Date Code 20011205
Trip and Target Logic
5-7
SEL-311B Instruction Manual
Figure 4.1
Figure 5.3: Three-Pole Open Logic (Top) and Switch-Onto-Fault Logic (Bottom)
Three-Pole Open Logic
Three-pole open (3PO) logic is the top half of Figure 5.3. It is not affected by enable setting
ESOTF (see Settings Sheet 2 in
Section 9: Setting the Relay
).
The open circuit breaker condition is determined by load current (50L) and either one of:
·
Circuit breaker status (52A = logical 0)
·
Positive-sequence voltage (|V1| < 27PO)
Select OPO = 52 if 3PO is determined by circuit breaker status. Select OPO = 27 if 3PO is
determined by positive-sequence voltage.
If OPO = 52, and the circuit breaker is open (52A = logical 0) and current is below phase pickup
50LP (50L = logical 0), then the three-pole open (3PO) condition is true:
3PO = logical 1
(circuit breaker open)
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