Sub-Cycle Electronic Switching

During Program 10, DSTAR commisioned a series of whitepapers on technological topics of common interest. The goal of this project was to deliver an overview treatment of three key technology areas that are relevant to modern distribution systems. The issues under consideration were:

  • The use of broaband powerline carrier technology for power equipment communication
  • The availability and application of sub-cycle electronic switching equipment
  • Impedance considerations for three-phase pad-mount transformers design

A sub-cycle electronic switch or static transfer switch (STS), is a solid-state unit capable of switching large amounts of power in less than one fourth of a 60 Hz cycle, fast enough to avoid momentary interruptions. As reliability and power quality are critical measures of system performance, the STS has become a popular choice for large industrial systems and critical customers. The rise in popularity is driving research in the area to produce lower-cost, more reliable and even faster switches in the future. Utilities need to be aware of the status direction of this technology and the potential for impact on their distribution systems.


The electronic switching white-paper examines the application of sub-cycle electronic switching on power distribution systems. This includes a general overview of the technology, a description of typical applications, and a critical look at the benefits, issues and challenges relevant to the application of the switches. The benefits, issues and challenges include voltage sag mitigation, momentary interruptions, installation and maintenance issues, operational issues, economic justification, and performance issues with respect to transfer time, feeder impedance, and cross-current.

The outline of the 39-page final report is shown below.


The final report for this project can be downloaded from: P10-11