A safe approach distance is the minimum separation in air from an energised overhead electric line that should be maintained by a machine, person, or object held by or in contact with that person.

The safe distance is a function of the overhead line voltage, the sort of work being undertaken whilst “in the vicinity of” and the skills and experience of the workers, nature of work, plant and equipment, site conditions and in some states whether the electric lines are insulated or bare, with or without consultation with the owner and the need for a spotter or safety observer.  Other considerations such as sag and sway of the lines become important as you move closer.  You don’t want to put yourself or others in danger nor damage the assets or property.

For overhead services – remember to always look up and live!

For underground services – remember to always dial before you dig!

The hazards and risks

Overhead lines are often uninsulated (bare) and high voltages will arc across (flashover) air gaps to objects of a different potential and therefore present as a serious hazard, if you or you equipment is in proximity.  Other occurrences such as lightning strikes and switching can cause significant transient voltage rise, increasing the potential for arcing.

Cranes and other plant working in close proximity to high tension lines can develop substantial induced voltages.  In such situations the plant should drag a chain to improve earthing.

In case of contact:

If the plant touches the energised overhead line then the plant may become energised and could conduct current.  That current may or may not cause network protection devices to trip and anyway such devices are designed to make several attempts to reset.  The currents can damage the plant so following such incidents the plant needs to thoroughly checked and repaired before going back into service.  The operator should try to move the plant clear and if not remain in the cabin and await help.  Both the operator and others who are not properly qualified must be careful because the plant will now be live and the ground to a distance of 8m from the plant will likely have serious gradient potential that can kill anyone who steps in the area.

If the operator needs to evacuate due to fire or other serious hazards then they must carefully jump clear of the vehicle, landing with feet together and not falling forwards.  When jumping, the operator must lose all contact with the vehicle before touching the ground.  They can then move away from the vehicle by shuffling or hopping, keeping both feet together at all times.  This should only be attempted if staying in the vehicle poses a strong likelihood of death, e.g. if it is on fire.  Report all incidents to the asset owner.

Working near overhead and underground assets

Each state and territory across Australia has a different set of rules for safe approach distances for working near overhead and underground assets.  Whilst the principles of safety, protection and maintaining asset integrity are the same it is difficult to find consensus between the parties for uniform safe approach distances.

Care should be taken as each jurisdiction publishes guidance material and it is important that you are aware of the particular requirements for the location that you are working, and it is often best to contact the local regulators and the owners of the assets to get full advice.

For a given circumstance the permitted approach distance published by each jurisdiction (other than Tasmania) lies within an Envelope of Safe Approach Distances.

Approach distance Zones for overhead lines

The figure identifies three distinct zones that define the approach distance in the vicinity of an overhead electric line:

Zone C: No Go Zone – requires written approval from the electricity supply authority for access.

Zone B: Authorised Persons – are workers who have successfully completed a recognised training course in overhead line electrical hazards.  Before the work starts, undertake a documented risk assessment and develop a safe system of work based consultation with the owner / supply authority and all work conditions imposed by them.

Zone A: Unauthorised Persons – are workers who have not received training in underground or overhead line electrical hazards and do not have sufficient training or experience to enable them to avoid the dangers from overhead electric lines and associated electrical equipment.

NEAR envelope approach distance

Work in the vicinity of or near overhead and underground electric lines is where there is a reasonable possibility a person will either directly or through a conducting medium, come within an unsafe distance to energised lines.  The vicinity will be a function of the line voltage, nature of work, site circumstances and competencies/authorisation

Use a risk management approach regarding any overhead line or possible underground service that may be in the vicinity.  Consider safety and other precautions, and where necessary seek appropriate advice:

• Underground Assets

Contact Dial-Before-You-Dig (call 1100) or www.1100.com.au to obtain map locations and identify asset owners for suitable work methods.  Note that the maps and records may not be up to date and the locations and depths can be in error, and you need to take that possibility into account.  Failure to take due precautions can be unsafe and disturbing or damaging a critical asset can result in severe penalties.  Carry out service searches as required and if a critical underground asset (eg power, gas or telecommunications) is in the area then consult with the owner before you commence.

• Overhead Assets

Determine the nature, voltage and approximate height of the lines.   If unsure contact the supply authority.  Establish a safe approach distance for the O/H line considering the nature of work, site, workers, plant and equipment.  This distance should be no closed than the relevant jurisdictional values.

The work vicinity will typically be several meters greater than that distance.

What is the voltage of an overhead line?

There may be a high voltage sign on a pole or transformer, or as a first approximation; a single HV insulation disc on the power pole will correspond to 11kV.  If there are 3 disks then the voltage is likely to be 33kv; five or six indicates 66kV.  Above that it might be difficult to assess and in any case talk to the network operator or asset owner.

Envelope approach distance for overhead assets

If you are going to undertake work where there is any possibility of being within 12m of an overhead asset then be aware of your obligations.

The following tables identify minimum acceptable envelope approach distances for the type of work.  You may be allowed to go closer than these envelope distances in some states.  Those circumstances are not defined here (as they are all different) but you should identify the specific rules and requirements and check for any possible reductions to the envelope approach distance prior to starting work.  In some cases you may simply need to refer to the local Regulation or other Code or Guidance Material. You may also need written approval or permit to work from the Asset Owner and / or Principal Contractor.

There may also be circumstances, for example, where accredited service providers working under a network safety management plan of an electricity supply distributor can go closer and an observer is not always required.

For the purpose of these tables the “approach envelope” is a rectangle limiting approach from the side and from below and the work/access restrictions extend vertically without height limit, anywhere above the lines.

When using these distances and depending on company or client requirements, competencies, terrain, weather, the design and operating characteristics of the plant, etc., your risk assessment, SWMS or Safe Work Procedures may identify additional hazards and/or risk controls (c.2).

Table 1   Safe approach distance to O/H power lines

UNTRAINED UNAUTHORISED PERSONS in Zone A

with Safety Spotter

Table 2   Safe approach distance to O/H power lines

TRAINED AUTHORISED PERSON in Zone B

with Safety Spotter

Table 3   Safe approach distance to O/H power lines

UNTRAINED UNAUTHORISED MOBILE PLANT in Zone A

with Safety Spotter

Table 4   Safe approach distance to O/H power lines

TRAINED AUTHORISED MOBILE PLANT in Zone B

with Safety Spotter

Table 5   Safe approach distance to O/H power lines

VEHICLES-IN-TRANSIT CLEARANCES in Zone A

Electrical Spotter

Spotters for overhead electrical lines shall have completed an endorsed spotter training course by a registered training provider and be competent in the following areas:

• the design envelopes for the equipment/plant being used
• the operation and uses of the equipment/plant being used
• the hazards posed by overhead electrical assets.

Where a spotter is to be used, the electrical contractor must ensure the spotter is fully inducted into all site safety procedures including the relevant Safe Work Method Statement (SWMS).

The spotter must remain on site for the duration of the work for the equipment being spotted and should only spot one piece of equipment at a time.

Envelope for erecting SCAFFOLDING near overhead lines

For voltages ≤ 33kV, the closest point of scaffolding should be no less than:

• 6 metres measured horizontally
• 5 metres measured vertically.

If the line voltage is > 33kV, then the minimum distances will be greater.

If you wish to erect the scaffolding closer, refer to jurisdictional requirements and consult with the supply authority or owner.  The approach distances in some states are less and you may also be allowed to erect barriers and take other measures to address the hazards.

Work near insulated low voltage service lines

For minor work near low voltage service lines (by unauthorised persons) with sound insulation observe the following approach distances:

Refer to No Go Zones and working around powerlines on the Energy Safe Victoria (ESV) website for further information.

Working near distribution authority’s network

To work on or near the electrical distribution network you need to be accredited by the Supply Regulator and authorised by the local distribution network service provider. Always contact the relevant provider / asset owner for requirements prior to starting work.

Where this is allowed the Network Operator’s Service and Installation Rules will detail working distances and service connections to the network pillars, poles and services.  The accredited person would also refer to the network operator’s Network Standards for working on or near their network.

You could well be working within the No Go Zone and you will need to have well documented safe systems of work including SWMS, access authorizations/permits and appropriately rated test instruments, tools, plant and equipment, and PPE.