The grid reliability tab is new for version 3.2, which will be released in late April. We accidentally shipped the version 3.2 help file with version 3.1.4. We're sorry for any confusion this caused.
You can simulate random outages in 3.1.4 with real time rates mode, but it's a little less intuitive. See this article: http://support.homerenergy.com/staff/index.php?/Knowledgebase/ViewKnowledgebase/Article/513
You can also simulate scheduled outages by clicking "Outage: prohibit grid purchases or sales" in the rate properties menu when specifying a scheduled (TOU) rate.