Safe isolation for low voltage

[edit] Introduction

In relation to electricity, the term 'isolation' refers to cutting off the electrical supply to an installation for safety reasons. Isolation of electrical equipment and systems is required under the Electricity at Work Regulations 1989 to protect technicians from dangerous working conditions. The regulations define isolation as ‘the disconnection and separation of the electrical equipment from every source of electrical energy in such a way that this disconnection and separation is secure’.

[edit] Purpose of safe isolation

Once the electrical supply has been isolated, the means of isolation must be verified so equipment is not accidentally reactivated. This process is generally referred to as safe isolation for low voltage.

Safe isolation can be used to prevent the risk of shock for people tasked with undertaking electrotechnical work. It can be broken down into a series of steps that should be taken when disconnecting an electrical device, system or installation from the circuit and testing to ensure that no live current is flowing during the process. Once safe isolation has been exercised, the device should be proven dead.

While safe isolation is a standard procedure taught to most apprentices in the electrical trades, there may be times when all of the recommended steps are not followed prior to the commencement of electrical work. This can lead to safety breaches that can cause serious injury and may sometimes be fatal.

[edit] Steps for safe isolation

In the Best Practice Guide 2 (Issue 3), Guidance on the management of electrical safety and safe isolation procedures for low voltage installations, published by Electrical Safety First, provides guidance for safe isolation procedures. The document offers a checklist of the minimum stages for safe isolation, including:

• Locate / positively identify correct isolation point or device.
• Check condition of voltage indicating device.
• Confirm that voltage indication device is functioning correctly.
• Switch off installation / circuit to be isolated.
• Verify with voltage indicating device that no voltage is present.
• Re-confirm that voltage indicating device functions correctly on known supply / proving unit.
• Lock-off or otherwise secure device used to isolate installation / circuit.
• Post warning notice(s).

[edit] Safe isolation equipment

Further guidance specifically advises against the use of volt sticks (or voltage sticks) for safe isolation procedures. These should only be used to identify live equipment and not to prove it is dead.

Instead, the use of voltage indicating devices (also referred to as voltage detectors) should follow the guidance and procedures recommended in Electrical test equipment for use on low voltage electrical systems GS38 (fourth edition) from the Health and Safety Executive.

These devices should comply with BS EN 61243-3:2014. The only approved devices that should be used are those intended for the specific type of application.

[edit] Related articles on Designing Buildings

• 18th Edition Wiring Regulations.
• Amendment 3 BS 7671 Requirements for Electrical Installations IET Wiring Regulations.
• Articles about electricity.
• Electrotechnical Assessment Specification guidance for installers.
• Electrical test equipment for use on low voltage electrical systems GS38.
• Electrical safety.
• Electrical wiring.
• Institution of Engineering and Technology.
• Lock out tag out LOTO.
• Low-voltage switchgear and protective devices.

[edit] External resources

• BSI, Live working. BS EN 61243-3:2014, Voltage detectors - Two-pole low-voltage type.
• Electrical Safety First, Best Practice Guide 2 (Issue 3), Guidance on the management of electrical safety and safe isolation procedures for low voltage installations.
• Health and Safety Executive, Electricity at Work Regulations 1989.