Sel SEL-421 - Settings; Ground Directional Element Settings; Ground Directional Element Settings AUTO Calculations

R.1.28
SEL-421 Relay Reference Manual Date Code 20111215
Protection Functions
Ground Directional Element
During the single-pole open condition (SPO is a logical 1), the relay
supervises the ground directional element with an open pole directional
element. The purpose of this directional element is to ensure secure operation
of the distance elements during the single-pole open condition. The operation
of the single-pole open directional element is indicated by the 32SPOF and the
32SPOR Relay Word bits.
As the single-pole open directional element may operate due to unbalance
currents generated during the single-pole open condition, it is recommended
that ground and negative-sequence overcurrent elements that are used for
single-pole tripping be supervised by the single-pole open condition. To
supervise overcurrent elements during the single-pole open condition, set the
element torque control equation (67GnTC or 67QnTC, where n equals 1
through 4) equal to NOT SPO.
Settings
Tab le 1.27 lists the relay settings corresponding to the ground directional
element.
If you set E32 to AUTO, the relay automatically calculates the settings shown
in Table 1.28.
Table 1.27 Ground Directional Element Settings
Setting Description Range
Default
(5 A)
E32 Directional Control Y, AUTO AUTO
ORDER Ground Directional Element Priority combine Q, V, I QV
50FP Forward Directional Overcurrent Pickup (A) (0.05–1) • I
nom
0.60
50RP Reverse Directional Overcurrent Pickup (A) (0.05–1) • I
nom
0.40
Z2F Forward Directional Z2 Threshold () 320/I
nom
3.90
Z2R Reverse Directional Z2 Threshold () 320/I
nom
4.00
a2 Positive-Sequence Restraint Factor, I2/I1 0.02–0.5 0.10
k2 Zero-Sequence Restraint Factor, I2/I0 0.1–1.2 0.20
Z0F Forward directional Z0 threshold () 320/I
nom
12.40
Z0R Reverse directional Z2 threshold () 320/I
nom
12.50
a0 Positive-Sequence restraint factor, I0/I1 0.02–0.5 0.10
E32IV Zero-sequence voltage current enable SEL
OGIC Equation 1
Table 1.28 Ground Directional Element Settings AUTO Calculations
Setting Equation
50FP 0.12 • I
nom
50RP 0.08 • I
nom
Z2F 0.5 • Z1MAG
Z2R Z2F + 1/(2 • I
nom
)
a2 0.1
k2 0.2
Z0F 0.5 • Z0MAG
Z0R Z0F + 1/(2 • I
nom
)
a0 0.1