1. Introduction

The modern power system has become a highly complex network, due to the integration of a large number of generating sources and large transmission and distribution networks. The above-stated reasons will affect the reliability of the smart grid. The main requirement of the power system is to provide electricity for a wide range of consumers with various requirements. It is not possible to serve the consumers continuously due to the random failures of equipment in the power system network. This causes the consumers' service interruptions frequently irrespective of the planned maintenance. It affects the reliability of power supply at the consumer bus and smart grid as well. Therefore the power engineers must consider the term "reliability" at the level of designing and planning of the power system network or smart grid. Reliability is the general quality of the system and defined as "It is an ability of the system to perform a desired function within a specified period of time under stated conditions" [1].

In view of above-mentioned reasons, there is a need for complete reliability assessment of the present power system. The evaluation of reliability plays an important role in power system analysis, design, upgrades and operations, especially in bulk power system. Power system reliability assessment methods have been developed over the years, and many publications are available on this subject [1–8].
