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SE-330AU Neutral-Earthing-Resistor Monitor
Rev. 4-I-101817
3. I
NSTALLATION
3.1 SE-330AU
Outline and panel-cutout dimensions for the SE-330AU
are shown in Fig. 4. To panel mount the SE-330AU,
insert it through the panel cutout and secure it with the
four included 8-32 locknuts and flat washers. If an
optional SE-IP65CVR-G Hinged Cover is used, follow
the included installation instructions. See Figs 6 and 7.
All connections to the SE-330AU are made with
plug-in, wire-clamping terminal blocks. Each plug-in
terminal block can be secured to the SE-330AU by two
captive screws for reliable connections.
Outline dimensions and mounting details for surface
mounting the SE-330AU are shown in Fig. 5. Fasten the
optional SE-330-SMA Surface-Mount Adapter to the
mounting surface and make connections to the adapter
terminal blocks. Follow Fig. 5 instructions to mount or
remove the SE-330AU.
Connect terminal 7 (G) to earth and connect terminal
6 (R) to the sensing-resistor R terminal.
Use terminal 1 (L1) as the line terminal on ac systems,
or the positive terminal on dc systems. Use terminal 2
(L2/N) as the neutral terminal on ac systems or the
negative terminal on dc systems. Connect terminal 3 (
)
to earth.
N
OTE:
Disconnect terminal 1 (L1) and terminal 2 (L2/N)
before performing dielectric strength testing of the control
panel.
N
OTE:
Connections to terminals 4 (SPG) and 5 (SPGA)
are not required when using the SE-330AU hardware
revision 10 and higher. However, it is recommended to
connect terminal 4 to terminal 5 to maintain backwards
compatibility with the older SE-330AU series (hardware
revision 01 and lower).
3.2 S
ENSING
R
ESISTOR
Outline and mounting details for the ER-600VC,
ER-5KV, ER-5WP, ER-15KV, ER-25KV, and ER-35KV
sensing resistors are shown in Figs. 8, 11, 12, 13, 14 and 15.
Install the NER and the sensing resistor near the transformer
or generator. An optional SE-MRE-600 Moisture Resistant
Enclosure is available for applications which may expose an
ER-600VC to moisture. See Figs 9 and 10. The weather-
protected ER-5WP shown in Fig. 12 is an ER-5KV with
moisture-resistant terminal covers. Use an ER-5WP in
applications in which it might be exposed to moisture. The
ER-15KV, ER-25KV, and ER-35KV include moisture-
resistant terminal covers. Use suitable water-tight fittings.
Connect terminal G to earth. Pass the sensing-resistor-to-
neutral conductor and the NER-to-neutral conductor
through the earth-fault-CT window as shown in Fig. 3.
Separately connect sensing-resistor terminal N and the NER
to the neutral to include neutral connections in the
monitored loop. Alternatively, if the NER connection to
system neutral need not be monitored, connect terminal N to
the NER neutral terminal.
If an earth fault in the sensing-resistor conductor is
unlikely, a minimal loss of protection will result if it does
not pass through the earth-fault-CT window. See Fig. 3.
N
OTE
:
Voltage at terminal N rises to line-to-neutral voltage
when an earth fault occurs. The same clearances are
required for sensing resistors as for NER’s.
N
OTE:
A parallel earth path created by moisture can
result in a false resistor-fault trip. Moisture sources
include wind-driven rain or snow, and condensation.
Sensing-resistor terminal R and its connection to SE-
330AU terminal R, including interposing terminal blocks,
must remain dry.
N
OTE
:
The neutral-to-sensing-resistor-terminal-N connection
is not a neutral conductor. Since current through this
conductor is always less than 250 mA, a 1.5 mm
2
conductor insulated to the system voltage is more than
sufficient.
N
OTE:
For outdoor installations, sensing resistors must be
in an IP14 enclosure.
3.3 E
ARTH
-F
AULT
CT
Select and install an earth-fault CT that will provide the
desired trip level. Typically, the CT-primary rating
should be approximately equal to the NER let-through-
current rating. This provides an appropriate EF TRIP
LEVEL setting range and analog-output scaling. The
primary rating of the EFCT-x is 5 A and the primary rating
of the SE-CS30-x is 30 A. See Sections 2.1.2 and 2.9.
Outline and mounting details for the sensitive EFCT-x
and SE-CS30-x current sensors are shown in Figs. 16, 17,
and 18. Earth-fault-CT connections and the typical earth-
fault-CT location are shown in Fig. 3. If an earth fault in
the NER is unlikely, a minimal loss of protection will
result if the earth-fault CT monitors the NER connection
to earth rather than its connection to neutral.
