Over-current Protective Strategies for Distribution System with Distributed Energy Resources and Fault Current Limiters

Abstract

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

Date of Award	2015 Aug 10
Original language	English
Supervisor	Hong-Tzer Yang (Supervisor)