Home Products Protection Relays DRAGON 3RLI 402D3 Line differential protection

RLI 402D3 Line differential protection

RLI 402D3 is designed as a main or back-up Protection IED for EHV and HV lines and includes possibilities of 5 zones Distance and Two/Three ends Line Differential protection. The Differential and directional back-up protection is practically suitable for all voltage levels and types of networks. Transformers and compensation coils within the differential protection zone are protected by means of integrated functions.

RLI 402D3 provides high speed and phase-selective short circuit measurement. Depending on the application (EHV or HV line) RLI 402D3 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
  • Line differential protection
  • Line differential protection high stage
  • 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.