Standards for the installation of backup machines in an electrical panel
Are there any standards for the installation of backup machines in switchboards?
As far as I know, there are no strict rules. And in chapter 1.2. PUE 7 in paragraph 1.2.11 it is said that the design of power systems should be carried out with the possibility of subsequent development (which implies backup machines). This is the only item that I managed to find about it.

