Transformers and transformer vaults shall be __________ to qualified personnel for inspection and maintenance.

Transformers and transformer vaults are critical components in electrical systems, and their accessibility plays a vital role in ensuring safety and operational efficiency. The correct answer emphasizes that these areas must be readily accessible to qualified personnel for inspection and maintenance.

This accessibility is crucial because transformers require regular checks to ensure they are functioning correctly and are safe to operate. Qualified personnel need to perform routine inspections, address any potential issues, and carry out necessary maintenance effectively. If transformers were difficult to reach or only accessible during emergencies, it would significantly hinder the ability to maintain optimal operation and could lead to hazardous situations if problems were to arise.

Moreover, while access restrictions to authorized personnel are necessary for safety and security, it's equally important that these authorized individuals can reach the equipment without delay. This balance allows for preventive maintenance while ensuring that only trained individuals can access potentially dangerous electrical equipment.