Dold Industries Ltd

11 Hamberts Rd. Blackall Ind. Estate
South Woodham Ferrers
GB-Essex, CM3 5UW
RN 9877

Phase monitor

RN 9877


Switching delay


Measuring voltage

Approvals and Markings


  • 0066425
  • RN9877.11/61 3/N AC175-525/100-300V
The measuring relays RN 9877 and RL 9877 of the VARIMETER series monitor overvoltage,... more

Product description

The measuring relays RN 9877 and RL 9877 of the VARIMETER series monitor overvoltage, undervoltage, voltage range, phase asymmetry and phase sequence in 3-phase or single-phase systems. The measurement is very simple and without extensive wiring as there is no auxiliary power supply necessary. The monitoring functions are easily selectable using a single turn switch without complex menu structure. The early detection of up-coming break downs and preventive maintenance avoid expensive damages. As user you profit from the reliability and availability of your plant.

Technical specifications

Width: 52,5 mm
1- / 3-phase: 1, 3
Standard measuring range: 3/N AC 175 - 525 V / 100 - 300 V
Measuring range max.: 525 V
Auxiliary voltage: Without
Output contacts: 1 C/O contact
Approvals: UL
Enclosure design: Distribution board
Type: RN 9877


  • Preventive maintenance
  • For better productivity
  • Always right directions of motors and pumps
  • Safe monitoring of motors and plants with phase failure detection
  • High repeat accuracy
  • Wide measuring voltage range
  • Selectable monitoring function
  • Easy setting


  • According to IEC/EN 60255-1
  • For monitoring of AC 3- and single-phase with 50 /60 Hz
  • Detection of
    - Overvoltage
    - Undervoltage
    - Voltage range excess
    - Phase failure
    - Phase asymmetry
    - Missing neutral e.g. broken neutral wire
    - And phase sequence in 3-phase systems
  • With or without neutral
  • Without separately auxiliary voltage (internal supply from all 3 phases)
  • Output: 1 changeover contact
  • De-energized on trip
  • Adjustable hysteresis for reset
  • Adjustable switching delay
  • Fast fault detection
  • Width:
    - RL 9877: 35 mm
    - RN 9877: 52.5 mm