EL731 Series

AC/DC Sensitive Earth-Leakage Relay

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The EL731 is a microprocessor-based AC/DC Sensitive Earth-Leakage Relay that offers complete coverage for all frequencies from 0 to 6,000 Hz. Two CTs are required for the entire frequency range, or one CT can be used for only low- or high-frequency detection. An RTD/PTC sensor input allows over-temperature protection for a motor or drive. The EL731 offers metering, password-protected alarm and trip settings and optional network communications. It is primarily used to add low-level ground-fault protection to variable-speed drives, and to dc circuits.

Earth Leakage Protection for VSD's

Features & Benefits

  • Adjustable pickup (30-5,000 mA)

    Adjustable trip setting provides a wide range of low-level protection and system coordination

  • Frequency range (0-90 Hz, 20-6,000 Hz)

    Operate in either AC or DC mode or both. Use single or combined ranges. Separate metering

  • 32-char OLED display

    Earth-leakage metering, setup and programming

  • Local LED indication

    Visual Trip, Alarm, CT connection indication

  • CT-Loop monitoring

    Alarms when CT is not connected

  • Analog output (4-20 mA)

    Connect to DCS. Allows connection to an optional meter (PGA-0520) or control system

  • Adjustable time delay

    Adjustable trip delay for quick protection and system coordination

  • Alarm and trip settings

    Detect a deteriorating condition before damage occurs

  • Temperature-sensor input

    Drive or motor temperature protection

  • Output contacts

    3 programmable: Operate 2 alarm and 1 trip circuit

  • Network communication

    Optional connection to plant network

  • Harmonic filtering

    Eliminates nuisance tripping due to harmonic noise

  • Microprocessor based

    No required calibration saves maintenance cost

  • Universal power supply

    Provides flexibility for numerous applications

Datasheets & Manuals

EL731 Datasheet

EL731 Manual

EFCT Datasheet

EL731 Devicenet Manual

EL731 Connection Diagram

EL731 White Paper - Ground Fault Protection with VFD's

Protection Relays Line Card



  • IEEE Device Numbers: AC ground fault (50G/N, 51G/N), DC ground fault (79G), PTC overtemperature (49), RTD temperature (38, 49)
  • Supply Voltage: 120/240 Vac/Vdc, 24 Vdc, 48 Vdc/24 Vac
  • Trip Level Settings: 30-5,000 mA AC and DC
  • Alarm Level Settings: 30-5,000 mA AC and DC
  • Trip Delay: 0.05-2 s
  • Output Contacts: 3 Form C (programmable)
  • Contact Operating Mode: Fail-safe & non-fail-safe
  • Reset: Front panel and remote
  • Freq. Response, CT1: 0-90 Hz
  • Freq. Response, CT2: 20-6,000, 190-6,000, 20-90, 20-3,000 Hz; selectable
  • Current Transformer: EFCT-x series
  • CT Detection: Open & short detection
  • Terminals: Plug-in, wire clamping, 24 to 12 AWG (0.2-2.5 mm2)
  • Communications: EtherNet/IP™, DeviceNet™, Profibus®, Modbus® TCP (optional)
  • Analog Output: 4-20 mA (selectable 0-5 A or 0-100% trip-level setting)
  • Conformal Coating: Standard feature
  • Dimensions: H 48 mm (1.9”); W 96 mm (3.8”); D 129 mm (5.0”)
  • Approvals: UL Listed (E340889), CSA, RCM (Australia), CE
  • Warranty: 5 years
  • Mounting: Panel; Surface and DIN (with optional AC700-SMK)

Ordering Information

When building a part number, replace the ‘X’ with ‘1’ for AS/NZS 2081:2011 compliant product, or ‘0’ otherwise.

EL731-00-X0120/240 VAC/VDCNone
EL731-01-X0120/240 VAC/VDCDeviceNet™
EL731-02-X0120/240 VAC/VDCProfibus®
EL731-03-X0120/240 VAC/VDCEtherNet/IP™
EL731-04-X0120/240 VAC/VDCModbus® TCP
EL731-10-X048 VDC & 24 VACNone
EL731-11-X048 VDC & 24 VACDeviceNet™

EL731-12-X048 VDC & 24 VACProfibus®
EL731-13-X048 VDC & 24 VACEtherNet/IP™
EL731-14-X048 VDC & 24 VACModbus® TCP
EL731-20-X024 VDCNone
EL731-21-X024 VDCDeviceNet™
EL731-22-X024 VDCProfibus®
EL731-23-X024 VDCEtherNet/IP™
EL731-24-X024 VDCModbus® TCP



EFCT Series Earth-Fault Current Transformer
Required zero-sequence current transformer specifically designed for low level detection.

AC700-CUA Series Communication Adapter
Optional network-interface and firmware upgrade communications adapters field-install in EL731.

AC700-SMK DIN-rail & Surface-mount Adapter
EL731 plugs into adapter for back-plane mounting.

Featured Case Study

Cliff Head Off-Shore Oil Rig

The Cliff Head Oil Field Platform (Cliff Head) in located in the Perth Basin about 270 kilometres north of Perth and 12 kilometres off the coast of Dongara in Western Australia. Cliff Head resides in the Production License WA-31-L which covers 72km², and the oil field covers 6km² in the Commonwealth Exploration Permit WA-286-P. Cliff Head is located at a water depth of 15-20 metres and is an integral part of the region’s oil drilling infrastructure.

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Top FAQs

A protection relay is a device that receives inputs typically from current transformers CT’s (but can be other sources) and then compares these inputs to set levels. If these inputs exceed the set levels a protection relay can then provide that information via display or indication, feed that information to other electronic control devices or it can be connected to a circuit breaker to isolate power.

Yes, currently Fuseco can offer both earth leakage and NER relays that are compliant to AS2081:2011. The relay manufacturer (Littelfuse) is also currently in the final stages of development for an AS2081:2011 compliant continuity relay that we expect to release in the near term.

An arc fault is a type of electrical fault that results from the breakdown of an insulating medium between two conductors where the energy is enough to sustain an arc across the insulator (often air) and can cause extreme amounts of light (arc flash), immense heat upwards of 19,000 degrees, and a resulting explosive pressure wave (arc blast). By using a relay that has optical sensors we can detect the flash of light the emanates from an Arc Flash and within 1 msec send a signal to a breaker to interrupt power. Because of the immense energy being released by an Arc Flash reaction time is critical. It can be seen on the graph that with a relay reaction time of only 1 msec (+ circuit breaker reaction time) we can interrupt power before the Arc Flash can result in critical damage.

An arc-flash happens when electric current flows through an air gap between conductors. There are several ways this can happen but the most common occurrence is when conductor insulation is worn or broken down.

The most important aspects of arc-flash relays are:

  • reaction time
  • trip reliability
  • ease of installation
  • sensor flexibility
  • software
  • sensor design
  • avoidance of nuisance tripping
  • scalability

To gain a deeper understanding of which features to consider when selecting an arc-flash relay please refer to the downloadable application guides.

Arc-flash relays are a necessary component in an electrical cabinet because they reduce the amount of incident energy in the system. While an arc-flash relay cannot prevent an arc flash from happening, it will protect critical assets and workers’ safety by reducing the severity of the flash. An arc-flash relay is an integral part of an arc-flash protection scheme that can minimize damage, and save money, time, and lives.

Three phase power systems are most often solidly earthed, however by using a Neutral Earthing Resistor (NER) a power system can be resistance earthed. This is done so that if an earth fault were to occur the amount of fault current will be limited by the NER resistance. One potential problem with a resistance earthed system is; what happens if the NER goes open circuit due to damage? If this were to happen the power system has now changed from a resistance earthed system to a system with no earth reference (floating). Now the NER is no longer restricting the amount of fault current and other devices that rely on an earth reference in order to operate, cannot do so. By using a NER monitoring relay the resistance and integrity of a NER can be continually monitored to detect for any variance in the NER resistance or integrity.

An earth fault can occur as a result of inadvertent contact between and energized conductor and earth or equipment frame. There can also be earth leakage from a system without “inadvertent contact”. This type of fault can be called capacitive earth leakage and it is caused by a capacitive effect between a high power conductor and earth. Small amount of earth leakage current can occur as a result of this capacitive effect. Whether it is smaller amounts current from capacitive earth leakage or larger amounts of current from direct inadvertent contact an earth leakage relay can detect this fault current. In all electrical circuits, current returns to its source. An earth fault relay can use a zero sequence CT to monitor phase current to ensure that all current coming from the source returns on those same conductors or it can monitor current in the connection between transformer neutral and earth. By either method the earth leakage relay detect any lost current to earth.

Applicable Industries

Hi Tim, just wanted to thank you and the Fuseco team for your help. You've managed to help us solve some nagging issues here and the Littelfuse SE-330AU relay installation has saved us a lot of time. Thanks!

Mark Sherman

PGS Silver, Queensland

Just wanted to send a note of thanks to you guys. When it comes to relays, your advice & service is high level & appreciated. Cheers.

Jesse Marshall

Newcrest WA

The Littelfuse SE-701 & the CT's are functioning well. Thanks guys, really appreciate your help. Good to work with people you can rely on.

Cliff Peligro

Alpha Coal, Queensland

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