EGN20 - Mains extension cables - use and safety testing

This Electrical Guidance Note (EGN) is one of a series under the framework document EGN 1 "Management of Electrical Safety at the BBC". The purpose of EGN 20 is to set safety standards and ensure that those who purchase use and maintain mains extension leads on behalf of the BBC are aware of their responsibilities under BBC Requirements, the Health and Safety at Work Act 1974 and the Electricity at Work Regulations 1989 and ensure that these items are safe to use.

 

It is intended to cover the use and testing of any mains extension lead, whether BS1363 13A plugtop type used in offices, workshops, studios, PSC or OBs, or cables using BS EN 60309-2 (BS4343) connectors which are used for studio lighting, studio practicals or on OBs. It also includes 110V extension cables. The document will apply to maintenance engineers, technicians, project engineers, broadcast engineers and those using extension cables in production or offices, in fact in all areas of the BBC, whatever Division.

 

It is the policy of the BBC that all electrical equipment, which includes mains extension cables, must undergo and pass a formal visual inspection and test before it enters service. The cables will then need regular testing in the future (see EGN 9). This guidance note also defines the maximum cable length that is allowable and the impedance figures etc. to be achieved when testing such cables. It is based on work first carried out in 1993 when there was no guidance from any other source on acceptable limits for the various test parameters. This work was published as Report 1993/07 by the department known then as Television Engineering & Project Services (TE & PS) and an updated version of the Report forms the basis of the technical part of this EGN.

 

There is some guidance available now from both the IEE and the British Standard for mains cable reels. However these conflict with each other and the IEE Guidance places unnecessary restraints on the maximum length of cable which can be used. It neither justifies its stated maximum lengths by any calculations nor specifies the fuse value to be used. The guidance given here is based on calculations using the relevant British Standards and is fully justified. By following the guidelines in this EGN it is possible to safely use cables longer than allowed by the existing IEE guidance.

 

The equipment covered by this Guidance Note will vary widely and will be found in:

 

The Requirements and Guidance given here therefore apply to a very large number of mains extension leads used in BBC undertakings. It will apply to BBC employees, and to Partners and Contractors to the BBC.

This EGN replaces all previous safety documentation with regard to mains extension leads (in particular Report 1993/07), issued by BBC Safety or by the former Engineering Management Safety Committee. It does not however, replace documents issued at Divisional or Departmental level, although such documents must neither conflict with nor set standards which are not as rigorous as those given here.

 

This document is intended both to draw attention to the requirements, which affect everyone who uses mains extension leads and also to give guidance to testers who must have technical knowledge appropriate to the level of testing being carried out. Appropriately trained personnel with electrical competence will be required to make judgements where cables longer than 35m are to be used.