An overcurrent is protected mainly by fuses in electrical circuits.
However, at high voltages, there are several limitations and challenges that make them less suitable:
Arc Formation & Extinguishing
Whenever a fuse blows, then it must be in the capacity of interrupting the electrical current.
At high voltage, the amount of energy which comes into play can cause a considerable amount of arc that is a discharge through the air of electrical energy.
This arc can be hard to stop and remains, may cause injuries or a fire is also possible.
Equipment such as circuit breakers is deliberately manufactured for the purpose of handling and extinguishing these arcs in the safest manner possible.
Insulation Requirements
Many voltages accompanied by high current necessitate high grade of insulation to enhance non-generation of undesired circuits and shield humans from possible electric shock.
The creation of a fuse that will be able to meet these needs and specs becomes extremely difficult and unfeasible as voltage level increases.
Energy Dissipation
Blown fuses imply that excess energy in the system has to be discharged to avoid a dangerous situation.
And at high voltages one can get the amounts of the energy which can be substantial and a fuse is unable to shunt this energy without getting damage itself.
The switching equipment like circuit breakers and other protective equipment are much more suitable for controlling the energy dissipation in these instances.
Mechanical & Physical Size
High-voltage fuses have to be physically large due to the increased electrical stresses and this is not suitable for most circuits.
If the voltage rises, the necessary spacing between conductors and insulation also rise and it makes devices bigger and complicated to fit in.
Limited Current Interruption Capability
Fuses are made to break over-currents, but at high voltage the current is very high which poses challenges of how the circuit can be safely cut.
Circuit breakers which are more enhanced and can be reset are in a better position to alternate high current interrupts.
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