Description of Operation
GARD 8000 Distance Relay
RFL Electronics Inc.
9.17
VOLTAGE UNITS
The GARD 8000 provides a large number of voltage units:
•
3 undervoltage units for each phase (27P)
•
3 overvoltage units for each phase (59P)
•
2 ground overvoltage units (59G)
9.17.1
PHASE UNDERVOLTAGE UNITS (27P)
The GARD 8000 has three independent phase undervoltage units.
The undervoltage units measure in each phase, and the output can be selected to be from each phase
separately (OR) or for all three phases (AND). This setting selection is done independently for each of
the three units:
•
AND
: The unit trips when all three phase elements pick up
•
OR
: The unit trips when any one of the three phase elements pick-up
The three units also have independent time delay settings.
The undervoltage elements pick up as soon as the measured voltage is below the set threshold, and a
trip signal is issued if the voltage maintains a value below for the duration of the timer. As soon as the
voltage rises above the set value plus the settable reset ratio (101-150%) the element and timer reset.
The undervoltage elements may be blocked by “Any pole open” or LOP (loss-of-potential) logic, if
selected by setting.
August 1, 2009
9-65
973.334.3100
