Medium and High Voltage Fuses

Current Limiting - Medium and High Voltage Fuses

Current Limiting

Current limiting medium and high voltage fuses are used as protection devices in medium voltage switchgear such as distribution transformers, motors, capacitor banks and voltage transformers. They offer a very fast current limiting operation in case of short-circuit failures.

Also known as HV fuse links, they are designed with a ceramic body, and many are also fitted with a with a striker mechanism that provides the user with a visual indication that the fuse link has operated. These mechanisms are driven by explosive charges or compressed springs that are triggered by a fuse wire that runs through the length of the fuse.

Generally divided into three types; back-up, general purpose and full range fuses.

Back-up fuses also known as partial-range fuses are designed to interrupt any current from their rated breaking capacity down to their minimum breaking current specified by the manufacturer.

General Purpose fuses will interrupt all currents from their rated breaking capacity down to a current that will melt the elements within one hour.

Full-Range Fuses will interrupt any current below the rated breaking capacity that melts the fuse elements satisfactorily.

Features of high voltage fuses include a reliable sealing system against humidity, dust and corrosion; high breaking capacity and low switching voltage, high current limitation, low power losses and low temperature rise and a high degree of service reliability based upon many years of field experience and advancements in the fabrication process.

Non-Current Limiting or Expulsion Type Fuses Non-Current Limiting Expulsion Type Fuses

Non-current limiting fuse links have short elements and incorporate some< means of lengthening the arc after the element melts, extinguishing the arc and preventing re-ignition.

Expulsion Fuse: An expulsion fuse is a vented fuse in which the expulsion effect of the gases produced by internal arcing, either alone or aided by other mechanisms, results in current interruption. An expulsion fuse is not current limiting and as a result limits the duration of a fault on the electrical system, not the magnitude.

 

Expulsion Power Fuses are divided into two types “Refillable” and “Replaceable”. Refillable fuses are constructed so that the inner components can be removed and reused when the assembly is recharged with a new refill. By reusing the spring and shunt assembly these components can be constructed with a heavy-duty design which allows the unit to have a higher Interrupting capability. Since the components are reused it is easy to change the fuse size by simply changing the refill.

 

Replaceable fuses a have lower installed cost by providing a more cost-effective construction. This is generally at the expense of higher interrupting ratings.



Boric Acid: A vented expulsion fuse in which the expulsion effect of gases and water vapor produced by the arc coming in contact with the fuse's boric acid liner extinguishes the arc.


Expulsion Power Fuses are divided into two types “Refillable” and “Replaceable”. Refillable fuses are constructed so that the inner components can be removed and reused when the assembly is recharged with a new refill. By reusing the spring and shunt assembly these components can be constructed with a heavy-duty design which allows the unit to have a higher Interrupting capability. Since the components are reused it is easy to change the fuse size by simply changing the refill.

 

Replaceable fuses have a lower installed cost by providing a more cost-effective construction. This is generally at the expense of higher interrupting ratings. For more information visit www.chfuses.com.

Fuse Mountings and Live Parts

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