Help with breakdown voltage x gap spacing graph

[portace]

Homework Statement

idk

Relevant Equations

idk

Hello! I'm studying a Dielectrics subject in my master's degree which is a little distant from my Electronics area. The teacher asked for a report on the following graph.In this case, the class was about rupture in gaseous dielectrics. The teacher is a little scattered and presents the class in a confusing way. But the caption before the graph is:

"From a practical engineering point of view, rod-to-rod gap and ball-to-ball gap are of great importance, as they are used for the measurement of high voltages and for the protection of electrical equipment such as transformers. The rupture characteristics of rod-rod gaps are shown below."
NOTE: Translated from Portuguese.

The professor asked to explain what happens and why there are different values of breakdown voltage when the impulses shown in the graph are added. However, I'm having difficulty interpreting this data and I'm not finding good references for my work (I'm not using the correct words in the search, I think).

Can you help me with references or textbooks? Thank you very much in advance

 

[berkeman]

Can you help me with references

A key term here is Paschen Curves -- Have a look at this Wikipedia article and some of its references for more background.

https://en.wikipedia.org/wiki/Paschen's_law

Also, on the different breakdown voltages for short pulses, look into the propagation time for the ionizing particles between the gaps...