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Electrical Applications 2 by David W. Tyler

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Fuse protection
A high earth loop impedance is dangerous since the metal case will
remain connected to the supply if insufficient current flows to cause
fuse clearance.
In certain situations equipment is run without an earth wire. Such
equipment is completely enclosed in a layer of insulating material or
so disposed in an insulated box so that it is impossible for the box to
become alive or for a person to push a finger in and so touch live
metal. A television set in a plastics or wooden cabinet is an example
of this type of construction.
FUSE PROTECTION Two types of fuse are in general use: