Your triple point is a triangle

Triangular relationships are complicated. That’s where the sparks fly. Many films deal with this topic and we as viewers are amused. In real life, it’s usually less fun.

The triangular relationship, also called the triple point or line, also exists in high-voltage engineering. As with people, this is the place where it is most likely to spark. Therefore, the triple point is of great importance in the design of high voltage equipment or systems.

The triple point is the place where at least three materials come together that have different dielectric constants. Most often this is a metal, an insulator and air. In high-voltage pulse technology, water is usually also involved.

If the dielectric property of the three materials is very different (for example, air has a dielectric constant of 1, polyethylene is 2.25, and metals can be assumed to have an infinitely high dielectric constant), the electric field distribution will be strongly deformed as a result. The electric field strength is then increased in the material with the lowest dielectric constant. In this situation, all that is needed is a free start electron and the avalanche is set in motion and the flashover can no longer be stopped. Depending on the energy in the system, the result will be fatal.

Sometimes it is not possible to choose a material combination that has a small difference in dielectric constants. Then other measures must be taken. Careful design to reduce electric field strength is one approach. Auxiliary electrodes or active field control are also helpful. In order to reduce the cost of expensive experiments, a simulation of the field distribution is a good way. Here, some design iterations can be performed quickly and effectively before the final design is validated in a test.

Simulation triple point in the high voltage by the R&D coach.

Of course, a great deal of experience in the design of triple points is also necessary to quickly arrive at a good design. Especially when there are many constraints to consider. I have been involved with triple points for over 15 years. I would be happy to let you benefit from my wealth of experience, so that you can relax and laugh at the next movie with a love triangle without worrying about your high-voltage system.

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