Original air date June 29, 2021

How to apply transfer switch time duration WCR

Learn how to simplify the selection of OCPD and enable selective coordination strategies


Transfer switches are critical components in the power system and they are tested to meet UL 1008: Standard for Safety – Transfer Switch Equipment. This course discusses some of the UL 1008 short-circuit testing and passing criteria and then demonstrates that high short-circuit and short-time withstand and closing rating help simplify the selection of overcurrent protection devices and enable selective coordination strategies. This course also touches on the differences between switchboards (UL 891) and switchgear (UL 1558).

Learning objectives:

  • Discuss the UL 1008 short-circuit testing requirements and derive the withstand/closing rating.
  • Learn about the difference between the short-circuit withstand/closing rating and the short-time rating.
  • Explain how the time-based short-circuit withstand and closing rating simplifies the selection of breakers.
  • Examine how the short-time withstand and closing rating enable selective coordination strategies.
  • Deliberate the major differences between switchboards and switchgear (UL 891 and UL 1558).

Presented By:
Hassan Obeid, Global Technical Advisor for Systems and Controls – Critical Protection, Cummins Power Generation

Moderated By:
Gary Cohen, Content Manager, CFE Media and Technology

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