Low Pass Filtering - ABB REL650 series Technical Manual

Section 7
Current protection
7.15.4.1
286
Mode
Set value:
CA
A
B
C
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 pickup signal PICKUP1(2) is activated if the
calculated power component is smaller than the pick up value. For directional overpower
protection, 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 hysteresis in the power function. The absolute hysteresis for
stage 1(2) is 0.5 p.u. for Power1(2) ≥ 1.0 p.u., else the hysteresis is 0.5 Power1(2).
If the measured power drops under the (Power1(2) - hysteresis) value, the over-power
function will reset after 0.06 seconds. If the measured power comes over the (Power1(2)
+ hysteresis) value, the under-power function will reset after 0.06 seconds. The reset
means that the pickup signal will drop out and that the timer of the stage will reset.

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
Formula used for complex power calculation
* *
= × -
S V ( I I )
CA C A
EQUATION2060-ANSI V1 EN
*
= × ×
S 3 V I
A A
EQUATION2061-ANSI V1 EN
*
= × ×
S 3 V I
B B
EQUATION2062-ANSI V1 EN
*
= × ×
S 3 V I
C C
EQUATION2063-ANSI V1 EN
1MRK 506 335-UUS A
(Equation 66)
(Equation 67)
(Equation 68)
(Equation 69)
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