ABB RET670 - Page 181

To verify zone 2 and zone 3 mho characteristic, at least two points must be tested. The
default measuring loop selected is maximum current phase to current loop. Hence the
below characteristics are tested with phase–to-ground fault conditions.
P1
P3
P4
X
R
LineAngle
ZxFwd
ZxRev
P2
IEC11000313-1-en.vsd
IEC11000313 V2 EN
Figure 43: Proposed four test points for phase-to-earth fault
Where,
ZxFwd
is the forward positive sequence impedance setting for zone x (where, x is 2- 3
depending on the zone selected)
ZxRev is the reverse positive sequence impedance setting for zone x (where x is 2- 3
depending on the zone selected)
LineAngle is the Impedance angle for phase-to-phase fault in degrees
Test points X R
P1 ZxFwd · sin( LineAngle ) ZxFwd · cos( LineAngle )
P2 (( ZxFwd - ZxRev / 2) · sin( LineAngle )) ZxFwd / 2 · (1 + cos( LineAngle ) + ZxRev /2 ·
(1 – cos( LineAngle ))
P3 (( ZxFwd - ZxRev / 2) · sin( LineAngle )) - ZxFwd / 2 · (1 – cos( LineAngle ) + ZxRev / 2
· (1 + cos( LineAngle ))
P4 - ZxRev · sin( LineAngle ) - ZxRev · cos( LineAngle )
1MRK 504 165-UUS - Section 11
Testing functionality by secondary injection
Transformer protection RET670 2.2 ANSI 175
Commissioning manual