What do most cutout fuse doors rated above 10,000 amps contain?

Most cutout fuse doors rated above 10,000 amps contain an expendable cap. The purpose of the expendable cap is to provide a safety mechanism that protects the fuse from accidental exposure to the system voltage under fault conditions. These caps are designed to withstand specified fault currents, and when subjected to excessive current, they will melt or blow away, helping to ensure that the fuse operates efficiently and safely during overloads or short circuits.

Having an expendable cap in higher-rated cutout fuse doors is a crucial aspect of ensuring reliable operation and safety in power distribution systems. This component helps prevent potential hazards, such as the risk of electric shock or equipment damage, by containing any arc or explosion that may occur when the fuse operates during a fault condition.