Instruction manual
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AQ G3x7 Generator protection IED
98 (211
)
Table 3-38: Setting parameters of the directional underpower protection function.
Parameter
Setting value, range
and step
Description
Operation
Off
On
Operating mode selection for the function. Operation can be
either disabled “Off” or enabled “On”.
Default setting is
enabled.
Start signal
only
Activated
Deactivated
Selection if the function i
ssues either “Start” signal alone or
both “Start” and after set time delay “Trip” signal.
Default is
that both signals are generated (=deactivated).
Direction
angle
-
179…180
by step of
1
Power direction angle setting, angle between P and Q.
Default setting is 0
Start power
1
…
200% by step of
0.1.
Minimum power setting. Default setting is 10.
Time delay
0
…
60000ms by step
of 1.
Definite time delay of the trip command. Default setting is
100.
3.2.20
D
IRECTIONAL OVER POWER
P>
(32)
The directional under-power protection function can be applied mainly to protect any elements
of the electric power system, mainly generators, if the active and/or reactive power has to be
limited in respect of the allowed minimum power.
The inputs of the function are the Fourier basic harmonic components of the three phase
currents and those of the three phase voltages.
Based on the measured voltages and currents, the block calculates the three-phase active and
reactive power (point S in figure below) and compares the P-Q coordinates with the defined
characteristics on the power plane. The characteristic is defined as a line laying on the point
S
S
and perpendicular to the direction of S
S.
The S
S
point is defined by the “Start power”
magnitude and the “Direction angle”. The over
-power function operates if the angle of the S-
S
S
vector related to the directional line is below 90 degrees and above -90 degrees.
A
t operation, the “Start power” value is decreased by a hysteresis value.