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A guide to electrical testing in construction

A guide to electrical testing in construction

by constructaquote - 25 October 2019


Almost every construction site undergoes some form of electrical equipment or electrical work. While most construction workers will be familiar with the potential dangers of electricity, unlike most other hazards that can be seen, felt or heard, electricity risks come with no clear warning and can result in serious injuries and even fatalities.

Accidents can happen due to a number of issues including faulty installations, a lack of maintenance, and damage to equipment. However, most accidents occur because people are working on or close to equipment that is either:

  • assumed to be dead, but is in fact live; or
  • known to be live, but workers have not received adequate training or adequate precautions have not been taken.

Therefore, it is crucial that construction workers are aware of these risks and manage ways to prevent them. The law states that workers must take precautions to prevent the risk of injury or death from electricity and all equipment must be safe and correctly maintained.

Electrical systems and equipment must be properly selected, installed, used and maintained and only ever worked on by a competent authorised person. Work on live electrical systems should only ever be carried out in exceptional circumstances and avoided as much as possible.

Electrical Risks in Buildings

Every year, around 3 workers are electrocuted during refurbishment work on commercial and domestic buildings. These workers include qualified electricians as well as other varied tradespeople.

As well as electrocutions, there are many other incidents which damage equipment and cause thousands of ‘near-misses’, that could have resulted in fatalities.

Refurbishment building work comes with high risks and must be planned, managed and monitored correctly to ensure that workers are kept safe. Additionally, the equipment used to carry out the work must be safe and properly maintained.

How To Manage The Electrical Risks During Refurbishment…

Refurbishment-related electrical incidents can be reduced by:

  • Understanding the system

Workers responsible for planning and managing refurbishment work must understand the electrical system of the whole building and liaise with the building occupier.

This will allow any additional building work to be planned and managed with the electrical system in mind for the workforce to remain safe.

  • Working dead

Certain parts of the electrical system should be isolated if the refurbishment work is likely to disturb or damage the existing electrical system and expose people to electrical danger.

  • Portable electrical equipment

DIY and domestic tools with plugs and cables are not suitable for construction site conditions. Only use cordless tools or those that operate from a 110V centre tapped to earth (CTE) supply system so that the maximum voltage to earth does not exceed 55V.

Any equipment used needs to be inspected and serviced regularly by a qualified electrician and removed from the site if damaged.

  • Residual current (trip) devices

If mains voltage (230v) is used and the equipment or leads are damaged, the risk of injury is high. 230v equipment must be visually checked for any damage before each shift as well as undergo a weekly and monthly inspection. Although not compulsory, it’s recommended to keep records of every check carried out.

An RCD is a safety device which detects some, but not all, faults in the electrical system and subsequently switches off the supply to prevent any accidents from occurring.

RCDs need to be installed and enclosed correctly; checked daily; treated with care; kept free of moisture and dirt; and protected against vibration and mechanical damage.

  • Lighting systems

Protect cabling and bulbs against breakage. If a bulb breaks, the exposed filament may present a hazard, therefore, cables and bulbs need to be protected against any potential damage. This can be done by checking bulbs regularly to maintain electrical safety and keep the site well-lit.

Electrical Risks in Overhead Power Lines

Incidents regarding overhead power lines have been known to result in severe injury and even death every single year, therefore, that law states that all work carried out on power lines must be planned and managed carefully to avoid contact with the lines.

Work involving tall machinery or equipment (scaffolding, cranes, tipper vehicles, etc.) are high risk, and many people often mistake live power lines for wooden telephone poles.

Incidents don’t only occur if something or someone comes into contact with the power lines, close proximity to a live conductor may also cause a ‘flashover’.

To prevent danger, the following safety measures should be considered:

  • Planning and preparation

Find out where the nearest power lines are where you are planning on doing any work. Always assume that any power lines you find are live, even you think they probably are not – unless you have been proved otherwise by the line owners

If there are any electric lines over the work area, near the site boundaries, or over access roads to the work area, you must inform the line owners and discuss the proposed work.

Diverting lines or making them ‘dead’ can take time and this should be factored into your plan.

  • Eliminating the danger

You can aim to reduce danger by:

  • Avoidance– find out if the work has to be carried out under or near overhead lines.
  • Diversion– divert all overhead lines outside of the work area; or
  • Isolation– make the lines dead while the work is in progress.

Where the danger cannot be eliminated, you must manage the level of risk by controlling access to the power lines and working beneath them.

  • Controlling the access

Defined passageways should be made anywhere the plant passes beneath the lines and the danger area should be as small as possible by restricting the width of the passageway to the minimum needed for safe crossing.

Passageways that cross the route of the line at right angles are considered the safest.

  • Controlling the work

If work beneath live overhead lines cannot be avoided, essential warning notices such as barriers and goal posts should be provided.

When managing risk, the following precautions may also be needed:

  • Clearance –the owner of the line should state the safe clearance area required beneath the overhead power lines;
  • Exclusion –any equipment or tools that could potentially reach above the safe clearance limit should not be underneath the line;
  • Modifications –equipment should be modified with physical restraints so that it cannot reach beyond the safe clearance line;
  • Additions –equipment with additional parts will also need further modification to prevent them from entering above the clearance line;
  • Supervision –all access to equipment, tools, and work using them should be supervised by a person responsible for managing health and safety on site.

Electricity Risks In Underground Cables

Accidents involving underground electric cables are the cause of many construction injuries and deaths, and workers must take the required precautions to avoid danger.

Injuries are usually caused by the effects of arcing currents exploding producing flames which can severely burn or even kill individuals.

This can occur when a cable is:

  • penetrated by a sharp object, or,
  • crushed severely enough to cause internal contact between conductors or sheathing,
  • damaged but left unrepaired or unreported.

There are, however, precautions that can be taken when working near buried cables:

  • Planning the work

The project client must provide relevant pre-construction information to architects and contractors regarding the underground services so that they can plan the work accordingly to reduce risks.

If you need to make the cables dead for the work to commence safely, take into consideration that electricity companies need to give their customers at least 5 days’ notice before they can disconnect their homes and businesses of power.

Careful planning is vital before the work starts.

  • Using cable plans

Before any work begins, all relative plans regarding the layout of underground cables should be assessed. If plans or information regarding the cables cannot be obtained, workers should presume there are live cables there and approach with caution.

  • Cable locating devices

Before work begins, underground cables must be located, identified and clearly marked using location devices. Any cables in the area of the work or vicinity of the work should be clearly pinpointed on all plans.

  • Safe digging practices

Excavation work must be carried out safely, following recognised digging practices. Before excavation can take place, location devices must be used to accurately determine any cable locations. Once this has been done, trial holes can be dug to confirm the cables position.

Insulated tools should be used when hand digging near electric cables.

Reducing Risks And Preventing Injury

Although trained and qualified, even electricians are not immune from electrical dangers and many are injured on site every year.

To ensure safety to all workers, it’s crucial to have well thought out plans and systems in place which are then carried out by competent, responsible individuals. These plans should be clear, stating exactly what work needs to be done and how it will be done, and made available to all persons working on the site.

Electricians should avoid working live where possible and make sure their work has been sufficiently completed before making any systems live. Safe isolation procedures should be followed at all times.

Disclaimer: The advice provided here are our own interpretations and opinions. We have tried to simplify the main points to create this article and the information provided is for general informational purposes only. While we try to keep the information up-to-date and correct, there are no representations or warranties, express or implied, about the completeness, accuracy, reliability, suitability or availability with respect to the information, products, services, or related graphics contained in this blog for any purpose. Any use of this information is at your own risk.