The responsibility for electrical safety in rented commercial premises will be decided by the terms of the rental lease. This, or a separate contract, should set out whether you or your landlord (or managing agent) takes on electrical safety duties.
As a tenant you must assess the risks of your business' use of electricity at work and take steps to control these risks. This may range from ensuring electrical installations are safe and providing suitable equipment to carrying out preventative maintenance and ensuring safe systems of work.
Your landlord is also likely to have a duty of care for wiring systems and electrical equipment.
If your property is experiencing a power cut or flickering lights you can contact Northern Ireland Electricity Networks 24 hours a day on 03457 643 643. What to do if you have no electrical power.