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Date Code 20010625
Inputs, Outputs, Timers, and Other Control Logic
7-37
SEL-311L Instruction Manual
High-Speed 87L Tripping—Example 1
The only trip setting required for high-speed line current differential protection is the Enable
High-Speed Trip setting, EHST. Select the total number of contacts enabled for high-speed
tripping (1 through 6). For example, to control high-speed output contacts OUT201 and
OUT202 with the line current differential high-speed tripping logic, set
EHST = 2
and connect output contacts OUT201 and OUT202 directly to the trip coils of the circuit breaker
as shown in Figure 7.28. OUT201 through OUT206 can interrupt trip current, so tripping
auxiliaries may not be required. In this example, contacts OUT201 and OUT202 close less than
10 microseconds after the line current differential protection detects an internal fault, resulting in
a typical tripping time less than one cycle.
As a reminder that OUT201 and OUT202 are enabled for high-speed tripping, it is permissible to
put the TRIP87 bit in the corresponding SEL
OGIC
control equations:
OUT201 = TRIP87L
OUT202 = TRIP87L
This does not change how the relay operates; it only serves as a reminder that OUT201 and
OUT202 are trip contacts.
dc2 (+)
dc1 (+)
(—)
(—)
OUT201
Trip Coil 1
52a1
OUT202
Trip Coil 2
52a2
DWG: M311L068
Figure 7.28: High-Speed Trip Contact Connections—Example 1
High-Speed 87L Tripping with Backup Protection Tripping—Example 2
Contacts OUT201 through OUT206 can be used for backup protection tripping, even if they are
also used for high-speed line current differential tripping. For example, to add backup protection
and manual tripping to the previous example, make SEL
OGIC
control equation settings
OUT201 = TRIP
OUT202 = TRIP
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