National Electric Transmission Congestion Study - W2agz.com

Glossary
Available transfer capability (ATC): A measure
of the transfer capability remaining in the physical
transmission network for further commercial activity
over and above already committed uses. It is defined
as Total Transfer Capability less existing
transmission commitments (including retail customer
service), less a Capacity Benefit Margin, less
a Transmission Reliability Margin.
Binding hours: Those hours when a transmission
element is operating at its maximum operating safe
limit; as a congestion metric, the % of time annually
that the element is loaded to its limit.
Binding hours shadow price: A congestion metric
that equals the average value of the shadow prices in
those hours when a transmission element operates
at its limit; the shadow price equals zero when the
element is below its limit.
CAISO: California Independent System Operator,
serving most of the state of California.
Congestion: The condition that occurs when transmission
capacity is not sufficient to enable safe delivery
of all scheduled or desired wholesale electricity
transfers simultaneously.
Congestion rent: As used in this report, congestion
rent equals the shadow price per MWh times the
MWh flowing through a transmission element,
summed over all the hours when that element is operating
at its maximum (binding) limit.
Constrained facility: A transmission facility (line,
transformer, breaker, etc.) that is approaching, at, or
beyond its System Operating Limit or Interconnection
Reliability Operating Limit.
Contingency: An unexpected failure or outage of a
system component, such as a generator, transmission
line, circuit breaker, switch or other electrical
element.
Control area: A geographic and electrical area
managed by a transmission or integrated utility,
ISO or RTO, the manager of which is responsible
for ensuring a continuous real-time balance of electrical
supply and demand.
Curtailment: A reduction in service required when
all demand cannot be served because a generating
unit, transmission line, or other facility is not functioning
due to maintenance, breakdown, or emergency
conditions.
Demand: The physical rate at which electric energy
is delivered to or by a system or part of a system,
generally expressed in kilowatts or megawatts, at a
given instant or averaged over any designated interval
of time.
Demand response: Demand response programs
are used to reduce consumers’ use of electricity during
times of peak demand, with incentives to curtail
electricity demand and reduce load during peak periods
in response to system reliability or market
conditions. Customers reduce their load by reducing
specific energy uses, by the utility curtailing the
customer’s use, or by using distributed generation
in place of utility-delivered energy. Demand response
can respond to price signals or directions
from distribution utilities or system operators.
Demand-side management: Activities or programs
undertaken by a retail electricity provider,
utility, energy service company, or energy end users
to influence the amount or timing of electricity they
use.
EIA: Energy Information Administration, an organization
within the U.S. Department of Energy.
Element: An electrical device with terminals that
may be connected to other electrical devices, such
as generators, transformers, circuit breakers, bus
sections, or transmission lines; an element may be
comprised of one or more components.
Energy: A capacity for doing work; electrical energy
is measured in watt-hours (kilowatt-hours,
megawatt-hours or gigawatt-hours).
ERCOT: Electric Reliability Council of Texas, an
ISO serving 80% of Texas’ load.
Facility rating: The maximum or minimum voltage,
current, frequency, or real or reactive power
flow through a facility that does not violate the applicable
equipment rating of any equipment comprising
the facility.
U.S. Department of Energy / National Electric Transmission Congestion Study / 2006 67