Which statement about supplementary overcurrent protection is correct?

The correct statement about supplementary overcurrent protection is that it shall not be used as a substitute for a branch circuit overcurrent protection device. This is important because the primary purpose of branch circuit protection, such as circuit breakers or fuses, is to protect both the wiring and connected devices from overloads and short circuits. Supplementary protection is intended to provide additional protection for specific devices or components, but it does not replace the need for primary protection.

Using supplementary protection as a substitute for branch circuit overcurrent devices could lead to inadequate protection of the branch circuit, potentially resulting in overheating, fire hazards, or damage to wiring and equipment. Therefore, while supplementary overcurrent devices can enhance safety and prolong the life of equipment, they must always be used in conjunction with the proper primary protection to ensure the overall integrity and safety of the electrical system.