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SE-330HV Neutral-Grounding-Resistor Monitor
Rev. 5-M-101817
FIGURE 14. ER-1000HV Simplified Connection Diagram.
3.3 G
ROUND
-F
AULT
CT
Select and install a ground-fault CT that will provide
the desired trip level. Typically, the CT-primary rating
should be approximately equal to the NGR let-through-
current rating. This provides an appropriate GF TRIP
LEVEL setting range and analog-output scaling. See
Sections 2.1.2 and 2.8.
Outline and mounting details for the EFCT- and
SE-CS30-series current sensors are shown in Figs. 15,
16, and 17. Ground-fault-CT connections and the
preferred ground-fault-CT location are shown in
Fig. 3. If a ground fault in the NGR is unlikely, a
minimal loss of protection will result if the ground-fault
CT monitors the NGR connection to ground rather than
its connection to neutral. A minimal loss of protection
will also result if the sensing-resistor-to-neutral
connection does not pass through the CT window. This
alternate CT location is shown in Fig. 3.
The accuracy of a typical current sensor decreases
below 5% of its current rating. CT-primary current-
injection testing is recommended to verify trip levels
below 5% of the CT-primary rating. See
Section 9.4. Littelfuse Startco current sensors are
designed for use at low levels and respond linearly to 2%
current rating.
N
OTE
:
The current-sensor insulation class is of no
consequence if its secondary is grounded and the
conductors through its window are insulated for the
system voltage. Bushing type CT’s are required for
applications using bare conductors on the NGR’s neutral
side.
