REX615 released – all-in-one protection and control for power generation and distribution applications

2024-04-29 - Release announcement

We are happy to introduce the next step for the 615 and 620 series relays, REX615 – the latest addition to the Relion® family of relays. With more than 1 million relays installed worldwide, the 615 and 620 series have been the choice of many over the years, demonstrating reliability and commitment to continuous evolvement.  

REX615 is ready to take over where the 615 and 620 series left off, protecting power generation and distribution applications within utilities, industry, data centers, marine and rail – and supporting IEC, ANSI and CN standards and conventions for a global reach. With hardware dimensions, modules and wiring connections remaining the same, REX615 is a perfect match for replacing 615 and 620 series relays. 

Combining multiapplication coverage with a fully modular and scalable hardware and software opens up entirely new possibilities, making sure REX615 is ready to evolve with the grid far into the future – with sustainability at the fore. 

Product range

Protection and control REX615

What’s new? 

Extensions for earth-fault protection

  • Non-directional earth-fault protection (50G, 50N) based on the IEC 61850 LN PIOC model
  • Touch voltage-based earth-fault current protection (46SNQ, 59N)
  • Cable fault detection (CFD)

Extensions for feeder current and impedance protection

  • Non-directional overcurrent protection (50P) based on the IEC 61850 LN PIOC model
  • Directional negative-sequence overcurrent protection (67Q)
  • Directional negative-sequence impedance protection (Z2Q)
  • Load blinder (21LB)

Extensions for machine protection

  • Thermal overload protection for rotors (64R)
  • Improved motor start counter (66)
  • Underpower factor protection (55U)
  • Accidental energization protection (27, 50)
  • Three-phase remanent undervoltage supervision (27R)

Extensions for transformer protection

  • Hot-spot and insulation ageing rate monitoring for transformers (26, 46HS)
  • Tap-changer control with voltage regulator (90V) – up to six parallel transformers

Extensions for interconnection protection and support for grid codes

  • Three-phase overvoltage variation protection (59.S1)
  • New instances for frequency protection (81) and load-shedding and restoration (81LSH) – up to ten instances
  • Improved operation times with voltage and frequency protection

Other protection functionality-related improvements

  • Compensated neutral unbalance voltage protection (59NU)
  • Current and voltage harmonics with individual harmonics up to the 11th harmonic component
  • Overall increase in the number of function instances


  • Freely configurable analog channels
  • New logics functionalities such as timers, calendar, mathematic operators, value comparators, etc., to allow more advanced logics
  • User-defined symbol engineering to allow tailoring IEC/ANSI symbols, naming functions or their I/Os – also visible via the LHMI
  • Flexible product naming (FPN) to facilitate mapping of the relay’s IEC 61850 data model to that of the customer


  • Remote communication protocol IEC 60870-5-104 for easy and direct connection to an upper-level system without a gateway
  • Secure communication as an option for DNP 3.0 and IEC 60870-5-104 according to the IEC 62351 standard – for further improved cyber security
  • Redundant Ethernet IEC 61850 station communication with IRIG-B (via serial RS-485) time synchronization
  • Double IP address for configuring a second communication network
  • IEEE 1588 time synchronization with IEC/IEEE 61850-9-3 (Power Utility Profile) for better compatibility
  • IEC 61850 Edition 2.1 data modelling compatibility and conformance certification to support the digitalization of the grid – still also supporting Edition 1
  • Flexible product naming (FPN) to facilitate mapping of the relay’s IEC 61850 data model to that of the customer
  • IEC 61850 cyclic reporting of measurement values

Hardware – new IEC 61869-compatible sensor module

  • Current measurements from Rogowski current sensors and voltages from voltage sensors
  • RJ45 combi-sensor input marked in red – including pins for currents and voltages according to IEC 61869
  • Io (sensitive 0.2/1A) still with traditional summation current transformer
  • Improved measurement dynamics and accuracy supporting accurate and  
    well-performing functions – class 0.5 accuracy for currents and voltages

Hardware – LHMI

  • Facelifted local human-machine interface (LHMI), harmonized for both IEC and ANSI installations, with a separate variant with Chinese characters
  • 4 new programmable function keys for the standard-sized relay

IEC 61850-8-1 GOOSE messaging

  • Sending of larger amount of data – increased number of IEC 61850 data sets (GoCB 6, RCB 27)
  • Faster analog GOOSE for sending data
  • Receiving simulated GOOSE (Generic Object Oriented Substation Event) messages for relay testing

Process bus IEC 61850-9-2LE SMV

  • Sending and receiving current and voltage samples in current and voltage protection applications
  • Sending one stream (one full set of currents and voltages)
  • Receiving up to two full streams
  • Automatic switching between streams – enabling main and backup measurements
  • Receiving simulated sampled measured value (SMV) messages for relay testing

Cyber security enhancements

  • Role-based account management including password hardening
  • Relay communication hardening with detection and shielding for Denial of Service attacks
  • Security event logging supporting Central Activity Logging (CAL) via Syslog
  • Secure communication with WebHMI and ABB’s relay setting and configuration tool, PCM600
  • Central Account Management with Windows AD (active directory)
  • Centralized security certificate management with public key infrastructure

Customer benefits

  • Wide application coverage with one freely configurable device for flexible and cost-effective tailoring to application-specific requirements
  • Ready-made application packages for convenient and smooth ordering
  • Easy and flexible adaptation to changing protection and communication requirements with fully modular hardware and software
  • Unique earth-fault protection portfolio for optimal selectivity, sensitivity and reliability – irrespective of the type of network and fault
  • The world’s first truly IEC 61850-based protection relay – designed to support the increasing digitalization of substations
  • Over 1 million 615 and 620 series relays installed worldwide – demonstrating reliability and commitment to continuous evolvement
  • Intuitive human-machine interface (HMI) with a large graphical display for showing customizable single-line diagrams (SLD)
  • Optional full conformal coating for outstanding performance also in the most extreme environments
  • Convenient, tailor-made retrofit connector kit for fast and easy replacement of SPACOM with REX615 relays

Product features

  • IEC 61850 Edition 2.1 and Edition 1, with redundancy support based on HSR and PRP
  • Ability to receive two streams of sampled measured values (SMVs) and send one via IEC 61850-9-2 LE-based process bus communication
  • Multifrequency admittance-based earth-fault protection (MFA) for optimal selectivity, sensitivity and reliability also in compensated and isolated networks
  • Touch voltage-based earth-fault protection for an optimal balance between safety and supply quality also in compensated networks
  • Compliance with the latest grid codes to ensure renewables remain connected during disturbances
  • Withdrawable plug-in unit design for swift installation, maintenance and testing
  • Optimal cyber security to promote secure connectivity and safeguard today’s network
  • Three lens-type arc flash light detection sensors for extended personnel safety

Target markets

REX615 is targeted at the global market for medium-voltage protection and control applications (IEC and ANSI).

Customer segments


  • Primary distribution
  • Conventional generation
  • Nuclear (non-critical processes)


  • Oil & gas
  • Petrochemicals
  • Chemical
  • Metals
  • Pulp & Paper
  • Mining & minerals

Transport & infrastructure

  • Data centers
  • Marine (vessel, offshore)
  • Rail (excl. rolling stock and catenary)

Supported languages

REX615 LHMI is available in English, Chinese, Spanish, German, Portuguese, French, Polish, Czech, Croatia, Italian, Finnish and Swedish. Additional language support will be announced later. For some languages other than English, the translation of certain text strings might not be available at the time of the release of new functionality. The language packages will be updated soonest. 

Release webinar 

Two webinars open to a public audience will be held to introduce REX615 and the new functionality, one on 29 May and the other on 5 June. Both will be available in two time zones. 

In the webinar on 29 May, marketing and sales manager Timo Eskola will introduce REX615, the next step for 615 and 620 series relays, with the focus on the new concept and value proposition.

For more information and registration, please follow the links below:

29 May @ 09:00-10:00 (CEST)
29 May @ 16:00-17:00 (CEST) 

In the second webinar on 5 June, product managers Markus Kortesluoma and Jarkko Mäkelä will introduce what’s new in REX615 compared to the 615 and 620 series, with the focus on the possibilities it brings.

For more information and registration, please follow the links below:

5 June @ 09:00-10:00 (CEST)
5 June @ 16:00-17:00 (CEST)


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