SE-330AU Series

Neutral-Earthing-Resistor Monitor

We're here to help

Talk to an expert today.
Our friendly team of highly trained specialists will quickly assist you.

Get a quote technical support 1300 387 326


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, and an analog output. A mini USB port is included to view measured values, configure settings, and check event records. An on-board micro SD card can be used for long-term data logging. 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.

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.

SE-330 PCN Document

SE-330AU Datasheet - New Revision

SE-330AU Datasheet - Previous Revision

SE-330AU Manual - New Revision

SE-330AU Manual - Previous Revision

SE 330 AU DeviceNet Electronic Datasheet EDS - New Revision

SE-330 AU DeviceNet Electronic Datasheet EDS - Previous Revision

SE-330 EthernetIP Electronic Data Sheet (.eds) - New Revision

SE-330 EthernetIP Electronic Data Sheet (.eds) - Previous Revision

SE-330 DeviceNet Manual - Previous Revision

SE-330 EthernetIP Manual - Previous Revision

SE-330 Profibus Manual - Previous Revision


  • Input Voltage: See ordering information
  • 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: C-Tick (Australian), CE
  • Communications: Mini USB (standard); DeviceNet (optional), IEC 61850 (optional), Modbus TCP and EtherNet/IP (optional)
  • Analog Output: 4-20 mA, self or loop powered
  • Conformal Coating: Standard feature
  • Warranty: 5 years
  • Mounting: Panel, Surface (optional)

Ordering Information


SE-330AU for all apps. 35 kV or less

SE-330HV for 72 kV apps.

0=120/240 VAC/VDC

2=48 VDC

0=USB Only 1=DeviceNet

3=EtherNet (Dual RJ45)

4=EtherNet (SC Fiber & RJ45)

5=EtherNet (Dual SC Fiber)

6=IEC61850 (Dual RJ45)

7=IEC61850 (SC Fiber & RJ45)

8=IEC61850 (Dual SC Fiber)

0=Normally Open 1=Normally Closed

ER Series Sensing ResistorRequired
Current TransformerRequired


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).