Excerpt
TABLE OF CONTENTS
DEDICATION
ACKNOWLEDGEMENTS
TABLE OF CONTENTS
LIST OF FIGURES
LIST OF ABBREVIATIONS
ABSTRACT
Chapter I
INTRODUCTION
1.0. Background
1.1. Problem Statements
1.2. Objectives of Study
1.3. Scope of work
1.4. Thesis Organization
Chapter II
LITERATURE REVIEW
2.0. Details of Relevant Theory
2.1. Review of Past Work on Fault Detection Methods
Chapter III
SYSTEM DESIGN
3.0. Circuit Description
3.1. Principle of Operation
3.2. Selection of Components
3.3. System control algorithm and Simulation
Chapter IV
RESULT AND DISCUSSION
4.1. Simulation, Construction and Testing
Chapter V
CONCLUSION AND RECOMMENDATION
5.0 Summary of Main Study
5.1 Directions for Future Research
REFERENCES
APPENDIX
DEDICATION
We would like to dedicate this project principally to the Almighty God for being our inspiration and strength throughout our stay in this university. Secondly, we dedicate this work to Mr. Forson Peprah of NEDco. We are very grateful for your immense contribution to the realization our plans. Finally, we recognise our families for their love and support throughout our years in school.
ACKNOWLEDGEMENTS
We would like to acknowledge the Almighty God who has been Our Guide and Inspiration throughout this project. Secondly, we express our sincere gratitude to our supervisor, Mr. Isaac Otchere for dedicating his time to ensuring that we choose and finetune our work to achieve maximum results. We also would like to acknowledge the Head of Department of Computer and Electrical Engineering, Dr. Eric Ofosu Antwi as well as the lecturers, who have imparted us with specialized knowledge over the years. Finally, we offer our heartfelt appreciation to Mr. Forson Peprah for his unflinching contribution, support and technical advice during this project right from the planning stages to the execution. We are eternally grateful.
LIST OF FIGURES
Figure II-1: Electrical line and circuit breaker for arc fault detection
Figure II-2: Experimental Basic Diagram of a Controlled Fuse
Figure III-1:Block Diagram of Fault Detection System
Figure III-2:Circuit Diagram of Fault Detection System with Proteus
Figure III-3: A Contactor in place of a Circuit Breaker
Figure III-4: Two Channel Optocoupler relay
Figure III-5: Current Transformer
Figure III-6:20x4 Liquid Crystal Display
Figure III-7: GSM Arduino Shield
Figure III-8:Arduino-UNO-R
Figure IV-1: System Simulation with Proteus Showing Normal Current Reading
Figure IV-2: Final Construction Showing Internal Components
Figure IV-3: Working Final Construction Showing Fault Condition
LIST OF ABBREVIATIONS
GSM Global System for Mobile Communication
ROCOFF Rate of Change of Frequency
CML Customer Minutes Lost
SCL Serial Clock Line
SDA Serial Data Line
SMS Short Message Service
NEDCo Northern Energy Distribution Company
ACS712 Alternating Current Sensor 715
HIL Hardware-In-the-Loop
CT Current Transformer
EC Electric Circuit
IDE Integrated Development Environment
LV Low Voltage
ABSTRACT
In Domestic Electrical Power Systems, protection schemes are essential for the protection of equipment and lives, as well as for providing a reliable and continuous supply of energy. In this thesis, a single-phase fault protection unit for domestic loads is proposed. This proposed scheme uses intelligent components, mainly: a microcontroller, Global System for Mobile Communication (GSM), relay, current transformer, and circuit breaker to implement a smart electrical fault protection system.
The design is simulated and analyzed with the Proteus Design Suit Software and a prototype is designed and tested. The successful implementation of the smart protection system prevents damage to domestic appliances.
Keywords: Single-Phase fault detection, Fault Protection Unit, Smart Protection Unit
Chapter I
INTRODUCTION
1.0. Background
An electrical power system is an assembly of electrical components deployed to supply, transfer and use electric power. An electrical load also referred to as domestic load in a household setting, is any electrical device or portion of a circuit that consumes electric power (Wikipedia). However, the domestic load is collectively referred to as the total energy consumed by electrical appliances in household work. An electrical protective unit is a combination of electrical devices employed to protect equipment and other devices against abnormal, unreliable, and unpredictable conditions that may alter system values or cause damage to domestic equipment. Protection of domestic loads has become necessary because of the occurrence of short circuits, overloading of equipment, abnormal variations in voltage supply, etc. Failure to protect domestic loads may result in severe electric shock, fire outbreaks, loss of lives, and further damage to property. Various protection schemes have been designed to prevent and reduce these costly effects. This study introduces a new and smart way of protecting domestic loads.
1.1. Problem Statements
Domestic electrical faults cause severe damage to life and property. Over the years, numerous incidences of domestic fires have been reported across the length and breadth of this country most of which has been attributed to electrical faults. Several protective schemes have been developed over the years most of which not so budget friendly for the average Ghanaian household.
1.2. Objectives of Study
The objectives of this project are:
- To design and implement a smart single-phase protection unit that is capable of reporting faulty domestic conditions remotely via SMS.
- To implement an algorithm for smart fault detection and control system using Arduino IDE and simulate in Proteus IDE.
- To develop a prototype and test a smart fault detection and control system.
1.3. Scope of work
This project is designed to detect and report short circuit faults when they occur in a single-phase configuration for domestic loads. It makes use of a microcontroller, a contactor (in place of a circuit breaker), a GSM, a relay, current transformers, an LCD, and a load.
1.4. Thesis Organization
This section describes the main elements of the thesis. This study consists of five chapters and are elaborated on below:
- Chapter I defines key terms related to this work and introduces protection for domestic loads.
- Chapter II reviews various schemes developed for domestic load protection.
- Chapter III contains the system design and construction procedure.
- Chapter IV analyses the results and performance of the system.
- Chapter V contains the conclusion and recommendations for future work.
Chapter II
LITERATURE REVIEW
2.0. Details of Relevant Theory
Protection in electrical systems is defined as the science, skill, and art of applying and setting relays and/or fuses to provide maximum sensitivity to faults and undesirable conditions but not to avoid their operation on all permissible or tolerable conditions [1]. It is a very important aspect of electrical installations and must be done properly. The protection scheme has the function of safeguarding the system, minimizing damage and repair costs when faults occur, and ensuring the safety of users. It must also possess the following qualities:
- Selectivity: the ability to detect and isolate the faulty part only.
- Sensitivity: the ability to detect even the smallest fault and operate at its right setting before any irreparable damage is done.
- Speed: the ability to operate in a timely manner.
- Stability: the ability to ensure continuity of all healthy parts.
- Dependability: the ability to trip when the need arises.
- Security: the ability to not trip when not necessary.
The protective devices normally used in electrical and electronic devices are Fuses, Miniature Circuit Breakers (MCBs), Earth Leakage Circuit breakers (ELCBs), and Earthing or Grounding.
2.1. Review of Past Work on Fault Detection Methods
2.1.1. Household Faults
2.1.1.1. Voltage Sags and Swells
Voltage sag or dip is a short-duration reduction in RMS which can be caused by a short circuit, overload, or starting of electric motors [2]. Like electrical surges, sags and dips in electrical supply can often be attributed to devices connected to your power grid that are faulty or made with substandard materials and draw a lot of power when they are turned on.
Voltage swells are the opposite of dips and describe surges in voltage of 10% or more above normal or recommended usage. They can cause problems with appliances and overall power quality in a system. Swells can occur when a large load is turned OFF and the voltage on the power line increases for a short period of time. These affect the overall performance of various household loads such as air conditioning compressors, lighting loads, sensitive equipment like computers, etc. [3].
There are several factors that cause voltage sags or swells most of which occur at the secondary distribution line although the effect is felt by the customer. When a line-to-ground fault occurs, there will be a voltage sag until the protective switch gear operates [2]. Sudden load changes or excessive loads can cause a voltage sag [4]. Voltage sags can arrive from the utility grid, but most are caused by in-building equipment. In residential homes, voltage sags are sometimes seen when refrigerators, air-conditioners, or furnace fans start up.
2.1.1.2. Earth faults
Earth Fault is an inadvertent fault between the live conductor and the earth. When an earth fault occurs, the electrical system gets short-circuited and the short-circuit current flows through the system. The fault current returns through the earth or any electrical equipment, which damages the equipment. Such faults can cause objectionable circulating currents or may energize the housings of equipment at a dangerous voltage. It also interrupts the continuity of the supply and may cause electrical shocks to the user. To protect the equipment and for the safety of people, fault protection devices are used in the installation. Normally earth fault relays, earth leakage circuit breakers, ground fault circuit interrupters, etc. are used to restrict the fault current [5].
2.1.1.3 Arc Faults
An arcing fault is a dangerous phenomenon that is produced in the residential electrical system [6][7]. In many cases, the arcing phenomenon can produce losses, damages in the system or wire, injuries, death, or cause a fire [6]. Many approaches for detecting arcing faults have been considered for domestic applications in the following papers [8][9][10][11]. Arc faults are more difficult to detect due to domestic appliances that have a current signature [9] like the signature of an arcing fault [7][10] and in the case of the masking loads on electric lines [11].
2.1.1.4. Short Circuit Faults, Open Circuit Faults, and Overload
An open circuit fault is a type of fault that occurs because of a break in a circuit. It is a type of circuit in which there is no current flow which can occur because of wire breakage [12].
Overload faults are a result of a device doing work more than its rated capacity. When this happens, the device/machine will be drawing current more than its rated capacity which will result in a higher temperature in the device or machine and over time might cause it to overheat leading to a fire outbreak if there is no breaker in the circuit.
A short circuit is an abnormal connection between two nodes of an electric circuit intended to be at different voltages. This results in an electric current limited only by the Thevenin equivalent resistance of the rest of the network which can cause circuit damage, overheating, fire, or explosion [13]. In a short-circuited system the resistance of the circuit reduces drastically giving way for excessive current to flow in the circuit.
A short circuit is usually disastrous because of the amount of current flowing which might damage other components parts of the system and causes the temperature of the circuit to increase which can also lead to the formation of an electrical arc flash. Several protective and preventive measures have been considered and proposed over the years by several others. Amongst the several reviewed, (S. Rathor et al) presents the behaviour of a system under fault condition and directs us to the design of a circuit breaker [14]. (A. Apostolov et al) also looks at ways of Reducing the Effects of Short Circuit Faults on Sensitive Loads [15].
2.1.2. Protection Equipment
2.1.2.1 Circuit Breaker Using HIL Strategy
A Circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected [16].
Typically, a breaker contains an electromagnet through which the current flows. If that flow exceeds a set level, the electromagnet becomes sufficiently energized to throw a mechanical switch, which breaks the circuit. A circuit breaker responds faster than a fuse and can also be reset manually instead of having to be replaced [17].
The various types of circuit breakers, their advantages and specific applications are discussed in [18][19][20]. (C Franck et al) also considers an overview of (High-Voltage Direct Current Circuit breakers) HVDC CBs, to identify areas where research and development are needed [21]. According to (J. Lezama et al), this method concerns the modelling of a typical electrical home installation which includes an electrical power supply, typical loads and series and parallel arc faults. This method of household protection considered two different loads (vacuum cleaner and kettle), and an arc in series on the electrical line [22]. The comparison between these models and real electric signals was done using harmonic analysis.
Finally, an arc-fault circuit breaker was proposed using Hardware-In-the-Loop (HIL) simulation approach.
The figure below from (Lezama et al., 2012) represents the domestic electrical network composed of a power supply, electrical wires, circuit breaker arc fault circuit interrupter and different loads (vacuum cleaner, drill, PC, kettle, fluorescent lamp…etc).
Abbildung in dieser Leseprobe nicht enthalten
Figure II - 1 : Electrical line and circuit breaker for arc fault detection .
Image Source:
Lezama, J., et al. “Modeling of a Domestic Electrical Installation to ARC Fault Detection.” 2012 IEEE 58th Holm Conference on Electrical Contacts (Holm), 2019, https://doi.org/10.1109/holm.2012.6336592.
This method has the advantage of ensuring the real functioning of a numerical detection algorithm by exploiting the models of the electric system to be protected. A major challenge with this method is its inability to detect other faults aside high arcs that may result in fire outages [22].
2.1.2.2 Overcurrent Protection with Electric Fuse
An electric fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit (Wikipedia). It is made of a metal wire of strip that melts when too much current flows through it, thereby interrupting the current [23]. All fuses’ posses a reverse characteristic of pre-arcing time or current that ranges from a definite minimum current level, below which they achieve equilibrium and can operate. The characteristic curve of these fuses because of this property makes it almost impossible to adjust the curve to improve the overall performance of the fuse. This makes it difficult in some applications to obtain the proper discrimination between protection electrical apparatus within the whole range of fault currents [24].
This special method of overcurrent protection according to (A. Plesca et al), implements a new type of fuse based on the concept of controlled fusing. The necessary energy to obtain the controlled fusing effect is provided by a current transform (CT) in connection with an adaptation electric circuit.
As represented in the figure below, the switch SW1 through the main circuit breaker (CB), supplies the autotransformer (ATR) which provides an adjustable voltage on the primary side of the current source (CS). A high adjustable current can be obtained on the secondary side of this electromagnetic device to perform experimental tests for both classical fuses and new fuse (FCF). The power for the electrode of the controlled fuse, is obtained from the secondary of the auxiliary transformer (AT) through the electronic switch (SW2).
The controlled fuse has an advantage of a very low cut-off current values compared to classical fuses although this method of fuse control is suited to blade-contact-type fuses [24].
Abbildung in dieser Leseprobe nicht enthalten
Figure II - 2 : Experimental Basic Diagram of a Controlled Fuse .
Image Source:
Plesca, Adrian, et al. “Overcurrent Protection Using a New Type of Electric Fuse.” 2016 International Conference and Exposition on Electrical and Power Engineering (EPE), 2016, https://doi.org/10.1109/icepe.2016.7781321.
2.1.2.3 Smart Fault Detection Using WSN
Wireless Sensor Networks (WSNs) can be defined as a self-configured and infrastructure-less wireless networks to monitor physical or environmental conditions [25]. The wireless available technologies are Bluetooth, Wi-Fi, Wi-Max, wireless HART, Bluetooth and Zigbee [26]. Wireless sensor networks (WSN) are mainly designed for specific applications. several papers exist on the inculcation of these communication networks in electrical fault reporting.
According to (B. Uddin et al) electrical faults are detected and reported by the implementation of wireless monitoring and detection, using ACS712 Hall effect current sensors because of its better compatibility and quick response time. It makes use of the Zigbee module configured by XCTU software. The current sensors sense the current values of different loads, then the Wireless Sensor Network establishes a network between the monitoring room and the process to be monitored. This method however works for a single-phase system only [27].
According to [J.R Rana et al], voltage in the overhead line is continuously sensed using phase voltage sense sequence. When fault occurs, the voltage and current values deviate from their nominal ranges, the microcontroller analyses the type of fault then a relay connected to it operates. The GSM allows an SMS text to be sent to the one responsible in the control or monitoring room and the fault is immediately cleared. The fault clearing is done by protective devices like the relays and circuit breakers [28]. Unlike ZigBee, GSM has the advantage of a relatively wider network coverage, although a SIM card is needed for communication which comes with extra cost of communication.
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