Home Products Protection Relays DRAGON 3RLI 401D3 Line distance protection

RLI 401D3 Line distance protection

RLI 401D3 is designed as a main or back-up Protection IED for EHV and HV lines and includes possibilities of 5 zones Distance protection. It is practically suitable for all voltage levels and types of networks.

RLI 401D3 provides high speed and phase-selective short circuit measurement. Depending on the application (EHV or HV line) RLI 401D3 can be configured for three phase or single & three phase circuit breaker trip and autoreclose. The protection is suitable for all types of current transformers -iron-core or linearized (Rogowski coil).

In case of missing a separate Bay control unit (BCU) for the corresponding line, local & remote control functions are provided.


Relay protection functions***

  • Distance protection
  • Power swing detection
  • Weak end in-feed detection
  • 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
  • Phase discontinuity detection
  • STUB protection
  • Three stages definite time over voltage protection
  • Three stages definite time under voltage protection
  • Two stages negative 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
  • Second harmonic blocking (inrush restraint)
  • Cold load pickup
  • Teleprotection
  • Autoreclosing
  • Fuse failure monitoring
  • Voltage balance protection
  • Breaker failure protection
  • Pole discordance 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 – 1 kHz/2 kHz
  • 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 Hz  / 10 Hz  / 1 Hz
  • 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


  • Up to 4 communication ports
  • Optional extension with I/O modules


Note: All flyers are subject to regular update.