Figure 635: Natural unbalance compensation. (a) Healthy condition when the natural
unbalance is recorded (b) Unbalance compensation during faulty conditions
The natural unbalance compensation for each phase is enabled based on the
settings
Natural Comp Ena PhA
,
Natural Comp Ena PhB
and
Natural Comp Ena PhC
respectively. For example, if
Natural Comp Ena PhA
is set to “FALSE”, the unbalance
current is not compensated. If
Natural Comp Ena PhA
is set to “TRUE”, the
compensated unbalance current for phase A is calculated based on the equation.
I I I
CompUnb_A Unb_A NatUnb_A
= −
(Equation 288)
I
CompUnb_A
Phase A-compensated unbalance current
I
Urb_A
Phase A-measured unbalance current
I
NatUnb_A
Phase A-recorded natural unbalance current
The phasewise-compensated unbalance current amplitudes and angles
I_COM_AMPL_A, I_COM_ANGL_A, I_COM_AMPL_B, I_COM_ANGL_B, I_COM_AMPL_C
and I_COM_ANGL_C are available in the monitored data view.
The phase angles of the unbalance currents indicate the branch of a faulty element
in a capacitor bank. For an internal fuse capacitor bank, the element failure branch
location is determined based on the phase angle of the compensated unbalance
current.
Table 1077: Detection of element failure location for internal fuse capacitor bank
Name of the phase angle
Phase angle of unbalance cur-
rent
Element failure branch loca-
tion
Figure 634
I_COM_ANGL_A ~+180° Phase A - Branch 1 or Phase A
- Branch 4
I_COM_ANGL_A ~0° Phase A - Branch 2 or Phase A
- Branch 3
Table continues on the next page
Protection functions 1MRS759142 F
1134 REX640
Technical Manual
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