Powering Europe - European Wind Energy Association

GatE ClosURE Is the point in time when generation and demand schedules are notified to the
system operator.
inERtia Of a power system is the sum of all rotating mass inertias of the connected
generation opposing a change of system frequency. The rotational speed of
synchronous generators is an exact representation of the system frequency. In
the very first moments after loss of generation the inertia of the rotating machinery
helps to keep the system running.
intERConnECtED systEM An INTERCONNECTED SYSTEM is a system consisting of two or more individual
electric systems that normally operate in synchronism and are physically connected
via TIE-LINES, see also: SYNCHRONOUS AREA (UCTE).
intERConnECtion An INTERCONNECTION is a transmission link (e.g. TIE-LINE or transformer)
which connects two CONTROL AREAS (UCTE).
loaD Means an end-use device or customer that receives power from the electric
system. LOAD should not be confused with DEMAND, which is the measure of
power that a load receives or requires. LOAD is often wrongly used as a synonym
for DEMAND (UCTE).
loaD faCtoR See CAPACITY FACTOR
MinUtE REsERVE {15 Minute Reserve} See: TERTIARY CONTROL RESERVE
n-1 CRitERion The N-1 CRITERION is a rule according to which elements remaining in operation
after failure of a single network element (such as transmission line /
transformer or generating unit, or in certain instances a busbar) must be capable
of accommodating the change of flows in the network caused by that single
failure (UCTE).
n-1 safEty Means that any single element in the power system may fail without causing a
succession of other failures leading to a total system collapse. Together with
avoiding constant overloading of grid elements, (N-1)-safety is a main concern
for the grid operator.
nEt tRansfER CaPaCity Maximum value of generation that can be wheeled through the interface between
the two systems, which does not lead to network constraints in either
system, respecting technical uncertainties on future network conditions.
PowER CURVE Relationship between net electric output of a wind turbine and the wind speed
measured at hub height on 10 min average basis.
PRiMaRy ContRol Maintains the balance between GENERATION and DEMAND in the network using
turbine speed governors. PRIMARY CONTROL is an automatic decentralised
function of the turbine governor to adjust the generator output of a unit as a
consequence of a FREQUENCY DEVIATION / OFFSET in the SYNCHRONOUS
AREA: PRIMARY CONTROL should be distributed as evenly as possible over
units in operation in the SYNCHRONOUS AREA.
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