protection, and phase distance elements associated with the
faulted phase (for example, AB and CA elements for an AG fault).
The Open Pole Detector also resets and blocks the Phase Selector
so the other distance elements may operate for evolving faults.
The Open Pole Detector also accounts for line charging current
and for weak infeed conditions.
Once the Open Pole Detector operates, a further trip will cause
the Trip Output to declare a three pole fault, indicating either an
evolving fault condition or a reclose onto a permanent phaseto-ground fault. This total logic simplifies the setting of the D60
for single pole tripping, and ensures dependable and secure
operation when faced with single line-to-ground faults.
The L90 Line Differential Relay and the L60 Line Phase Comparison
Relay are both phase-segregated, current only relays. Single pole
tripping on these relays does not present any unusual challenges,
as each phase of the protection element operates independently
of the other unfaulted phases.