Handbook of Electrical Installation Practice - BeKnowledge

CHAPTER 16
HBC Fuses and Fusegear in
Low Voltage Systems
J. Feenan, MBE, CEng, FIMechE
(Electrical Consultant and formerly Technical Director, Fusegear
Division, GEC Installation Equipment Ltd)
Revised by P.G. Newbery, BSc, CEng, MIEE
(Technical Director, Cooper Bussmann, Cooper (UK) Ltd)
A major change in the UK Wiring Regulations occurred in 1981 with the introduction
of the 15th edition of the IEE Wiring Regulations. These regulations differed
considerably from the 14th and previous editions in that they were aligned with
the wiring regulations of the International Electrotechnical Commission (IEC)
which were more specific on many aspects of electrical protection, including overcurrent
protection and protection against electric shock.
The 16th edition of the IEE Wiring Regulations, which contained amendments
arising from further agreements reached in CENELEC, was introduced in 1991 and
this in turn was accepted by BSI as BS 7671 Regulations for electrical installations
in 1992.
When the first set of Wiring Regulations was issued in 1882 by the Society of
Telegraph Engineers and Electricians, mention was made of the fuse as an ideal
device for ‘the protection of wires’. Over a century later the fuse, in the form of the
hbc fuse, is still a major protective device. In fact, BS 7671 gives precise regulations
regarding overcurrent protection in which the l.v. hbc fuse emerges as a unique
device for fault current protection as well as providing the necessary overload protection
to PVC insulated cables which are acknowledged to be the most difficult to
protect under overload conditions.
The design of the hbc fuse has progressed during the last 60 years until it has
become a highly sophisticated protective device with very precise characteristics.
The British and International Standards covering l.v. fuses have also progressed
during these years and in June 1981 agreement was finally reached in the committee
of the International Electrotechnical Commission dealing with l.v. fuses
(SC32B), for one set of time-current ‘gates’ within which the time-current characteristics
of all fuses for general purpose applications must fall. This decision was the
culmination of many years of intense activity in IEC and it is significant to note that
the time/current characteristics of the modern British hbc fuse-link fall within these
agreed ‘gates’, thus indicating that British practice with regard to hbc fuse-link
design has been the correct one. It is therefore an opportune time to consider the
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