ELE/Cable Work/TBT-ELE-012

Isolation and Safe Systems of Work

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Isolation and Safe Systems of Work

Toolbox Talk Record

Ref: TBT-ELE-012  |  Issue: 1  |  Date: March 2026
PresenterProject
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What?

  • Electrical isolation means disconnecting a circuit from its source of supply to make it dead.
  • The Electricity at Work Regulations 1989 require safe systems of work for all electrical tasks.
  • Isolation must be carried out by a competent person authorised to work on electrical systems.
  • A "prove dead" procedure using an approved voltage indicator is essential after isolation.
  • Voltage indicators must be checked before and after use with a proving unit.
  • Lock-off devices and danger tags must be applied to prevent re-energisation.
  • Multiple isolations may be needed where more than one supply feeds the circuit.
  • Safe isolation applies to both high voltage and low voltage systems on construction sites.
  • An inadequate isolation procedure is one of the most common causes of electrical fatalities.
  • Never assume a circuit is dead — always test using the correct equipment.

Why?

Prevent electrocutionContact with live conductors can cause fatal electric shock or severe burns in an instant.
Legal dutyThe Electricity at Work Regulations 1989 require that circuits are made dead before work begins wherever reasonably practicable.
Protect othersProper isolation and lock-off protects all workers in the area, not just the person carrying out the electrical task.
Do Don't
  • Follow the safe isolation procedure: isolate, lock off, prove dead
  • Use an approved voltage indicator to confirm the circuit is dead
  • Test the voltage indicator with a proving unit before and after use
  • Apply lock-off devices and personal danger tags at every isolation point
  • Identify all sources of supply — some circuits have multiple feeds
  • Ensure only competent and authorised persons carry out isolation
  • Obtain a permit to work where required by your site procedures
  • Verify isolation at the point of work, not just at the distribution board
  • Keep keys for lock-off devices under the personal control of the isolator
  • Re-check isolation after any break or shift change before resuming work
  • DON'T work on any electrical circuit without confirming it is isolated
  • DON'T rely on switching off alone — always lock off and prove dead
  • DON'T use a multimeter as a substitute for an approved voltage indicator
  • DON'T remove another person's lock or danger tag without authorisation
  • DON'T assume a circuit is dead because equipment has stopped working
  • DON'T bypass or defeat interlocks on switchgear or control panels
  • DON'T allow unauthorised persons to re-energise isolated circuits
  • DON'T forget to check for stored energy in capacitors or batteries
  • DON'T skip the proving unit test — faulty indicators give false readings
  • DON'T rush the isolation process even under time pressure

See also: Electrical Safety Awareness | RCD Protection and 110 Volt Use
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