ABB Relion REG670, Technical Manual

Page: 430 / 1298

Set value: Mode Formula used for complex power calculation
L1
*
1 1
3
L L
S U I
= × ×
EQUATION1703 V1 EN
(Equation 84)
L2
*
2 2
3
L L
S U I
= × ×
EQUATION1704 V1 EN
(Equation 85)
L3
*
3 3
3
L L
S U I
= × ×
EQUATION1705 V1 EN
(Equation 86)
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) . For directional underpower protection, a start signal START1(2) is
activated if the calculated power component is smaller than the pick up value. For
directional overpower protection, a start signal START1(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 start signal is still active. At
activation of any of the two stages a common signal START 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 low forward 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 start signal will drop out and
that the timer of the stage will reset.
8.10.7.1 Low pass filtering
In order to minimize the influence of the noise signal on the measurement it is possible
to introduce the recursive, low pass filtering of the measured values for S (P, Q). This
will make slower measurement response to the step changes in the measured quantity.
Filtering is performed in accordance with the following recursive formula:
Section 8
1MRK502052-UEN B
Current protection
424
Technical manual