![Schweitzer Engineering Laboratories SEL-421-4 Instruction Manual Download Page 435](http://html.mh-extra.com/html/schweitzer-engineering-laboratories/sel-421-4/sel-421-4_instruction-manual_1216726435.webp)
6.99
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Applications Examples
EHV Parallel 230 kV Underground Cables Example
Nonhomogeneous Correction Angle
TANGG, the nonhomogeneous angle setting, also helps prevent overreach or
underreach for ground faults at a specific fault location by compensating the
angle of the reactance line.
Set TANGG to prevent the Zone 1 quadrilateral ground-distance reactance mea-
surement from overreaching for ground faults located at the remote bus. Use the
result from
(T2 in
Quadrilateral Ground Polarizing Quantity on
TANGG :=
—2.2
.
Nonhomogeneous Correction Angle (–40.0 to +40.0 degrees)
Zero-Sequence Current Compensation Factors
Zero-sequence current compensation helps keep the phase and ground-distance
elements at the same reach if you set the phase reach and the ground reach equal
per zone (e.g., Z1MP = XG1). Ground-distance elements should measure fault
impedance in terms of positive-sequence impedance only.
The relay has three zero-sequence current compensation factors (k01, k0, and
k0R). The Zone 1 ground-distance element has a dedicated zero-sequence current
compensation factor (k01). Advanced Settings are enabled for this particular
example (EADVS := Y), so you must set two additional independent zero-
sequence current compensation factors, one for forward-looking zones (k0) and
one for reverse-looking zones (k0R).
The zero-sequence cable impedance depends on the return path of the ground
fault current during ground faults. The zero-sequence current compensation fac-
tors must be set so the Zone 1 ground-distance elements do not see ground faults
external to the protected cable, while Zone 2 and Zone 3 ground-distance ele-
ments must see all internal ground faults.
to calculate the A-Phase-to-ground distance
reactance measurement.
Equation 6.61
Figure 6.24
Nonhomogeneous Angle Setting
X
R
TANGG > 0
TANGG = 0
TANGG < 0
XAG
Im V
A
I
POL
e
j
TANGG
•
•
*
•
Im z1
I
A
k01 3I
0
•
+
I
POL
e
j TANGG
•
•
*
• •
------------------------------------------------------------------------------------------------------------------------------
=
Summary of Contents for SEL-421-4
Page 6: ...This page intentionally left blank ...
Page 14: ...This page intentionally left blank ...
Page 30: ...This page intentionally left blank ...
Page 104: ...This page intentionally left blank ...
Page 128: ...This page intentionally left blank ...
Page 536: ...This page intentionally left blank ...
Page 584: ...This page intentionally left blank ...
Page 616: ...This page intentionally left blank ...
Page 696: ...This page intentionally left blank ...
Page 750: ...This page intentionally left blank ...
Page 755: ...Instruction Manual PM400 01 NB SEL 400 Series Relays Instruction Manual 20171006 ...
Page 776: ...This page intentionally left blank ...
Page 932: ...This page intentionally left blank ...
Page 976: ...This page intentionally left blank ...
Page 1024: ...This page intentionally left blank ...
Page 1038: ...This page intentionally left blank ...
Page 1064: ...This page intentionally left blank ...
Page 1128: ...This page intentionally left blank ...
Page 1206: ...This page intentionally left blank ...
Page 1316: ...This page intentionally left blank ...
Page 1350: ...This page intentionally left blank ...
Page 1464: ...This page intentionally left blank ...
Page 1468: ...This page intentionally left blank ...
Page 1492: ...This page intentionally left blank ...
Page 1518: ...This page intentionally left blank ...