In the normal working condition of the electrical network, the current flowing through the network is within the rated limit. If a fault occurs in the network mainly phase to phase short circuit fault or phase to ground fault, the network current crosses the rated limits.
This high current may have a very high thermal effect which will cause permanent damage to the valuable pieces of equipment connected to the electrical network. So, this high fault current should be interrupted as fast as possible. This is what an electrical fuse does.
A fuse is a part of the circuit that consists of a conductor which melts easily and breaks the connection when the current exceeds the predetermined value. An electrical fuse is the weakest part of an electrical circuit that breaks when more than a predetermined current flows through it. phase-to-ground
It consists of a heat-resisting body having metal endcaps to which is welded silver current-carrying element. The space within the body surrounding the element is completely packed with a filling powder. The filling material may be chalk, plaster of Paris, quartz, or marble dust and acts as an arc quenching and cooling medium
Under normal load conditions, the fuse element is at a temperature below its melting point. Therefore, it carries the normal current without overheating. When a fault occurs, the current increases, and the fuse element melts before the fault current reaches its first peak. The HRC fuse has inverse time characteristics, i.e., if the magnitude of the fault current is high, then their rupturing time is low and for low magnitude fault current the rupturing time is high.