Can High-Voltage Current-Limiting Fuses Restrict Short-Circuit Current?
High-voltage current-limiting fuses work to restrict short-circuit current. The circuit will be disconnected immediately once the short-circuit current surpasses the melting threshold of the fuse element.
High-Voltage Current-Limiting Fuse
High-voltage fuses serve to safeguard circuits and electrical equipment against short-circuit faults and overloads. Circuit isolation is achieved through the melting of low-melting-point metal wires or strips, namely fuse elements. They stand out for simple construction, low procurement cost and hassle-free maintenance.
Based on installation sites, high-voltage fuses are categorized as indoor and outdoor models. In terms of current-limiting performance, they are grouped into current-limiting and non-current-limiting types.
The porcelain housing of a current-limiting high-voltage fuse is filled with quartz sand. When a short-circuit fault melts the fuse element and triggers an electric arc, tiny gaps between quartz sand grains squeeze the arc column. Together with the strong cooling effect of quartz sand, the arc gets quenched before the short-circuit current climbs to its steady-state value, which delivers the current-limiting function.
Key Parameters and Features of High-Voltage Current-Limiting Fuses
1. Rated Voltage: It refers to the continuous voltage the fuse can bear after fault interruption, which should match or exceed the rated voltage of the protected line or equipment.
2. Rated Current: Covering the rated current of the fuse assembly and the fuse element, this parameter defines the maximum continuous current the fuse can carry. In most cases, it is chosen to be 1.5 to 3 times the rated current of the protected device.
3. Rated Breaking Capacity: It describes the fuse’s ability to safely clear overload and short-circuit currents under fault conditions, indicated by breaking current or breaking capacity.
4. Insulation Level: This specification is defined by power-frequency withstand voltage and lightning impulse withstand voltage.
5. Ampere-Second Characteristic: It illustrates the correlation between fuse operating time and through-current, provided by the manufacturer. This characteristic is essential for proper protection coordination. Without proper matching, unwanted upstream tripping and other protection misoperations may take place.