Vers dix heures, il n’y avait plus de courant dans tout l’immeuble.

Not exactly. Vers dix heures means around ten o’clock or approximately ten o’clock.

• vers = around, approximately
• dix heures = ten o’clock

So it suggests an approximate time, not a precise one.

Il y a is a very common French expression meaning there is or there are.

In the past, it becomes il y avait, which means there was or there were.

So:

• il y a du courant = there is power/electricity
• il y avait du courant = there was power/electricity

In this sentence, the full idea is negative:

• il n’y avait plus de courant = there was no more power

Also, the il here does not mean a real he. It is just part of the fixed expression il y a.

Because plus and pas do different jobs.

• ne ... pas = not
• ne ... plus = no longer / no more

So:

• il n’y avait pas de courant = there was no power
• il n’y avait plus de courant = there was no more power / there was no longer any power

The sentence implies that the power existed before, and then it stopped.

The y is part of the fixed expression il y a.

Breakdown:

• il y a = there is / there are
• in the imperfect: il y avait = there was / there were

When negated:

• il n’y avait plus...

The ne becomes n’ before a vowel sound, so:

• ne y avait is not possible
• it becomes n’y avait

You should think of il y a / il y avait as a set expression rather than translating each word separately every time.

The imperfect (avait) is used because the sentence describes a situation or state in the past, not a single completed action.

Here, the sentence is setting the scene:

• Around ten o’clock, there was no more power in the whole building.

This is a past condition/state, so the imperfect is natural.

French often uses the imperfect for:

• background information
• descriptions
• ongoing situations in the past

So il n’y avait plus de courant is describing the situation at that time.

Yes, literally courant can mean current, but in everyday French le courant often means electricity or power supply.

So:

• Il y a du courant = The electricity is on / There is power
• Il n’y a plus de courant = The power is out / There is no more electricity

This is a very common everyday use.

Because after a negation like ne ... pas or ne ... plus, French usually changes du / de la / des to de.

Compare:

• Il y a du courant. = There is power.
• Il n’y a plus de courant. = There is no more power.

So the positive form would normally be du courant, but after plus it becomes de courant.

This is a very common pattern in French:

• J’ai du pain. → Je n’ai pas de pain.
• Il y a de l’eau. → Il n’y a plus d’eau.

Dans tout l’immeuble means throughout the whole building or in the entire building.

• dans = in
• tout l’immeuble = the whole building

The preposition dans is important because it shows location: the lack of power was in the whole building.

So the sentence means the power was out everywhere inside the building.

Because immeuble is singular and masculine.

• tout
  • singular masculine noun
• toute
  • singular feminine noun
• tous
  • plural masculine noun
• toutes
  • plural feminine noun

So:

• tout l’immeuble = the whole building
• toute la maison = the whole house
• tous les appartements = all the apartments
• toutes les pièces = all the rooms

Here there is one building, so tout is correct.

Usually un immeuble means a building, especially an apartment building or block of flats.

Depending on context, it is often more specific than the English word building. In many everyday contexts, it suggests a residential building with multiple apartments.

So dans tout l’immeuble often sounds like:

• throughout the whole apartment building
• in the entire building

A very natural translation would be:

• Around ten o’clock, the whole building lost power.
• At around ten, there was no more power in the whole building.
• Around ten o’clock, the power was out throughout the building.

The French sentence literally uses there was no more power, but in natural English we often say the power was out or the building lost power.

Yes. The sentence starts with a time expression:

• Vers dix heures, ...

Then comes the main statement:

• il n’y avait plus de courant...

This is very normal in French. French often begins a sentence with a time phrase to set the scene.

So the structure is:

• [time] + [main clause]

Here:

• Vers dix heures = around ten o’clock
• il n’y avait plus de courant dans tout l’immeuble = there was no more power in the whole building

This kind of structure is extremely common in narration and description.