Pelliott321 wrote:
200,000 amp? Really?
That is not the fusing current. It is the capacity of the fuse to break the current if the fuse value is exceeded. A fuse like this could very well be connected to a supply line that could produce 100 times the rated current or more on a dead fault. If the fuse cannot interrupt the resulting arc when the fuse element melts, current may continue to flow. That could be catastrophic. Fuses like this have the conducting element encased in a granular silica. When the fuse blows, the silica melts, absorbing heat and essentially melting into glass which further stops the arc.
When specifying or replacing fuses, you have to be cautious to consider interrupting capacity. I have seen people replace a 20 amp ABC fuse that has a similar construction in a piece of electronics with a 32 volt rated AGC fuse of the same amp capacity that is simply a piece of fuse wire in an glass tube. There is a high probability that if the AGC fuse blows it may not be able to suppress the resulting arc.