Date Code 20001006 Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements 3-9
SEL-351 Instruction Manual
To understand the operation of Figure 3.8 and Figure 3.9, follow the explanation given for
Figure 3.1, Figure 3.2, and Figure 3.3 in the preceding Phase Instantaneous/Definite-Time
Overcurrent Elements subsection, substituting current I
N
(channel IN current) for phase currents
and substituting like settings and Relay Word bits.
For sensitive earth fault (SEF) applications, the SEL-351 Relay should be ordered with channel IN
rated at 0.05 A nominal. For this channel IN rating, the increased pickup sensitivity of the neutral
ground overcurrent elements is noted in the following setting ranges.
Figure 3.7: Levels 1 Through 4 Phase-to-Phase Instantaneous Overcurrent Elements
Courtesy of NationalSwitchgear.com
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