ELRv21-31 > Differential Relays TYPE B

ELRv21-31 Differential Relays are type B earth leakage current limiting relays.

Combined with a measuring toroid and a circuit breaker, they can be used on low-voltage TT, IT and TNS networks to perform the following functions:

  • Protection against direct contact
  • Additional protection against indirect contacts
  • Limitation of leakage current
  • Protection against fire

Their enhanced immunity and True RMS measurement technique guarantee maximum safety and continuity of electrical operation, avoiding untimely disconnections. What’s more, they have a pre-alarm output so that insulation faults can be anticipated without tripping.

The ELRv30 and ELRv31 have an automatic reclosing function to maintain the continuity of service required in certain sensitive or isolated installations.

Features & Benefits

  • LCD display
  • Programmable sensitivity
  • 2 relay outputs: main alarm + reclosing or pre-alarm end-of-cycle contact
  • Alarm test and reset via keypad or external command
  • Connection test with toroid
  • Auto reset function


  • Timer setting
  • Trigger setting
  • Sensitivity setting (I∆n) : 0.030 – 0.1 – 0.2 – 0.3 – 0.5 – 1 – 2 – 3A
  • Hysteresis setting
  • Alarm outputs: 1 RT contact per alarm, 8A/250Vac on resistive load
  • External control
  • Operating temperature : -5 to +55°C
  • Protection rating: IP20
  • Insulation: 2kV-50Hz-1min (between power supply and outputs)
  • Snap-in cabinet mounting on symmetrical DIN rail
  • Universal auxiliary power supply: 20 to 250Vac and 20 to 250Vdc


  • Digital output RS485 Modbus/Jbus protocol

Regulatory Compliance

  • IEC 610008-1
  • IEC 60755

DATASHEET (pdf) | MANUAL (pdf) |