Thank you for your answer. I was working in a company and they asked me to find a rough estimation. Because I'm a structural engineer, I'm not very familiar with railroad design. If there is a way to estimate problem roughly, by just considering the catenary, I would appreciate a lot.
I should say : a translation of about 5 cm will probably be all right.
In fact, you have to check that the catenary is still in the middle of the pantograph on the average and that it stays in the safe zone (in fact, that it doesn't go in too close to the extremities.) This has to be checked with the local catenary specialist and the rolling stock people.