Sel SEL-421 - Quadrilateral Ground Distance Elements; Quadrilateral Ground Distance Element Settings

R.1.54
SEL-421 Relay Reference Manual Date Code 20111215
Protection Functions
Quadrilateral Ground Distance Elements
Quadrilateral Ground Distance Elements
The SEL-421 has five independent zones of quadrilateral ground distance
protection. The quadrilateral ground distance protection only operates for
single phase-to-ground faults.
Set the reactance (XG) and resistive (RG) reach for each zone independently.
Rather than 90 degrees (purely reactive), the reactance measurement lies along
the setting Z1ANG (complex).
Zone 1 and Zone 2 distance elements are forward only, while you can set
Zone 3 through Zone 5 distance elements either forward or reverse.
You select whether the quadrilateral ground distance elements use negative- or
zero-sequence current to polarize the reactance line when the Advanced
Settings are enabled (setting EADVS := Y); otherwise, negative-sequence
current is the default setting.
The Zone 1 zero-sequence compensation factor (k01) is independent from the
forward and reverse compensation factors (k0 and k0R) that the relay uses for
quadrilateral ground distance protection for the other zones.
When setting E21XG (Quadrilateral Ground Distance Zones) is 1 or more,
there are two selections for setting XGPOL (Quadrilateral Ground Polarizing
Quantity): I2 or IG. When the setting XGPOL is I2, set the first selection in
the setting ORDER (Ground Directional Element Priority) to Q. When the
setting XGPOL is IG, the first selection in the setting ORDER must be Q or V.
Table 1.44 Quadrilateral Ground Distance Element Settings
Name Description Range
Default
(5 A)
E21XG Quadrilateral Ground Distance Zones N, 1 to 5 N
XG1 Zone 1 Reactance () OFF, (0.25–320)/I
nom
OFF
RG1 Zone 1 Resistance () (0.25–250)/I
nom
12.48
XG2 Zone 2 Reactance () OFF, (0.25–320)/I
nom
OFF
RG2 Zone 2 Resistance () (0.25–250)/I
nom
18.72
XG3 Zone 3 Reactance () OFF, (0.25–320)/I
nom
OFF
RG3 Zone 3 Resistance () (0.25–250)/I
nom
3.64
XG4 Zone 4 Reactance () OFF, (0.25–320)/I
nom
OFF
RG4 Zone 4 Resistance () (0.25–250)/I
nom
31.20
XG5 Zone 5 Reactance () OFF, (0.25–320)/I
nom
OFF
RG5 Zone 5 Resistance () (0.25–250)/I
nom
50.00
XGPOL
a
a
Advanced Setting if EADVS := Y. If the Advanced Settings are not enabled (setting
EADVS := N), the relay hides the settings.
Quadrilateral Ground Polarizing Quantity I2, IG I2
TANG
a
Nonhomogeneous Correction Angle () –40.0 to +40.0 –3.0