GE D60 Instruction Manual page 422

GROUPED ELEMENTS
Table 5-37: Quantities for "calculated 3I0" configuration
Directional unit
Polarizing mode
Voltage
Current
Dual, Dual-V, Dual-I
Table 5-38: Quantities for "measured IG" configuration
Directional unit
Polarizing mode
Voltage
where:
5
ECA = element characteristic angle
IG = ground current
When
NEUTRAL DIR OC1 POL VOLT
figure explains the usage of the voltage polarized directional unit of the element.
The figure shows the voltage-polarized phase angle comparator characteristics for a phase A to ground fault, with:
• ECA = 90° (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)
The element incorporates a current reversal logic. If the reverse direction is indicated for at least 1.25 of a power system
cycle, the prospective forward indication is delayed by 1.5 of a power system cycle. The element is designed to emulate an
electromechanical directional device. Larger operating and polarizing signals results in faster directional discrimination
bringing more security to the element operation.
The forward-looking function is designed to be more secure as compared to the reverse-looking function, and therefore is
to be used for the tripping direction. The reverse-looking function is designed to be faster as compared to the forward-
looking function and is to be used for the blocking direction. This allows for better protection coordination.
Take the bias into account when using the neutral directional overcurrent element to directionalize other protection
elements.
5-244
Direction Compared phasors
Forward –V_0 + Z_offset × I_0
Reverse –V_0 + Z_offset × I_0
Forward IG
Reverse IG
Forward –V_0 + Z_offset × I_0
IG
Reverse –V_0 + Z_offset × I_0
IG
Direction Compared phasors
Forward –V_0 + Z_offset × IG/3
Reverse –V_0 + Z_offset × IG/3
is set to "Measured VX," one-third of this voltage is used in place of V_0. The following
Overcurrent unit
I_0 × 1∠ECA I = 3 × (|I_0| – K × |I_1|) if |I
op
I = 3 × (|I_0|) if |I
op
–I_0 × 1∠ECA
I_0
–I_0
I_0 × 1∠ECA
or
I_0
–I_0 × 1∠ECA
or
–I_0
IG × 1∠ECA
–IG × 1∠ECA
D60 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
| > 0.8 pu
1
| ≤ 0.8 pu
1
Overcurrent unit
I = |IG|
op