13. Switching High Voltages

Switching 11 000 Volts and more requires special equipment because it is so dangerous.
This modern switchgear is housed within the powerhouse of the Clyde Dam. The small space it occupies and absence of visible wires is possible because all circuits are insulated with Sulfur hexa-fluoride in the pipe work. Notice also the three phases colour coded red, yellow and blue - Image: Heurisko Ltd.

As High Voltage switches open or close sparks (arcs) may occur between the switch surfaces.

These arcs

  • damage the switches
  • damage other equipment
  • become more damaging at high voltages

Why can't it be switched by hand?

If a person tried to open a high voltage using a simple lever switch they stand a good chance of being injured, and the switch would almost certainly be destroyed.

  • Even the fastest movement would be too slow and an arc would be drawn right across the switch gap.
  • The heat generated by the arc would cause molten copper and porcelain to be sprayed everywhere.