Improving directional decision algorithm of directional protective devices based on fault current analysis of distribution system with distributed generation
Improving directional decision algorithm of directional protective devices based on fault current analysis of distribution system with distributed generation
- 주제(키워드) 보호협조 , 방향판단 알고리즘 , 동기기 기반 분산형 전원 , 인버터 기반 분산형 전원
- 발행기관 아주대학교
- 지도교수 정재성
- 발행년도 2019
- 학위수여년월 2019. 8
- 학위명 석사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000029057
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
The integration of DG (Distributed Generation) into distribution system brings several advantages in aspect of economic, environment, and grid operation. On the other hand, it causes several protection coordination problems. This is because the integration of DG changes the power flow of distribution system from uni-direction to bi-direction. Furthermore, it is because different reverse fault current from DG sides is contributed according to the type of interconnection transformer and DG. Therefore, conventional protection scheme cannot be applied for protection coordination of distribution system with DG. Thus, directional decision algorithm is operated for protection coordination of distribution system with DG. However, the algorithm cannot determine directional decision when zero-sequence voltage is very low during ground fault. This may happen problems such as sympathetic tripping or blinding of protection. To prevent the problems, the algorithm should be improved so that directional decision is made without zero-sequence voltage when the voltage is comparatively low during ground fault. First of all, this thesis investigates the reverse fault current contributed toward fault location according to the type of interconnection transformer and DG. For this, the methodology to calculate the fault current according to the type of transformer and DG is introduced. Using the methodology, the fault current contribution from each transformer and DG is analyzed separately to eliminate the mixed contribution from both transformer and DG. Furthermore, the mixed fault current contribution from the different combination of transformer and DG is analyzed. Based on the fault current contribution analysis, the thesis introduces improved algorithm to determine correct directional decision without zero-sequence voltage during ground fault. For this, the existing algorithm and its problem are investigated. The reliability evaluation of the algorithm is performed based on real distribution system with Inverter-Based Distributed Generation (IBDG) happened sympathetic tripping and blinding of protection. Furthermore, in the real distribution system, the characteristic of fault current contributed toward directional protective device is analyzed. Based on the analysis, the improved algorithm is introduced. Finally, it is verified that the introduce algorithm can determine correct directional decision although zero-sequence voltage is lower than the threshold value.
more목차
Abstract i
Table of Contents iii
List of Tables v
List of Figures vi
I. Introduction 1
II. The methodology for the fault current analysis by the integration of DG 5
II.A. Sequence network model by the type of transformer 5
II.B. Sequence network model by the type of DG 7
II.C. The methodology for the fault current analysis by the integration of DG 9
III. The reverse fault current contribution by the type of transformer 16
III.A. The reverse fault current contribution by D-Yg transformer 18
III.B. The reverse fault current contribution by Yg-Yg transformer 20
III.C. The reverse fault current contribution by Yg-D transformer 21
IV. The reverse fault current contribution by the type of DG 23
IV.A. The reverse fault current contribution by SBDG 24
IV.B. The reverse fault current contribution by IBDG 25
V. The reverse fault current contribution by the type of transformer and DG 29
V.A. The reverse fault current contribution by SBDG and different type of transformer 30
V.B. The reverse fault current contribution by IBDG and different type of transformer 33
VI. The Existing DOCGR Algorithm Based on Zero-Sequence Component and Its Threshold 39
VI.A. Maximum Torque Angle 39
VI.B. Directional decision algorithm during phase fault 41
VI.C. Directional decision algorithm during ground fault 43
VI.D. Existing directional decision algorithm 44
VI.E. The problem of protection coordination according to the threshold value 45
VII. The Reliability Verification of Protection Coordination Based on Existing Directional Decision Algorithm 47
VII.A. Out-of-section SLGF in distribution system with DG 48
VII.B. SLGF between substation and DG 51
VIII. The Reliability Verification of Improved Directional Decision Algorithm 54
VIII.A. Improved directional decision algorithm 54
VIII.B. The reliability verification of Improved directional decision algorithm 59
IX. Conclusion 64
References 66
