Littelfuse SE-330AU User Manual

Protection Relays & Controls

Neutral-Earthing-Resistor Monitoring

SE-330AU SERIES

Neutral-Earthing-Resistor Monitor

Description

The SE-330AU is an advanced earth-fault and earthing-resistor
monitoring relay for low- and medium-voltage transformers and
generators. It monitors neutral current, neutral-to-earth voltage, and
neutral-to-earth resistance. It provides continuous monitoring of the
neutral-to-earth path to verify that the neutral-earthing resistor (NER)
is intact. This is of utmost importance—an open NER renders
current-sensing earth-fault protection inoperative and could result in a
false belief that the system is functioning properly. The SE-330AU
earth-fault function complies with AS/NZS 2081.3:2002. Outputs
include four relay outputs, an analog output, and an RS-232 interface.
Network communications options are available. For non-AS/NZS 2081
applications, see the SE-330 or SE-330HV.

Resistor Monitoring

The SE-330AU combines the measured values of resistance, current,
and voltage to continuously determine that the NER is intact. It is
able to detect a resistor failure with or without an earth fault present.
Sensing resistors are matched to the system voltage and are used
to monitor NGRs on systems up to 35 kV.

Simplified Circuit Diagram

CT

NER

B

ER SERIES

(Sensing Resistor)

A

L1
L2

SE-330AU
SERIES

(NER Monitor)

Ordering Information

ORDERING
NUMBER

COMMUNICATIONS

SE-330AU-00-0X RS-232
SE-330AU-01-0X RS-232 & DeviceNet
SE-330AU-02-0X RS-232 & Profibus

™

®

SE-330AU-03-0X RS-232 & EtherNet/IP & Modbus TCP

NOTE: For 48 Vdc Control Power use part numbers SE-330AU-20-00, SE-330AU-21-00,

SE-330AU-22-00 or SE-330AU-23-00 respectively.

ACCESSORIES REQUIREMENT

ER Series Sensing Resistor Required

Current Transformer Required

SE-IP65CVR-G Optional

SE-MRE-600 Optional

RK-332 Optional

CONTROL
POWER

120/240 Vac/Vdc

120/240 Vac/Vdc

120/240 Vac/Vdc

120/240 Vac/Vdc

Earth-Fault Monitoring

The SE-330AU uses a 5- or 30-A-primary current transformer to
provide a pickup-setting range of 0.125 to 5 A or 0.75 to 30 A to
comply with AS/NZS 2081.3:2002. DFT filtering ensures that false
trips due to harmonic noise from adjustable-speed drives do not
occur. Open-CT detection is provided.

Accessories

A

B

ER Series Sensing Resistor

Required interface between the power system
and the SE-330AU. Eliminates hazardous voltage
levels at the relay.

EFCT Series Earth-Fault Current Transformer

Sensitive earth-fault current detection (5 A primary).

SE-CS30 Series Earth-Fault Current Transformer

Sensitive earth-fault current detection (30 A primary).

Specifications

Input Voltage 80 to 265 Vac/Vdc or 36 to 72 Vdc
Dimensions H 213 mm (8.4”), W 98 mm (3.9”), D 132 mm (5.2”)
GF Trip-Level Settings 0.125 to 30 A
GF Trip-Time Settings 0.1 to 0.5 s
Vn Trip-Level Settings 20-2,000 Vac (≤5 kV systems)

100-10,000 Vac (>5 kV systems)

Output Contacts Two Form A, Two Form C
Operating Mode Fail-Safe
Harmonic Filtering Standard feature
Reset Front panel push button and remote input
Approvals CSA certified; C-Tick (Australian)

Communications RS-232; (standard) DeviceNet™, Profibus®,

Ethernet (optional)

Analog Output 4-20 mA, self or loop powered
Conformal Coating Standard feature
Warranty 5 years
Mounting Panel, Surface (optional)

© 2013 Littelfuse Protection Relays & Controls
Littelfuse.com/se-330au

Rev: 4-B-050213

Based on Manual Rev 3