Relates to the application of low voltage fuse-links complying with BS 88, Part 5 to the protection of underground distribution systems, and for the protection of distribution transformers it specifies the operational parameters and time/current zones for high voltage fuse-links complying with BS 2692, Part 1. High voltage fuse-links would normally form part of a ring main or fuse-switch combination unit and be provided with striker pins to operate a 'trips all phases' device.