Which codes and standards provide guidance regarding the earthing of a mobile generator?

An excellent starting point is to visit the Health and Safety Executive (HSE) website via the focussed search; HSE Generator Earthing. The following link will then appear:


This web site location offers an excellent overview of the responsibilities and requirements to ensure an installed generator will meet the necessary earthing and referencing to ensure the safety of personnel and safe operation of connected electrical equipment.

Specific engineering standards which cover the subject of electrical system earthing and referencing are listed below.

  • BS 7430 Code of Practice for Earthing
  • BS 7375 Code of practice for distribution of electricity on construction and building sites.
  • BS 7671 Requirements for electrical installations. Better known as the IET (IEE) wiring regulations.

When considering a generating set as a power source for an electrical distribution system there is a significant need for the responsible generating-set person to gain a full understanding of that electrical distribution systems configuration. Such an investigation begins with establishing if the system is TN, TT, or an IT type scheme. Then follows the necessary checks and understanding of how the generating set has been configured in terms of which part of the ac generators output windings has been connected to an identified ‘earth’ terminal on the structure of the generating set assembly.

The need to bond the generator to ‘earth’ is covered in the above identified codes, standards and requirements. They include explanations of the methods, necessary tests and then measurements to ensure a low impedance connection path exists between key points within the electrical distribution system back to the installed connection to Mother earth; or to an identified reference point if an equipotential zone of exposed conductive surfaces has been decided upon as being the protective policy.

AMPS FAQ 1013A covers the subject of RCDs. It may provide the reader with useful information regarding RCD selection against tripping current levels, and the avoidance of nuisance tripping.