First time I put it behind my machines, and it worked. Later, I've read that the Energy Link will try to drain up to 72EU/t, so I put it behind a Batbox, in order to make it only drain at most 32EU/t (enough to make my Quarry and a Refinery work at decent speeds).
But I though like fabricator77 that with only the LV Transformer, it should work in the first place, when my Energy Link was before my machines. But I still don't know why, it has to be behind.
Now, I have a setup that works properly : MV Solar Arrays -> MFSU -> MV Transformer -> LV Transformer -> Energy Link and machines. With my Energy Link connected to a Quarry and a Refinery (and sometimes a Pump, when I find some oil). With this setup, I've got always more EU than I need, and I can make my machines work everytime I need.
In the future, I will upgrade my machines and delete the LV Transformer from my setup. In this way, my energy link will be able to drain 72EU/t, so I maybe will add a second Quarry or one Refinery. At maximum speeds, a Quarry drains ~25EU/t, a Refinery ~25EU/t ; and I don't know for a Pump, but it seems not to be much.
To get back to the first topic, if someone has the same issue, what I've learnt from you guys is that the Energy Link will try to drain 72EU/t, so if one wants to make some machines on the same circuit work, one has to limit the draining with a Batbox or a LV Transformer.
Thank you !