First, watch this incredibly educational video from the Electric Infrastructure Security Council:
Watch this threat briefing by Center for Security Policy Founder Frank Gaffney:
The Implications of a Long Term Black Out: A Presentation by the Secure the Grid Coalition
2017 Briefing-Threats to the Grid 090117(Please note that the embedded links do not work for the videos and documents in the above presentation. To view the presentation with active links, press the “Click Here” button directly below.)
To view a full PDF copy of the above briefing, 
To view a full PDF copy of Guilty Knowledge: What the U.S. Government Knows about the Vulnerability of the Electric Grid but Refuses to Fix,
To order a printed copy of Guilty Knowledge: What the U.S. Government Knows about the Vulnerability of the Electric Grid but Refuses to Fix,