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Smart Grid is a new and currently developing platform in the electric power industry. Two of the major characteristics of a smart grid are: utilization of emerging/intelligent devices and improved communications. In recent years, the evolution of modern digital protection systems has been remarkable and lead to non-conventional protection schemes to be developed. However, a quantitative reliability assessment is required to measure and predict the actual performance of networks which utilize these non-conventional protection schemes. This assessment supports the decision makers when it comes to different alternative technologies. An example of such protection system is the Ground Fault Neutralizer (GFN). Instead of tripping the faulty feeder, the GFN cancels out the fault current by injection of an anti-phase current into the neutral. This interception is very fast and has no impact on the convey of payload over the faulty feeder - single phase-to-ground faults can be handled without customer outage. This paper studies the impact of the GFN protection scheme on the distribution network from a reliability point of view. The widely used reliability indices are used in this study including SAIFI, and SAIDI to measure the reliability of the network. The IEEE-RBTS is used as a reference system . The reliability of the system without implementing the GFN is predicted. Then, the reliability of the network is predicted with the GFN protection scheme implemented. The results show that the GFN protection scheme outperforms conventional more expensive and advanced systems. It is observed that the GFN reliability is an important element when it comes to the system overall reliability. Also, for the GFN to perform well, it is better to be implemented in underground cables that experience more single phase to ground faults.
Date of Conference: 17-20 Dec. 2011