Relay Element Settings 2-37
SEL-300G Instruction Manual Date Code 20020206
Setting Calculation
Information Needed
• Generator continuous current unbalance withstand capability, percent of rated current
• Generator negative-sequence current short-time withstand capability, seconds
Recommendations
Set the 46Q1P equal to or just greater than the generator continuous unbalance current capability.
12%–846Q1P =
Set the 46Q1D time delay greater than the maximum system phase-fault clearing time. This
delay setting will prevent undesired unbalance current alarms for system faults that are cleared
normally.
seconds 5.046Q1D =
Set the 46Q2P setting greater than the generator continuous unbalance current capability.
12%–846Q2P =
Set the 46Q2K setting equal to the generator short-time negative-sequence current capability.
1046Q2K =
If there are operating conditions under which you wish to prevent negative-sequence overcurrent
element operation, define those conditions in the 46QTC torque-control setting. Normally, the
negative-sequence overcurrent elements should be enabled all the time.
146QTC =
Negative-Sequence Overcurrent Tripping
Negative-sequence overcurrent tripping generally is applied to the generator main breaker only.
This permits rapid resynchronization after the system unbalance condition is cleared. Refer to
Section 4: SEL
OGIC
®
Control Equations for more detail and examples of tripping SELOGIC
Control Equations.
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