A lesson learned from recent cascading outages: Coupled interface and its impact on the smart-grid development

In this paper, we present a preliminary study on the technical causes to cascading outages. In the investigation reports on the recent blackouts, we noticed that a coupled interface structure could be problematic to mitigation and prevention of cascading outages - in almost all reports, it can be found that such structure either directly imposed negative impact on the post-contingency stability, or increased the possibility of malfunction of grid protection system. We further developed two simple examples to illustrate the possible mechanism of impact of coupled interface structure, according to the scenarios reported of the recent large-scale blackouts in India. Moreover this paper discusses some of the possible reasons for having coupled interface structures in a large-scale power grid. The implications to the development of future smart-grid also are discussed.