National Electric Transmission Congestion Study - W2agz.com

Flowgate: An individual or a group of transmission
facilities (e.g., transmission lines, transformers)
that are known or anticipated to be limiting elements
in providing transmission service. This term
is used principally in the Eastern Interconnection.
Generation: The process of transforming existing
stored energy into electricity; also, an amount of
electric energy produced, expressed in kilowatt-hours
(kWh) or megawatt-hours (mWh).
Interconnection: When capitalized, any one of the
three major alternating current (AC) electric system
networks in North America (Eastern, Western, and
ERCOT).
ISO: Independent System Operator, an independent,
federally regulated entity that coordinates regional
transmission in a non-discriminatory manner
and ensures the safety and reliability of the electric
system within its footprint and in coordination with
neighboring entities.
ISO-NE: Independent System Operator for New
England, covering the states of Maine, Vermont,
New Hampshire, Connecticut, Rhode Island and
Massachusetts.
Limiting element: An electrical element that is either
1) operating at its appropriate maximum rating,
or 2) would be operating at its maximum rating following
a limiting contingency; a limiting element
establishes a system limit.
LMP: Locational Marginal Price, a method for
pricing wholesale power based on actual grid conditions.
The LMP at a specific point on the grid reflects
the full cost of supplying the next MWh of
electricity at that location, including the marginal
cost of generating the electricity, the cost of delivering
it across the grid, and the value of energy lost in
delivery. Differences at a given time in LMPs at different
locations reflect the impact of transmission
congestion—LMPs at two points will be the same
when the congestion they face is the same, but diverge
if transmission congestion obstructs delivery
of less expensive energy to one of them, raising
LMP in the constrained area by the cost of the congestion.
Load: An end-use device (or a customer operating
such device) that receives power from the electric
system.
Load flow model: A detailed model, also referred
to as a power flow model, that represents the interdependencies
of energy flow along different paths
in the system.
Load pocket: A load center (such as a large metropolitan
area) that has little local generation relative
to the size of the load, and must import much of its
electricity via transmission from neighboring areas.
MISO: The Midwest ISO, the Regional Transmission
Operator serving all or portions of Arkansas,
Illinois, Indiana, Iowa, Kentucky, Minnesota,
Montana, Nebraska, North Dakota, Ohio, Pennsylvania,
South Dakota, Virginia, Wisconsin, and
West Virginia.
MMWG: NERC’s Multi-regional Modeling
Working Group, which develops a dataset of information
about grid elements (power plants and transmission
facilities) and their ratings for use in regional
reliability modeling.
Node: A node is used in simulation modeling to
represent an aggregation of significant amounts of
electrical demand and/or supply, to simplify the
modeling calculations (relative to modeling each
power plant or load center individually). Each Interconnection
is broken down into a set of nodes connected
to each other by transmission paths.
Nomogram: A graphic representation that depicts
operating relationships between generation, load,
voltage, or system stability in a defined network. On
lines where the relationship between variables does
not change, a nomogram can be represented simply
as a single transmission interface limit; in many areas,
the nomogram indicates that an increase in
transfers into an area across one line will require a
decrease in flows on another line.
NYISO: New York Independent System Operator,
serving New York State.
68 U.S. Department of Energy / National Electric Transmission Congestion Study / 2006