CHAPTER ONE

INTRODUCTION

1.1       Background of study

Over voltage occur in a system when the system voltage rises over 110% of the nominal rated voltage. There is always a chance of having an electrical power system burnt due to abnormal over voltages. This abnormal overvoltage may be caused due to various reasons such as sudden interruption of heavy load, lightening impulses, switching impulse etc. This over voltage stresses may damage insulation of various equipment and insulators of the power system. Although, all the over voltage stresses are not strong enough to damage the insulation of a system, but still these over voltages are avoided to ensure the smooth operation of electrical power system. This constructed model helps in detecting the overvoltage and tripping the load from the mains such that the load does not suffer from any damage. The main purpose of the relay is to isolate the load from over voltage conditions by controlling the relay tripping coil with an Arduino. Generally domestic and small commercial load are protected from over current by fuse and no protection against over voltage .This project primary aims to develop an overvoltage relay using Arduino.  It uses a variable rheostat, an electronic mechanical relay and low burden electronic current sensor (ACS712), voltage sensor and also a LCD display unit.

1.2       Statement of problem

Over voltage is the main power quality issue nowadays. These can occur at any stage of the power system supply including the distribution area and at consumer’s house. The sudden over voltage might result in decline in power supply. Whenever over voltage occur,  power supply failure occur  where the main switch at the distribution board is turn off  permanently and causes damages to the domestic appliance since there is no protection circuit or device towards over voltage problem. Turning the main switch without safety verification will cause hazard to the user. Thus, the users need to call the electricity utility personnel to come and fix the problem. It costs time, while daily activities which consume mostly electricity could be interrupted. If the power failure happens while the consumers are not at home or not aware of this problem, it will disrupt the operation of electrical appliances such as refrigerator, computer, air condition, and safety devices like camera and automated gate. Thus, this project is proposed to provide additional protection to the end circuit due to over voltage difficulties.    

1.3       Motivation                                    

The idea behind this project is to protect electrical equipment from high voltage so as to avoid damage to them, with the aid of an arduino UNO, voltage sensor and relay in the circuit.  

1.4       Aim and Objective                              

            The aims and objectives of this project are to:

            i. To detect and control the relay if overvoltage occurs.       

            ii. To Protect equipment from damage.

            iii. To protect load from undesirable voltage.

            iv. To avoid equipment failure due to abnormal condition.

1.5       Methodology 

The software program for monitoring the system is arduino software and is encoded into a microcontroller arduino Uno. Hence it is the microcontroller that read input, compares the input fluctuations with the preset value. If the fluctuations are within the limit, then it  make the pin connected to the relay high, this controls the relay based on the program encoded into it .The block diagram of an arduino based overvoltage relay for protection is illustrated in the blocked diagram of fig.1.1.

                        Fig.1.1: Block diagram of an arduino based over voltage relay

The input main supply from the public utility where the device will be energized is connected directly to the relay contacts in the device which connects the load to the supply. The supply voltage is within 200V-240V AC as input to the transformer. A step down transformer is used to reduce the voltage to 12v.The rectifier converts AC to DC, the obtained dc is a pulsating dc, and a voltage regulator is used to regulate the supply for the arduino. A potentiometer is used for adjusting the amount of voltage and current. The arduino perform the functions of decision and control. The arduino monitors the input voltage for comparison with the programming sent into the microcontroller. The voltage sensor and the current sensor interfaces with the arduino to monitor the supply voltage and current, the LCD display the voltage and current value as it is being varied by a potentiometer and also display “overvoltage” if it reaches the predefined value. The relay then switches off the load from the supply.

1.6       Limitation

The relay only operates on the preset value.

1.7       Project outline

The project consists of five chapters, chapter one contain the background of study, statement of problem, motivation, aims and objectives, methodology, limitation and project outline. The literature review is explained in chapter two, chapter three deals with construction and packaging while chapter four consists of testing and result, and finally conclusion and recommendation make up chapter five.

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