Description
ABSTRACT
Distribution networks are inherently radial and passive owing to the ease of operation and unidirectional power flow. Proper installation of Distributed Generators, on the one hand, makes the utility network active and mitigates certain power quality issues e.g., voltage dips, frequency deviations, losses, etc., but on the other hand, it disturbs the optimal coordination among existing protection devices e.g., over-current relays. In order to maintain the desired selectivity level, such that the primary and backup relays are synchronized against different contingencies, it necessitates design of intelligent and promising protection schemes to distinguish between the upstream and downstream power flows. This research proposes exploiting phase angle jump, an overlooked voltage sag parameter, to add directional element to digital over-current relays with inverse time characteristics. The decision on the direction of current is made on the basis of polarity of phase angle jump together with the impedance angle of the system. The proposed scheme at first is evaluated on a test system in a simulated environment under symmetrical and unsymmetrical faults and, secondly, as a proof of the concept, it is verified in real-time on a laboratory setup using a Power Hardware-in- loop (PHIL) system. Moreover, a comparative analysis is made with other state-of-the-art techniques to evaluate the performance and robustness of the proposed approach.
TABLE OF CONTENTS
COVER PAGE
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE PROJECT
- PROBLEM STATEMENT
- AIM AND OBJECTIVE OF THE STUDY
- SCOPE OF THE STUDY
- MOTIVATION OF THE STUDY
- SIGNIFICANCE OF THE STUDY
CHAPTER TWO
LITERATURE REVIEW
- OVERVIEW OF THE STUDY
- DISTRIBUTION SYSTEM PLANNING
- REVIEW OF RELATED WORKS
- OVERCURRENT PROTECTION
- PROTECTION COORDINATION METHODS IN A DISTRIBUTION NETWORK
- REVIEW OF SUBSTATION
- COMPONENTS OF 3*300KVA, 11/0.415KV DISTRIBUTION SUBSTATION
CHAPTER THREE
3.0 METHODOLOGY
- STEPS IN IMPLENTING THE DESIGN OF 3x300KVA ,11/0.415KV SUBSTATION
- DESIGN CONSIDERATIONS
CHAPTER FOUR
4.1 RESULTS AND DISCUSSIONS
CHAPTER FIVE
5.1 CONCLUSION
5.2 RECOMMENDATION
REFERENCES
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Industrial revolution 4.0 has brought a broad scope of installing intelligent and autonomous devices to upgrade the existing system to remain robust against abnormal conditions. Abnormalities include abrupt changes into the network characteristics due to different contingencies i.e., increased loading, frequent interruptions, sustained faults, etc. (Ukil et al., 2016). The traditional utility networks, being radial and passive are highly exposed to external disturbances but maintain their safety and security using conventional protection devices. Such protection devices lose their selectivity, to operate at the time of event for systems having intermittent power sources e.g., Distributed Generations (DGs) due to the bi-directional power flows (Juan et al., 2018). In order to upgrade the existing protection schemes, two strategies are available, (1) changing internal settings of relays online and (2) adding directional element. However, exploiting directional element is a feasible option to ensure optimal operation and coordination of protection devices under faulty conditions (Łukasz et al., 2016).
With inception of faults, the network experiences voltage sag and the Sensitive Equipment (SE) may trip if its value is higher than the immunity level [6]. The parameters characterizing the voltage sag are its magnitude, duration and phase angle jump. The magnitude of voltage sag depends upon the type of fault and impedance of the network while its duration and phase angle jump rely on the fault clearing time and total X/R ratio of the network, respectively (Chen et al., 2016). However, installed DGs are expected to support system’s voltage during sag conditions caused by prevailing contingencies (Katyara et al., 2021). However, when a fault occurs on the feeder, with DG installed between the fault point and protective devices, the relay senses a reduced fault current due to high fault impedance. Making installed protection scheme more sensitive is also not a desirable effect because it results into sympathetic and false tripping of relays even for transient events or faults occurring near the adjacent networks (Jennet et al., 2021).
Time coordination among relays (blue, green and red) with dedicated protection zones is shown by associated characteristics curves providing primary and backup functionalities.
To avoid false tripping and maintain standard Coordination Time Interval (CTI) be- tween the primary and backup relays, for effective protection coordination, two parameters i.e., Pick Current (IP) and Time Multiplier Setting (TMS) of over-current relays need to be designed according to the network conditions (Anthony et al., 2015). The backup protection has an important role in coordination scheme as the level of current seen by it is always assumed to be in their forward operating zone otherwise should not be activated. However, the primary relays are designed to operate for forward as well as for reverse directions to discriminate between the upstream and downstream fault currents (Katyara, et al., 2015). To estimate fault direction while ensuring coordination among network relays, lead-lag angle between phase voltage and current is used as directional variable (Horak et al., 2016). We, in this research, following a similar idea, used phase angle jump approach instead. The intuition states that when the impedance angle is positive and phase angle jump is retarding, the direction is forward and if impedance angle is negative and phase angle jump is progressing then its reverse.
1.2 PROBLEM STATEMENT
Most often when efforts are made to increase power generation and expand transmission systems, the power still does not get to the end users as expected. Disruption and technical losses abound. Both the supply authority and its customers suffer the socio-economic challenges, the only thing I think can be done is to critically look into our methods and of designing our substations. The importance of having a standard distribution network cannot be over emphasized as most of inhabitants in our society cannot even afford personal generator but rather depend on government supply of electricity in Nigeria (Srivastava et al., 2016).
This issue of incorrect design of distribution network has caused so many people to look for alternate source of electricity power supply such as the so called “I-better pass my neighbor” which has been polluting our environment with exhausted fumes which is so dangerous and unfriendly to our lives, even this alternate source of electricity is being used in universities and other organizations. Nevertheless, since they need to carry out their day-day activities to fend for their needs, they cannot be banned. Painfully, anyone who cannot afford all these sorts of alternate sources of supply of electricity will unavoidably live in total black out and wallow in darkness, which is very common in Nigeria today (Srivastava et al., 2016).
Now, the only solution and option available for us is to start checking each part that contribute to our stages of supply of electricity step by step where the correct design of distribution network plays a very paramount role hence it cannot be looked down upon.
The aim of this project is to study how to have an effective electrical distribution network planning with emphasis on feeder protection and coordination.
Objectives of the project
Hence this project intends to:
- Improve electric power distribution network
- Recommend ways to reduce the rate at which electricity interruption occur in distribution network
- Prescribe solutions to minimize overloading and losses along the distribution
- Ensure optimal operation and coordination of protection devices under faulty conditions
The scope of this work covers studying effective electrical distribution network planning methods, making emphasis on feeder protection and coordination.
To ensure an effective electric power distribution to consumers by making proper planning without violating voltage and frequency deviation and to make sure there is a high reliability in power supply according to the international standard.
1.6 SIGNIFICANCE OF THE STUDY
This study will help to improve efficiency and allow future demand. This study will be of great benefit to all electrical students and electrical engineers by exposing them on how to substation are been made.
5. RECOMMENDATION AND CONCLUSION
Design is defined as a road map, strategic approach for achieving a unique expectation in creating an object, system, network which defines the specifications, parameters, values, cost, activities, processes “how and what ” to do within legal, political, social and environmental safety and economic constraints in achieving the goals or objectives (Oyeleye ,2015).It therefore be concluded that the objectives and the aim of this research work were met satisfactory according to the guideline
Firstly, the transformer sizing was carried out using the load estimation method. Through the design and construction of 3X300kVA sub-station transformers, the little available supply can be enjoyed by the consumers. More so, loss of consumers’ properties can be reduced. 3X300kVA, 11/0.415kVkV can be designed as a relief substation also, since relief sub-station gives a good quality of power supply, and also guarantee the life span of equipment such as transformer. Moreover, it saves life because when the conductors are overloaded, it is prone to sagging which can lead to conductor snap causing electrocution. Losses of power is also reduced which is uneconomical. Good quality supply of electricity improves cash collection of the utility company, also reduces loss of customers properties due to power surge and erratic power supply.
Hence, at the end of this research report the designer of the electricity project with the transformer rating of 3X300kVA will be guided a lot by this report and as such costly mistake of selecting wrong size of cable and type, feeder pillar, bus bar etc. which will as well lead to a reliable power supply, avoidance of costly maintenance of the project because, the constructor will accurately be guided by this report.
In order to achieve high operational performance of 11/0.415 kV substation, the followings are recommended:
- transformer should be design to operate at 60% loading without future expansion consideration,
- adequate substation future expansion should be put into consideration,
- transforms should not be designed to operate at 100% loading (previous loading), and
- derating factor should be considered to avoid cable
- this work can be applied to substation
