ABB RELION REX640 Technical Manual page 1042

Section 4
Protection functions
1036
GUID-33558AA1-9ADE-47F5-B568-1BB85FC5C74F V1 EN
Figure 559: 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
GUID-4407D6AF-65FE-4677-BF44-1694BD16039D V1 EN
I Phase A-compensated unbalance current
CompUnb_A
I Phase A-measured unbalance current
Urb_A
I Phase A-recorded natural unbalance current
NatUnb_A
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.
1MRS759142 C
(Equation 243)
REX640
Technical Manual