Power line safety

Contact with live power lines is a major risk for machine and equipment operators.

Cranes and other high-reaching machines are particularly vulnerable, but any large, moveable machines – including motor graders – may come into contact with underground or overhead power lines.

Power lines have the capacity to carry voltages up to 750,000 volts, and temperatures can reach more than 982 degrees Celsius. That means that making contact with the lines can be fatal.

Causal factors

In South Africa, an average of 150 people die in construction site accidents each year, and contact with live power lines is one of the major contributors to these deaths.

Not knowing exactly where power lines are buried is one causal factor. Underestimating the reach or height of machinery is another.

Something often overlooked is that it's not equipment operators who are most at danger. Instead, it's workers standing close to "live" machines that are most vulnerable to death and serious injury.

An operator has some protection because the vehicle itself can provide grounding. Those nearby, however, don't have this protection – and electricity can arc out from the source.

How to prevent power line accidents

To implement power line safety, it’s essential to formulate a proper plan. Any power lines onsite, whether underground or overhead, should be identified, mapped and appropriately flagged with hazard signage.

Create no-go buffer zones

It’s a good idea to impose a line clearance distance, or no-go zone, that no equipment or personnel may breach. A safe distance for 50-volt lines is around three metres. Anything higher than that voltage demands a 10-metre clearance distance.

Move or power-down the lines

If buffer zones are impractical, ask the relevant electricity department or authority to move or power down the lines until construction is complete. You can also request that barrier protection, such as insulating sleeves, be attached to the live lines.

Request the exact location of underground lines

Underground power lines pose a particular threat because operators can't see them. The easiest way to prevent grader-related accidents is to request the exact location of the lines from the power supplier.

High visibility warning signs and human observers

Warning signs or signals should be erected on poles for optimal visibility. Underground lines should be tracked on either side by flagged barriers.

Human observers offer a practical solution. They can act as a second pair of eyes for operators who don't have clear line of sight due to the bulk and size of heavy machinery or loads.

How to react to power line contact

If a motor grader operator hits an underground power line while digging, this person may escape injury. Anyone standing close by, however, could suffer the full brunt of the electrical shock.

Do not leave the machine

Under these circumstances, the operator must remain seated in the vehicle. No one must approach the machine or offer any assistance, apart from alerting the electricity department. It's safe to disembark only once the line has been powered down.

If, for any reason, it’s dangerous to remain in the vehicle, the operator must jump clear of the machine, and land squarely on both feet. Touching the grader when in contact with the ground must be avoided at all costs, or electrocution will occur.

Move away in small shuffling steps

Once safely on the ground, the operator should move away from the machine in small shuffling steps. Anyone standing close by must do the same.

This is because electrical current moves outwards in concentric circles of high and low energy. Step from a low energy sector into a high energy sector and the electrical current can move up the legs, causing injury or death.

Following these basic power line safety tips can protect operators, bystanders and valuable equipment.

At KH Plant, we specialise in restoring Caterpillar 140G, 140H and 140K motor graders to as-new condition – so you can get the benefits of a new grader at a fraction of the cost of a new machine. Contact us for more information or to discuss your needs.