由於近年來電能需求增加，於系統中加入分散式電源成為未來電網發展趨勢，但分散式電源可能改變故障電流大小與方向，進而影響原有系統的保護協調；又若系統中加入故障電流限制器，雖可限制故障時的電流大小，並使保護設備正常運行，但此舉亦可能影響原有的保護機制。一旦保護協調失效，不僅擴大失電範圍、增加用戶損失，亦可能影響電網運作、損毀設備、甚而導致火災等嚴重影響。
本文旨在提出過流保護策略以避免因分散式電源與系統安裝故障電流限制器所帶來的影響。考慮到保護電驛是否可彼此相互通訊，所提出的方法可針對此兩種裝置情況而有相對應的保護措施。就具通訊功能之電驛系統而言，本文提出一以對等網路架構為基礎的過流保護策略，使具有通訊功能的數位型電驛可分享彼此的資料表、並依據表中電流、電壓等資訊計算本文所提出之故障指標，最後根據訂定之決策流程判斷各電驛的運行狀態。此策略不僅節省電驛設定前的準備工作，亦可適應系統變化，準確並迅速的隔離故障區。對於無法彼此交換資訊的電驛來說，本文則以前述故障指標為基礎另行設計一目標函數，搭配混合式GA-NLP方法優化並設定過電流電驛的參數，以確保系統安全、提升系統可靠度。
為驗證所提過流保護策略之可行性，本文利用IEEE 30-bus、IEEE 37-bus、以及既有32-bus等三個系統進行模擬分析，並考慮各系統中加入分散式電源或故障電流限制器等不同情況，以評估所提保護策略之正確性與適應性。除此之外，上述三個系統亦用於分析不同目標函數下不具通訊功能之過流保護電驛的參數最佳化，並根據結果進行評比。由模擬結果可知，本文所提出之配電系統過流保護策略不僅可透過電驛間互傳的資訊偵測故障位置，並迅速且正確的保護系統，亦能克服傳統電驛參數最佳化方法中，可能無法求得最佳解的問題；另一方面，對於可由最佳化方式尋得電驛設定之系統來說，本文設計之目標函數能在最短運算時間內獲得最佳解，相較於文獻現有方法能更有效率的完成保護系統的設計。

As the demand of power consumption increases rapidly these days, it becomes a trend to equip power systems with distributed energy resources (DERs). In addition, fault current limiters (FCLs) may also be installed in order to limit the short circuit current such that it won’t exceed the capacity of equipment. However, those mentioned above have great influence on the protective system and may lead to mis-operation of relays. Once the protective system failed to isolate the fault area, it may increase the loss of customers, damage equipment, and even cause fire. Therefore, it is important to have a robust and adaptive protective strategy to ensure the reliability and stability of a power system.
This thesis aims to present over-current protective strategies for distribution systems with DERs and FCLs. Given that some relays have communication ability and some do not, the proposed method can meet the need of both. For the former kind of relays, each of them can share and collect information of its neighbors, such as voltage, current, and whether connected with DERs. Based on the data, relays can calculate the proposed fault index, compare the results with neighbors, and determine their operating states. This strategy can not only decrease pre-work time but also adapt to system variations and isolate fault areas in a short time. As for the latter kind of relays, the calculated fault index is combined into the proposed objective function for optimizing parameters of overcurrent relays (OCRs). With the GA-NLP optimization method, three different objective functions are used for comparison.
Three distribution systems, IEEE 30-bus, IEEE 37-bus, and an existing 32-bus system, are used to verify the effectiveness of the proposed overcurrent protective strategies. Due to the DERs and FCLs installed and, therefore, the changed system configuration, various conditions are considered in simulations to ensure the correctness and adaptability of the method. Also, the same systems are used for the evaluation of different objective functions when optimizing parameters of OCRs.
Compared with the systems that can hardly find a solution for all relay settings, results show that the proposed strategy based on data transmission can save time, isolate faults quickly, and adapt to various system configurations. In addition, when a system is equipped with relays that are not able to communicate, the designed objective function can obtain the optimal value in the shortest time. Results also show that all the test systems can be well protected by the proposed method in a more efficient way, and the performance of relay settings optimization can be improved as well.

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