UNIVERSITI TEKNOLOGI MALAYSIANOTES : * If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the letter from the organisation with period and reasons for confidentiality or restriction. PSZ 19:16 (Pind. 1/07) DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT Author’s full name : MUHAMMAD FAISAL HASSAN BIN ISMAIL Date of birth : DICEMBER 9 th 1989 Title : AUTOMATIC RECLOSE EARTH LEAKAGE CIRCUIT BREAKER Academic Session : 2011/2012 I declare that this thesis is classified as: I acknowledged that Universiti Teknologi Malaysia reserves the right as follows: 1. The thesis is the property of Universiti Teknologi Malaysia. 2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose of research only. 3. The Library has the right to make copies of the thesis for academic exchange. Certified by: SIGNATURE SIGNATURE OF SUPERVISOR 891209-14-5625 DR. MOHD FADLI BIN RAHMAT (NEW IC NO. /PASSPORT NO.) NAME OF SUPERVISOR Date: 20 th JUNE 2012 Date: 20 th JUNE 2012 CONFIDENTIAL (Contains confidential information under the Official Secret Act 1972)* RESTRICTED (Contains restricted information as specified by the organization where research was done)* OPEN ACCESS I agree that my thesis to be published as online open access (full text) AUTOMATIC RECLOSE EARTH LEAKAGE CIRCUIT BREAKER MUHAMMAD FAISAL HASSAN BIN ISMAIL A report submitted in partial fulfillment of the requirements for the award of the degree of Bachelor of Engineering (Electrical) Faculty of Electrical Engineering Universiti Teknologi Malaysia JUNE 2012 ii “I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in terms of scope and quality for the award of the degree of Bachelor of Engineering (Electrical)” Signature : ............................................ Name of Supervisor : DR. MOHD FADLI BIN RAHMAT Date : 20 th JUNE 2012 iii “I declare that this thesis entitled “Automatic Reclose Earth Leakage Circuit Breaker” is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.” Signature : .................................................... Name : MUHAMMAD FAISAL HASSAN BIN ISMAIL Date : 20 th JUNE 2012 iv Specially dedicated to my beloved mother, father, brothers, sisters, to others who encouraged and helped, and who inspired me throughout my journey of education v ACKNOWLEDGMENT Alhamdulillah. Thanks to the Almighty Allah S.W.T, for His blessings and guidance for giving me inspiration and strengths to complete this project with good health until the last day of the project report has been submitted. First and foremost, I would like to express my appreciation to my supervisor, Dr. Fadli Bin Rahmat who has helped me a lot in giving me ideas, opinions and valuable comment in the making of this project. I am deeply grateful to have him as my supervisor and also my mentor. His guidance and supervision will help me in the future life. Last but not least, thanks to everyone who involved directly or indirectly in completing this project either opinion, advice or support from the beginning of the project until its completion. Thank You So Much vi ABSTRACT Earth Leakage Circuit Breaker (ELCB) is a protective device that used to isolate the faulty area from power supply when fault current occurred. For home appliance, ELCB are used to protect the user from electrical shock that caused by fault current by disconnecting the power supply. The fault current can occur due to lightning or short circuit from line to ground when someone accidently touches the energized part of the circuit. Therefore ELCB are designed to trip and isolate this fault fast enough to prevent the lethal shock. But, the current ELCB that are implemented at home cannot turn on automatically and need to turn on manually. Therefore the idea to create an automatic reclose device for ELCB come from this problem and the design to overcome this problem has been developed. This thesis will present the development of automatic reclose device for ELCB that will differentiate between permanent fault current and temporary fault current. vii ABSTRAK Alat Pemutus Litar Bocor ke Bumi (PLBK) adalah salah satu alat perlindungan yang digunakan untuk memisahkan kawasan kesilapan daripada sumber bekalan kuasa apabila kesilapan arus berlaku. PLBK yang digunakan untuk aplikasi kediaman melindungi pengguna daripada kejutan elektrik yang disebabkan oleh kesilapan arus dengan memutuskan bekalan kuasa. Kesilapan arus boleh berlaku disebabkan oleh kilat atau litar pintas daripada wayar hidup ke bumi apabila seseorang menyentuh litar aktif secara tidak sengaja. Oleh itu, PLBK direka untuk terbelantik dan memisahkan kesilapan ini sepantas yang boleh demi menghalang kejutan yang boleh membawa maut. Tetapi, PLBK yang ada sekarang tidak boleh dihidupkan secara automatik dan perlu dihidupkan secara manual. Idea untuk mencipta alat penghidup automatik datang daripada masalah ini dan rekaan untuk mengatasi masalah ini telah pun dibangunkan. Tesis ini akan membentangkan tentang pembangunan alat penghidup automatik untuk PLBK yang voleh membezakan kesilapan arus kekal dan kesilapan arus sementara. viii TABLE OF CONTENTS CHAPTER TITLE PAGE I II SUPERVISOR’S DECLARATION AUTHOR’S DECLARATION DEDICATION ACKNOWLEDGEMENT ABSTRACT ABSTRAK TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS LIST OF APPENDICES INTRODUCTION 1.1 Background of Study 1.2 Research Objectives 1.3 Research Scope 1.4 Report Outline LITERATURE REVIEW 2.1 Introduction ii iii iv v vi vii viii xi xii xv xvi 1 2 3 4 5 ix III IV 2.2 Circuit Protection Device 2.2.1 Fuses 2.2.2 Transducer 2.2.3 Relays 2.2.4 Circuit Breaker 2.2.4.1 Oil Circuit Breaker 2.2.4.2 Air Blast Circuit Breaker 2.2.4.3 Vacuum Circuit Breaker 2.3 Earth Circuit Leakage Breaker 2.3.1 Voltage Operated Circuit Breaker 2.3.2 Current Operated Circuit Breaker 2.4 ELCB Construction 2.5 Electrical Fault 2.6 Previous Project METHODOLOGY 3.1 RC Servo Motor 3.1.1 Servo Power 3.1.2 Servo Speed 3.1.3 Servo Torque 3.1.4 Servo Wire Connection 3.2 Device Component 3.2.1 PIC Micro Controller 18F4550 3.2.2 Voltage Regulator LM7805 3.2.3 Crystal Oscillator 3.3 Hardware Development CIRCUIT OPERATION AND DISCUSSION 4.1 Introduction 4.2 Project Flow 4.3 Circuit Design 7 7 8 10 11 12 12 13 14 15 17 18 20 22 23 26 26 27 27 29 29 32 33 34 35 36 37 x V REFERENCE APPENDIXES 4.4 Micro Controller PIC 18F4550 Operation 4.4.1 PIC Programming 4.4.2 Pulse Width Modulation 4.5 Circuit Operation 4.6 Result 4.7 Discussion CONCLUSION AND RECOMMENDATION 5.1 Conclusion 5.2 Recommendation 38 38 41 42 44 45 46 47 48 51 xi LIST OF TABLES xii LIST OF FIGURES FIGURE TITLE PAGE 2.1 Fuse 7 2.2 Typical Fuse Derating Curve 8 2.3 Current Transformer 9 2.4 Voltage Transormer 9 2.5 Electronic Overcurrent Relay 10 2.6 Circuit Breaker 11 2.7 Oil Circuit Breaker 12 2.8 Air Blast Circuit Breaker 13 2.9 Vacuum Circuit Breaker 14 2.10 Earth Leakage Circuit Breaker 14 2.11 2.12 2.13 2.14 TT Earthing System Voltage Operated ELCB Earth Leakage Using An Electrode Current Operated ELCB 15 16 16 18 xiii 2.15 ELCB Schematic Diagram 18 2.16 ELCB is Taken Core Balanced Operated Method With an Amplifier 20 3.1 Servo Motor 24 3.2 Servo Component and Servo Internal Part 24 3.3 PWM Waveform 25 3.4 Servo Speed 26 3.5 Servo Torque 27 3.6 Servo Connection 28 3.7 Servo Wire Code 28 3.8 PIC 30 3.9 Interface Using MPLAB IDE 30 3.10 PIC 18F4550 31 3.11 Voltage Regulator LM7805 32 3.12 Voltage Regulator Schematic Diagram 32 3.13 Schematic Diagram 33 3.14 Typical Capacitor Value 33 3.15 Flow Chart Of the Overall Project Implement 34 4.1 Circuit Operation Block Diagram 36 4.2 4.3 Circuit Design PWM Input Signal 37 42 xiv 4.4 4.5 Operation Flow Hardware Design 43 44 xv LIST OF ABBREVIATIONS TNB - Tenaga Nasional Berhad ELCB - Earth Leakage Circuit breaker PIC - Peripheral Interface Controller RCD - Residual Current Device DC - Direct Current AC - Alternating Current V - Voltage RC - Radio Control IC - Integrated circuit S - Signal PWM - Pulse Width Modulation ms - Mili seconds oz - ounces lbs - pound MCU - Microcontroller Unit MHz - Mega Hertz gnd - ground - - - - - - - xvi LIST OF APPENDICES APPENDIX TITLE A B C RC Servo C36R User‟s Manual PIC 18F4550 Data Sheet Why Electronic not Electromechanical ELCB 1 CHAPTER I INTRODUCTION 1.1 Background of Study Tenaga Nasional Berhad (TNB) has stated that each premise and building needs to equip with over current protection device for the safety. In Malaysia, Earth Leakage Circuit Breaker (ELCB) was used widely as the protection device for current fault. ELCB is one of the important electrical devices to protect the load when temporarily damage or permanent earth leakage occurred that would lead to the short circuit [1]. Earth Leakage Circuit Breaker is an electrical device that can detect the unbalanced current between the live conductor and neutral conductor hence disconnect the circuit [2]. ELCB one of the protective device in electrical power system that help to prevent electric shock to human. If there were any current leakage to the earth from any electrical device, it will cut off the supply off to the house [2]. 2 The „blackout‟ or the cut off electrical supply for such a long time will cause a trouble for electrical users. It becomes even worse when the users are away or not at home for a long time. This will caused to the problem of the damage of food in the refrigerator or the death of fish in an aquarium and malfunction of security alarm. These are the reasons why it is so important to have the automatic reclosed ELCB implemented in our home. Without automatic reclosed ELCB in our market nowadays have give, the negative effect to the users especially in the industrial sector which electricity is the life for their business. Therefore, the continuously electrical supplies are important to make sure that our daily routine do not disturb. The aim of this project is to design and develop a unit of auto reclosed ELCB that can differentiate and act differently with different types of fault. The ELCB will trip if current fault occurred. There are two types of fault. Temporarily fault and permanent fault. Temporarily fault is caused by lightning strike and the ELCB will close back automatically after 60 seconds. Permanent fault are caused by short circuit to the ground by electric device or human. The ELCB close the switch automatically two times and then stop the operation. This will indicates the permanent error had been detected. Therefore, the fault needs to repair first before the ELCB will close again [3]. 1.2 Research Objectives The first objective of this project is to study and understanding the operation of automatic reclosed with Earth Leakage Circuit Breaker (ELCB). The function of automatic reclosed is to pull up the ELCB switch during tripping to close the circuit. 3 The second objective is to design and build a driver for auto reclosed ELCB. The driver was built by the electronic component that will function to pull up the ELCB switch automatically. To achieve this objective, servo motor and mechanical concept is used. The last objective is to minimize the electrical disturbance due to the ELCB tripping. Electrical disturbance is one of the problems that commonly occurred at residential area. By implementing the automatic reclosed ELCB at our home, the electrical disturbance can be minimizing. 1.3 Research Scope The scope of this project is to design a circuit as simple as possible that can be implemented at home. To achieve that, the used of smaller and cheaper component are needed to reduce space and cost but highly safety. The driver must be small enough to put at a small place and does not need too much space. The project we focused on ELCB that will implemented at single-phase home user, which used 240 V input voltage and have the current rating 60 ampere. The servo motor used must be strong enough to pulled up the ELCB switch. To pull up the ELCB switch, it must have the pulled force of 3kg and pull stroke about 20 mm. 4 1.4 Report Outline Chapter I will explain about the early process before begin the project. It includes the project background, research objectives, scope of project and thesis outline. Project background is about ELCB and the problem related to it. Research objectives are the target to resolve the problem. Scopes of project are the limitation of problem to solve. Chapter II will explain about the literature review. The explanation are about the protective device that used in the power system, types of circuit breaker, types of ELCB and the types of fault current occurred. The function of ELCB was also explained in detail. Chapter III will discuss about the methodology that are used to solve the problem. The explanations are including the types of component used to solve the problem, their function in detail and the operation of the component to achieve the research objective. Chapter IV will explain about the development of automatic reclose device. The explanations include the operation of the circuit design, the function of servo motor and how the PIC will control the entire device operation. This chapter also discuss about the result obtain and the problem that encountered during the making of device. Chapter V will explain about the conclusion that had been made from the result obtain. Also the recommendation on future research to produce a perfect automatic reclose device for ELCB at home. 5 CHAPTER II LITERATURE REVIEW 2.1 Introduction Safety and protection is the important aspect in our life. There are so many ways to protect ourselves from danger. In other way, we might know the danger that will come to us but we do not have the ability to fell the presence of electricity and the danger that we will encountered. This is because electric current are fast and flow like a surge. We are lucky because there is a regulation nowadays that was made to ensure the safety in using electricity [11-13]. Based on IEEE Standard Dictionary of Electrical and Electronic Terms, fourth edition, the definition of „protection system‟ is The electric and mechanical devices and circuitry, from sensors of the process variable to the actuation device input terminal, involves in generating those signals associated with the protective function [18]. Meanwhile, „protective function‟ gives the meaning of The sensing of one or more variables associated with a particular generating station condition, the signal processing, and the initiation and completion of the protective action at values of the variables established in the design bases [18]. Furthermore, the definition of 6 „protective action‟ is the initiation of the operation of a sufficient number of actuators to affect a protective function [18]. The function of protective equipment is to cause prompt removal from service of any network element which suffering from abnormal manner that may cause damage to electrical installation. Abnormal manner is a condition when an event occurs that causes the operation of any system component to exceed its normal operating limits. The protection system is another engineering system designed not to prevent faults but to respond to their occurrence and minimized their effects [13-18]. There are so many method and technique created to protect user from electricity danger. These protective electrical systems are available in variety shape from fuse until circuit breaker. Circuit breaker that are commonly used can isolate the load system from damaged that might be happened. So far, circuit breaker are widely used and become the solution in electrical protective system [12]. It should realise that protective equipment can minimize [13]: - 1. The cost of repairing the damage 2. The speed of fault to other equipment causing damage from overheating and abnormal mechanical forces. 3. The time equipment is out of service. 4. The loss in revenue. 7 2.2 Circuit Protection Device Circuit protection device are used to protect wires and connectors from being damaged by excessive current flow caused by over current or short circuit. The examples of circuit protective devices are fuses, fuse elements, fusible link, and circuit breaker. There are available in variety of types, shapes, and specific current rating [10]. 2.2.1 Fuses Figure 2.1: Fuse Fuse is a type of low resistance resistor that functions to provide over current protection for load or source circuit. A fuse also a combination of protective device and circuit breaker. It is the most common protection device and places in an electrical circuit. The fuse will blows out when the current flow exceeds its rating. The excessive current will be due to short circuit, overloading mismatched loads or device failure [13]. 8 Figure 2.2: Typical Fuse Derating Curve The fuse element will melt, opening the circuit and preventing other component of the circuit from being damaged by the over current. The excessive current will caused excessive heat. This excessive heat will melt the fuse element. The rating of the fuse will be determined by the size of the metal element. Fuses are protective device that only can be used once. After blown, they need to be replaced. Figure 2.2 showed the typical derating curve for fuse that used to determine the fuse rating [7]. 2.2.2 Transducer The current transformer (CT) will reduced the high magnitude primary current to values suitable for relay operation. CT essentials to insulate the secondary (relay) circuit from the primary (power) circuit and provide currents in secondary, which are proportional to those in the primary. The primary winding of CT carries the actual power system current, which is connected to the load [13]. 9 Figure 2.3: Current transformer In case of high voltage system, it is not possible to connect the voltage coil of the protective device directly to the system. Therefore, it is necessary to step down the voltage and insulate the protective equipment from the primary circuit. This can be achieved by using voltage transformer or which is similar to a power transformer [13]. Figure 2.4: Voltage transformer 10 2.2.3 Relays Relay is a protective device that functions to isolate a faulty section with the least interruption to service by controlling the circuit breaker when fault occurred. Therefore, the relay must be able to detect and to measure abnormal condition and close the contacts in the tripping circuit [13]. Figure 2.5: Electronic Overcurrent Relay Overcurrent relay will operates when its current exceeds a predetermined value. It can be instantaneous and not inherently directional. Differential relay is intended to respond to the difference between incoming and outgoing electrical quantities associated with the protective apparatus. Directional relay responds to the relatives phase position of current with respect to another current [18]. 11 2.2.4 Circuit Breaker Figure 2.6: Circuit Breaker Circuit breaker is an electrical switch that operated automatically to protect electric circuit from damage caused by overload or short circuit. It function is to detect a fault condition and disconnect the current flow immediately. Unlike fuse, circuit breaker can be reset to resume the normal operation. Circuit breaker is available in variety size from small size for domestic appliances up to large switchgear to protect high voltage circuit. A circuit breaker has two contacts, a fixed contact, and a moving contact. Under normal condition, these two contacts remain in closed position. When the circuit breaker is required to isolate the faulty part, the moving contact moves to disrupt the circuit [4]. 12 2.2.4.1 Oil Circuit Breaker Commonly used for voltages up to 300 kV, oil circuit breaker was designed in two types, dead-tank, and live-tank. The steel tank in dead-tank breaker is partly filled with fluid. On the top of the tank, there are mounted porcelain bushings to provide insulation from line voltage to the ground tank. The bushing also permits the connection of the high-voltage element to the breaker element submerged in the oil [18]. Figure 2.7: Oil Circuit Breaker 2.2.4.2 Air blast circuit breaker Air blast circuit breaker is suitable for high current interruption at low voltage. Air at atmospheric pressure is used as an arc-extinguishing medium. It occupy to pairs of contact, main contact and arcing contact. The main contact carries 13 current when the breaker is closed. It will separate first when the contact is opened while the arching contact remains closed. The current then shifted to the arching contact from the main contact. The arching contact separate later and the arc are drawn between them [13-15]. Figure 2.8: Air Blast Circuit Breaker 2.2.4.3 Vacuum Circuit Breaker Vacuum circuit breaker is very simple and compact that power required to close and open its contact is much less compare to other breaker. Without producing excessive transient overvoltage, it is capable of interrupting capacitive and small inductive current. The advantages of vacuum circuit breaker are like suitable for repeated operation, least maintenance, silent operation, long life, high speed of dielectric recovery, and less weight of moving part [13-14]. 14 Figure 2.9: Vacuum Circuit Breaker 2.3 Earth Leakage Circuit Breaker An Earth Leakage Circuit Breaker (ELCB) is a device used to detect current leaking to earth from electrical installation and cut the power supply. It will detect fault current from live to the earth (ground) wire within the installation it protects. It also will switch off the power if sufficient voltage appears across the ELCB‟s sense coil and remain off until manually reset. The purpose of ELCB is to prevent humans and animal to get injury from electric shock [1-2]. Figure 2.10: Earth Leakage Circuit Breaker 15 ELCB were mainly used on TT earthing system. Most ELCB nowadays are replaced by Residual Current Device (RCD) especially in the new construction [3]. The first design ELCB only responded to sine wave fault current, but not to rectified fault current. Disadvantages of ELCB over RCD are they are less sensitive to fault condition therefore having fewer nuisance trips [6-8]. Figure 2.11: TT Earthing System 2.3.1 Voltage Operated ELCB Introduced in the early 20th century, voltage operated ELCB have provided a major advanced in safety for main electrical supplies with inadequate earth impendence. It detects the increasing in potential between the protected interconnected metalwork and a distant isolated earth reference electrode. ELCB also has a second terminal for connecting to the ground. This terminal was connected to the earth rod that passes through the ELCB by connecting to its two earth terminals. One terminal goes to the earth wire and the other terminal goes to other type earth connection. [6] 16 The voltage operated ELCB cannot be used anymore because it lack of compatible and efficiency. The installation of voltage operated ELCB was very difficult, which the electrode must be cultivated far away from other metal that will reduce the efficiency of ELCB to react [6-7]. Figure 2.12: Voltage Operated ELCB Figure 2.13: Earth Leakage Using an Electrode 17 This system commonly used in a places, which grounding is very high but earth loop impedance value should not more than 5 ohms (for housing). The leakage current will flow into the coil in operation and continued to E1, when there is leakage current between the conductor and the earth in the voltage exceeds 45V. The operating coil will become a complete circuit and draw switch breaker circuit to the position “off” and disconnect the supply. A direct connection with the resistance R will be created when the test switch is pressed. Switch test is used to test the circuit breaker still operated or not. To ensure the operation of this circuit is always in a state of good or efficient, this test should be performed monthly [4-6]. 2.3.2 Current Operated ELCB Commonly called Residual Current Device (RCD), current operated circuit breaker will disconnect a circuit whenever it detects than the electric current is not balanced between the energized conductor and the return neutral conductor [6-8]. This imbalanced indicate that someone has accidently touching the live part of the circuit and the current leakage through this body, which is grounded. The result of these conditions is the lethal shock. This device was designed to disconnect quickly enough to prevent injury caused by the shock. Current operated ELCB also can disconnect the circuit when there is over current due to lightning strike and short circuit conditions [7]. In normal condition, the current flow in the neutral and live conductor is same. Therefore, no flux will produce. However, if there is the leakage current to the earth, the current will flow through earth coil and not flow through the neutral conductor. Flux will produce and the voltage in the secondary coil will triggered a signal to cut off this electrical system [11-12]. 18 Figure 2.14: Current Operated ELCB 2.4 ELCB Construction Figure 2.15: ELCB Schematic Diagram 19 Electrical appliance and device are manufactured using different material. Some of these substances are good material and some are good conductor of electricity. This is the reason many types of ELCB were invented. Nowadays, most of the ELCB available at home are the „core balanced‟ type [4]. A „toroid‟ (wire wound around an iron ring) has the Active & Neutral conductors passing through the centre of it. If the current in one wire does not match the current in the other, a secondary current (the toroid is a current transformer & not a voltage transformer) is produced at the terminals of the toroid, which is then used to activate the trip mechanism. ELCB are generally available for two wire, three wire, & four-wire system in arrange of tripping current and tripping speed. For home application, there will be either two wires or four-wire system [9]. (a) 20 (b) Figure 2.16: (a) and (b) ELCB is taken core balanced operating method with an amplifier The vector quantity of the current flowing in each phase becomes Ia + Ib + Ic = 0 if there is no leakage of electricity in the equipment and no voltage will be induced in the secondary winding of the zero phase current transformer (same result even when the current of each phase is not in balanced). However, if the ground fault occurred due to the failure of insulation of the equipment and circuit, vector quantity of the current will be Ia + Ib + Ic = Ig, thus including a voltage equivalent to Ig in the secondary winding of the ZCT. This voltage is very small that it cannot trip the ELCB directly. Therefore, it will feed to the amplifier, excites the shunt trip coil, and activates the ELCB [6]. 2.5 Electrical Fault The abnormal situation in electrical system in which the current may or may not flow through intended part. Equipment failure also attribute to some defect in the circuit, for example are loose connection, insulation failure, or short circuit. A fault 21 which current flow bypasses the normal load is called short circuit fault. An open circuit fault occurs if a circuit is interrupted by some failure [13]. The fault current that occurs in power system is usually large and dangerous. The short circuit fault are the commonest and most damaging since the excessive current will cause thermal and mechanical damaging to the plant carrying it. The occurrence of fault cannot be prevented because of aging, human error and external interference [13]. Faults can damage or disrupt power systems in several ways [13-15]:- 1. Large faults current will cause overheating of power system component. 2. The extremely high temperature in arc due to short circuits will aphorized any known substances, causing equipment destruction. 3. The system voltage can be lowered or raised outside their acceptable ranges. 4. Three-phase system can become unbalanced thus causing three phases to operate improperly. 5. Faults block the flow of power 6. Faults can cause the system to become unstable and „break up‟ 22 2.6 Previous Project For previous project, the researcher had made a research about the force that is needed pulled the ELCB switch. These devices have to convert from high AC voltage to low DC voltage, very costly and inefficient due to battery supply. He successfully completed the project and creates the automatic reclosed ELCB but this device will continuously on the ELCB after tripping [9-10]. The second researcher had improved the device by adding one timer, therefore will operate to switch the ELCB based on times only. If the ELCB tripped more than two times, a permanent fault is assumed to be occurred. Although the device had been improved, the device still needs to convert the high AC voltage to low DC voltage [11]. The third researcher also creates the automatic reclosing ELCB that the device will switch on the ELCB two times after tripping and manage to reduced his project cost by using battery as the main supply. Nevertheless, the ac input voltage still used as input supply for motor. In his design, relay and counter are used to enable the circuit to operate two times. The designed used AC motor 240 V and counter with 9 V voltage supply. This device probably will harmed the circuit if lightning current flow through main supply [12]. The designed that are used before used counter that will count two times the number of tripping. Relay are used as switch for circuit which in normal condition, the relay will prevent the supply connected to the circuit completely. In tripping condition, transistor will received the signal from counter to operate the motor and switch on the ELCB [9-12]. 23 CHAPTER III METHODOLOGY 3.1 RC Servo motor [26] Radio Control (RC) servo motor are a small actuators that designed for remotely operating model vehicle like cars and airplanes. Nowadays, RC servo motors are very popular with robotic design because of its ability to rotate and maintain at certain position, location or angle. These movements can be control by pulses from only a single wire. Inside this small box of RC servo motor contain of small motor, gearbox, a potentiometer and electronic circuit. A potentiometer is used to measure the position of output gear, while the electronic circuit control the motor to the desired position with specific gear change. Servo motors have three wires that connect to power wire (V+), ground wire (V-), ad signal wire (S). The power wire is in red colour typically and connected to the supply 5 volts. The ground wire is in brown colour and connected to the ground point at the circuit. The signal wire is in orange colour and connected to the signal pin at microcontroller PIC. The signal wire will received Pulse Width Modulation (PWM) signal from external controller circuit. 24 Figure 3.1: Servo Motor The servo controller is the external electronic device that control RC Servo by generates and sending pulse width modulation signal (PWM). The electronic part inside the servo will translate this PWM signal into position values and instructed the servo to move. The PWM signal was converted to electrical resistance value and powered on the DC motor. The rotation of motor also makes the potentiometer to rotate and produce the electrical resistance. This electrical resistance value then sent back to the servo electronic until the potentiometer value matches the position value translated from PWM signal. (a) (b) Figure 3.2: (a) Servo Component (b) Servo Internal Part 25 The “neutral” position of the servo is the position when pulse width signal (PWM) of approximately 1.5 ms (1500 µs). Neutral is defined as a point when the amount of potential rotation of counter clockwise and amount of potential of clockwise are exactly the same. The servo moves some number of degrees counter clockwise from the neutral when the pulse signal (PWM) sent to servo is less than 1.5 ms. The servo also moves some number of degree clockwise from the neutral point when the pulse is greater than 1.5 ms. For servo motor the maximum pulse input will be 2.0 ms, the minimum pulse input will be 1.0 ms and the stop movement (neutral) at 1.5 ms. Figure 3.3: PWM Waveform 26 3.1.1 Servo Power Servo power is a term that defined as the amount of DC voltage needed to operate a servo without damage. RC servo motor commonly run on 5 volts DC but they often work with voltages between 4.5 – 6.0 volts with the current range from 200 mA to 1 Amp. Servo motor tends to be faster and stronger at higher voltage but can heat up faster when stalled or in a hold position with stress forces against the servo output shaft. 3.1.2 Servo Speed Servo speed is a term that defined as the amount of time ( in seconds ) that a servo arm attached to the servo output shaft will move from 0 to 60 degrees. The lower the time (seconds) the faster the servo can move an attached wheel or arm. For example a servo rated at 0.20 seconds/ 60 degrees takes 0.20 seconds to sweep through a 60 degrees arc. But the faster the servo may results in lower of torque available. Figure 3.4: Servo Speed 27 3.1.3 Servo Torque Servo torque is a term that defined as ounce-inch (or oz-in) force in ounces times inches. It is the total push or pulls power a servo can apply on one servo arm when moving. Servo torque is measured by the amount of weight (in ounces) that a servo can hold at 1-inch out on the servo output arm in the horizontal plane. Figure 3.5: Servo Torque 3.1.4 Servo Wire Connection There are three connections for RC servo motor, VCC, grounding and signal. The colour for each wire is different depends on their type. 28 Figure 3.6: Servo Connection Figure 3.7: Servo Wire Code 29 3.2 Device Components There are several components that used as a driver for automatic reclose Earth Leakage Circuit Breaker (ELCB). The components choose for these projects are: a) RS Servo Motor C36R b) PIC Microcontroller 18F4550 c) Voltage Regulator 7805 d) Crystal e) Basic switch f) Resistor g) capacitor h) Battery 12 V 3.2.1 PIC Microcontroller 18F4550 [23-24] Nowadays, almost all modern devices used embedded microcontroller that can be programmed to perform any number of task. There are many types of application that used the number of different types of microcontroller. The easiest and the most popular microcontroller used for such task oriented applications are the 8-bit PIC 18F4550 microcontroller from Microchip. The PIC 18 family of MCUs (Microcontroller Unit) with a maximum clock speed of 40 MHz and 128 Kb of Flash memories are some of the fastest and most feature loaded 8-bit PIC on the market. 30 Figure 3.8: PIC These PIC are small enough for embedded application but powerful enough to allow a lot of freedom and complexity in design process. The centralized interface between the programmer and the device is allowed by using MPLAB Integrated Development Environment (MPLAB IDE). For low cost real time debugging of all PIC, the MPLAB ICD 2 In-Circuit is the most powerful and cost efficient tools. Figure 3.9: Interface using MPLAB IDE 31 One of the typical PIC 18F4550 feature-loaded is every I/O pin are connected to an internal peripheral device. The other feature including 8 and 16 bit timer modules with various feature, master synchronous serial port modules, capture/compare/PWM module, 10 bits analogue to digital converter, universal synchronous receiver and transmitter and many more. Interestingly, all of these feature can be turn on and off in the program code. Figure 3.10: PIC 18F4550 Some special feature include 100,000 erase/write cycle Enhanced Flash program memory typical, 1,000,000 erase/write cycle data EEPROM memory typical and the Flash/Data EEPROM Retention can last for more than 40 years. One of the application that used PIC 18F4550 is to control the servo motor. With a simple programming using MPLAB IDE, the servo motor can easily control to move at desired position. 32 3.2.2 Voltage Regulator LM7805 [19] Voltage regulator is one of the DC-DC Converter that converts the DC voltage of input supply into the desired DC voltage. It usually has three legs and converts the varying input voltage and produces a constant regulated output voltage. The family of 78XX voltage regulators are designed for positive input. Figure 3.11 Voltage Regulators LM7805 The LM7805 can hold current up to 1 Amp and the input leg can hold the voltage up to 36 VDC. The capacitor is recommended to put parallel between an output leg and common leg for maximum voltage regulation. Basically, 0.1mF was used to eliminate any high frequency AC voltage that will combine with output voltage. For LM7805 voltage regulator, the output voltage should be 5 VDC. Figure 3.12: Voltage Regulator Schematic diagram 33 3.2.3 Crystal Oscillator [20,22] Crystal oscillator is the combination of Micro Controller Unit (MCU) internal circuitry for the needed in microcontroller clock frequency. Crystal oscillator is used to provide a separate clock source that is compliant with both USB low speed and full speed specification. This is due to the unique requirement from USB module to produce a stable clock source. Figure 3.13: Schematic Diagram Figure 3.14: Typical Capacitor Value 34 3.3 Hardware Development Figure 3.15: Flow chart of the overall project implementation Literature Review Proposal Implementation & Testing Methodology Design Discussion & Conclusion END 35 CHAPTER IV CIRCUIT OPERATION & RESULT 4.1 Introduction The aim of this project is to build a driver to pull up the ELCB switch automatically without using human help. To achieve that, servo motor was used as a mechanical power to pull up the ELCB switch. Servo motor was controlled by PIC microcontroller that will send a signal to servo motor based on programming fixed. The shaft of servo motor will rotate and pull up the ELCB switch and return back the supply. Micro controller PIC 18F4550 is the device that control the entire operation of the circuit. The sensor will detect the condition of ELCB whether it is trip or not and send signal to the PIC. PIC will afterwards send PWM signal to servo motor and make it rotate based on the ELCB condition 36 4.2 Project Flow Figure 4.1: Circuit Operation Block Diagram ELCB DC VOLTAGE SUPPLY 5V SENSOR 1 SENSOR 2 SERVO MOTOR PIC 18F4550 37 4.3 Circuit Design Figure 4.2: Circuit Design ISIS POFESSIONAL is software that used to design the circuit. There are four main components that used in the design. There are servo motor, micro controller PIC 18F4550, sensor and crystal oscillator. The entire component characteristic had been discussed in the previous chapter. The type of sensor that are used in this project are basic switch that function to give a signal to Micro controller PIC based on the condition of ELCB. 38 4.4 Micro controller PIC 18F4550 Operation As mention before, PIC 18F4550 is the brain of the device hat control the entire operation. PIC was function when a certain programming was debugging into the PIC chip. The programming using the C language contains the instruction for the operation of servo motor. The programming can be done by using MPLAB IDE software. 4.4.1 PIC Programming This is the programming language or instruction to the servo motor to operate. //========================================================================== // include //========================================================================== #include <p18f4520.h> // this sample code is using 18F4520 !! #include "delays.h" #include "usart.h" // configuration //========================================================================== #pragma config OSC = HS // HS oscillator #pragma config FCMEN = OFF // Fail-Safe Clock Monitor disabled #pragma config IESO = OFF // Oscillator Switchover mode disabled #pragma config PWRT = OFF // PWRT disabled #pragma config BOREN = OFF // Brown-out Reset disabled in hardware and software #pragma config WDT = OFF // WDT disabled (control is placed on the SWDTEN bit) #pragma config MCLRE = ON // MCLR pin enabled; RE3 input pin disabled #pragma config PBADEN = OFF // PORTB<4:0> pins are configured as digital I/O on Reset 39 #pragma config CCP2MX = PORTC // CCP2 input/output is multiplexed with RC1 #pragma config LVP = OFF // Single-Supply ICSP disabled #pragma config XINST = OFF // Extended Instruction Set // define //========================================================================== #define servo LATBbits.LATB1 #define sw1 PORTBbits.RB6 #define sw2 PORTBbits.RB7 #define MHZ *1000L /* number of kHz in a MHz */ #define KHZ *1 /* number of kHz in a kHz */ #define DelayUs(x) { unsigned char _dcnt; \ _dcnt = (((x)*(20MHZ))/(24MHZ))|1; \ while(--_dcnt != 0) \ continue; \ _dcnt = (((x)* (20MHZ))/(24MHZ))|1; \ while(--_dcnt != 0) \ continue; } //===========================Sub function==================================================== void delay(unsigned long data) //delay function, the delay time { //depend on the given value for( ;data>0;data-=1); } void DelayMs(unsigned char y) { unsigned char i; do { i = 4; do { DelayUs(250); } while(--i); } while(--y); } //============================main function============================================= void main(void) { unsigned int loop; 40 TRISB = 0b11000000; //servo motor is RB1 PORTB = 0b00000000; //clear port B if(sw1==1) { for(loop=0;loop<50;loop++) { servo=1; DelayMs(3); DelayUs(250); DelayUs(250); DelayUs(250); servo=0; DelayMs(16); DelayUs(250); } } // _ _ _ // | | | | | | // | | | | | | // | |_________________| |________________| |____________________ // 0.7ms 19ms 0.7ms 19ms 0.7ms 19ms // | | // |<-------20ms------>| else if(sw2==1) { for(loop=0;loop<50;loop++) { servo=1; DelayUs(100); servo=0; DelayMs(19); DelayUs(250); DelayUs(250); DelayUs(250); DelayUs(150); } } 41 else { servo=0; } } 4.4.2 Pulse Width Modulation Pulse Width Modulation is the signal waveform which PIC sent to servo motor as the instructor for servo motor to move. PIC will generate this square waveform from the programming that already set into it. The controller circuit in the servo motor will read this waveform and translate it in term of the motion by motor and gearbox. Servo motor that used in this project is the type that can rotate 180º. This waveform will determine the rotation of servo motor shaft. To pull up the ELCB switch, the motor shaft needs to rotate counter clockwise 180º. The pulse length needs to set at 0.1 ms to make the motor shaft rotate counter clockwise. Then, the motor shaft need to turn back to its initial position. Therefore the motor shaft needs to rotate 180º clockwise. The pulse length needs to set at 1.25 ms so that motor shaft will rotate clockwise. 42 Figure 4.3: PWM Input Signal 4.5 Circuit Operation At normal condition, servo was set at standby mode. There are two sensors that were putted at ELCB switch. Sensor 1 was put at the bottom of the ELCB switch and sensor 2 at the top. These sensors were in the type of basic switch that connected to the PIC. When tripping occurred due to short circuit, sensor 1 will detect the tripping. When tripping occurred, ELCB switch will push the sensor 1 and send the signal to the microcontroller PIC 18F4550.PIC will generate PWM signal waveform and send the signal to the servo motor. The controller circuit in the servo motor will read the PWM signal and translate it in the form of motor movement. 43 The movement of the motor make the gearbox, feedback potentiometer and motor drive shaft also move. Feedback potentiometer was function to give a resistance to the motor. The resistance of feedback potentiometer is corresponding to the angle that had been set from translated PWM waveform signal. The motor shaft will rotate counter clockwise 180º and at the same time pulled up the ELCB switch. When the rotation had reach 180º, the feedback potentiometer will give a resistance and stop the motor movement. When the ELCB switch had fully pulled up, the ELCB will on and return back the power supply. Sensor 2 will detect it and send the signal to the PIC. PIC will generate PWM signal waveform and send the signal to servo motor. The controller circuit will read the signal and translate it in the form of motor movement. The motor shaft will rotate clockwise 180º at return back to its initial position. This is to make sure if the tripping occurred again, the servo shaft will not prevent the ELCB to trip. Figure 4.4: Operation Flow ELCB TRIP Sensor 1 detect the tripping and send signal to PIC PIC will generates PWM impulse signal to the servo motor Servo motor received the signal and rotate counterclockwise The rotation will be 180º and pulled up the ELCB switch When the ELCB switch had fully on, sensor 2 will detect it and send signal to PIC PIC will generates PWM impulse signal to the servo motor. Servo motor received the signal and rotate counterclockwise The rotation will be 180º and back to its initial position. 44 4.6 Result Figure 4.5: Hardware Device The hardware was successfully develop and functioning well to pull up the ELCB switch. If the tripping occurred and the ELCB switch is pulled up once and return back the power supply, assumption can be made that the fault occurred is temporary type. The fault maybe due to the lightning. If the tripping occurred and the ELCB switch is pulled up but tripping occurred again, the motor will stop its movement. This is because the PIC was set to stop the motor if sensor 2 was push twice. An assumption can be made that the permanent fault type had been occurred. 45 4.7 Discussion The automatic reclose device was successfully performing their duty to pull up the ELCB switch but there are still some problem that need to be considered. One of the problems encountered in this project is about the PIC programming itself. The programming was set to perform the motor movement and rotate to the desired position. But the motor only moves for the next action after the reset button was push. That‟s mean the operation was not continuous. Therefore some changing need to be done to the programming so that the motor can perform a continuous action without pushing the reset button. In this project, the motor was set to stop their operation if the tripping occurs two times subsequently. That incident happened maybe due to short circuit current. But we need to considered if the lightning occurred two times or more that make the ELCB trip twice and the motor stop their operation because of it mistaken it with permanent fault current. 46 CHAPTER V CONCLUSION & RECOMMENDATION 5.1 Conclusion ELCB is one of the protective devices that will isolate the load from electrical supply if fault current occurred. ELCB was widely used and can operate efficiently and effectively. Nevertheless, there is no mechanism to turn on the ELCB automatically for home appliance. Therefore, this research was conducted to study and understanding the operation and mechanism of automatic reclose device with Earth Leakage Circuit Breaker. The function of auto reclose device is to pull up the ELCB switch after tripping and return back the power supply. Then, the device was successfully design and develop and functioning well to pull up the ELCB switch. 47 5.2 Recommendation The automatic reclose device was functioning well to pull up the ELCB switch but there are some feature that should be added to make it perfect Therefore further research need to be conducted to create a design that can be commercialize for house appliance. These are some recommendation that should be consider for future work. Firstly, the servo motor needs to change to the type that can rotate 360º. In this project, the servo motor used only can rotate 180º. Thus two sensors are needed to make the servo rotate to pull up the ELCB switch and return back to its initial position. By using 360 º rotation servos, only one sensor is needed. In this project, power supply for servo motor and PIC driver comes from adapter. In commercial design, we need to use the rechargeable battery as a power source. We also need to put the converter to recharge the battery from the ac input source. This to make sure the continuous input source for the driver. The most important things are to make the smaller and cheaper driver. Smaller are the important aspect in commercial design because it easier for the user to buy it from electrical shop. Cheaper also important because user prefer the electrical device that high in quality and low price. Lastly, the design should be creative and small enough so that user will just buy it and put it at the ELCB like plug and play. This is more convenient for home appliance and definitely highly safety. 48 REFERENCE 1. 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Shenzhen Jinghua Crystal Electronic, Crystal Oscillator, http://jinghuajingying.com/en/news_show.asp?id=80 21. Geoff Trudgen (July 2009),IC Crystal Oscillator Circuit, www.rakon.com (UK Ltd) 22. Intel Application Note AP-155, Oscillator for Microcontrollers, 1983 23. Microchip Technology Inc. (2007), PIC 18F2455/2550/4455/4550 Data Sheet. 24. Michael Aeberhard, 8-Bit PIC 18 Microcontroller Units, A Technology Review. Not Publish. 25 Bradley E. Bishop, Jenelle Armstrong Piepmeier, George Piper, Kenneth A. Knowles, Kinleong Ho, Bryan Hudock. The Use of LOW-Cost RC Servos in a Robotics Curriculum 26 Blue Point Engineering (2007), Servomotor Information, pdf. 51 APPENDIX A 64 APPENDIX B 70 APPENDIX C