GE L60 Instruction Manual page 332

5.5 GROUPED ELEMENTS
The positive-sequence restraint must be considered when testing for pick-up accuracy and response time (multiple of
pickup). The positive-sequence restraint is removed for low currents. If the positive-sequence current is less than 0.8 pu,
then the restraint is removed by changing the constant K to zero. This results in better response to high-resistance faults
when the unbalance is very small and there is no danger of excessive CT errors, since the current is low.
The operating quantity depends on the way the test currents are injected into the L60. For single phase injection:
= ⅓ × (1 – K) × I
• I
op
= (1 – K) × I
• I
op injected
The directional unit uses the negative-sequence current (I_2) and negative-sequence voltage (V_2).
The following tables define the negative-sequence directional overcurrent element.
Table 5–25: NEGATIVE-SEQUENCE DIRECTIONAL OVERCURRENT UNIT
MODE
Negative-sequence
Zero-sequence
Table 5–26: NEGATIVE-SEQUENCE DIRECTIONAL UNIT
DIRECTION
Forward
Reverse
Forward
Reverse
5
The negative-sequence voltage must be greater than the

DISPLAY PROPERTIES
forward nor reverse indication is given. The following figure explains the usage of the voltage polarized directional unit of
the element.
The figure below shows the phase angle comparator characteristics for a phase A to ground fault, with settings of:
ECA = 75° (element characteristic angle = centerline of operating characteristic)
FWD LA = 80° (forward limit angle = ± the angular limit with the ECA for operation)
REV LA = 80° (reverse limit angle = ± the angular limit with the ECA for operation)
5-204
for I_2 mode.
injected
for I_0 mode if I_1 > 0.8 pu.
OPERATING CURRENT
I = |I_2| – K × I_1|
op
I = 3 × (|I_0| – K × |I_1|) if |I_1| > 0.8 pu
op
I = 3 × |I_0| if |I_1| ≤ 0.8 pu
op
COMPARED PHASORS
–V_2 + Z_offset × I_2
–V_2 + Z_offset × I_2
–V_2 + Z_offset × I_2
–V_2 + Z_offset × I_2
menu to be validated for use as a polarizing signal. If the polarizing signal is not validated neither
L60 Line Phase Comparison System
I_2 × 1∠ECA
–(I_2 × 1∠ECA)
I_2 × 1∠ECA
–(I_2 × 1∠ECA)
VOLTAGE CUTOFF LEVEL
5 SETTINGS
setting specified in the
PRODUCT SETUP
GE Multilin