BS 6907-2:1988

Foreword
Committees responsible
Recommendations
Section one. General
1 Scope
Section two. Protection against electric shock in
                normal service
2 Protection against direct contact by limitation of
    voltage
3 Complete protection by means of barriers or
    enclosures
4 Protection from contact with overhead line
    conductors
Section three. Protection against electric shock in
                case of a fault
5 General
6 Power systems
7 Protective measures for TN-S systems
8 Protective measures for TT systems
9 Protective measures for IT systems
10 Earth fault current limitation devices
11 Earthing arrangements and protective conductors
Section four. Protection against overcurrent and fault
                current
12 General
13 Types of protective device
14 Automatic interruption: protection against
    overcurrent due to overload
15 Automatic interruption: protection against short-
    circuits
16 Co-ordination of overcurrent and short-circuit
    protection
17 Limitation of overcurrent by nature of the source
Appendix
A Selection of factor k for calculating the minimum
    cross-sectional area of protective conductors
Tables
1 Minimum size of earthing conductors
2 Selection of minimum cross-sectional area for
    protective conductors
3 Minimum cross-sectional area of aerial and suspended
    protective conductors
4 Minimum cross-sectional area of supplementary
    equipotential bonding conductors
5 Values of k for insulated protective conductors not
    incorporated in cables and not bunched with cables
    or for bare protective conductors in contact with
    cable covering
6 Values of k for protective conductor as core in a
    cable or bunched with cables
7 Values of k for protective conductor as a sheath or
    armour of a cable
8 Values of k for bare protective conductors where
    there is no risk of damage to any neighbouring
    material by the temperatures indicated
Figures
1 Power system TN-S with separate neutral and
    protective conductors throughout the system
2 Power system TT
3 Power system IT with independent earth electrodes
4 Power system IT with common earth electrode
5 Power system IT using external TT or TN system as a
    source
6 Illustration of the elements of a typical earthing
    arrangement

Guiding principles for installation and operation of electrical equipment to ensure safety of persons, livestock and property, proper functioning of the plant and protection in normal and fault conditions.

This Part of BS 6907 gives recommendations for protection against direct contact and electric shock for all installations in normal service, and in cases of fault, overcurrent and fault current.

For winning, slacking and processing machinery, pumps and low signal level and communications systems, exemptions from these recommendations and supplementary recommendations are given in BS 6907-4, which should, therefore, be read in conjunction with this Part.

The recommendations given for low voltage installations are essentially from the IEE “Regulations for Electrical Installations?? (the Wiring Regulations), as applicable.

NOTE 1 A glossary of terms used in this standard is given in BS 6907-1.

NOTE 2 The titles of the publications referred to in this standard are listed on the inside back cover.