Protection, threats, zeroing, differential old electrical installations without PE and residual current circuit breakers.

In this video we discuss ways to protect against electric shock and the threats associated with old electrical installations that do not have an RCD, protective conductor and other currently standard protections. I will show how protection against electric shock is provided in such installations, we will consider:

Can a residual current device (RCD) be used in an old installation?**
How to connect an electrical socket in an old installation?
Why is the pin in the socket connected to the protective contact?
What is zeroing, how to do it, what to pay attention to.