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RFI D Overcurrent protection and control

RFI D is a powerful Protection and Control IED for practically all voltage levels as main or back-up protection. The device is suitable for radial and ring type networks.

RFI D can be applied in all kind of network grounding – solidly or resistance earthed, isolated and compensated.

In case of Transformer back-up protection Restricted Earth fault function for the internal transformer earth faults clearance is also available. The protection is suitable for all types of current transformers -iron-core and linearized (Rogowski coil).

RFI D can also be applied as element (Peripheral Unit) of the decentralized differential busbar and breaker failure protection RBP D.

Relay protection functions***

  • Four stages directional/non-directional definite time/instantaneous overcurrent protection
  • Directional/non-directional Inverse time overcurrent protection with 12 inverse time characteristics
  • Four stages directional/non-directional definite time/instantaneous ground fault protection
  • Directional/non-directional Inverse time ground fault protection with 12 inverse time characteristics
  • Definite time undercurrent protection
  • Negative Sequence overcurrent protection
  • Phase discontinuity detection
  • High harmonic content ground fault detection
  • Restricted earth fault protection
  • Admitance protection
  • Three stages definite time over voltage protection
  • Three stages definite time under voltage protection
  • Two stages negative sequence over voltage protection
  • Two stages positive sequence under voltage protection         
  • Two stages positive sequence over voltage protection
  • Wattmetric / Varmetric power ground fault protection
  • Directional overpower protection
  • Directional underpower protection
  • Three stages neutral voltage displacement
  • Four stages definite time over frequency protection
  • Four stages definite time under frequency protection
  • Four stages definite time rate of change of frequency protection
  • Thermal overload protection
  • Voltage vector shift protection
  • Arc protection
  • Second harmonic blocking (inrush restraint)
  • Cold load pickup
  • Teleprotection
  • Autoreclosing
  • Fuse failure monitoring
  • Voltage balance protection
  • Breaker failure protection
  • Clockwise and anticlockwise phase rotation function
  • Trip circuits supervision
  • Current circuits supervision functions
  • Circuit breaker life time monitoring
  • Synchrocheck

*** All relay protection functions meet all ANSI and IEC standards' requirements.

Automation and remote control functions

Disturbance (Fault) Recorder 

  • Sampling rate – 1kHz / 2kHz
  • User defined trigger conditions and records duration
  • Recording mode -overwrite (ring buffer) or saturate
  • Each sample consists of instantaneous values of all analog and digital values
  • File format – COMTRADE

Data Logger

  • Sampling rate – 50 / 10 / 1Hz
  • User defined trigger conditions, records duration and values
  • The function could be enabled or disabled
  • Recording mode -overwrite (ring buffer)
  • Each sample contains RMS values of all selected analog values
  • File format – COMTRADE

Event Recorder 

  • Up to 1000 records
  • Each event consists of information about the event’s type, some additional data (such as pick-up current, voltage, the time elapsed and so on) and the time stamp of the event (year, month, day, hour, minute, second, millisecond)
  • Recording mode – overwrite


  • SCADA communication - IEC 61850, IEC 60870-5-103, IEC 60870-5-104, MODBUS RTU/TCP
  • Configuration tool - ROCON MMI protocol
  • Web-based interface - HTTP
  • Time synchronization - PTP (IEEE 1588), NTP / SNTP, IRIG-B or PPS
  • File system access – FTP

Configuration, setting and administration

  • Web server


  • Optional extension with I/O modules