IEEE Power & Energy Magazine - November/December 2016 - 57

The load displacement mechanism has been
understood since Super Bowl frequency
disturbances were first observed.
Bowl while watching a live display of system frequency
measurements. A frequency jump of about 20 mHz immediately following the end of the last play of Super Bowl
XLVII (which came at 22:44:59 that year) similarly suggests that a number of television sets were switched off
nearly simultaneously. Starting about 22:50, there was a
prolonged period (about 8 min) of abnormally low frequency. This low frequency is almost certainly the result
of the concurrence of a number of household activities that
had been deferred during the game.

Super Bowl 50 (7 February 2016)
The most recent Super Bowl (called 50) produced relatively
few frequency events. Watching the Super Bowl and knowing the effect that the brightness of the TV screen has on
the EI frequency made it easy to predict how the frequency
would respond to the images on the screen during Super
Bowl 50 in 2016. For example, at 20:09 EST, a commercial
came on for the new Independence Day movie that was very
dark. Within a second or two of the commercial airing, the
frequency went up very quickly, resulting in a rise of around
31 mHz. Conversely, at 21:11 there was a commercial for
Butterfinger candy that was noticeably bright, creating a
drop in frequency of around 29 mHz.
In addition to the reactions of the grid to the bright and
dark levels on the TV sets, there was also a very distinct
slow drop-off for several minutes after the completion of
the first half of the game. This was caused by deferred load,
rather than the reaction of TV screens. Many Super Bowl
viewers got off of their couches and engaged in electricityconsuming household activities. This same phenomenon
also occurred at the end of the game. The effect of deferred
load is not as fast or precisely synchronized as the effect of
the load of the TV screens.
Sometimes the frequency event would begin just prior to
the time we observed a change in brightness. This is likely
due to people watching the game with different receiving technologies. For example, the high-definition (HD)
cable broadcast is several seconds behind the over-the-air
(antenna) broadcast. The Internet stream lagged behind the
HD cable broadcast by more than a minute. We did not have
the opportunity to view over satellite TV, so we do not know
what delay occurs over that reception method. given that the
frequency event began slightly before the brightness change
was observed on HD cable, it seems reasonable to assume
that a significant portion of TV sets were receiving the overthe-air signal.
november/december 2016

Responses of Various Video Displays
To reproduce and confirm the data collected from the field
fault recorders during the Super Bowl, the game, including the Super Bowl XLVII power outage, was replayed
through four display devices. The displays used were a
19-in CRT monitor, a 42-in liquid-crystal display (LCD),
a 56-in LCD, and a 70-in light-emitting diode (LED) display. The devices received a video graphics array input at
a resolution of 1,200 × 1,600 from a replay computer to
regenerate the images as seen during the live game. The
fault recorder measured the current draw of each display,
sampling data at 60 samples/s and using 16 points per
cycle to calculate the RMS.
The cathode ray tube (CRT) screen was not completely
dark during the dark simulation. To simulate a true dark
screen, the display was disconnected from the computer; as
a result, the current dropped to 0.21 A, a true black screen.
The results of this simulation are shown in Table 1. All
screens showed a linear relationship between the brightness of the screen and current draw for each device, with the
exception of the LED television. For the LED, the relationship between the brightness and current draw was a curved
function, but it was still a positive relationship.

Discussion of Frequency Events
Display Brightness
Changes in image brightness during widely watched television programs, such as the Super Bowl, are the cause of
many frequency events. More specifically, events occur
when such changes in image brightness persist for at least a
few seconds. The change in brightness caused by the black
screen often seen when transitioning from the game telecast
to commercials is not always long enough to cause a notable
frequency event. There are two principal reasons why the
change in brightness of the television image needs to be
more prolonged to significantly affect frequency.
table 1. AC current in amperes for displays.
Bright

Dark

19-in CRT

0.81

0.67

42-in LCD

0.84

0.79

56-in LCD

1.72

0.96

70-in LED

1.17

0.36

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