Date Code 20010625
Trip and Target Logic
5-11
SEL-311L Instruction Manual
Figure 5.5 and the following discussion describe the three-pole open (3PO) logic and the SOTF
logic.
Figure 5.5: 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 5.5. It is not affected by enable setting
ESOTF (see the settings sheets in
Section 9: Setting the Relay
).
The open circuit breaker condition is determined by load current (50L) and either one of:
v
Circuit breaker status (52A = logical 0), recommended
v
Positive-sequence voltage (|V1| < 27PO), not recommended when 87L protection is
enabled
Select OPO = 52 if 3PO is determined by circuit breaker status. Select OPO = 27 if 3PO is
determined by positive-sequence voltage and if 87L protection is not used.
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