GE G60 Instruction Manual page 408

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)
Take the bias into account when using the neutral directional overcurrent element to directionalize other protection
elements.
5-232
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
G60 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
| > 0.8 pu
1
| ≤ 0.8 pu
1
Overcurrent unit
I = |IG|
op