The electrical power grid has been described as the largest machine in the world. Although we customarily assume our electrical outlets provide a steady sinusoidal voltage with a frequency of 60 Hz (in North America), the variations from that ideal are easy to observe using the methods described in this article. These frequency variations are important since, as can be shown with introductory-level physics concepts, they arise when power generation and usage are not balanced on the electrical grid. The challenge of balancing the electrical grid will increase over the coming years as we adopt more sustainable but less predictable energy sources, and this connection to one of our current societal challenges makes this project interesting to students.
REFERENCES
1.
Mihai
Sanduleac
, “
Energy storage needs for clean power systems and the potential support from electrical vehicles: A simplified assessment on Romanian case
,” in 10th International Conference and Exposition on Electrical and Power Engineering
(
EPE
, 2018
), pp. 458
–464
.2.
Bahman
Zohuri
and
Patrick
McDaniel
, Introduction to Energy Essentials
(
Academic Press
,
London
, 2021
), p.228
.3.
Paul
Breeze
, Power System Energy Storage Technologies
(
Academic Press
,
London
, 2018
), p. 15
.4.
Loren
Lockwood
, “
Answer to question #68. 60.000 Hz? synchronization of the power grid
,” Am. J. Phys.
68
(8
), 690
–691
(2000
).5.
Hong
Chen
, Power Grid Operation in a Market Environment
(
IEEE Press
,
Piscataway, NJ
, 2017
), pp. 4
–10
.6.
Mohamed A.
El-Sharkawi
, Electric Energy: An Introduction
, 3rd ed. (
CRC Press
,
Boca Raton, FL
, 2013
), p. 530
.7.
Angelo
Baggini
, Handbook of Power Quality
(
John Wiley & Sons
,
West Sussex
, 2018
), p. 6
.8.
“
Balancing and frequency control – A technical document prepared by the NERC resources subcommitee
,” January 26, 2011, North American Electrical Reliability Corporation, available at <https://www.nerc.com/docs/oc/rs/NERC%20Balancing%20and%20Frequency%20Control%20040520111.pdf>9.
Specified in the North American Energy Standards Board document WEQBPS-004 available at <https://www.naesb.org/pdf2/weq_bklet_011505_tec_mc.pdf>.
10.
Capacity Factors for Utility Scale Generators Primarily Using Non-Fossil Fuels <https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_6_07_b>.
11.
Capacity Factors for Utility Scale Generators Primarily Using-Fossil Fuels <https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_6_07_a >.
12.
The FNET web site is < http://fnetpublic.utk.edu>.
13.
Joseph E.
Fleckenstein
, Three-Phase Electrical Power
(
CRC Press
,
Boca Raton, FL
, 2013
), pp. 66
–72
.14.
Tony R.
Kuphaldt
, Lessons in Electric Circuits
, Volume
II – AC
, 6th ed. (
Koros Press
,
London
, 2012
), pp. 283
–296
, available online at <https://www.ibiblio.org/kuphaldt/electricCircuits/AC/AC.pdf>.15.
This derivation follows that in
John J.
Grainger
and
William D.
Stevenson
, Jr.
, Power System Analysis
, 1st ed. (
McGraw-Hill
,
New York
, 1994
), pp. 699
–701
.16.
There are many suitable examples of these GPS units, commonly using one of the u-blox NEO series of chips. They can be coupled with the required external antenna for a total price of approximately $20.
17.
The 5V PowerBRICK from digilentinc.com provides both +5 V and −5 V from a PC's USB port and is priced under $15.
18.
Digilent BASYS 3, under $120 after academic discount.
19.
The FPGA source files, bitstream file, and a Windows application to collect the data sent to the host PC over the computer's serial connection are available for download at <https://sites.google.com/georgiasouthern.edu/wbaird/home/power-quality>.
20.
Jonathan E.
Hardis
,
Blair
Fonville
, and
Demetrios
Matsakis
, “
Time and frequency from electrical power lines
,” in Proceedings of the 48th Annual Precise Time and Time Interval Systems and Applications Meeting
,
Monterey
,
California
, January (2017
), pp. 372
–386
.21.
In the US, residences and small businesses are typically served by one of three phases (sine wave) with an amplitude of approximately 340 V. The secondary side of the distribution transformer is center-tapped and center-referenced to ground, so that the common NEMA 5 outlet has a potential of 120 Vrms between the phase and neutral.
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2021
Author(s)
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