What is the purpose of a supplementary overcurrent protective device?

The purpose of a supplementary overcurrent protective device is to provide limited overcurrent protection in specific applications. This type of device is intended to support existing overcurrent protection systems by offering an additional layer of safety. It may be used in scenarios where equipment is not sufficiently protected by the primary overcurrent devices, thereby reducing the risk of damage from overloads or short circuits.

Supplementary overcurrent protective devices can be installed in various locations throughout an electrical system, often downstream from the main protective device. They serve to protect particular devices or circuits without affecting the overall coordination of the electrical system's protection strategy.

The notion of limited overcurrent protection is crucial because it implies that these devices are not meant to replace the primary protection but rather enhance it for specific conditions or equipment, allowing for tailored protection that aligns with the nature of the load and the context in which the equipment operates.