October 13, 2017, Andy Greenberg from Wired Magazine wrote an article: “Hacking a Power Grid in Three (Not So Easy Steps)”. The gist of the article was that it would take a significant amount of work and even then it would be difficult to “turn off the power”. However, I don’t believe it would be as difficult as the Wired article suggests.
NERC issued the draft guideline “Forced Oscillation Monitoring and Mitigation”, dated June 2017. The report states that simulation studies show that if a forced oscillation interacts with a system mode that has weak damping, it can lead to wide-area resonant oscillations of large amplitude that can lead to potential blackouts such as the August 10, 1996 blackout in the Western Interconnection. The sustained presence of significant forced oscillations on the Bulk Power System could lead to long-term effects such as equipment fatigue and potential damage to rotor shafts exposed to such sustained, high magnitude oscillations. Power quality may also be a concern depending on the amplitude and frequency of the forced oscillations.