Environmental Engineering Reference
In-Depth Information
tunities for reducing total construction, thereby enabling siting of facilities so as to produce the
required amount of power with minimum adverse environmental impact (Hamilton 1980, 44-45;
1979, 127).
Interconnection meant electric utilities might share the perceived benefits of building larger,
often jointly owned generators to serve their combined electricity demand. Interconnection also
reduced the amount of extra capacity or “reserve margin” each utility had to maintain to assure
reliable service. With growing demand for new power plants came a need for higher voltage in-
terconnections to transport additional power over longer distances. In the western states, the U.S.
Bureau of Reclamation and Bonneville Power Administration played major roles in development
of larger interconnected systems by linking their own power-generating facilities and by exer-
cising leadership in a series of studies with private electric utilities during the 1950s and 1960s
(Hamilton 1980, 42-45). Over time, three large interconnected systems evolved in the United
States (USEIA 2011a).
Transmission and distribution lines owned by an individual utility are no longer resources
that can be used only by that firm. Firms routinely transmit electric energy over lines owned by
other firms, paying for the service. Buyers and sellers of electricity may be geographically widely
separated. Consequently, close oversight of operations within the three power grids is needed to
keep the various components operating smoothly and linked together (NERC 2011c). The inter-
connected systems now include over 3,200 electric distribution utilities, over 10,000 generating
units, over 334 million customers (USEIA 2011a), and about 394,549 miles of transmission and
distribution lines with greater than 100kV capacity (NERC 2011a, 34).
Originally, each generating company was responsible for maintaining its own electrical system
safely and planning for the future needs of its customers. Later, voluntary standards were devel-
oped by the electric utility industry to ensure coordination for linked interconnection operations.
These voluntary standards were instituted after a major blackout in 1965 that darkened New
York, a large portion of the East Coast, and parts of Canada (USEIA 2011a; Hamilton 1979, 128).
Now, planning is done in a somewhat more coordinated manner to achieve adequacy of supply,
to establish and oversee formal operational standards for running the bulk power systems, and to
address security concerns for critical electrical infrastructures. All of this coordination is admin-
istered under mandatory procedures set up by the electric power industry's electricity reliability
organization pursuant to the Energy Policy Act of 2005 (16 USC §8240), with oversight provided
by the Federal Energy Regulatory Commission and the U.S. Department of Energy.
Yet interconnection and integration are incomplete. There is no national power grid. As noted
above, there are actually three power grids operating in the forty-eight contiguous states: (1) the
Eastern Interconnected System (for states east of the Rocky Mountains) with about 692,658 MWe
generating capacity, (2) the Western Interconnected System (from the Pacific Ocean to the Rocky
Mountain States) with about 158,407 MWe generating capacity, and (3) the Texas Interconnected
System with about 73,857 MWe generating capacity in 2010. Together, these systems had about
924,922 MWe generating capacity in 2010, but they generally operated independently of each other,
with limited links between them (USEIA 2011b, Table 4.2.A). The Texas system is not synchro-
nously connected to the Eastern or Western Interconnection but can exchange about 860 MWe with
neighboring states and Mexico through direct-current links. Interregional transfer capabilities are
not generally relied upon to maintain transmission reliability or address capacity shortages, although
emergency support arrangements are in place that provide for mutual support over asynchronous
ties or through block load transfers (NERC 2011a, 176). Electric utilities in Texas have long avoided
interstate interconnections in order to avoid regulation of wholesale sales of electricity by the Fed-
eral Energy Regulatory Commission. Despite the absence of any insurmountable technical barrier,
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