GE LPS-O Instruction Manual page 56

2.3 PROTECTION SETTINGS 2 CALCULATION OF SETTINGS
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
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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.
2- LPS-O Line Protection System GE Power Management
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