Trends in the design of high-voltage high-rupturing-capacity fuses

High-voltage high-rupturing-capacity fuses are now the most popular form of short-circuit protection for distribution-transformer circuits up to 1000kVA, and are increasing in popularity as the best form of short-circuit protection for high-voltage motor circuits up to, for example 3000hp at 3.3kV. The paper describes the progress made in recent years in the standardisation of dimensions and characteristics of h.v. fuses suitable for the protection of distribution-transformer circuits, and suggests that, with the increasing demand for suitable fuses for motor-circuit protection, particularly from overseas, there is justification for the existence of fuses with time/current characteristics which permit maximum utilisation of the motor-starting capabilities of contactors. The paper illustrates the problems facing the fuse manufacturer in producing suitable motor-circuit fuses, by describing some of the design concepts employed in a typical fuse, and discusses the advantages gained in its application. In addition to describing recent trends in the design of voltage-transformer fuses, the paper discusses the difference between the `backup¿ fuse and `general-purpose¿ fuse as defined in the recently published. IEC Recommendation 282-1 `High voltage fuses¿, and the problems which have had to be overcome in designing and testing general-purpose fuses. Finally, a basis for selecting the appropriate type for each of the popular applications is suggested.