SCU switchbay control and protection unit

Not active product since 2010

This product has been phased out, a replacement kit is available with a significant increase in functionality and a more modern design.

ABB 's protection and control device SCU combined the functions of a protection relay and of a control device. Since the introduction of the device it has been used in a lot of switchgear for power distribution worldwide.

As ABB products are designed for continuous evolution, it is ABB‘s goal to protect our customers‘ investment beyond the life-cycles of the underlying platform products. Findings and advanced requirements, e.g. in the area of the connection to the SCADA system, resulted in a revised and improved type of protection and control device, the REF542plus. Despite a significant increase in functionality and a more modern design, it is functional compatible to its predecessor in nearly all aspects. Therefore ABB has defined REF542plus as the recommended replacement solution for SCU.

Although the mechanical design of the REF542plus is different, there is a replacement kit available for the SCU. This kit makes it possible to mount the REF542plus at the same place where the SCU has been without the need for changes at the panel door. Furthermore the connection of the SCU and REF542plus are largely the same, so the existing wiring harness can be continued to use with only minor adaptations. Thus, the exchange is feasible with only a short downtime.

The operational concept of the REF542plus is based on the SCU and represents a consistent further development. This will facilitate the change to the new generation of protection and control devices for the operating and maintenance personnel.


  • REF542plus control and protection device is based on same base design as the SCU and therefore it will enable a comprehensive solution because of similarities in hardware and software.
  • REF542plus is having most comprehensive functional hardware and software coverage for replacement of SCU on the market.
  • REF542plus is in active life-cycle phase and under active development. New functionality is developed for customer projects and design activities for securing life-cycle care are continuously done.
  • As SCU units have been delivered in ABB switchgear, best capabilities to design and deliver the replacement solution is therefore in ABB Service units closely related to ABB.



  • Bay control and protection unit

Product benefits

  • A variety of functions precisely programmed for the requirements and the substation

Product features

  • Measurement
  • Monitoring
  • Control
  • Protection
  • Communication
  • Substation automation.

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