BS 7909, the Code of Practice for temporary electrical supplies, has just been revised, as Voltimum shows

Because of the nature of the work, tight schedules, often poor weather, continuously changing plans and so on, temporary events (both indoors and out) need electrical installations that can be quickly and safely assembled and disassembled. This is especially so with a touring production. As the IET has said, in its 'Wiring Matters' magazine, the temporary element, in effect, and beyond the fixed electrical installation, is purely a kit-of-parts assembled to suit the situation or event'.

When the venue is a small one, such as a pub with a local band playing, the electrical equipment is typically supplied from local socket-outlets that are - ideally - carefully positioned. Extension leads are often used to provide more socket outlets where necessary.

The scenario is rather different for large temporary venues, such as a music festival, where the electrical equipment can be complex and very varied. With demands for on-site temporary power, and the potential risks for general public, stage hands, retail salespeople and performers alike, careful design, full safety measures and a full understanding of correct earthing and bonding techniques are all crucially important.

So a temporary electrical installation is not allowed to be of a lower standard; indeed, it has to be higher because the operating conditions are more difficult. Despite this, electrical contractors and installers have been known to treat temporary electrical supplies as being less dangerous than permanent electrical installations and associated hazards. Why is it that temporary electrical wiring on projects is treated differently than permanent electrical wiring with regard to the workmanship, wiring methods, and applying safe work practices? Is it because it is only temporary?

And how temporary is temporary? The only significant difference between temporary wiring and permanent wiring (apart from 'hardening' and waterproofing etc) is the length of time it is in service.

Note that while the industry has developed good and robust electrical distribution equipment that withstands the arduous conditions that touring puts it through while facilitating rapid 'plug and play' installation, this - however - has reportedly led to some complacency on occasion, which has increased the risk of shock and fire.

Event organisers, contractors and others using electrical equipment must do all that is reasonably practicable to ensure that electrical installations and equipment at a temporary event are properly selected, installed and maintained so as not to cause death or injury.

The regulations:

All electrical installations and equipment must comply with the Electricity at Work Regulations 1989 and only competent persons should carry out electrical installation work (find out more at www.hse.gov.uk/electricity). A competent person (as defined in BS7671:2008 (2011) must have the abilities needed to take overall responsibility for the safe installation, testing, operation and deconstruction of temporary electrical installations.

The Electricity at Work Regulations 1989, places duties on employers, designers and installers to insure all systems are safe. Such issues have been covered, in terms of good practise and safety, by BS 7909 - the Code of practice for temporary electrical systems for entertainment and related purposes.

The standard was first published as BS 5550-7-5-1 in 1981, and first published as BS 7909 in December 1998, with a second edition published in November 2008, followed by this third edition in August 2011. BS 7909:2011 therefore supersedes BS 7909:2008, and it came into effect on 31st August 2011.

This is a major revision and contains a significant number of changes, including:

• An increase in the range of events that use temporary electrical distributions
  
• Recognition of the range and quantity of electrical equipment, and the related staff that are hired in for a given event
  
• The management of temporary electrical distributions
  
• Temporary distributions have been split into 'small/simple' or 'large/complex' and are treated separately
  
• The requirements and terminology of BS 7671: 2008 (2011) have been adopted where appropriate
  
• The annexes have been fully revised and new several new annexes have been added to give guidance and information on system earthing issues, testing and RCDs.

BS7909 is used in a broad range of events beyond the scope of the IEE Regulations. The Standard outlines the necessary management arrangements and the required range of electrical supplies, heavy-duty flexible cables and portable distribution units needed. The systems used range from very simple to highly complex and the Standard gives recommendations for all temporary electrical systems. This BS, therefore, provides recommendations for management, design and operation of temporary electrical systems using low voltage (LV) AC electricity, for entertainment and related purposes. It covers systems operating at low voltage and supply equipment normally operating at 230V AC or 400V AC 50Hz.

BS 7909:2011 gives recommendations for the provision of a safe and suitable temporary electrical system for an event and the duties and work to implement this.

The Regulations apply to the design, erection and verification of electrical installations such as those of construction sites, exhibitions, shows, fairgrounds and other installations for temporary purposes, including professional stage and broadcast applications.

Further, the Regulations (BS 7909:2011) are intended to be applied to electrical installations generally but, in certain cases, they may need to be supplemented by the requirements or recommendations of other British Standards or by the requirements of the person ordering the work. Such cases include the following: the design and installation of temporary distribution systems delivering AC electrical supplies for lighting, technical services and other entertainment related purposes.

Requirements of BS 7909:2011:

To see a summary of the requirements of BS 7909:2011, please click on the link to the article at the bottom of this web page.

Planning at events:

Planning ahead properly, with a suitable risk assessment is vital to ensure, not only that the electrical installation(s) is completed in time and that it works correctly first time, but also that it is compliant with regulations and that it is safe. Planning and managing temporary electrical installations need consideration of the following:

1) On-site:

• Layout (performance areas, traders, public areas, access routes etc)
  
• Power requirements
  
• Details of and access to any mains (utility) power supply
  
• Location of any existing overhead power lines or buried cables
  
• Environmental conditions
  
• Electrical environment as defined in BS 7909
  
• Emergency power requirements.

2) At the event:

• Timetable of power requirements
  
• Use of gensets
  
• Earthing
  
• Routing of temporary overhead or underground cables
  
• Main isolators controlling the electrical supplies to the stage lighting, sound, special effects, emergency lighting and lifting equipment
  
• Special power supplies for some equipment, eg non-UK equipment, hoists, portable tools etc.
  
• Electrical requirements for emergency lighting and exit signs
  
• Power supplies for catering equipment, first-aid points, incident control room, CCTV cameras etc.
  
• Power supplies for heating or air conditioning
  
• Control and restriction of access to electrical installations by unauthorised people
  
• Use and/or integration of renewable power sources such as solar PV cells or wind turbines and associated equipment such as inverters
  
• Use of battery charged equipment (e.g. radio communication equipment for event staff).

For further reading:

HSE and other organisations have produced guidance on electrical safety (from which some of the above has been taken) that is suitable for a wide range of industries and technical competencies. The information produced by HSE is either free for immediate download or available to order at low cost. The following publications are available:

• Electrical safety for entertainers
  
• Maintaining portable electric equipment in low-risk environments
  
• Electrical Safety Council: Selection and use of plug-in socket-outlet test devices
  
• Electrical Safety Council: Guidance on the management of electrical safety and safe isolation procedures for low voltage installations
  
• Electrical safety at places of entertainment
  
• Charity and voluntary workers
  
• Avoidance of danger from overhead power lines.

For more information, go to www.hse.gov.uk/event-safety/electrical-safety.htm

To see a summary of the recommendations of BS7909:2011, please click on the link near the bottom of this web page.

To find information on the requirements for cables in temporary electrical installations, see the attached article from The IET's 'Wiring Matters' magazine by clicking on the second link near the bottom of this web page. Please note that the version of BS7909 referred to in this Wiring Matters article is 2008, not the latest version (2011).