsigned int total_samples = 59;
int sample A[total_samples], sample_B[total_samples],
sample_C[total_samples], sample_G[total_samples];
unsigned int i, relay_type, reclose = 0;
int sum;
float sum_devide_samples, rms_A, rms_B, rms_C, rms_G;
float psm_A, psm_B, psm_C, psm_G, psm;
float plug_setting_phase_relay, plug_setting_ground_relay;
float tms_phase_relay, tms_ground_relay;
float alpha, beta;
unsigned long ot, ot_phase_relay, ot_ground_relay;
unsigned long tt, lcd_time, trip=4200000000;
LiquidCrystal lcd(2,3,4,5,6,7);
void setup()
{
pinMode(9, OUTPUT);
digitalWrite(9, LOW);
pinMode(12, INPUT_PULLUP);
lcd.begin(16, 2);
while(digitalRead(12)==HIGH)
{
relay_type = analogRead(CH_SET);
lcd.clear();
lcd.setCursor(3, 0);
lcd.print("Relay Type");
if(relay_type <= 203)
{
lcd.print("Instantaneous");
}
else if(relay_type >= 204 && relay_type <= 407)

{
lcd.print("Definite Time");
}
{
lcd.print("Normal Inverse");
alpha = 0.02;
beta = 0.14;
}
else if(relay_type >= 612 && relay_type<= 815)
{
lcd.print("Very Inverse");
alpha = 1;
beta = 13.5;
}
else if(relay_type >= 816)
{
lcd.print("Extreme Inverse");
alpha = 2;
beta = 80;
}
delay(15);
}
lcd.clear();
lcd.print("Saving");
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
{
plug_setting_phase_relay = analogRead(CH_SET);
plug_setting_phase_relay = ((5 * plug_setting_phase_relay) / 1023);
lcd.clear();
lcd.print("Plug Setting");
lcd.print("Phase Relay ");
lcd.print(plug_setting_phase_relay);
delay(15);
}
lcd.clear();
delay(500);
lcd.print(".");
delay(500);

lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
{
plug_setting_ground_relay = analogRead(CH_SET);
plug_setting_ground_relay = ((5 * plug_setting_ground_relay) / 1023);
lcd.clear();
lcd.print("Plug Setting");
lcd.print("Gnd Relay ");
lcd.print(plug_setting_ground_relay);
delay(15);
}
lcd.clear();
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
if(relay_type >= 204 && relay_type <= 407)
{
{
tms_phase_relay = analogRead(CH_SET);
tms_phase_relay = ((10 * tms_phase_relay) / 1023);
lcd.clear();
lcd.print("Operating Time");
lcd.print("Phase Relay ");
lcd.print(tms_phase_relay);
delay(15);
}
lcd.clear();
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
{
tms_ground_relay = analogRead(CH_SET);
tms_ground_relay = ((10 * tms_ground_relay) / 1023);

lcd.clear();
lcd.print("Operating Time");
lcd.print("Gnd Relay ");
lcd.print(tms_ground_relay);
delay(15);
}
lcd.clear();
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
}
{
{
tms_phase_relay = analogRead(CH_SET);
tms_phase_relay = (tms_phase_relay / 1023);
lcd.clear();
lcd.print("TMS Phase Relay");
lcd.print(tms_phase_relay);
delay(15);
}
lcd.clear();
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
{
tms_ground_relay = analogRead(CH_SET);
tms_ground_relay = (tms_ground_relay / 1023);
lcd.clear();
lcd.print("TMS Gnd Relay");
lcd.print(tms_ground_relay);
delay(15);
}

lcd.clear();
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
}
lcd.clear();
lcd.print("Setup is");
lcd.print("Completed");
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
lcd.print(".");
delay(500);
}
void loop()
{
for(i=0; i<total_samples; i++)
{
sample_A[i] = analogRead(CH_A);
sample_B[i] = analogRead(CH_B);
sample_C[i] = analogRead(CH_C);
}
for(sum=0, i=0; i<total_samples; i++)
{
sample_A[i] = (sample_A[i] - 511);
sum = (sum + sq(sample_A[i]));
}
sum_devide_samples = (sum/total_samples);
rms_A = sqrt(sum_devide_samples);
rms_A = ((rms_A * 20 * 1.15)/ 512);
psm_A = (rms_A / plug_setting_phase_relay);
{
sample_B[i] = (sample_B[i] - 511);
sum = (sum + sq(sample_B[i]));
}
rms_B = sqrt(sum_devide_samples);
rms_B = ((rms_B * 20 * 1.15)/ 512);
psm_B = (rms_B / plug_setting_phase_relay);

{
sample_C[i] = (sample_C[i] - 511);
sum = (sum + sq(sample_C[i]));
}
rms_C = sqrt(sum_devide_samples);
rms_C = ((rms_C * 20 * 1.15)/ 512);
psm_C = (rms_C / plug_setting_phase_relay);
{
sample_G[i] = (sample_A[i] + sample_B[i] + sample_C[i]);
sum = (sum + sq(sample_G[i]));
}
rms_G = sqrt(sum_devide_samples);
rms_G = ((rms_G * 20 * 1.15)/ 512);
psm_G = (rms_G / plug_setting_ground_relay);
lcd.clear();
lcd.print("Ir=");
lcd.print(rms_A);
lcd.print("Iy=");
lcd.print(rms_B);
lcd.print("Ib=");
lcd.print(rms_C);
lcd.print("Ig=");
lcd.print(rms_G);
delay(2000);
psm = max(psm_A, psm_B);
psm = max(psm, psm_C);
if(psm>1 || psm_G>1)
{
if(relay_type <= 203 || reclose>0)
{
ot = 0;
}
{
ot = min(tms_phase_relay, tms_ground_relay);
ot = round(ot * 1000);
}
{

ot_phase_relay =
round(tms_phase_relay*1000*(beta/(pow(psm,alpha)-1)));
ot_ground_relay =
round(tms_ground_relay * 1000 * (beta/(pow(psm_G,alpha)-1)));
ot = min(ot_phase_relay, ot_ground_relay);
}
tt = millis() + ot;
if(tt<=trip)
{
trip = tt;
}
if(millis()>=trip)
{
digitalWrite(9, HIGH);
lcd.clear();
if(psm_A>1 && psm_B>1 && psm_C>1 && psm_G>1)
{
lcd.print("R-Y-B-G fault");
}
else if(psm_A>1 && psm_B>1 && psm_C>1)
{
lcd.print("R-Y-B fault");
}
else if(psm_A>1 && psm_B>1 && psm_G>1)
{
lcd.print("R-Y-G fault");
}
else if(psm_B>1 && psm_C>1 && psm_G>1)
{
lcd.print("Y-B-G fault");
}
else if(psm_C>1 && psm_A>1 && psm_G>1)
{
lcd.print("B-R-G fault");
}
else if(psm_A>1 && psm_B>1)
{
lcd.print("R-Y fault");
}
else if(psm_B>1 && psm_C>1)
{

lcd.print("Y-B fault");
}
else if(psm_C>1 && psm_A>1)
{
lcd.print("B-R fault");
}
else if(psm_A>1)
{
lcd.print("R-G fault");
}
else if(psm_B>1)
{
lcd.print("Y-G fault");
}
else if(psm_C>1)
{
lcd.print("B-G fault");
}
if(reclose==0)
{
ot = round(ot/1000);
lcd.print("TripTime ");
lcd.print(ot);
lcd.print(" sec.");
}
delay(2000);
reclose++;
if(reclose <= 3)
{
trip=4200000000;
for(i=5; i>0; i--)
{
lcd.clear();
lcd.print("Reclosing(");
lcd.print(reclose);
lcd.print(")");
lcd.print("After ");
lcd.print(i);
lcd.print(" sec.");
delay(1000);
}

delay(1000);
}
else
{
digitalWrite(9, HIGH);
{
lcd.clear();
if(psm_A>1 && psm_B>1 && psm_C>1 && psm_G>1)
{
lcd.print("R-Y-B-G fault");
}
else if(psm_A>1 && psm_B>1 && psm_C>1)
{
lcd.print("R-Y-B fault");
}
else if(psm_A>1 && psm_B>1 && psm_G>1)
{
lcd.print("R-Y-G fault");
}
else if(psm_B>1 && psm_C>1 && psm_G>1)
{
lcd.print("Y-B-G fault");
}
else if(psm_C>1 && psm_A>1 && psm_G>1)
{
lcd.print("B-R-G fault");
}
else if(psm_A>1 && psm_B>1)
{
lcd.print("R-Y fault");
}
else if(psm_B>1 && psm_C>1)
{
lcd.print("Y-B fault");
}
else if(psm_C>1 && psm_A>1)
{
lcd.print("B-R fault");
}
else if(psm_A>1)
{

lcd.print("R-G fault");
}
else if(psm_B>1)
{
lcd.print("Y-G fault");
}
else if(psm_C>1)
{
lcd.print("B-G fault");
}
delay(2000);
lcd.clear();
lcd.print("Feeder Tripped");
lcd.print("Permanently...");
delay(2000);
}
trip=4200000000;
reclose = 0;
}
}
else
{
lcd_time = (trip - millis());
lcd_time = round(lcd_time / 1000);
lcd.clear();
lcd.print("Overcurrent in");
if(psm_A>1)
{
lcd.print("R");
}
if(psm_B>1)
{
lcd.print("Y");
}
if(psm_C>1)
{
lcd.print("B");
}
if(psm_G>1)

{
lcd.print("G");
}
delay(2000);
lcd.clear();
lcd.print("CB will trip");
lcd.print("After ");
lcd.print(lcd_time);
lcd.print(" sec.");
delay(2000);
}
}
else
{
trip=4200000000;
reclose = 0;
lcd.clear();
lcd.print("Feeder Operating");
lcd.print("Normally");
delay(2000);
}
}
[/code]

CONCLUSION & FUTURE SCOPE
In this project, we have designed and implemented three phase feeder protection
scheme based on the numerical overcurrent relays using Arduino UNO. ACS712, 20A Hall
Effect current sensor is used to measure all three line currents. In this project three lamp
banks connected in star are used as load and also used to create the fault. Each lamp bank
has the current capacity of 5 Amps. Since Hall Effect current sensor, ACS712 used in this
project has the current capacity of 20A, all three sensors are directly connected in series
with three phase line. But, in actual feeder where line current is very high, the Hall Effect
current sensors cannot be connected directly in series with the main line. In that case
they should be connected in series with secondary of current transformer. In that case
current transformer having secondary current rating of 5A or 1A should be selected. The
burden offered by the ACS712 current sensor to secondary of current transformer is 1.2
milliohms only. So, in future for the further development, current sensors should be
connected across secondary terminals of current transformer rather than directly
connecting in series with primary for higher values of line current.

REFERENCES
 Books:-
1) Badri Ram and D.N. Vishwakarma, Power System Protection and Switchgear,
Tata McGraw-Hill, New Delhi.
2) Sunil S. Rao, Switchgear Protection and Power System, Khanna Publishers, New
Delhi.
3) Y.G. Paithankar and S.R. Bhide, Fundamentals of Power System Protection,
Prentice-Hall of India Private Limited, New Delhi.
 Datasheets:-
Datasheets of Arduino UNO, ACS712, TLP250, LCD display, 7815, 7812, 1N4007, 12V
Cube relay.
 Websites:-
1) www.arduino.cc
2) www.alldatasheets.com
Thank You

Major_project_b.tech_sem8_may_2018

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