A empresa restabeleceu o fornecimento de eletricidade.

Restabeleceu means restored, re-established, or resumed.

In this sentence, it means the company made the electricity supply available again after it had been interrupted. It is a fairly formal, official-sounding verb, so it fits well in news reports, utility announcements, or formal written language.

It is the pretérito perfeito simples: the simple past / preterite.

More specifically, restabeleceu is the 3rd person singular form of restabelecer.

• eu restabeleci
• tu restabeleceste
• ele/ela/você restabeleceu

It shows a completed action in the past: the company restored the supply.

Because a empresa means the company.

Portuguese usually uses a definite article when talking about a specific noun:

• a empresa = the company
• o governo = the government
• a escola = the school

If you said just empresa, it would sound much less natural here. If you said uma empresa, that would mean a company / one company, not a specific known one.

Because fornecimento is a masculine noun, so it takes o.

• o fornecimento = the supply
• um fornecimento = a supply

The noun comes from the verb fornecer, meaning to supply.

So:

• fornecer eletricidade = to supply electricity
• o fornecimento de eletricidade = the supply of electricity

Using o fornecimento de eletricidade is more formal and precise.

It focuses on the service/supply being restored, not just electricity in a general sense.

Compare:

• A empresa restabeleceu o fornecimento de eletricidade.
  = The company restored the electricity supply.
  More formal, official, technical.

• A empresa restabeleceu a eletricidade.
  = The company restored the electricity.
  Also understandable, and often more natural in everyday speech.

So the sentence you have is perfectly natural, but it sounds a bit more like an announcement or report.

Because de eletricidade here means of electricity in a general, classificatory sense.

In Portuguese, after a noun like fornecimento, de + noun is often used to show the type of supply:

• fornecimento de água = water supply
• fornecimento de gás = gas supply
• fornecimento de eletricidade = electricity supply

If you used da eletricidade, it would sound more specific, as if you were referring to a particular electricity already identified in context. In most cases here, de eletricidade is the normal choice.

Yes. The structure is very close to English:

• A empresa = the company
• restabeleceu = restored
• o fornecimento de eletricidade = the electricity supply / the supply of electricity

So the sentence follows a straightforward subject + verb + object pattern.

That makes this sentence easier for English speakers than many other Portuguese sentence types.

Yes, it sounds neutral to formal.

It would fit well in:

• news reports
• official statements
• utility company notices
• written reports

In more everyday speech, people might say things like:

• A empresa voltou a fornecer eletricidade.
• A eletricidade voltou.
• Já há eletricidade outra vez.

These are less formal and more conversational.

Yes, you may see both, depending on the spelling standard being used.

• eletricidade is the current standard spelling
• electricidade is the older spelling that still appears in older texts and in some contexts

So if you come across electricidade, do not be surprised. It is the same word.

Yes. Restabeleceu can often be translated as either restored or re-established.

• restored sounds more natural in everyday English
• re-established is closer to the structure and often sounds more formal

So in this sentence:

• The company restored the electricity supply is the most natural translation
• The company re-established the electricity supply is also possible, but more formal

Both match the Portuguese well.