5.87
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Functions
Quadrilateral Phase-Distance Elements
Quadrilateral Phase Nonhomogeneous Setting (TANGP)
Nonhomogeneous negative-sequence networks can cause distance elements to
underreach or overreach. Use the network in
to determine whether
the negative-sequence network is homogeneous. Z
LEFT
is the total impedance up
to the fault (F) on the left-hand side, while Z
RIGHT
is the total impedance up to
the fault on the right-hand side.
Figure 5.67
Quadrilateral Phase-Distance Element Characteristic (TANGP = –10 degrees)
Zone 3
TANGP = —10 degrees
Zone 2
Zone 1
Z1ANG
RP1
XP1
XP2
XP3
jX
—RP
RP2
RP3
R
Figure 5.68
Network to Determine Homogeneity
IF
F
IF
Z
RIGHT
Z
LEFT
Z1S
m
•
Z1L
(1 — m)
•
Z1L Z1R
S
R
Summary of Contents for SEL-421-4
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