GE LPS-O - 602: 50_DIRCNL; 603: 50 PICKUP; 604: 50 PICKUPFF; 605: 50 G

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16
LPS-O Line Protection System GE Power Management
2.3 PROTECTION SETTINGS 2 CALCULATION OF SETTINGS
2
602: 50_DIRCNL - Directional Control Of 50
The
50
function can be set to be either directional or nondirectional. Directionality is obtained through the use
of the Zone 2 phase distance functions. Protection Setting 201 must be set to
Z2PHASE
= YES to make the
50
function directional.
If
50
is made directional, the setting is based on the maximum fault current for a fault at the remote end of the
line. When
50
is made non-directional, then the setting is based on the maximum fault current for a fault at
either end of the line. If the maximum fault current for a fault at either end of the line is approximately the same,
then it is proposed that the
50
function be made non-directional.
603: 50PICKUP - 50 Pickup Setting
50
provides direct tripping for multi-phase faults, and it operates on the highest of the three delta currents,
IA-IB, IB-IC, or IC-IA. This permits
50
to have the same response for all multi-phase faults at the same location.
If
50PICKUP
is non-directional, then it should be set at least 25 percent greater than the maximum delta
three-phase fault current for a fault at either terminal of the line. If
50PICKUP
is directional, then it should be
set at least 25 percent greater than the maximum delta three-phase fault current for a fault at the remote termi-
nal of the line. The setting is calculated on the basis of the delta current which for a three phase fault is equal
to the square root of three times the phase current.
604: 50PICKUPFF - 50 Pickup During Fuse Failure
If
50
is made directional and potential is lost to the relay, then directional control will be lost and the
50
function
will not be able to provide any protection. To overcome this drawback, a second setting (
50PICKUPFF
) can be
made on the
50
function to provide some backup during a loss of potential. A
50PICKUPFF
setting must
always be made and it must always be set at least 25 percent greater than the maximum delta three-phase
fault current for a fault at either terminal of the line.
605: 50G - Ground Instantaneous Overcurrent
The
50G
function can be used in many applications to provide high speed, direct tripping for heavy close-in
faults. To use the ground instantaneous overcurrent trip function, set
50G
= YES, otherwise set
50G
=NO. See
Settings 606 and 607 for further discussion on use of
50G
function.
606: 50G_DIRCNL - Directional Control Of 50G
The
50G
function can be set to be either directional or nondirectional. Directionality is obtained through the use
of the negative sequence directional functions by requiring operation of the NT (forward looking) function
and
non-operation of the NB (reverse looking) function.
If
50G
is made directional, the setting to be made on the function is based on the maximum fault current for a
fault at the remote end of the line. When
50G
is made non-directional, then the setting is based on the maxi-
mum fault current for a fault at either end of the line. If the maximum fault current for a fault at either end of the
line is approximately the same, then it is proposed that the
50
function be made non-directional.
607: 50GPICKUP - 50G Pickup Setting
The considerations used to determine the
50G
setting depend on whether
50G
is nondirectional or directionally
controlled. If
50G
is nondirectional, then it must be set not to operate on the worst case external fault at
either
end of the line. If
50G
is controlled by the negative sequence directional functions, then it must be set not to
operate for the worst case external fault at the
remote end of the line. In general, directional control should be
used when the operating current for a fault behind the relay location is much greater than the operating current
for a fault at the remote end of the line.