INTERNATIONAL JOURNAL of RENEWABLE ENERGY RESEARCH M. Ahmed Dawoud et al., Vol. 10, No. 4, December, 2020 A Proposed Passive Islanding Detection Approach for Improving Protection Systems Mohamed Ahmed Dawoud*‡, Doaa Khalil Ibrahim*, Mahmoud Ibrahim Gilany*, Aboul’fotouh El'Garably** *Department of Electrical Power Engineering, Faculty of Engineering, Cairo University, Giza, Egypt. **Department of Electrical Power & Machines, The High Institute of Engineering at El-Shorouk City, Cairo, Egypt. (en_dawoud_91@yahoo.com, doaakhalil73@gmail.com , drgilany@gmail.com and a.abdelreheem@sha.edu.eg) ‡ Corresponding Author; Mohamed Ahmed Dawoud, Department of Electrical Power Engineering, Faculty of Engineering, Cairo University, Giza, Egypt, Tel: +96551653108, en_dawoud_91@yahoo.com Received: 22.10.2020 Accepted: 23.11.2020 Abstract— Nowadays, distributed generation (DG) is commonly used in networks. In spite of the numerous benefits of DG units in these networks, several challenges are introduced such as unintentional islanding, reverse power flow, protection concerns, etc. In this paper, a new passive islanding detection approach is proposed depends on the production of voltage sequence components at every relay location not only at the DG point of common coupling. The proposed approach uses only one threshold value for all relays in the distribution network. The performance of the proposed approach is not influenced by changes in type, capacity or location of DG. The proposed approach is evaluated under different transient conditions such as capacitor switching, load switching and DG switching. Also, the performance of the suggested islanding approach has been compared with most prevalent islanding detection techniques. The performance of the proposed algorithm is stable during balanced and unbalanced conditions. Moreover, detecting the islanding case at all relays provides the ability to improve the protective relays performance by updating the protection setting for all relays based on local measurement only without the need for fault current limiters (FCLs) or a communication network. The proposed approach is evaluated using the Canadian distribution system embedded with DG units in MATLAB/Simulink simulation. The achieved results demonstrate that the proposed approach is robust during all non-islanding events. Also, it succeeds to detect islanding condition with high confidence without non detection zone (NDZ). Keywords: Distributed generator, local measurements, microgrid, non detection zone, passive islanding detection, protection system, and voltage sequence components. 1. Introduction Distributed generation (DG) would offer reliable, quality and efficient supply to consumers. However, great challenges arise to the existing conventional protection schemes as a result of integrating DG units into the distribution network [1]. To maintain the continuity of service in case of main utility outage, the critical loads are fed by the DG units, and the islanded mode is formed [2]. Islanding cases can be divided into intentional or unintentional. The scheduled maintenance to the main grid is considered intentional islanding, while the occurrence of faults or other uncertainties at any time in the power system is described by unintentional islanding. In fact, islanding detection is considered an important mission for integrated power distribution networks, so standards of UL 1741 and IEEE 1547 explain both planned and unplanned power islanding, DG interconnection and other considerations for correct operation [3]. Unintentional islanding is considered a hazard to power system security that may possibly injury the maintenance workers and damage utility operations, and equipment. During islanding case, the DG units may not be able to contribute sufficient fault current to activate the traditional protection relays and consequently islanding operation may destroy the system equipment, affect power system reliability and threaten the maintenance worker’s life. Therefore, islanding in power distribution networks is considered an actual challenge for protection engineers. Furthermore, in the event of unintentional islanding, overload conditions may occur because of the suspended utility operation, which significantly affects the frequency and voltage levels of DG units. Moreover, as DG incorporation rises, the necessity for unintentional islanding detection will be more substantial and challenging [4]. Different techniques are discussed in the literature for