Home Products Protection Relays DRAGON 3RTI 403D3 Three winding transformer differential protection

RTI 403D3 Three winding transformer differential protection

RTI 403D3 is designed to be used as a main Protection IED for a selective clearance of all kinds of short circuits in three winding Power Transformers of practically all voltage levels. Restricted Earth fault protection for a sensitive internal earth faults identification and clearance is also provided.

Depending on the application (EHV or HV line) RTI 403D3 can be used for three-phase or single-phase power transformers.

The protection is suitable for all types of current transformers - iron-core and linearized (Rogowski coil).


In case of missing a separate Bay control unit (BCU) a Local & Remote control functions are also included.

Relay protection functions***

  • Transformer differential protection
  • Transformer differential protection high stage
  • Four stages non-directional definite time/instantaneous overcurrent protection
  • Non-directional Inverse time overcurrent protection with 12 inverse time characteristics
  • Four stages non-directional definite time/instantaneous ground fault protection
  • Non-directional Inverse time ground fault protection with 12 inverse time characteristics
  • Negative Sequence overcurrent protection
  • Phase discontinuity detection
  • Restricted earth fault protection
  • Thermal overload protection
  • Second harmonic blocking (inrush restraint)
  • Breaker failure protection
  • Clockwise and anticlockwise phase rotation function
  • Trip circuits supervision
  • Current circuits supervision functions

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

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.