Clarification regarding wires

[BloodDrunk]

Hi guys, I have a question regarding these wires, what is the black wire for?
The location is Europe, Slovenia.

I understand traditionally brown is live, blue is neutral and yellow/green is earth, but why is here a black wire, too? And how do I connect it, to what.

 

[westward10]

Who knows is it for two way lighting?
Who installed it?

 

[BloodDrunk]

Hi, thanks for response!

It is not for lighting, it is the main electric cables for breaker box. The house is about 100 years old.
Currently I am looking for someone that can maybe recognize it, I have absolutely no luck finding such setup online, anywhere, so it is very weird to me.

 

[vjsmarwick]

Look to me as if someone maybe didn’t have twin and earth and therefore decided maybe to save extra expense just to use a 3core and earth ! Probably someone untrained and doing a fix around ! It’s about the only reason I could think of.

 

[brianmoooore]

That doesn't look a very big cable for the supply to a property. Could it be a 3 phase supply, in which case they'd be a bit more of a suitable size? There's no neutral, but maybe combined neutral and earth are allowed for supplies in Slovenia?