SUPPLEMENT TEST & MEASUREMENT
ESSENTIAL TEST EQUIPMENT for safe installation and maintenance
Implementing safe isolation procedures is essential to achieve compliance
with HSG85 Electricity at Work Regulations, which are there to ensure that workers on site are not exposed to danger when working on or near live electrical systems.
Selecting the right tools for the job is critical to implementing an effective procedure to stay safe and avoid potentially fatal accidents and heavy penalties. With this in mind,
Martindale Electric looks at what test equipment and procedures are required to ensure circuits have been de-energised and properly isolated prior to maintenance and modifications of electrical instrumentation and equipment
WHAT EQUIPMENT IS NEEDED TO CARRY OUT SAFE ISOLATION? Electrical Safety First has produced a guidance document that covers best practice for safe isolation (Best Practice Guide 2 Iss.3 2015). This includes guidance on proving that isolated equipment or circuits are dead by using suitable test lamps and voltage detectors. Using the right equipment is one of the most important parts of the procedure. The essential test tools and equipment needed are locking off devices with unique keys and a clear method of labelling the hazard, a dedicated voltage indicator and a proving unit to verify the voltage indicator. Comprehensive locking off kits are
available to ensure the right locking off device is always to hand for the circuit being worked on. A basic kit should include the following: • Selection of MCB & breaker locks • Padlock with a unique key • Hasp for when more than one person is working on a system • Lock out tags & warning labels Multi-lock hasps ensure a circuit cannot be re-energised until each operator has finished work and removed their own padlock. Locking off the circuit correctly is just one part of the procedure. Before carrying out any work on the circuit, you must verify that the circuit is definitely dead before proceeding. Circuits are frequently mis-labelled so there is no certainty that the correct circuit is locked off. In some instances where neutrals are ‘borrowed’ they can become live if an energised load on another circuit is connected to it. To prove dead, it’s essential to use a dedicated voltage indicator and a proving unit.
WHAT IS THE CORRECT EQUIPMENT FOR PROVING DEAD? With a wide range of voltage detectors and
S18 Find out more:
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OCTOBER 2016 | INSTRUMENTATION: TEST & MEASUREMENT SUPPLEMENT
indicators available, it’s important to understand why some equipment, such as multimeters and non-contact voltage detectors, should not be used for this process. Multimeters are not
suitable as it’s all too easy to select the wrong range. In addition multimeters rely on battery power to function, thus there is a great margin for error in making a false ‘dead’
reading on a live circuit. Non-contact voltage detectors also
require a battery in order to work, and are typically sensitive to other signals, such as static electricity. In addition it is impossible to prove this type of device is working correctly with a standard proving unit. Whilst these units can be used to detect live cables, they cannot reliably be used to prove dead. Electrical Safety First states that you should use a dedicated voltage indicator and a proving unit when carrying out this procedure. The list of suitable equipment includes two- pole voltage indicators, such as the Martindale VI13800 or VI-15000 or test lamps, such as the Drummond MTL10
or MTL20. Martindale voltage indicators for safe isolation are fully compliant with the latest standards and are designed for safety, with no batteries or switches which could lead to false indication. The procedure for proving dead is to take your voltage indicator and check it against a known source, such as a proving unit, then test the circuit, then test the voltage indicator against the known source again to prove the tester has not failed
during testing. Whilst you can use a known live source to test your voltage indicator, it’s recommended to use a dedicated proving unit matched to the voltage indicator to ensure that all LEDs on all ranges are working, and in many cases a known live source may not be available on-site. All equipment should be in accordance
with the latest edition of HSE GS38 (Edition 4 June 2015) which includes the most recent standards for test equipment and useful information on how to avoid accidents when working on electrical systems.
NEW KITS SIMPLIFY COMPLIANCE There have been many developments which now make it easier to choose the right equipment and ensure the correct locking off device is always available. These include complete kits with voltage indicators, matching proving units and a comprehensive range of locking off devices for MCBs and fuse carriers. Kits are supplied in combination carry cases to ensure that proving devices are always at hand and provide the simplest solution for implementing safe isolation practices on-site.
Martindale Electric
www.martindale-electric.co.uk
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