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5.117
Date Code 20171021
Instruction Manual
SEL-421 Relay
Protection Functions
Switch-Onto-Fault Logic
59P
n
D1 (Overvoltage Level 1 Time Delay)
When the system voltage exceeds the overvoltage setting value, the overvoltage
timer starts timing. Set the delay (in cycles) for which the timer must run before
the output asserts.
Switch-Onto-Fault Logic
The switch-onto-fault (SOTF) logic permits specified protection elements to trip
for a settable time after the circuit breaker closes. Specify these elements in the
SEL
OGIC
control equation TRSOTF (switch-onto-fault trip). The SOTF logic
works in two stages: validating a possible SOTF condition and initiating
(enabling) the SOTF protection duration.
The relay validates an SOTF condition by sensing the following:
➤
Upon circuit breaker opening
: detection of a pole-open condition
(3PO or SPO) when setting 52AEND (52A Pole-Open Qualifying
Time Delay) is other than OFF
➤
Upon circuit breaker closing
: detection of a pole-open condition
(3PO or SPO) when setting CLOEND (CLSMON or Single-Pole
Open Delay) is other than OFF
Select either or both methods for the validating procedure.
The relay initiates SOTF protection at these corresponding instances:
➤
Circuit breaker opening
: 52AEND timer timeout
➤
Circuit breaker closing
: CLOEND time timeout and SEL
OGIC
control equation CLSMON assertion
Circuit Breaker Opened SOTF Logic
Set ESOTF to Y and set 52AEND to other than OFF to enable the circuit breaker-
opened SOTF logic. When the circuit breaker opens, the 52AEND timer operates
when one or three poles open (SPO or 3PO assert). The logic includes the SPO
condition if setting ESPSTF := Y (see
). When the
3PO or SPO condition lasts longer than the 52AEND timer, the relay asserts
Relay Word bit SOTFE (SOTF Enable).
When the circuit breaker closes, either Relay Word bit 3PO deasserts after the
3POD dropout time or Relay Word bit SPO deasserts after the SPOD dropout
time. When 3PO or SPO deasserts, the relay continues to assert Relay Word bit
SOTFE for dropout time SOTFD or until the logic detects a healthy voltage con-
dition (if EVRST := Y, see
).
Setting
Prompt
Range
Default
Category
59P
n
D1
a
a
n
= 1–6.
O/V Element
n
Level 1 Delay
0.00 to 16000 cyc.
10
Group
Содержание SEL-421-4
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