I was reading around yesterday when I ran across some articles dated back around June talking about an experiment which was to be conducted over the course of a year by US power utilities.

Essentially, they were going to stop mandating that an average 60 Hz line frequency be met over a 24 hour period. It's been standard practice over the years for generating plants to run a bit fast at night because during peak load times during the day, they can experience "slowing" of their mains frequency.

Here is one article discussing it:

The AP has released an “exclusive” story concerning the nationwide “experiment” that will be conducted on the US power grid. The experiment will relieve the power providers from the duty of regulating the frequency of power on the line.
Oddly enough, I was unable to find any more recent articles on the matter. If things did indeed go on as planned, they could presumably be doing this right now.

Off the top of my head, this could affect a myriad of end user equipment such as AC motors, variable frequency drives, DC power supplies, old-fashioned clocks, fluorescent lamps, just to name a few. Obviously some would be affected more than others.

Does anyone know if this has actually been happening or is going to happen?