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5.81
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Functions
Mho Phase-Distance Elements
elements and are useful in applications with series compensation. For more infor-
mation on setting relays to protect series-compensated lines, see AG2000-11:
Applying the SEL-321 Relay on Series-Compensated Systems
.
NOTE:
If the relay is using a remote
data acquisition system, such as TiDL,
the operating times will be delayed by
1.5 ms. Use caution when setting the
relay coordination times to account
for this added delay.
The SEL-421-5 has three independent zones of high-speed mho phase-distance
protection. The high-speed mho phase-distance protection operates for phase-to-
phase, phase-to-phase-to-ground, and three-phase faults. The first three zones of
mho phase-distance protection (Zone 1, Zone 2, and Zone 3) are for high-speed
operation; typical detection time is less than one cycle.
Table 5.52
Mho Phase-Distance Elements Relay Word Bits
Relay Word Bit
Description
MAB1
Zone 1 mho A-B phase element
MBC1
Zone 1 mho B-C phase element
MCA1
Zone 1 mho C-A phase element
Z1P
Zone 1 phase-distance element
MAB2
Zone 2 mho A-B phase element
MBC2
Zone 2 mho B-C phase element
MCA2
Zone 2 mho C-A phase element
Z2P
Zone 2 phase-distance element
MAB3
Zone 3 mho A-B phase element
MBC3
Zone 3 mho B-C phase element
MCA3
Zone 3 mho C-A phase element
Z3P
Zone 3 phase-distance element
MAB4
Zone 4 mho A-B phase element
MBC4
Zone 4 mho B-C phase element
MCA4
Zone 4 mho C-A phase element
Z4P
Zone 4 phase-distance element
MAB5
Zone 5 mho A-B phase element
MBC5
Zone 5 mho B-C phase element
MCA5
Zone 5 mho C-A phase element
Z5P
Zone 5 phase-distance element
Summary of Contents for SEL-421-4
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