4.12.3.3
Functionality
The shunt capacitor bank switching resonance protection, current based, function
SRCPTOC is used for detecting three-phase resonance caused by capacitor
switching or topology changes in the network. The operating characteristic is a
definite time (DT).
SRCPTOC contains a blocking functionality. It is possible to block function outputs,
timers or the function itself, if desired.
4.12.3.4
Operation principle
The function can be enabled and disabled with the
Operation setting. The
corresponding parameter values are “On” and “Off”.
The operation of SRCPTOC can be described by using a module diagram. All the
modules in the diagram are explained in the next sections.
Figure 416: Functional module diagram
Resonance current calculation
This module calculates the resonance current per phase set as per setting
Tuning
harmonic Num. The resonance current for phase A is calculated with the equation.
I
RESO
A
I
I
I
I
RMS
A
A
DC
A
K
A
_
_
_
_
_
_
=
−
−
−
2
1
2
2
2
(Equation 149)
I
RMS_A
RMS value of current in phase A (contains up to 11
th
harmonic)
I
DC_A
DC-component in phase A current
I_A
Fundamental component in phase A current
I
K_A
K
th
harmonic component in phase A current, K is defined by setting
Tuning harmonic Num
I_RESO_A
Calculated resonance current for phase A
The resonance current is calculated through the filter implementation. The DC and
fundamental components are removed by passing the total RMS current through
1MRS757644 H
Protection functions
620 series
Technical Manual
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