PGR-8800 Series

Arc-Flash Relay

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How Do Arc Flash Relays Work?


The PGR-8800 is a microprocessor-based relay that limits arc-fault damage by detecting the light from an arc flash and rapidly tripping. Phase-current-transformer inputs are provided for current-constrained arc-flash protection and, when so equipped, a programmable definite-time overcurrent function can be enabled. An optical sensor on the PGR-8800 and adjustable trip level reduce the chance of nuisance tripping by setting a threshold for ambient light. Sensors, inputs, and connections are monitored to ensure fail-safe operation. A secondary solid-state trip circuit provides a redundant trip path. A USB port is used for configuration and access to event logs and graphs.

Arc-Flash Detection and Response in less than 1ms

Arc-Flash Relay saved a plant from catastrophic damage

Optical Sensors

The PGR-8800 accepts both PGA-LS10 and PGA-LS20/ PGA-LS30 optical sensors, designed to collect light over a wide angle and with high sensitivity. For fast fault location, front-panel and sensor LED’s indicate sensor health and which sensor detected an arc fault.

Sensor Placement

The PGR-8800 Arc-Flash Relay and sensors are easily installed in retrofit projects and new switchgear with little or no re-configuration. Even elaborate systems with multiple power sources take minutes to configure using the relay’s built-in USB interface software.

Generally, it is recommended to mount 1 or 2 sensors per cubicle to cover all horizontal and vertical bus bars, breaker compartments, drawers, and anywhere that there is potential for an arc-fault. Threading a fiber-optic sensor through the cabinets and in areas where point-sensor coverage is uncertain results in complete coverage and an added level of redundancy. Even if policy is to only work on de-energized systems, all maintenance areas should be monitored to prevent potential damage and additional cost. At least one sensor should have visibility of an arc fault if a person blocks the other sensor(s).

Features & Benefits

  • Arc-Flash trip time <1 ms

    Limits arc-flash damage and risk of injury

  • Multiple sensors (up to 24)

    Single module can monitor 6 sensors. Up to 4 PGR-8800 units can be linked into one system

  • Fail-safe system

    Continuous monitoring of optical sensors and inputs ensures protection

  • Redundant trip circuit

    Solid-state backup arc-detection circuit adds a second layer of safety

  • Adjustable light sensitivity

    Allows for operation in bright environments and maximum sensitivity in dark environments

  • LED indication (on unit and each sensor)

    18 LEDs provide at-a glance status for module and I/O state

  • Current detection

    Phase-CT inputs provide overcurrent protection and prevent nuisance trips

  • Optical detection

    Point and fiber-optic sensors provide wide detection area with sensor health trip indication

  • Digital inputs (6)

    Two each: remote trip, inhibit, and reset inputs

  • Service mode

    Allows for system test without tripping

  • Trip coil contact

    Solid-state 24-300 Vdc/24-300 Vac IGBT

  • Indication contacts

    Form C and status outputs

  • USB interface

    Data logging and configuration software uses a USB interface with no drivers or software installation

  • Built-in sensor

    Can be used in single-sensor systems, as a seventh sensor, and for calibration

  • Universal power supply/Battery backup

    100-240 Vac, 14-48 Vdc, or 110-250 Vdc supply accepted. Ability to charge and run off an external, user-supplied 24 Vdc battery.

  • Data logging

    On-board event recorder helps with system diagnostics

  • Modbus

    Remotely view measured values, event records & reset trips

  • Upstream Tripping

    Ability to trip upstream device if the local breaker fails to clear the fault

Datasheets & Manuals

PGR-8800 Datasheet

PGR-8800 Manual

Littelfuse Arc-Flash Relay Brochure

Littelfuse Arc Flash Energy Reduction Workbook

Littelfuse Arc-Flash Relay FAQ

PGR-8800 Arc-Flash Relay Application Guide

Arc-Flash Case Study


  • IEEE Device Numbers: Overcurrent (50), Arc Flash (AFD)
  • Input Voltage: 100-240 Vac, 14-48 Vdc, and 110-250 Vdc
  • Dimensions: H 130 mm (5.1”); W 200 mm (7.9”); D 54 mm (2.1”)
  • Optical Trip Settings: 9-25 klux, 800 μs-20 s
  • Current Trip Setting (A): Programmable
  • Indication Contact Mode: Fail-safe
  • Trip Coil Voltage:* 24-300 Vdc, 24-300 Vac
  • Trip Coil Contact Mode: Selectable fail-safe or non-fail-safe
  • Redundant Trip Circuit: Standard feature
  • Input Monitoring: Standard feature
  • USB Interface: Standard feature
  • Trip, Reset, Service Buttons: Standard feature
  • Expandable System: Link up to 4 PGR-8800 units
  • Warranty: 5 years
  • Mounting: Surface, DIN (with D0050 adapter clips)
  • Approvals: FCC, DNV type approval, ABS type approval 

* Contact Fuseco for trip coil voltages higher than 300 VDC/VAC

Ordering Information

PGR-8800-00 (UL, CE, CSA, RCM)Arc-Flash Relay
PGR-8800-00-CC (UL, CE, CSA, RCM)Arc-Flash Relay, Conformally Coated
PGA-LS20, PGA-LS30Required
Current TransformerRecommended


PGA-LS10 Point Sensor
Line-of-sight light sensor detects an arc as small as 3 kA within a 2-m half-sphere. Sensor health and trip indication. Dimensions: See PGR-8800 Manual

PGA-LS20/PGA-LS30 Fiber-Optic Sensor
360° light sensor for tricky installations with many shadows or to run along bus bars. Sensor health and trip indication. Dimensions: See PGR-8800 Manual

PGA-1100 Diode Logic Unit
This module allows multiple PGR-8800 relays to trip the same breaker, for example an upstream or a tie-breaker. Dimensions: H 80mm (3.15”) W 20mm(0.79”) D 70mm(2.76”)

Current Transformers
Eliminate nuisance arc-flash trips and use for overcurrent protection.

Featured Case Study

Littelfuse Arc-Flash Relay Saves Plant from Catastrophic Damage

Tim Deschamp from Evans Enterprises, Tulsa, Oklahoma, was working with a customer to help them resolve and reduce a critical issue with an electrical hazard in their furnace control room. An earlier arc-flash analysis had determined that one 480-volt cabinet, which was fed from a 3500 kVA transformer, exceeded an arc-flash Hazard Risk Category 4 (HRC).

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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.

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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!

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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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