Calculated measurements - Arc protection - Motor protection - Feeder protection - Back-up protection - Technical Manual - REX610 Protection and control - 1.2 - IEC - ANSI - 17.02.2023

REX610 Technical Manual

Calculated residual current and voltage

The residual current is calculated from the phase currents according to equation:
Figure 1. Equation
image/svg+xmlIoIIIABC=−++()
The residual voltage is calculated from the phase-to-earth voltages when the VT connection is selected as “Wye” with the equation:
Figure 2. Equation
image/svg+xmlUoUUUABC=++()/3

Sequence components

The phase-sequence current components are calculated from the phase currents according to:
Figure 3. Equation
image/svg+xmlIIIIABC03=++()/
Figure 4. Equation
Figure 5. Equation
The phase-sequence voltage components are calculated from the phase-to-earth voltages when VT connection is selected as “Wye” with the equations:
Figure 6. Equation
image/svg+xmlUUUUABC03=++()/
Figure 7. Equation
image/svg+xmlUUaUaUABC123=+⋅+⋅()/
Figure 8. Equation
When VT connection is selected as “Delta”, the positive and negative phase sequence voltage components are calculated from the phase-to-phase voltages according to the equations:
Figure 9. Equation
image/svg+xmlUUaUABBC123=−⋅()/
Figure 10. Equation
image/svg+xmlUUaUABBC23=−⋅()/
The phase-to-earth voltages are calculated from the phase-to-phase voltages when VT connection is selected as "Delta" according to the equations.
Figure 11. Equation
image/svg+xmlUUUUAABCA=+−()03/
Figure 12. Equation
image/svg+xmlUUUUBBCAB=+−()0/3
Figure 13. Equation
image/svg+xmlUUUUCCABC=+−()0/3
If the image/svg+xmlU0 channel is not valid, it is assumed to be zero.
The phase-to-phase voltages are calculated from the phase-to-earth voltages when VT connection is selected as "Wye" according to the equations.
Figure 14. Equation
image/svg+xmlUUUABAB=−
Figure 15. Equation
image/svg+xmlUUUBCBC=−
Figure 16. Equation
image/svg+xmlUUUCACA=−