First, consider immediate danger
If there is smoke, fire, a shock or an immediate risk to people, move away and contact 112. Stay away from fallen wires, wet equipment and damaged electrical enclosures. Do not assume equipment is safe because lights are off.
Observe the extent
Without entering restricted areas, note whether neighbours or common areas also appear to be affected. A wider interruption may involve the distribution network; a fault limited to the home may need an electrician. These observations help explain the situation but do not confirm the cause.
Use official network information
For a suspected network fault, use E-REDES official fault information and reporting. If the issue is within a building, the condominium or landlord may also need to be involved. For immediate danger, use the emergency services rather than a routine electrical enquiry.
Further information
Electrical Safety First: warning signs · E-REDES: faults and network information · Portugal emergency contacts
General safety information, not a diagnosis or a guide to electrical work. UK-specific installation rules are not presented as Portuguese requirements.