Articles

The Big Electricity Build – Avoiding Shocking Conditions to Keep Construction Workers Safe

With Australia’s energy transition being built at a rapid pace, there is a very large number of significant electrical construction projects either underway or being planned to support it. Projects for major wind and solar generation, battery energy storage, electric transportation and new transmission lines and substations are being built apace.

These integrate with and are often built closely alongside live high voltage electrical systems that can pose safety risk to construction workers. The industry sadly remembers workers who have lost their lives on the job because of earthing related safety hazards, and too often the lessons learnt are forgotten.

SITE SAFETY ESSENTIALS

Electrical hazards from direct contact are understood as a major emphasis of Safety within the construction industry. Electrical Safety forms part of any set of site safety essentials, providing workers with a basic awareness of the hazards of live conductors or poorly maintained electrical leads, plant and equipment. However, beyond the basics of avoiding contact with live wires or faulty equipment, non-electrical workers are rarely aware, or have little understanding of other electrical hazards particularly those related to earthing and indirect shock.

Big projects command big multi-trade construction workforces of varying backgrounds and experiences in the electrical industry. With the unique and sometimes obscure nature of indirect electrical shock hazards it is very important that site electrical managers are equipped to identify, communicate and control risks, and that workers have a basic awareness and understanding of the controls that are keeping them safe.

When construction is occurring in or near environments where High Voltage (HV) systems are present, earthing related electrical hazards need to be understood and controlled to ensure safety, as electrical hazards can appear in locations and to plant that are normally otherwise safe. In principle, an electrical hazard is caused by the ability to contact two things at different voltages. This includes the ground beneath your feet being at a different voltage to something you are contacting with your hand, or voltage appearing between two things you can simultaneously touch. This could be anything from a wire, electrical tool, a fence even the crib room frame. These voltages can be caused through many different mechanisms, such as a system fault resulting in:

• An Earth Potential Rise and voltage between different points on the ground.
• Transferred voltages along metallic paths, particularly where a path is insulated from the ground such as a cable screen or strung conductor. Figure 3 illustrates hazard transfer via an earthwire.
• Induction related hazards on long metallic structures or pipes.

Other hazards can be persistent and associated with proximity to energised systems, such as:
• Capacitive charging of objects like crane in the vicinity of HV lines and busbar. Figure 1 shows an example of a hazard at new equipment being built in a live yard.
• Magnetic fields from current flow in one conductor causing induced hazards on nearby conductors, such as a strung line in a shared easement.

Regardless of the mechanism that creates these hazards, workers with non-electrical background, or low literacy in electrical risk are often unaware of the mechanism, and not equipped to identify or control the term such as during a fault can also lead to complacency among workers. But HV systems are ubiquitous as part of the utility electrical supply network. As such faults can and do occur creating hazards in an instant without warning.

Whilst trained workers such as engineers and electricians are responsible for designing and implementing controls for these hazards, the constantly changing nature of work sites means it is vital that workers gain a basic understanding to be able to identify where these hazards might next impact their work tasks.

Further, if construction is occurring on or near a HV asset such as major substation, workers are generally not permitted onsite until they have gained a basic understanding of earthing related electrical hazards.

Controls such as equipotential bonding (shown in Figure 2), equipotential work zones, isolation matting and panels, insulated work methods, and sourcing of temporary power, can be easily overlooked by workers who are ill-equipped to identify the risk or how to best manage it.

A LONG TIME PERIOD

Often large projects will have a long time period over which energisation and commissioning progressively occurs in parallel with ongoing construction. While the final system or infrastructure will have permanent safety controls to keep people safe including bonding, a well-designed earth grid, or surface coverings to reduce shock risk, these controls may not be in place during ongoing construction works.

Knowing how to manage worker safety across different work streams in these situations is extremely important since workers can be in vulnerable situations for exceedingly long time periods, thereby increasing their exposure to hazards. Even a substation that is completely de-energised may have earthing hazards appear if it’s earthing is connected via cable screens (or similar) to another energised substation that may transfer hazards. Even new transmission lines that are away from other assets can transfer induced or earthing related hazards many kilometres down the line to workers as it is being strung. Lightning also poses a risk on long interconnected transmission systems where a lightning event at one end can cause hazards to appear at distant locations.

There have been countless instances in Australia of workers receiving indirect shocks; from plumbers cutting metallic pipes, to cable jointers and line workers receiving shocks from induced voltages while working under permit, to electric shock from mobile plant operating within easements and beneath HV lines, to fencing contractors receiving shocks while installing new fences adjacent to in-service plant.

Unfortunately, and very sadly, these situations have resulted in preventable fatalities that could have been avoided with proper awareness and basic training.

As a means of training and equipping workers to understand these hazards, Safearth has worked with a number of project customers to provide such training and develop an effective means of communicating with construction workers of different trade backgrounds and levels of understanding.

AWARD WINNING EARTHING AWARENESS VIDEO

One example of the training tools that Safearth has developed is an award winning Earthing Awareness video that provides an introduction into electrical earthing safety.

It is important that information that is key to safety is presented to a workforce in an engaging and clear way. This introductory video has been designed to present the fundamentals of earthing and electrical safety in a clear an engaging manner. The video is not designed to just provide information but as a means to equip workers to identify possible electrical hazards and arm them with a basic toolkit of safe work practices to minimise these hazards, and not inadvertently defeat controls that have been put in place.

This safety video has been utilised as part of the induction process on many large worksites where interaction with HV earthing and power systems pose risks to multi-trade workforces. Several power companies utilise this type of training to assist in providing a clear understanding to those who may be entering and working within their HV installations or substations.

From providing videos, to training, staged construction planning and engineered designs, Safearth are enthusiastic to continue to provide solutions for the improvement of safety in the electrical construction industry as it embarks on the great energy transition.

By Mr Joshua Bowman, Consulting Engineer / Mr Matthew Bale, Engineering Director -Safearth

For more information contact Safearth on 1800 327 844

safearth.com | enquiries@safearth.com