High-voltage current-limiting fuse are protective electrical devices featuring simple construction, reliable protection and low capital cost. As precision-engineered components requiring stringent manufacturing processes and quality assurance, they can deliver optimal protection performance if properly selected and applied. Improper selection or operation may result in loss of protective functions.

Performance Characteristics of High-Voltage Current-Limiting Fuses

1. High Breaking Capacity: Domestic high-voltage current-limiting fuses offer a rated short-circuit breaking capacity (rms prospective value) of 50 kA, while some imported models reach 63 kA.

2. Current-Limiting Performance: For a typical domestic 100 A high-voltage current-limiting fuse, the peak cut-off current is approximately 18 kA under a prospective short-circuit rms current of 50 kA. Imported 100 A fuses also feature a peak cut-off current of 18 kA under the same condition.

3. Minimum Breaking Current for Transformer Protection: Fuses used for transformer protection have a minimum breaking current, which is generally 3 to 5 times the fuse rated current. During selection, ensure the minimum melting current of the fuse is no greater than the minimum short-circuit current of the protected circuit.

 Key Considerations for Selecting High-Voltage Current-Limiting Fuses

1. Selection of Rated Current

   1. Avoid maloperation caused by the inrush magnetizing current during transformer energization. The time-current characteristic curve of the high-voltage fuse shall lie to the right of the transformer inrush characteristic curve A. The transformer inrush current is 10 to 12 times the full-load current and lasts for 0.1 s.

   2. The current value at the intersection point of the time-current characteristic curves of the high-voltage fuse and low-voltage fuse shall be higher than the maximum fault current on the load side of the low-voltage fuse.

   3. If the fuse is installed inside an enclosed cabinet or tube, select a higher rated current. A de-rated selection of rated current is required to ensure stable operation under overload conditions within the enclosed housing.

   4. Increase the selected rated current if the ambient temperature exceeds standard operating conditions.

   5. The fuse rated current shall not be excessively large, and shall meet the transfer current requirement for coordination with upstream protective devices.

   6. The pre-arcing current of the fuse within the 10-second window on its time-current curve shall be sufficiently low to provide effective transformer protection. To verify this, review the fuse time-current characteristic curve or consult the manufacturer for equivalent replacement recommendations for high-voltage current-limiting fuses.