Trees and powerlines

Vegetation near powerlines

Powerlines are an important part of our everyday lives, bringing electricity to our homes and businesses. Vegetation needs to be cleared from around powerlines to avoid power outages through damage to the lines, fires, or risks to people's safety.

It is a legal requirement that electricity network operators and occupiers or owners of private property maintain safe clearance distances between vegetation and powerlines.

Maintaining clearance zones around powerlines – who is responsible?

The clearance distances between vegetation and powerlines are a legal requirement outlined in the Electricity Regulations (Principles of Vegetation Clearance) 2010. The electricity network operator, SA Power Networks (ElectraNet for powerlines on large steel towers), local council, or the occupier or owner of a private property may be responsible for maintaining the vegetation clearance zones around powerlines.

Responsibilities of the electricity network operator

In South Australia, the electricity network operator (SA Power Networks) is responsible for establishing and maintaining clearances around all public supply lines, except in certain areas where the responsibility may be shared with local councils.

If a powerline crosses private land but does not supply the occupant of that land, it is a public supply line and SA Power Networks is responsible for vegetation clearance.

SA Power Networks is also responsible for clearing naturally occurring, non-nurtured vegetation such as self-sown or uncleared scrub around private supply lines.

In non-bushfire risk areas, the electricity network operator may enter into an agreement with a council to conduct the tree-pruning program around public powerlines. This includes trees hanging onto the land from a private property. These clearance programs are usually conducted in three-year cycles.

Responsibilities of occupier or owner

The occupier of a private property is responsible keeping the required clearance zone free of vegetation around:

  • private supply lines that supply the property
  • any trees or other vegetation overhanging the property from a neighbouring property.

This includes someone who is renting a property. If a property is unoccupied, the owner is responsible.

If you are considering planting new trees, see Planting trees near powerlines.

To find out legal clearance distances, see 'Determining required clearance distances between vegetation and powerlines – advice for property owners or occupiers' below.

What happens if I don't maintain the required clearance zone?

If you do not maintain the required clearances on a property, the electricity operator may clear the vegetation at your expense.

Clearance objections and complaints

The electricity network operator, SA Power Networks has to give the occupier or owner 30 days' notice of proposed vegetation clearance on private property. Emergency clearances are exempt from this requirement.

In the first instance, any objection to the proposed clearance should be discussed with the electricity network operator. If the objection is unresolved, you may contact the Office of the Technical Regulator (OTR) for further clarification. You can also lodge a written objection with the OTR (within 21 days of receipt of the notice) about matters set out in the notice.

Please note that the OTR may not consider your objections if you have not attempted to discuss and resolve them with the electricity network operator.

Emergency clearances during fire danger season

During fire danger season vegetation that is too close to powerlines can be an extreme fire hazard.

If the responsible occupier or owner has not maintained the safe clearance zones around the private supply lines, the electricity network operator may clear the vegetation at the occupier or owner's expense.

If the electricity network operator is unable to clear the vegetation in time, the supply lines may be disconnected at the occupier or owner's expense. The disconnection may affect other properties in the area.

Which areas are defined as bushfire risk areas?

Large areas of South Australia are defined as bushfire risk areas in schedule 4 of the Electricity (Principles of Vegetation Clearance) Regulations 2010.

In these bushfire risk areas, greater clearances are needed between powerlines and vegetation to minimise the risk of fires.

Most of the Adelaide metropolitan area and many developed townships are non-bushfire risk areas.

Use the Location SA Map Viewer to find out if your property is in a bushfire risk area. To turn on the bushfire map overlay, go to datasets, then click land management, then property and planning, then tick the box next to Electricity Regulations Boundaries.

If you are unsure contact the OTR.

On days of exceptionally high fire danger power may be disconnected in identified bushfire risk areas until the risk is reduced.

Example of a bushfire boundary map

Determining required clearance distances between vegetation and powerlines – advice for owners and occupiers

To determine the required clearance distance of vegetation from a powerline you need to know:

  • whether the powerline is located in a defined bushfire risk area - greater clearances are required in these areas
  • the voltage and the type of the powerline
  • the type of conductor – ie bare or insulated powerline wires
  • the distance between the stobie poles or transmission towers, called the span, is a factor in determining how much a powerline conductor will move in wind or sag due to heat – greater distances between poles increase the amount of movement
  • the distance between the vegetation and the closest stobie pole – powerline conductor movements are greater midway between the poles and this means that greater clearances are needed for the central areas between the poles than the areas close to the pole.

Determining the voltage and type of powerline

To find out the voltage of the powerlines in your area contact SA Power Networks or the OTR.

The OTR has also developed a basic identification guide, see Identifying powerlines.

High voltage powerlines are those of more than 1,000 volts (1 kV) of electricity. Low voltage powerlines refer to lines of less than 1,000 volts or less.

Clearance zones and buffer zones

A clearance zone is the minimum safe distance between vegetation and powerlines at all times allowing for the movement of the trees and powerlines.

It is a legal requirement for electrical network operators if the powerline is considered a public line, and responsible occupier if the powerline is private, to keep the clearance zone free of vegetation.

A buffer zone is an additional area around a clearance zone that allows for tree movement and growth without breaching the clearance zone.

Pruning and trimming trees and vegetation within the buffer zone will usually ensure the clearance zone stays clear until the next pruning is due without excessive removal of vegetation.

This also ensures safe working conditions for those undertaking the trimming.

Vertical and horizontal dimensions of the clearance zone vary according to the type and voltage of the conductor

Non-bushfire risk areas – clearance zones

Fully insulated conductors (powerline wires)

Fully insulated powerlines such as aerial bundled cables (ABC) always require a clearance zone of 10 cm (0.1 metre) in all areas.

Bare low-voltage or partially insulated conductors (powerline wires) in non-bushfire risk areas

Require a clearance zone of 10 cm (0.1 metre).

Bare high-voltage or partially insulated conductors (powerline wires) in non-bushfire risk areas

Bare high voltage powerlines in non-bushfire risk areas require different vertical (above or below the conductor) and horizontal (to each side of the conductor) clearance distances depending on the distance of the conductor (powerline wire) from the poles.

Dividing the length of the conductor between two adjacent poles into four sections, the two middle sections of the cable require greater vertical and horizontal clearances. This is because the middle parts of the cable can swing or sag more than the sections closer to the poles.

Table 1: Clearance distances for bare and partially insulated conductors in non-bushfire risk areas (in metres)
VoltageClearance
at the pole
Span
0-50 m
Span
50-100 m
Span
100-150 m
Span
150-200 m
Span
200-300 m
Span
300-400 m
Span
over 400 m
Less than 1 kV P: 0.1 mV:0.1 m
H:0.1 m
V:0.1 m
H:0.1 m
V:0.1 m
H:0.1 m
----
7.6 kV to 11 kV P: 0.5 mV:1.5 m
H:1.5 m
V:2.0 m
H:2.5 m
V:2.5 m
H:3.5 m
V:2.5 m
H:4.5 m
V:2.5 m
H:6.0 m
V:2.5 m
H:6.0 m
V:2.5 m
H:6.0 m
19 kV P: 0.5 mV:1.0 m
H:1.0 m
V:1.0 m
H:1.0 m
V:1.0 m
H:2.5 m
V:1.0 m
H:2.5 m
V:1.5 m
H:5.0 m
V:2.0 m
H:7.0 m
V:2.0 m
H:9.0 m

Clearance zones diagram for bare powerlines in non-bushfire risk areas

Non-bushfire risk areas – buffer zones

The dimensions of buffer zones for powerlines located on private property in non-bushfire risk areas are:

  • two metres from the outer edge of the clearance zone for distribution powerlines
  • three metres from the outer edge of the clearance zone for transmission powerlines.

For trees and vegetation on public land in non-bushfire risk areas, there is no prescribed buffer zone.

Bushfire risk areas – clearance zones

Fully insulated conductors (powerline wires)

Fully insulated powerlines such as ABC, always require a clearance zone of 10 cm (0.1 metre) in all areas.

Bare or partially insulated powerlines in bushfire risk areas

Bare or partially insulated powerlines in bushfire risk areas require different vertical (below the conductor) and horizontal (to each side of the conductor) clearance distances depending on the distance of the conductor (wire or cable) from the poles. There is no ceiling on the vertical clearance above the conductor.

Dividing the length of the conductor between two adjacent poles into four sections, the two middle sections of the cable require greater vertical and horizontal clearances. This is because the middle parts of the cable can swing or sag to a greater extent than the sections closer to the poles.

Table 2: Clearance distances for bare and partially insulated conductors in bushfire risk areas (in metres)
VoltageClearance at
the pole
Span
0-50 m
Span
50-100m
Span
100-150 m
Span
150-200 m
Span
200-300 m
Span
300-400 m
Span
over 400 m
Less than 1kV V:0.5 m
H:0.5 m
V:1.0  m
H:1.0 m
V:1.5 m
H:2.5 m
V:1.5 m
H:3.5 m
 - - - -
7.6 and 11 kV V:0.5 m
H:0.5 m
V:1.5 m
H:1.5 m
V:2.0 m
H:2.5 m
V:2.5 m
H:3.5 m
V:2.5 m
H:4.5 m
V:2.5 m
H:6.0 m
V:2.5 m
H:6.0 m
V:2.5 m
H:6.0 m
19 kV V:0.5 m
H:0.5 m
V:1.0 m
H:1.0 m
V:1.0 m
H:1.0 m
V:1.0 m
H:2.5 m
V:1.0 m
H:2.5 m
V:1.5 m
H:5.0 m
V:2.0 m
H:7.0 m
V:2.0 m
H:9.0 m

Clearance and buffer zone diagram for bare or partially insulated conductors in bushfire risk areas

Bushfire risk areas – buffer zones

In bushfire risk areas, the buffer zone for bare wires is a space similar to an inverted triangle. To determine this triangular buffer zone:

  • draw a line between the outermost point of the conductor on the stobie pole and the ground directly under it (perpendicular to the ground)repeat this for the conductor on the other side of the stobie pole
  • from the points where these lines contact the ground, draw two slanted lines outwards and upwards at an angle of 45° to the ground
  • extend the slanted lines until a horizontal line connecting their ends (base of the triangle) is five meters higher than the highest point on the stobie pole.

While it is not a legal requirement to prune vegetation within the buffer zone, doing so will maximise safety around powerlines.

Safety when working near powerlines

Working near powerlines can be dangerous. If you intend to carry out the vegetation clearance yourself, you need to be familiar with safety principles of working near powerlines.

For information on safe practices when working near powerlines see Working safely near overhead powerlines .

If you do not wish to carry out the maintenance yourself, consider the following alternative options:

  • Arrange for a contractor or the electricity network operator to clear or trim the vegetation for you.
  • Have trees chemically treated to slow their growth rate.

In some cases, you might also:

  • Arrange with the electricity network operator to have underground powerlines installed.
  • Arrange for the electricity network operator to rebuild the supply line with insulated conductors or ask for a shorter span between the stobie poles.
  • Ask the electricity network operator to relocate the powerline.

Dangers of vegetation near powerlines

Dangers of trees near powerlines

Powerline wires can swing and sag due to wind, temperature, the weight of the lines and is also dependent on the distance between the poles.

Contact between trees and high voltage powerlines can:

  • cause an electric shock to a person if the bark of the tree is wet and a person touches it
  • start a fire
  • interrupt power supply.

Even without direct contact trees that are too close to powerlines can cause:

  • a flash over between a high voltage powerline and a tree
  • injuries to anyone climbing the tree
  • damage caused by falling branches breaking the powerline wires or stripping the insulators off them.

Dangers of broken powerlines

Broken powerlines are extremely dangerous because:

  • live wires may fall to the ground
  • live wires can cause fires or may contact stobie poles and cause an electric shock to a person touching the pole
  • high voltage powerlines falling on low voltage powerlines can cause flashovers and power surges – this can result in a fire
  • flashovers and power surges can damage electrical appliances and cause an electric shock to people touching the appliances at that time.

Vegetation can prevent safe access to powerlines

Trees grown too close to powerlines can restrict safe access to powerlines by maintenance workers. This can cause delays in power restoration and may have severe consequences in the event of an emergency.

Reducing the risk of vegetation near powerlines

Electricity network operators and occupiers or owners of private properties are legally required to maintain safe clearance distances between powerlines, trees and other vegetation.


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Page last updated 24 October 2017

Provided by:
Department of the Premier and Cabinet
URL:
https://www.sa.gov.au/topics/energy-and-environment/electrical-gas-and-plumbing-safety-and-technical-regulation/powerline-safety/trees-and-powerlines/vegetation-clearance-near-powerlines
Last Updated:
24/10/17
Printed on:
12/12/17
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