Introduction to Electricity Transmission

Introduction to Electricity Transmission

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November 18, 2022
Introduction to Electricity Transmission
The U.S. electricity transmission system connects the
The Federal Energy Regulatory Commission (FERC)
electricity generation system—where electricity is made—
regulates the rates these transmission owners charge for
and the electricity distribution system—where electricity is
delivering electricity across state lines. FERC also can
used.
approve financial incentives for certain construction and
operational activities. For example, FERC can incentivize
Figure 1. Electric Power Sector System Schematic
the use of new technologies and participation in regional
transmission organizations in which power resources are
shared in a region. Power sharing is believed to increase
reliability and lower overall costs for consumers.
The federal government does not have general siting
authority for transmission lines—in most cases, state and
local governments have authority for siting. Federal permits
may be necessary for portions of some transmission lines,
such as those that cross federal lands (e.g., National
Forests) or waters under jurisdiction of the U.S. Army
Source: CRS, adapted from U.S.-Canada Power System Outage Task
Corps of Engineers. Congress gave FERC backstop
Force, Final Report on the August 14, 2003, Blackout in the United States
authority for siting transmission lines in areas designated by
and Canada: Causes and Recommendations, April 2004, p. 5.
the U.S. Department of Energy (DOE) to be in the national
Notes: Not al types of components in each system are shown.
interest. In these cases, FERC can site transmission lines
when state or local governments fail to take action or deny
The transmission system includes hundreds of thousands of
an application. To date, no transmission lines have been
miles of power lines that carry electricity at relatively high
approved under this authority.
voltages. Transmission line voltages range from 230
Perceived Transmission Needs
thousand volts (kV) to 765 kV, though lower voltages can
be used as well. The higher the voltage, the more power can
Some advocates have expressed interest in expanding and
move through the line. Approximately 98% of the U.S.
enhancing the U.S. transmission system. Part of this interest
transmission system uses alternating current (AC) power, in
relates to a desire to use more renewable energy for
which the direction of electrical charge changes 60 times
electricity generation. Many of the country’s best renewable
per second. The remainder uses direct current (DC), in
energy resources are concentrated in a few areas: onshore
which the direction of charge does not change. AC power
wind in the central United States, solar in the Southwest,
can be converted relatively easily and cheaply between high
and offshore wind in the Northeast. New transmission lines
and low voltages, making it more suitable for delivering it
are likely needed to cost-effectively develop these resources
to customers that use low voltage AC (e.g., 120 V for most
and deliver the electricity to consumers. Some of the
household uses). DC lines require expensive conversion
advocates propose a greater use of DC transmission to
stations, but can be more efficient over very long distances
move electricity from these areas across the country. A
and better suited for specialized applications, such as
number of transmission projects have been proposed
undersea cables.
associated with these areas of strong renewable energy
resources, as shown in Figure 2. (The figure also shows
The transmission system also includes thousands of
proposed lines that would allow greater import of
transformers that change voltage levels, “stepping up” or
hydropower from the Canadian province of Quebec.) These
“stepping down” voltages to higher or lower levels,
proposed projects are unique from other transmission
respectively. Transformers also provide electric stability to
projects in that they cross multiple states and connect
the grid. High-voltage transformers vary in size (measured
different regions of the electricity grid with each other.
in input/output voltage or power levels), and typically are
custom-built for specific locations in the transmission
system.
Ownership and Regulation
Most transmission lines are owned by private, for-profit
companies, though some are owned by public entities: the
federal government, publicly-owned utilities (e.g., divisions
of a municipal government), or member-owned electric
cooperatives.
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Introduction to Electricity Transmission
Figure 2. Existing and Proposed Transmission Lines
examine potential changes in its cost allocation
methodology.
Some proponents of new transmission lines criticize the
time required to permit, finance, and construct projects—
reportedly 10 years or so on average. They say a main
reason for this timeline is the current regulatory framework,
under which local approval is required along the length of a
transmission line. Multiple proposed transmission lines in
recent years have been delayed or cancelled over landowner
opposition. Opposition to new transmission lines varies by
project, though typical concerns are the environmental
impacts (e.g., tree clearing) of new transmission lines,
Source: DOE, National Transmission Planning Study, “Technical
visual impacts, and loss of property values. Despite high
Review Committee Meeting #1,” May 20, 2022, p. 45.
profile examples of cancelled projects, overall investment
Notes: AC = alternating current; HVDC = high voltage direct
in the U.S. transmission system has been increasing since
current; kV = kilovolts. Narrow lines of various colors show existing
the mid-2000s.
transmission lines. Thick lines show proposed transmission lines, with
colors indicating different voltage levels.
Additional challenges relate to planning and supply chains.
The current planning process is not optimized for
transmission lines that connect different regions of the grid.
Additional interest relates to the reliability, resilience, and
Such transmission lines are believed to be helpful in
security of the transmission system. Some areas of the
promoting use of renewable energy and improving
country (e.g., Texas, California, New England) have
reliability and resilience. FERC also is evaluating
elevated risks of electricity supply shortages during certain
transmission planning as part of its transmission rulemaking
times of the year. Additional transmission lines could help
process. For a discussion of supply chain issues for
deliver electricity from neighboring regions during times of
transformers, see CRS Insight IN12048, Electric Power
electricity shortages, alleviating reliability risks. Resilience
Transformers: Supply Issues.
is not formally defined, but typically refers to the ability of
the transmission system to withstand and recover from
117th Congress Action and Options
disruptions such as wildfires, hurricanes, or attacks.
The 117th Congress enacted legislation aimed at
Transmission lines can be strengthened in various ways to
accelerating transmission development. For example, the
better withstand some events. Measures include using
Infrastructure Investment and Jobs Act (IIJA; P.L. 117-58)
stronger materials for supporting structures and burying
amended FERC’s backstop siting authority and
lines underground. Components of the transmission system
appropriated $11 billion in grant programs for grid
are vulnerable to physical and cyberattacks. FERC’s
reliability and resilience (some of which may be used for
statutory authority over transmission reliability includes
the distribution system). IIJA also appropriated $2.5 billion
security. FERC administers both mandatory standards and
for a new Transmission Facilitation Program through which
financial incentives aimed at improving security.
DOE can provide financial and technical assistance for
Perceived Transmission Challenges
transmission line construction. Other pre-existing programs
administered by DOE and the U.S. Department of
Two main issues have been raised as challenges to
Agriculture provide financial assistance for certain types of
addressing perceived transmission needs—costs and
transmission projects. These received supplemental
permitting.
appropriations from IIJA and P.L. 117-169, commonly
known as the Inflation Reduction Act. Congress could
Ultimately, electricity consumers bear the cost of building,
consider oversight activities for these programs.
operating, and maintaining the transmission system. The
construction of new transmission lines or upgrades to
Congress could consider reforms to the transmission
existing lines raise costs for consumers. FERC and state
permitting process. For instance, a proposal to give FERC
regulators seek to balance these costs with any benefits,
authority for permitting a broader number of transmission
such as increased use of renewable energy or improved
lines was included as part of an infrastructure permitting
reliability, resilience, or security. In many cases, these
reform package released by Senator Manchin, Chairman of
benefits are difficult to monetize, complicating a benefit-
the Senate Committee on Energy and Natural Resources, in
cost comparison. Additionally, benefits may be distributed
September 2022.
among many consumers, even those far away from a new or
upgraded transmission line. Historically, transmission costs
Other options for Congress could include conducting
have been allocated mostly to nearby consumers. Critics
oversight on transmission issues or providing statutory
say this approach makes it more challenging for
guidance for FERC’s transmission policies. Congress also
transmission projects to demonstrate positive benefit-to-
might consider additional legislation to address any of the
cost ratios when benefits are distributed broadly.
perceived needs or challenges related to transmission.
Proponents say this approach protects consumers from
higher electricity prices by having them pay only for
transmission projects with direct and clear benefits to them.
Ashley J. Lawson, Analyst in Energy Policy
In April 2022, FERC began a rulemaking process to
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Introduction to Electricity Transmission

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