Set value:
Mode
Formula used for complex power calculation
C,A
EQUATION2043 V1 EN (Equation 112)
A
EQUATION2044 V1 EN (Equation 113)
B
EQUATION2045 V1 EN (Equation 114)
C
EQUATION2046 V1 EN (Equation 115)
The active and reactive power is available from the function and can be used for
monitoring and fault recording.
The component of the complex power S = P + jQ in the direction Angle1(2) is
calculated. If this angle is 0° the active power component P is calculated. If this angle
is 90° the reactive power component Q is calculated.
The calculated power component is compared to the power pick up setting Power1(2).
A pickup signal PICKUP1(2) is activated if the calculated power component is larger
than the pick up value. After a set time delay TripDelay1(2) a trip TRIP1(2) signal is
activated if the pickup signal is still active. At activation of any of the two stages a
common signal PICKUP will be activated. At trip from any of the two stages also a
common signal TRIP will be activated.
To avoid instability there is a settable hysteresis in the power function. The absolute
hysteresis of the stage1(2) is Hysteresis1(2) = abs (Power1(2) – drop-power1(2)). For
generator reverse power protection the power setting is very low, normally down to
0.02 p.u. of rated generator power. The hysteresis should therefore be set to a smaller
value. The drop-power value of stage1 can be calculated with the Power1(2),
Hysteresis1(2): drop-power1(2) = Power1(2) – Hysteresis1(2)
For small power1 values the hysteresis1 may not be too big, because the drop-
power1(2) would be too small. In such cases, the hysteresis1 greater than (0.5 ·
Power1(2)) is corrected to the minimal value.
If the measured power drops under the drop-power1(2) value the function will reset
after a set time DropDelay1(2). The reset means that the pickup signal will drop out ant
that the timer of the stage will reset.
1MRK505222-UUS C Section 7
Current protection
481
Technical reference manual
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