The distribution grids are among the most critical infrastructures which integrates advanced control and communication technologies atop of power systems. This paper presents a comprehensive modeling framework suited to study the resiliency and dependability of the next generation distribution grid. It focuses on revealing insight in the complex interaction and dependencies between the ICT based control system and the powergrid. It looks into the role of automation and new technologies in future distribution grids. The objective is through a quantitative assessment to identify vulnerabilities and to study alternative design principles and architecture of the automated distribution grids. The modeling framework is general and modular based on a stochastic activity networks using the Mobius tool. For illustration, a case study is included at the end.

An extensive use of ICT is a key feature in the development of next generation smart grids. The ability of the ICT system to meet the real time requirements of the powers system, even when it is degraded due to failures, is essential. This simultaneous study of dependability (reliability) and performance are referred to as performability.This paper presents a method for a performability study on ICT support system of smart grid. It looks into how performance associated properties (timing failures) can be modelled together with properties affecting dependability such as omission or conventional component failures. A two tier model using ns-3 and SAN is developed to study the peformability of an IEC 61850 based communication infrastructure for a protection application. For illustration, a simulation is conducted to study the reliability and unavailability of an IEC 61850 based communication architecture, where the impact of both timing failures and omission failures are investigated and compared. The result revealed that the availability and reliability is highly dependent on the requirements for the protection application, maximum delay per packet and maximum number of consecutive delayed packets the protection application can tolerate. It also shows that timing failures have a higher impact than omission failures for a protection application with shorter time requirement.

The future smart distribution grid will be consisting of new components and technologies with enhanced capability whose failure behaviour can not be determined with certainty. In studying the reliability of these distribution grids, it is important to look into various possible failure semantics of the new components and how would they possibly affect the reliability of the distribution grid. This paper aims to investigate/study how the various failure modes of the new components affect the reliability of distribution grids. The focus is on (limited to) reliability evaluation of the feeder protection function of next generation distribution grids considering omission and value type failure semantics. A generic and modular modeling framework based on a stochastic activity networks is used to model the distribution grid. An IEC61850 based automation/substation communication network (SCN) is considered. And, for illustration, different scenarios with different SCN architectures are investigated.

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