GE D30 Instruction Manual page 4

ADDENDUM
(NOT VA_LOW & NOT VB_LOW & VC_LOW)
where
√
VA_LOW = |V_A + V_0| < 0.98 *VBC/ 3, similarly for B and C phases
Additionally multi-phase fault is determined if at least 2 phases are below 85% of the nominal:
M-PH= (VA < 0.85pu & VB < 0.85pu) OR (VB < 0.85pu & VC < 0.85pu) OR ( VC< 0.85pu & VA < 0.85pu)
Permission is always granted to phase distance by setting FLGAB, FLGBC and FLGCA flags to logic '1', unless following
condition is satisfied:
PKP_I0 & PKP_I2 & SLG & NOT M-PH,
meaning that if there are negative- and zero-sequence currents present in the fault signal, voltage signatures indicate pres-
ence of the SLG fault and not multi-phase fault. If at least one of these conditions is not satisfied, permission to be contin-
ued granted to all phase distance loop.
But in case this condition is satisfied, angles between I_0 and I_2 are additionally checked to still grant permission to the
phase distance loops, shown below for the ABC rotation.
If abs[ang(I_0)-ang(I_2)+120°] <70°, then FLGAB=1,
If abs[ang(I_0)-ang(I_2)+240°] <70°, then FLGCA=1,
If abs[ang(I_0)-ang(I_2)] <70°, then FLGBC=1,
Phase distance fault type supervision is suppressed during open pole conditions and for delta connected VTs.
Fault type supervision is applied to phase distance zone1 to zone 3 only with an option to disable fault type supervision by
setting phase distance zone 5 Voltage level setting to non-zero-value (regardless zone 5 is enabled or not). G60 and L60
relays are not employing fault type supervision for the phase distance in all zones.