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Line Protection
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SEL-421 High-Speed Line
Protection, Automation, and Control System
- Apply complete pilot protection for primary and backup, and
single- or three-pole tripping schemes on transmission and subtransmission
lines.
- Make settings for up to four shots of automatic breaker reclosing
for one or two circuit breakers, with synchronism and voltage
checks to optimize system restoration.
- Use the built-in fault locator to efficiently dispatch line
inspection and repair personnel.
- Implement breaker failure logic for one or two circuit breakers.
- Schedule as-needed circuit breaker maintenance and send alarms
when the breaker monitor detects excess breaker contact wear
from the number of operations and magnitude of interrupted current.
- Alarm for low-voltage conditions on one or two station batteries.
- Track average and last circuit breaker operate time. Alarm
on slow circuit breaker.
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SEL-311L Line Current
Differential Protection and Automation System
- Apply a complete multiprinciple protection scheme in one relay.
In addition to a superior differential function, a complete
distance and directional overcurrent relay is included in the
standard product.
- The Alpha plane restraint principle, used in the SEL-311L
Relay, is more secure, provides better sensitivity, and is easier
to set than percent restraint, dual slope restraint, charge
comparison, or phase comparison relays offered by our competition.
- Applying the differential protection of the SEL-311L can be
done for the large majority of applications (overhead lines
and cables, all voltage classes) by simply selecting the CT
ratio for all terminals and configuring the communications channels.
No fault studies are required.
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SEL-311 Phase and Ground Distance Relay
- Economical phase and ground distance protection for utility
intertie connections.
- Backup transformer and generator protection with zone distance
and overcurrent elements.
- Built-in fault locator for efficient use of line inspection
and repair personnel.
- SELOGIC® control equations for customizing advanced
protection and control schemes.
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SEL-321 Phase and Ground Distance Relay
- Select the SEL-321 Relay for complete distance protection
including single-pole tripping and series-compensated lines.
- Apply the SEL-321 Relay for primary and/or backup single-
or three-pole trip transmission line protection, including series-compensated
lines.
- Use the advanced single-pole tripping logic with phase selection,
open-pole interval protection, and phase discordance logic with
three-pole trip to protect against excessive single-pole open
events.
- Select the load-encroachment feature to prevent operation
of three-phase elements under high load conditions.
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SEL-351 Directional Overcurrent and Reclosing
Relay
- Protect and control radial or looped transmission, subtransmission,
or distribution circuits.
- Use pilot protection on transmission or subtransmission circuits,
including three-terminal lines.
- Apply directional and nondirectional overcurrent protection
for transformer/bus main/bus-tie breaker.
- Protect small generators and distributed generation interconnections.
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