SPECIALIST INSTALLATION

Exhibition & Event Electrical: Temporary Installations BS 7909

Everything electricians need to know about temporary electrical installations for exhibitions, festivals, and events — BS 7909 requirements, responsible person duties, temporary distribution systems, generator earthing, 30 mA RCD protection, TN-S earthing, and pre-energisation checks.

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14 min readUpdated 2026-05-18Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

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Key Takeaways

  • 1BS 7909:2011 (Code of Practice for Temporary Electrical Systems for Entertainment and Related Purposes) is the primary standard for temporary electrical installations at exhibitions, festivals, conferences, and other events in the UK.
  • 2A responsible person (RP) must be appointed for every temporary electrical installation. The RP takes professional responsibility for the design, installation, and safe operation of the electrical system throughout the event.
  • 3Temporary distribution systems use a hierarchical structure: primary distribution from the power source (mains or generator), secondary distribution to areas or stages, and final distribution to individual supplies. Each level must be documented.
  • 4Generator connections must be made by a competent person. The generator earthing arrangement (typically TN-S for temporary event installations) must be correctly established before any loads are connected.
  • 530 mA RCD protection is required for all socket outlet circuits. Time-delayed upstream RCDs provide discrimination so a fault at one socket does not black out the whole event.
  • 6A pre-energisation check (sometimes called a BS 7671 inspection and test) must be carried out on every temporary installation before it is energised for the first time. This includes insulation resistance testing, continuity testing, and RCD functional testing.
01 · Specialist Installation

BS 7909: Temporary Electrical Systems for Entertainment

BS 7909:2011 — Code of Practice for Temporary Electrical Systems for Entertainment and Related Purposes — is the primary technical standard governing temporary electrical installations at UK events. It applies to exhibitions, trade shows, music concerts, outdoor festivals, film and television productions, conferences, sports events, and any other temporary gathering requiring an electrical installation designed for a defined period.

  • Relationship to BS 7671 — BS 7909 is complementary to, not a replacement for, BS 7671. Temporary event installations must comply with both BS 7671 (which sets the fundamental electrical safety requirements) and BS 7909 (which addresses the specific management, documentation, and operational requirements of temporary systems). Where BS 7909 is silent, BS 7671 applies.
  • Legal framework — while BS 7909 is not in itself a statutory instrument, compliance with it provides a means of satisfying the legal duties imposed by the Electricity at Work Regulations 1989 and the Health and Safety at Work etc. Act 1974. Local authorities licensing events and venue operators routinely require evidence of BS 7909 compliance. The Event Safety Guide (the Purple Guide) also references BS 7909.
  • Temporary vs. permanent — a temporary electrical installation is defined as one designed and installed for a specific event or series of events over a defined period. It is erected before the event and dismantled after. The temporary nature does not reduce the safety standards required — a temporary installation must be as safe as a permanent one.

Electricians working on temporary event installations should be familiar with BS 7909, BS 7671:2018+A4:2026, and the Electricity at Work Regulations 1989. The IET has published guidance notes specific to entertainment installations.

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02 · Specialist Installation

The Responsible Person: Roles and Duties

The responsible person (RP) is central to the BS 7909 framework. The RP is a competent individual who takes professional responsibility for the electrical installation from design through to de-energisation. On large events, a team of RPs may be appointed, each responsible for a defined area or system.

  • Competence requirements — the RP must have adequate knowledge of BS 7671 and BS 7909, experience in designing and supervising temporary electrical systems, and hold appropriate qualifications. In practice, RPs are typically qualified electricians with experience in the entertainment sector, often holding additional training certificates specific to event electrical work.
  • Design responsibilities — the RP reviews or produces the electrical design, including the single-line diagram, cable schedules, protection coordination, earthing design, and load calculations. On smaller events the RP may be the designer; on larger events the RP reviews designs produced by others.
  • Pre-energisation check — the RP oversees or carries out the pre-energisation check (PEC) and signs off the installation as safe to energise. This is a formal process with recorded test results. The RP must be satisfied that the installation complies with the design before energisation.
  • Emergency procedures — the RP must establish and communicate emergency shutdown procedures to all relevant event staff. The location of all isolation points, the de-energisation sequence, and the actions to take in an electrical emergency must be documented and rehearsed before the event opens.
03 · Specialist Installation

Temporary Distribution Systems

Temporary event electrical distribution typically follows a hierarchical structure, from the primary power source through secondary and tertiary distribution to individual loads. Each level of the hierarchy has defined protection and documentation requirements.

  • Primary distribution — from the power source (mains incomer or generator) to primary distribution boards (PDBs). Primary distribution typically uses large-section armoured or rubber-insulated flexible cables and Ceeform or camlock connectors rated at 200 A to 400 A. Overcurrent protection at the primary level uses moulded case circuit breakers (MCCBs).
  • Secondary distribution — from PDBs to secondary distribution boards (SDBs) serving individual areas, stages, or zones. Secondary distribution cables are typically 16–70 mm² flexible rubber insulated. Secondary distribution boards incorporate MCBs or RCBOs per outgoing circuit with appropriate time delays for discrimination.
  • Final distribution — from SDBs to 32 A or 16 A socket outlet boards, lighting dimmer racks, or directly to fixed equipment. Every socket outlet circuit at the final level must have 30 mA RCBO protection. Socket outlet boards used at events must be purpose-built for event use — domestic consumer units are not suitable.
  • Cable management — all cables in public areas must be protected against damage and must not create trip hazards. Cable ramps, cable bridges, and overhead cable routes are standard. All cables must be clearly labelled at both ends and at regular intervals. Cable routes must be marked on the event site plan.
04 · Specialist Installation

Generator Connections for Temporary Events

Generators are the primary power source for many outdoor events and for indoor events where the venue's mains supply is insufficient. Generator connections must be made correctly to establish a safe earthing arrangement before any loads are connected.

  • Generator earthing — a generator supplying a temporary installation must be earthed by connecting its star-point neutral to an earth electrode driven at or near the generator. This establishes a TN-S system where the neutral and protective earth conductors are separate throughout the distribution system. The neutral must NOT be connected to the generator's metallic frame without first establishing an earth electrode connection.
  • Earth electrode resistance — the earth electrode at the generator must be tested before the generator is loaded. For a TN-S system, the earth electrode resistance must be low enough to ensure that the prospective fault current is sufficient to operate the overcurrent protective devices within the required disconnection times.
  • Generator output cables — output cables from the generator must be rated for the generator's full output and for the physical conditions at the site. Connections must be made using appropriate connectors rated for the current and installed by a competent person. Generator output cables in public areas must be routed to prevent damage from vehicles or foot traffic.
05 · Specialist Installation

RCD Protection in Temporary Event Installations

RCD protection is the primary line of defence against electric shock in temporary event installations. The combination of outdoor environments, high pedestrian traffic, flexible cables subject to damage, and large numbers of members of the public makes comprehensive RCD protection non-negotiable.

  • 30 mA for all socket outlet circuits — every socket outlet circuit at the final distribution level must be protected by a 30 mA RCBO. This is a mandatory requirement under BS 7671 Regulation 411.3.3 and is reinforced by BS 7909. There are no exceptions for temporary event installations.
  • Discrimination — upstream time-delayed RCDs — primary and secondary distribution boards should incorporate time-delayed RCDs (S-type, with a short time delay) rated at 100 mA to 300 mA. These provide discrimination so that a 30 mA trip at a socket outlet level does not trip the upstream 300 mA device, preserving power to the rest of the event.
  • RCD testing before energisation — all RCDs must be functionally tested as part of the pre-energisation check. The test records must include the operating time at IΔn and at 5× IΔn. Only calibrated test instruments must be used; the test button on the RCD face does not verify operating time.

Record all RCD test results in the Elec-Mate inspection report app as part of the pre-energisation check documentation.

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06 · Specialist Installation

TN-S Earthing for Temporary Electrical Systems

TN-S earthing is the preferred and most straightforward earthing arrangement for temporary event electrical installations. Understanding why TN-S is preferred — and why PME (TN-C-S) must not be used — is essential for electricians working in the events sector.

  • Why TN-S for temporary systems — in a TN-S system, the neutral and protective earth conductors are separate from the source to every point in the installation. A break in the neutral conductor does not cause dangerous voltages on the protective earth conductor and hence on equipment metalwork. In temporary systems, where cable connections are made and remade many times, this separation provides a critical safety margin.
  • Why PME must not be used — in a PME (TN-C-S) system, the protective earth is derived from the combined PEN conductor. If this conductor is broken between the source and a connected piece of equipment, the equipment's metalwork can rise to near-full line voltage. In temporary systems, an open PEN fault is a realistic risk. For this reason, BS 7909 and network operator engineering standards restrict the use of PME for temporary event installations.
  • Isolation transformers — where a mains supply providing only PME earthing is the available power source, an isolation transformer may be used to derive a local TN-S (or IT) system. The transformer secondary is earthed via a local earth electrode, establishing a safe TN-S arrangement for the temporary installation.
07 · Specialist Installation

Pre-Energisation Inspection and Handover

A formal pre-energisation check (PEC) is required before any temporary installation is energised for the first time. The PEC follows the same principles as an initial verification under BS 7671 and must be carried out by a competent person appointed by the responsible person.

  • Insulation resistance testing — all distribution cables and board wiring must be tested for insulation resistance before energisation. Tests are carried out phase-to-neutral, phase-to-earth, and neutral-to-earth using a 500 V DC insulation resistance tester. The minimum acceptable value is 1 MΩ per BS 7671.
  • Protective conductor continuity — continuity of all protective earth conductors must be verified from each load point back to the main earthing terminal. Earth continuity must be confirmed before energisation, as a break in the protective conductor is not detectable during normal operation until a fault occurs.
  • RCD functional testing — all RCDs at every distribution level must be tested with a calibrated RCD tester before energisation. Operating times at IΔn and 5× IΔn must be recorded and verified against BS 7671 maximum values.
  • Documentation — all PEC test results must be recorded and retained as part of the event documentation package. The RP signs off the PEC report and retains it throughout the event. The PEC report should be available for inspection by the local authority or safety officer if requested.
08 · Specialist Installation

For Electricians: Temporary Event Electrical Work

Temporary event electrical work is a demanding and rewarding specialism. Exhibition, festival, and event electricians need excellent knowledge of BS 7909 and BS 7671, physical stamina for installation work in all weather conditions, and the ability to work to tight deadlines. Day rates for experienced event electricians and responsible persons are typically above the national average for electrical work.

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Frequently Asked Questions About Exhibition and Event Electrical Installations

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