3-24 Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements Date Code 20001006
SEL-351 Instruction Manual
Neutral Ground Time-Overcurrent Element
Figure 3.18: Neutral Ground Time-Overcurrent Element 51NT (With Directional Control
Option)
To understand the operation of Figure 3.18, follow the explanation given for Figure 3.14 in the
preceding Phase Time-Overcurrent Elements subsection, substituting current I
N
(channel IN
current) for maximum phase current I
P
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 time-overcurrent element is noted in Table 3.4.
Courtesy of NationalSwitchgear.com
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