Schweitzer Engineering Laboratories SEL-751 - Figure 2.44 Switchgear Application Example

2.47
Date Code 20170927 Instruction Manual SEL-751 Relay
Installation
Arc-Flash Protection: System Installation
The clear-jacketed fiber loop should be returned through the same general
area as the forward path, providing dual opportunity to sense the same arc-
flash event. This approach ensures that the maximum distance between the
relay and the light-producing event remains below 35 m, irrespective of the
SEL-751 dual V-pin connector orientation.
Application Example
Figure 2.44 shows a typical switchgear application example with one incom-
ing and two radial (outgoing) feeders. All three feeders are protected with an
SEL-751 controlling breakers 1, 2, and 3. Radial feeder breakers 2 and 3 must
be tripped for downstream faults, normally located in the outgoing cable ter-
mination compartment. To obtain better coverage, multiple sensors can be
installed in the same compartment, as shown in the lower right corner of the
Figure 2.44 with sensors marked LS1 and LS2.
Bus compartment and the outgoing breaker compartments for breakers 2 and
3 are protected by the incoming feeder breaker 1, with sensors LS1, LS2, and
LS3 connected directly to the incoming feeder relay (upper right hand corner
of Figure 2.44). Sensor LS1 is implemented as a clear-jacketed fiber loop
enclosing entire length of the bus.
When desired, you can use radial feeder relays sensors (such as LS3 con-
nected to the lower right hand relay) to transfer trip the upstream breaker.
Logic equations for this function are shown in Output Logic Programming in
Section 4: Protection and Logic Functions.
Figure 2.44 Switchgear Application Example
Ordering Arc-Flash
Fiber Sensors
Arc-flash fiber sensors can be ordered with or without splices. To configure
the standard multimode fiber-optic arc-flash detection point and fiber-loop
sensor cable assemblies without additional splice connectors, use the C804
Multimode Fiber-Optic Arc-Flash Detection (AFD) Sensors Model Option
Table (MOT). For multimode fiber optic arc-flash detection sensors with addi-
3 2
1
LS2
LS3
LS3
LS1
LS1
LS2
Bus
LS1—LS4 are arc-flash detection inputs, point or clear-jacketed fiber sensors.
SEL-751
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