Sel SEL-421 - Circuit Breaker Closed SOTF Logic; SOTF Options; SOTF Settings; SOTF Relay Word Bits

R.1.85
Date Code 20111215 Reference Manual SEL-421 Relay
Protection Functions
Switch-Onto-Fault Logic
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
condition (if EVRST := Y, see SOTF Options).
Circuit Breaker
Closed SOTF Logic
You can detect circuit breaker close bus assertion by monitoring the dc close
bus. Connect a control input on the SEL-421 to the dc close bus. The control
input energizes whenever a manual close or automatic reclosure occurs. Set
SEL
OGIC control equation CLSMON (Close Signal Monitor) to monitor the
control input (e.g., CLSMON := IN102) and consequently detect close bus
assertion.
Set ESOTF to Y and set CLOEND to other than OFF to enable the circuit
breaker-closed SOTF logic. The CLOEND timer operates when one or three
poles open (SPO or 3PO asserts). If the 3PO or SPO condition continues
longer than the CLOEND time and the close bus asserts (SEL
OGIC control
equation CLSMON equals logical 1), Relay Word bit SOTFE asserts and
remains asserted for dropout time setting SOTFD or until the logic detects a
healthy voltage condition (if EVRST := Y, see SOTF Options).
SOTF Options
If the setting EVRST (Voltage Reset Enable) is enabled (EVRST := Y), Relay
Word bit SOTFE resets automatically when the relay measures healthy
balanced positive-sequence voltage at greater than 85 percent nominal
voltage.
If setting ESPSTF (Single-Pole SOTF Enable) is enabled (ESPSTF := Y), the
relay provides SOTF protection for a single-pole open (SPO) condition.
Tabl e 1 . 61 SOT F Set tin gs
Setting Description Range
Default
(5 A)
ESOTF Switch-Onto-Fault Y, N Y
ESPSTF Single-Pole Switch-Onto-Fault Y, N N
EVRST Switch-Onto-Fault Voltage Reset Y, N N
52AEND 52A Pole Open Time Delay (cycles) OFF, 0.000–16000 10.000
CLOEND CLSMON or Single Pole Open Delay
(cycles)
OFF, 0.000–16000 OFF
SOTFD Switch-Onto-Fault Enable Duration
(cycles)
0.500–16000 10.000
CLSMON Close Signal Monitor SEL
OGIC Equation NA
Tabl e 1 . 62 SOT F Re la y Wo rd B its
Name Description
SOTFE Switch-onto-fault trip logic enabled