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Underground AutoRANGER Fault Indicator

The SEL-ARU is a reliable faulted circuit indicator suitable for applications with fault current 50 A and up. It automatically selects a minimum trip threshold based on sampled load current to better coordinate with upstream protection. SEL underground AutoRANGER technology supports system-wide adaptability, eliminating the need to deploy different fixed-trip threshold fault indicators. Being able to use one indicator across many applications simplifies ordering, inventory, installation, and crew training.

You can choose from a variety of displays: a target-only (no LED) display option to eliminate the need for a battery, BEACON Bolt LED models that minimize travel to the field to replace batteries, and auxiliary contact options that provide an economical way to indicate status to SCADA systems.

Accessories and Tools for Fault Indicators and Sensors

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Underground Fault Detection—Find faults quickly on underground distribution systems. Display options are available for pad-mounted, vault, and manhole installations. Line-powered and restoration reset features provide a long indicator life and no- or low-maintenance performance for any application.

Subsurface Vaults and Manholes—Use the SEL-ARU in subsurface applications with the RadioRANGER Underground Wireless Fault Indication System. The RadioRANGER System provides remote indication of the fault indicator status without accessing the vault, minimizing patrol time.

Underground Reliability Improvement—Increase reliability on underground distribution circuits by installing underground AutoRANGERs in the following applications:

  • Pad-mounted transformers
  • Pad-mounted switchgear
  • Subsurface vaults
  • Junction boxes
  • Unfused taps
  • Midfeeder disconnect or sectionalizers
  • Long feeders

Auxiliary contact options provide an economical way to indicate status to SCADA systems, and you can choose from a variety of remote displays.



  • Line-Powered Functionality. Energy required to power the microprocessor comes from monitored load current rather than a battery, decreasing maintenance and the cost of ownership.
  • Dynamic Trip Response. By monitoring current, the SEL-ARU automatically adjusts the trip response time to better coordinate with upstream protection.
  • Self-Adjusting Trip Threshold. Automatic trip-level selection based on sampled load current makes underground AutoRANGERs suitable for applications with fault current 50 A and up. This feature simplifies ordering, reduces inventory, and saves installation time by allowing you to use one device model across your system.
  • Dynamic Backfeed Restraint. Protection from backfeed reset is inherent in underground AutoRANGER design. Each SEL-ARU derives a normalization current threshold as a function of measured circuit load. They use the normalization current threshold to distinguish circuit restoration from backfeed current. With the right selection of features, the SEL-ARU can even maintain its fault indication through an automatic circuit reconfiguration event.
  • Current-Activated or True Timed Reset. The SEL-ARU can be factory-set to automatically reset upon circuit restoration (select the 0-hour CATR setting when ordering). Alternatively, the SEL-ARU can automatically reset sometime after circuit restoration (with a 2-, 4-, or 8-hour CATR setting). Another option uses both methods, with automatic reset upon circuit restoration or after expiration of a timer, whichever comes first.

Some configurations, such as those with an LED or timed-reset feature, may contain a battery. For configurations with a battery, please see the lithium metal battery warning.

You can choose from a variety of remote displays:

  • Mechanical target (no LED) display options to eliminate the need for a battery.
  • BEACON Bolt LED display options that provide bright indication with industry-leading battery maintenance intervals.
  • A RadioRANGER System that reduces the need to access vaults and manholes.


How To Install Underground AutoRANGER Fault Indicator With Fiber-optic Beacon Display

The Firmware IDs for older versions of the firmware can typically be found in Appendix A of the instruction manual.

Instruction Manuals