Title Page

Contents

LIST OF ABBREVIATIONS 11

Chapter 1. Introduction 13

1.1. Background 13

1.2. Significance and Necessity of Distribution system protection 19

1.3. Statement of the Problem 22

1.4. Objectives 24

1.5. Methodology 25

1.6. Thesis Outline 27

Chapter 2. Literature Review 28

2.1. Related Works 28

2.2. Summary and implications 32

Chapter 3. Mathematical Model 35

3.1. Objective Function 35

3.2. Constraints 37

3.3. Constraints enforcement function 38

Chapter 4. Research Design 40

4.1. Harris Hawks Optimization 40

4.1.1. Exploration phase 41

4.1.2. Transition from exploration to exploitation 43

4.1.3. Exploitation phase 45

4.1.4. Flowchart of Harris Hawk Optimization 52

4.2. Modified Harris Hawk Optimization 54

4.2.1. Crowding Distance Sorting 54

4.2.2. Roulette Wheel Selection 56

4.2.3. MHHO workflow 56

Chapter 5. Results and Discussion 60

5.1. Test systems for HHO 60

5.1.1. IEEE 9-Bus System 61

5.1.2. IEEE 15-Bus System 65

5.1.3. IEEE 14-Bus System 69

5.2. Test systems for MHHO 75

5.2.1. IEEE 8-Bus Network 75

5.2.2. IEEE 15-Bus Network 80

Chapter 6. Conclusions 86

Chapter 7. Future Works 88

REFERENCES 89

APPENDICES 107

요약 109

Table 3.1. Relay characteristics parameters 36

Table 5.1. HHO parameters used during simulation 60

Table 5.2. Optimum values of TDS and PS for IEEE 9-Bus system 62

Table 5.3. Comparison of HHO with other up-to-date algorithms 64

Table 5.4. Current transformer ratio for IEEE 15-Bus system 66

Table 5.5. Optimum values of TDS and PS for IEEE 15-Bus system 67

Table 5.6. Comparison of HHO with other up-to-date algorithms 69

Table 5.7. Current transformer ratio for IEEE 14-Bus system 70

Table 5.8. Optimum values of TDS and PS for IEEE 14-Bus system 72

Table 5.9. Comparison of HHO with other up-to-date algorithms 73

Table 5.10. Parameters of MHHO used for simulation 75

Table 5.11. Fault currents data and Primary-Backup Relays 76

Table 5.12. Optimum values of TDS and PS by MHHO (8-Bus network) 78

Table 5.13. Percentage of improvement by MHHO for 8-Bus network 79

Table 5.14. Optimum values of TDS and PS by MHHO (15-Bus network) 82

Table 5.15. Percentage of improvement by MHHO for 15-Bus network 84

Figure 1.1. Overview of modern power system network 13

Figure 1.2. Radial distribution system 16

Figure 1.3. Ring-main distribution system 17

Figure 1.4. Inter-connected distribution system 18

Figure 3.1. Outline of DOCR operation for an electrical network 37

Figure 4.1. Harris Hawk Optimization model 41

Figure 4.2. Escaping energy trend for two runs 45

Figure 4.3. Hard besiege scenario considering one hawk 47

Figure 4.4. Soft besiege mode of hawks with progressive rapid dives 50

Figure 4.5. The position vectors for hard besiege mode with progressive rapid dives in 2D and 3D space 52

Figure 4.6. Flowchart of HHO 53

Figure 4.7. Crowding Distance Elaboration 54

Figure 4.8. Flowchart of MHHO 59

Figure 5.1. Single-line diagram of IEEE 9-Bus system 62

Figure 5.2. Convergence characteristic of HHO for 9-Bus system 64

Figure 5.3. Single-line diagram of IEEE 15-Bus system 65

Figure 5.4. Convergence characteristic of HHO for 15-Bus system 68

Figure 5.5. Single-line diagram of IEEE 14-Bus system 71

Figure 5.6. Convergence characteristic of HHO for 14-Bus system 74

Figure 5.7. Single-line diagram of IEEE 8-Bus network 76

Figure 5.8. Algorithm-wise objective function comparison for 8-bus network 79

Figure 5.9. Single-line diagram of IEEE 15-Bus network 81

Figure 5.10. Algorithm-wise objective function comparison for 15-Bus network 84