ABB Relion 620 Series - Page 796

the High pass filter. The K
th
harmonic component is removed by passing the
High pass filter output through the K
th
harmonic Band stop filter. The magnitude
response of the High pass filter and all the harmonic Band stop filters are shown in
Figure 417 .
Figure 417: Magnitude response of High pass and all the harmonic Band stop filters
Similarly resonance current is calculated in the same way for phase B and phase
C. Resonance currents I_RESO_A, I_RESO_B and I_RESO_C are available in the
monitored data view.
The maximum of the three calculated resonance currents is further considered for
calculation.
I RESONANCE Max I RESO A I RESO B I RESO C_ ( _ _ _ _ _ _= , , )
(Equation 150)
If a capacitor bank is used only for reactive power compensation and
there is no series reactor in a filter branch, the resonance protection is
very important. In this case, the setting Tuning harmonic Num should be
set to 1 because the capacitor branch is not tuned for a special frequency
as in tuned filter applications. Even though Tuning harmonic Num is set
to 1, the fundamental component is subtracted only once from I
RMS
.
Level detector 1
The maximum calculated resonance current is compared to the set Alarm start
value . If the calculated I_RESONANCE exceeds the set Alarm start value , the module
sends the enabling signal to the Timer 1 module.
Level detector 2
The maximum calculated resonance current is compared to the set
Start value . If
the calculated I_RESONANCE exceeds the set Start value , this module sends the
enabling signal to the Timer 2 module.
Protection functions
1MRS757644 H
796 620 series
Technical Manual