Date Code 20060320 Instruction Manual SEL-311C Relay
Appendix F
Setting Negative-Sequence
Overcurrent Elements
Setting Negative-Sequence
Definite-Time Overcurrent Elements
Negative-sequence instantaneous overcurrent elements 50Q1 through
50Q4 and 67Q1 through 67Q4 should not be set to trip directly. This is
because negative-sequence current can transiently appear when a circuit
breaker is closed and balanced load current suddenly appears.
To avoid tripping for this transient condition, use negative-sequence definite-
time overcurrent elements 67Q1T through 67Q4T with at least 1.5 cycles of
time delay (transient condition lasts less than 1.5 cycles). For example, make
time delay setting:
67Q1D = 1.50
for negative-sequence definite-time overcurrent element 67Q1T. Refer to
Figure 3.23 for more information on negative-sequence instantaneous and
definite-time overcurrent elements.
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