Can I connect an electric oven in Brezhnevka without grounding?

Hello! What does the “2.5 kW” meter mean, if you yourself write a current of 5A - this is 1 kW. In addition, your counter, I suppose, is not designed for 5A most likely, but 5 (60) A is indicated on its front panel, which means that it can take into account up to 60A. Have you installed the new 16A assault rifle for the whole apartment or only in the kitchen?

If I’m right about the counter, then you can safely use such an electric oven, although there are models with less power. It is forbidden to connect differential machines and RCD without grounding in accordance with the PUE p. 1.7.80, but it can be used if you connect the "earth" wire of the device with zero to the RCD. This is also a bad decision. The danger is that, without grounding, a leak can occur in most cases through your body when you touch a damaged electrical device. At the same time, an RCD or a difavtomat may not work (no one cancels the option of marriage or other cases). Connecting the protective conductor of the oven to zero BEFORE the RCD or the difavtomat is also bad, this is zeroing, if the input is zero, the cabinet will be energized.

However, if you simply put an RCD or differential on the control cabinet, it is not 100% likely that it will work, but the safety of using the cabinet is still increased, and the likelihood that in the event of a leakage the protective device will work and you will not be shocked by electric shock. Therefore, if you want - put it, do not want it - do not put it.