International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 05 Issue: 09 | Sep 2018 www.irjet.net p-ISSN: 2395-0072 © 2018, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 630 Underground Three Phase Supply Fault Detection System Kumar Saurav 1 , Prakash Kumar 2 1,2 Student, Dept of Electrical Engineering, University of Petroleum and Energy Studies, Dehradun, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract:- This article is based on the concept of Ohm’s law. Any fault like Line to Ground or Line to Line occurs, the current varies, since current is directly proportional to the voltage and inversely proportional to the resistance. So voltage drop in underground cable vary depending on the length of the cable. Three phase supply line is represented by different sets of resistors and the fault in line is detected by the change in voltage level using ADC converter. The Atmega microcontroller will perform the necessary calculations to detect the type of fault in particular phase and it will display it’s location on the LCD screen. While in practical situations this concept is implemented by using a relay instead of switch for automatic tripping to detect the fault. Key Words: Ohm’s law, Underground cable, Line to Ground Fault, ADC, Microcontroller. 1. INTRODUCTION Analysis of the fault in the underground cable has always been a challenging task. With advancement in technology the conventional methods have become more efficient and other fault detection methods are also gaining popularity. Method of OHM’S law for detecting the underground cable faults is the most widely used and well-known fault detecting technique [1]. In past few decades there were many advancements had done in this method of fault detection technique, now a days, Microcontrollers can now be used to detect the faults in underground cable As India move towards the technical advancements in the field of underground cable, and detection of fault in the underground cable, it become crucial for students like us who are pursuing their B. Tech in electrical engineering to develop the efficient technique related to detect the faults in the underground cable. Major portion of this article includes design and development of the system to detect the faults in the underground cable. Design and development of the circuit was carried out at a electrical lab of the University of Petroleum and Energy Studies, Dehradun. 1.1 Types of Faults OPEN CIRCUIT FAULT:- Open circuit occurs mainly due to the break in the conductor of a cable, it is called open circuit fault. Any interruption in the circuit, such as an open switch, a break in the wiring, or a component such as a resistor that has changed its resistance to an extremely high value will cause current to cease [2]. The EMF will still be present, but voltages and currents around the circuit will have changed or ceased altogether SHORT CIRCUIT FAULT:- When two conductors of a multi-core cable come in electrical contact with each other due to insulation failure, it is called as short circuit fault. A short circuit is simply a low resistance connection between the two conductors supplying electrical power to any circuit [3]. This results in excessive current flow in the power source through the 'short,' and may even cause the power source to be destroyed. GROUND FAULT When the conductor of a cable comes in contact with the earth, it is called as earth fault or ground fault. A ground fault is a inadvertent contact between an energized conductor and ground or equipment frame [4]. The return path of the fault current is through the grounding system and any personnel or equipment that becomes part of that system. Ground faults are frequently the result of insulation breakdown 1.2 Fault Detection Methodology The AC source 230V/50Hz is step down using step down transformer. The step down AC source is rectified by the diode bridge rectifier to get ripple DC voltage, and further with the help of a capacitor we will able to get a pure DC. Further the 9V DC voltage is reduced to 5V using voltage regulator LM7805. The ripple free 5V DC voltage is fed to the microcontroller and also distributed where it is required all over the circuit. This fault detection technique is based on the concept of Ohm’s law. Any fault like Line to Ground or Line to Line occurs, the current varies, since current is directly proportional to the voltage and inversely proportional to the resistance. So voltage drop in underground cable vary depending upon the length of the cable [5] and the change in voltage level is detected by ADC converter. So ADC analog voltage data is converted to digital form and it will fed to the microcontroller to perform the necessary calculations to detect the faults in phase and its location. Hence it will display on the LCD screen.