Date Code 20001006 Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements 3-57
SEL-351 Instruction Manual
Figure 3.32: Voltage Swell Elements
Voltage Interruption Elements:
If the magnitude of a phase voltage drops below the voltage interruption percentage setting of the
positive-sequence memory voltage magnitude for one cycle, the corresponding INT Relay Word bit
for that phase asserts (INTA, INTB, or INTC). If all three phase INT elements assert for one
cycle, an additional Relay Word bit asserts - INT3P. The INT elements remain asserted until the
magnitude of the corresponding phase voltage rises and remains 5% above the interruption pickup
threshold for at least one cycle.
Note: Reset has priority over sag.
Figure 3.33: Voltage Interruption Elements
Courtesy of NationalSwitchgear.com
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