IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE) e-ISSN: 2278-1676,p-ISSN: 2320-3331, Volume 15, Issue 1 Ser. II (Jan – Feb 2020), PP 28-41 www.iosrjournals.org DOI: 10.9790/1676-1501022841 www.iosrjournals.org 28 | Page Reliability Indices evaluation of Ring Distribution Systems without and with DG Saadia K. Mousa 1 , Moneer A Faraj 1 , Fathi K. Amoura 2 , Wafa S.Shuaieb 1 1 Electrical and Electronics Engineering Department, Omar Al-Mukhtar University, Al Baida, Libya 2 Electrical power EngineeringDepartment, Yarmouk University, Irbid, Jordan Abstract: Distribution system reliability receives more attention nowadays. This is mainly due to the wide use of electric energy in industrial, commercial and residential applications. Reliability modeling and evaluating of ring distribution systems do not receive enough attention in the literature compared to the radial distribution systems. Many types of indices have been used toevaluatethe power distribution system. This study develops equations to evaluate the reliability indices of ring distribution systems without and with Distributed Generation (DG). The impact of DG on the reliability indices are studied assuming perfect switching.The study derives equations to calculate the frequency of failure "F m ", probability of failure "P m " and average outage time of failure "U m " at load points of ring distribution system, assuming that the DG is connected to specific load points. The method has been generalized to accommodate any number of locations supplied by DGs. Furthermore, a numerical example is presented, in which the difference between the reliability indices with and without DG is calculated. Key words: Reliability Indices, Distributed Generation (DG), Ring Distribution Systems, Reliability Evaluation -------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 07-02-2020 Date of Acceptance: 22-02-2020 -------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION The reliability is the ability to generate and supply electric energy when required i.e. providing uninterrupted electrical power. Reliable power system is necessary to promote industrial growth and economic development. Assessment of customer power supply reliability is important to evaluate distribution systems operation[1, 2]. The customers’ willingness to pay for a higher level of reliability has lead to deregulation of power systems, which creates a competitive market to meet customer demands. It follows that the traditional configurations of distribution systems is changing continuously. Consequently, it is necessary to investigate reliability enhancement of distribution systems and to evaluate the benefits received from reliability upgrades. The ultimate goal is to reduce the impact caused by failures of distribution systems so that electric utilities can provide continuous and high quality electric service to customers at reasonable rates [3]. The distribution reliability indices evaluate the impact of interruptions on customers. Nowadays the developments of automatically controlled production lines, information-network services, and energy-saving technologies and the proportion of digital and electronic loads, are increasing rapidly. The trend to connect distributed generation (private generator, wind and solar units) adds new challenge to researchers to evaluate reliability indices of complicated modern systems [4, 5, 6, 7]. In the recent years, utilities are devoting great deal of efforts to improve the performance of the distribution systems and subsequently its reliability. One of these efforts is to make the maximum possible use of the distributed generation (DG), which is normally connected to the distribution system. The reliability indices will change when DG is connected to distribution systems by minimizing the chance of power interruptions, which is one of the most important issues [5, 8]. DG refers to the power generation supplied by small generating units connected to the distribution systems. DG is playing an increasing role in the electric power systems, able to feed the electrical power required in a distributed manner [9, 10]. Distribution system is a portion of a power system that delivers energy from transformation points on the transmission system to the customer. Distribution systems are designed to be efficient at peak load demand [11].