This British Standard gives recommendations for the distribution of electricity on construction and demolition sites, and gives guidance on the application of the requirements of BS7671 on such sites. It is intended for use by builders, contractors, engineers and others concerned with the provision of electrical installation equipment suitable for individual site conditions. This British Standard is limited to those supply systems operating at nominal voltages not exceeding 440V a.c. between conductors, or 250V a.c. between conductors and earth. The following are outside the scope of this British Standard: high voltage incoming supplies and equipment; NOTE1 For some site installations, supplies at a higher voltage, e.g. 11kV a.c. and 33kV a.c., are used. underground mining operations; current-using equipment; output circuits of frequency changers (see Note2). NOTE2 Where high frequency power tools are used, a frequency changer is necessary for their connection to a source of supply. This British Standard is applicable only to the input circuits of such devices.