BS 2692-2:1956

Section one: General
1. Scope
2. Basis of specification
3. Definitions
Section two: Rating
4. Voltage-rating
5. Current-rating
6. Breaking-capacity ratings
Section three: Marking
7. Fuse-links
8. Current-limiting impedances
Section four: Service conditions
9. Service conditions
Section five: Operation in service
10. General requirements
11. Liquids
12. Time/current characteristics
13. Cut-off current characteristic (for current-limiting
     fuses only)
14. Temperature-rise limits at rated current
Section six: Construction
15. Components
16. Contacts
17. Fuse-links
18. Fuse-carriers and fuse-mounts
19. Current-limiting impedances
20. General
21. Test for temperature-rise
22. High-voltage test: wet test for outdoor fuses
23. Impulse-voltage tests
24. Oil-penetration test for oil-tight cartridge fuse-
     links
25. Sealing test for liquid fuse-links
26. Weatherproof test for powder-filled cartridge-fuses
     for outdoor use
27. Tests for breaking-capacity
28. Criteria of failure in tests for breaking-capacity
Section eight: Routine tests
29. General
Appendices
A. Notes on terms in the standard relating to
     performance of fuses
B. Selection of fuses
C. Calculation of short-circuit fault-currents
D. Measurement of prospective current and cut-off
     current
E. Measurement of power-factor
F. Measurement of recovery-voltage
G. Example of data to be included in a report of type-
     tests for breaking-capacity
H. Insulation co-ordination
J. Correction factors for atmospheric conditions during
     impulse-voltage tests, and for air density during
     wet withstand voltage tests
K. Virtual time

Definitions, ratings, standard conditions of use, type tests.

This British Standard relates to fuses for use indoors or outdoors on alternating current systems having line-to-line voltages above 1 000 volts at a frequency of 50 cycles per second, and with breaking-capacities corresponding to three-phase values from25 MVA to 750 MVA for power fuses and from50 MVA to 2 500 MVA for voltage-transformer fuses (or equivalent values for other systems).

In general, these fuses are suitable for short-circuit protection only, leaving other devices for protection against over-currents.

The requirements of this standard apply to fuses for use in air and to fuses for use immersed in oil.

This standard relates only to expulsion fuses.

Where fuses depend for their correct operation as fuses on the movement of some component to provide an insulating gap, this feature is considered as part of the fuse operation and comes within the scope of this standard.

On the other hand, there are fuse-links that contain tripping devices for initiating the opening of a switch. These fuse-links are required to comply with this standard, but the satisfactory operation of the equipment operated by the tripping devices is outside the scope of the standard.

The range of breaking-capacity ratings of 25 MVA to 750 MVA covers the usual applications of high-voltage fuses for power-system and voltage-transformer protection. It is recognized, however, that voltage-transformer fuses may also be required for use on systems having short-circuit capacities in excess of 750 MVA. Where such fuses are designed to operate in series with current-limiting impedances, the values of which are more than 100 times the impedance of the system, their performance is practically unaffected by the short-circuit current of the system, hence they may be safely used, with the appropriate impedance, on circuits having greater short-circuit capacities than 750 MVA. Voltage-transformer fuses without current-limiting impedances for use on systems with short-circuit currents greater than those corresponding to 750 MVA may be deemed to comply with this standard provided that all the requirements other than the tests set out in Clauses 27 and 28 are met; in such cases tests for breaking-capacity should be the subject of agreement between purchaser and manufacturer.