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Performance Specifications
Covered Conductor System
SWER 12.7kV and 22kV 1-3 Phase Applications
APRIL 2016
TABLE OF CONTENTS
1. BACKGROUND INFORMATION ...................................................................... 2
2. VICTORIAN RURAL POWERLINE CHARACTERISTICS ................................ 4
Single and Three Phase Lines ................................................................................... 4
SWER (Single Wire Earth Return) Powerlines ........................................................... 5
Powerline Related Bushfire Ignition ............................................................................ 6
3. DESIGN CONSIDERATIONS ........................................................................... 6
4. TECHNICAL REQUIREMENTS ........................................................................ 9
Conductor Ratings ..................................................................................................... 9
Additional Performance Requirements ..................................................................... 11
Standards ................................................................................................................ 12
5. CONSTRUCTION STANDARDS .................................................................... 14
SECV ....................................................................................................................... 14
Stringing Charts ....................................................................................................... 14
APPENDIX A – STRINGING CHARTS ................................................................. 15
APPENDIX B – ERGON DWG 3014 STRINGING CHART .................................. 19
APPENDIX C – COMMON VOLTAGE SYSTEMS ............................................... 20
Victoria ..................................................................................................................... 20
Queensland.............................................................................................................. 20
South Australia ......................................................................................................... 20
NSW ....................................................................................................................... 20
Western Australia ..................................................................................................... 20
APPENDIX D – LINE HARDWARE AND EQUIPMENT........................................ 21
Poles ....................................................................................................................... 21
Insulators ................................................................................................................. 21
Cross Arms .............................................................................................................. 23
SWER Line and Multi-Phase Line Photos ................................................................ 24
APPENDIX E – EXAMPLE OF VEGETATION CONTACT ................................... 26
1. BACKGROUND INFORMATION
The State of Victoria has over 28,000km of 12.7kV open wire Single Wire Earth Return (SWER) systems and
over 60,000km of 22kV multi-wire distribution lines (excluding the CitiPower network).
Most of the SWER system is in regional areas servicing small loads, and which are in grass or forest high
bushfire risk regions. Approximately 50,000km of the multi-phase open wire system is in rural areas and
some is located in high bushfire risk areas.
The majority of the SWER system and much of the rural multi-wire system has been constructed using
overhead cable comprised of 3 strands of 2.75mm or 2.64mm (imperial 12 gauge) diameter steel conductor
with either a galvanised coating or aluminium cladding. The majority has the older galvanised coated
conductor and is referred to as 3/2.75 or 3/.12 SC/GZ, while the newer aluminium coated conductor is
referred to as 3/2.75mm SC/AC. Within the electricity industry the cable is often simply referred to as 3/2.75
Steel or 3/.12 Steel.
The use of steel conductors with high tensile strength in these rural areas enabled the pole spacing to be
increased, thereby reducing costs. The SWER system uses only one overhead conductor and relies on an
Earth return path which also reduced the amount of hardware required on the poles. Steel conductor is
lightly loaded and has a narrow construction envelope due to the taut stringing, resulting in minimal
conductor sway.
The nature of these low cost steel conductor systems for SWER and rural multi-wire lines (long spans, taut
stringing, minimal pole furniture, light loads, narrow envelopes) makes them expensive to replace with fully
insulated cables if the line happens to be in an extreme risk bushfire zone.
In the low population density rural areas there is also some 3/4/2.5mm and 6/1/3.0mm Aluminium
Conductor Steel Reinforced (ACSR) and 19/3.25 All Aluminium (AAC) cables that are also in high bushfire risk
areas. There is also a need to replace these with covered conductors in some locations.
The State is therefore seeking an insulated conductor system to replace the following bare overhead cables:

3/2.75 Steel;

3/4/2.5 ACSR;

6/1/3.0 ASCR; and

19/3.25 AAC.
This will preferably involve the direct replacement for the existing cables or may involve the use of other
overhead line technology solutions such as a support cable in conjunction with an insulated conductor. There
is a higher priority on the development of an insulated replacement of the bare steel cable as this is more
prominent in the high bushfire risk areas.
As the changeover to a covered conductor is primarily to reduce the bushfire risk, a different conductor may
be appropriate to those used overseas for primarily network reliability. As a covered conductor is not fully
screened it is treated in Victoria the same as a live conductor for the purposes of electrical safety. Touching
the covered conductor is not considered safe, however the insulation will provide a degree of protection to
electric shock if it is in good condition. Covered conductor has been used to improve public safety in some
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cases overseas and the degree of protection to touching or grabbing is to be considered in the design of the
covered conductor.
Cable that includes a screen will also be considered provided it can approximately achieve the required span
distance for a taught strung conductor for each of the bare conductors to be replaced.
It is recognised that there will be a trade-off between the ability to use the proposed covered conductor as a
direct replacement for the existing bare wires and the time period and voltage that the electrical insulation
can withstand. Therefore proposals that do not fully comply with the above will be considered.

Significant challenges for R&D are:

the development of overhead covered conductor systems that can replace these bare overhead
cables and deliver the required electrical performance;

utilise the existing poles and their pole spacings for each type of bare overhead cable;

insulation capable of withstanding lightning strikes, either by the covered conductor construction
design, provision of screening and/or the use of suitable protective devices;

able to withstand intermittent rubbing from trees or tree branches;

able to maintain its insulating properties with a tree or tree branch resting on the covered conductor
cable, or if the cable is in contact with the ground or other earthed metallic object, for reasonably
long periods such as days or preferably weeks while in normal service;

provide a reasonable degree of protection from electric shock from touching a fallen covered
conductor;

able to operate at ambient temperatures that can reach 48o Celsius in summer;

able to operate with a conductor temperature at -10o Celsius in winter;

able to operate with a wind pressure of 950Pa;

able to withstand the vibrations that can be expected with the insulated conductor system on the
long spans that exist in rural networks;

able to connect to existing overhead powerline cables;

limited flammability and preferably non-flammable;

resistant to attack by fauna or vermin;

resistant to UV degradation over its life;

low maintenance cost;

able to easily assess the condition of the insulation, conductors and any strain wires or other
material in the field following an impact by a falling tree or tree limb and as part of a routine
inspection or monitoring program;

able to make connections to the cable in the field while working at pole top height from an EPV;

preferably able to utilise the same fittings unless this will compromise the performance or long term
integrity of the cables; and

achieve a design life of 45 years.
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2. VICTORIAN RURAL POWERLINE CHARACTERISTICS
Lightly loaded rural powerlines in Victoria have primarily been constructed using 3/2.75 Steel conductor.
Rural powerlines with heavier loads could have Aluminium Conductor Steel Reinforced (ACSR), some All
Aluminium conductor (AAC) and some older lines may still have Copper (Cu) conductor.
This R&D package seeks to develop a replacement for the 3/2.75 Steel cable, 3/4/2.5 and 6/1/3.0 ACSR and
19/3.25 AAC cables under tight stringing conditions.
The SECV steel cable Stringing Chart VX18/50 is the stringing chart that applies to this cable in rural SWER
and one and three phase conditions.
VX18/50 typically allows span lengths of 300-350m over flat ground with 12.5m poles. Under extreme
conditions – hilltop to hilltop for example – span lengths of 500+m can be achieved.
The circumstances where SWER or one or three phase powerlines and bushfire prone areas co-exist, there
are likely to be span lengths of 200-350m through forested or bush country, and 300-350m across grasslands,
under stringing chart VX18/50. In special circumstances such as valley crossings SWER powerlines can span
distances of approximately 1 km.
A covered conductor system to replace steel conductor must be able to meet the VX18/50 stringing chart
requirements for tensile strength, sag, sway and temperature ranges of -10°C and +65°C. The weight of the
insulation will also affect the tension on strain and angle poles under the taut stringing.
Similarly, a covered conductor system to replace ACSR cables must be able to meet the EVX18/42D for
3/4/2.5 mm cable and EVX18/37E for 6/1 cable stringing chart requirements. The weight of the insulation will
also affect the tension on strain and angle poles under the taut stringing. EVX18/42D typically allows span
lengths of 200 to 260 meters and EVX18/37E of 100 to 135m over flat ground.
For 19/3.25 AAC, stringing chart EVX18/49 shows span lengths up to 200 meters but typical span lengths are
between 60 to 140 meters.
Single and Three Phase Lines
Typical of rural roadside powerlines radiating out from local provincial centres to service farming areas, there
is an extensive network of one and three phase lines throughout Victoria. Given they are typically on road
reserves, or run parallel to road reserves, they are regularly in close proximity to vegetation.
Replacement with covered conductors need not be across an entire powerline, and therefore consideration
should be given to the technical issues and costs associated with connecting insulated and bare conductors.
The one and three phase networks tend to be protected by Automatic Circuit Reclosers (ACRs) that may be
located at the tee off of a major artery powerline, or mid-powerline on the main feeder for the rural area.
ACRs on one and three phase systems are capable of detecting most earth faults, however their sensitivity
and operating speed does not enable them to detect and operate fast enough for all earth faults that may
result in a ground fire start.
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The use of covered conductor systems will be most likely targeted at existing lines that are in close proximity
to vegetation and in the highest fire risk areas.
As part of the Powerline Bushfire Safety Program a separate initiative is to install Rapid Earth Fault Current
Limiters (REFCL) at Zone Substations that have powerlines feeding into high bushfire risk areas. The
operation of a REFCL for an earth fault means that the voltage of the un-faulted phases will increase to 22kV
phase to earth. The conductor could therefore be exposed to a line voltage equal to the full phase to earth
voltage for many hours and this must to be taken into account in the design of the covered conductor.
SWER (Single Wire Earth Return) Powerlines
SWER powerlines tend to be point-to-point, in that they cross properties to take the shortest “as the crowflies” distance from one supply point to the next. Rarely are they contained within road reserves.

The key reason for building SWER powerlines is economics. Only having one conductor results in:

point-to-point construction often with a shorter powerline route length;

less poletip weights at terminations and angle poles, meaning that poles can be slimmer and
cheaper, thus generally wood poles have been utilised in SWER rather than concrete;

removal of inter-phase conductor clashing risk, thus span lengths can be much longer than 2 or 3
wire systems;

minimal pole furniture (ie crossarms, insulators) thus each structure is cheaper;

minimal electrical load present, therefore a light, strong cable can be used;

steel cable resistivity is higher, while it is important, it is a secondary consideration to cost, thus steel
conductors and an earth return is acceptable;

a physically more adept system at negotiating tight corridors, less need for cable sway allowance for
a given span, pole weights are lighter, less tree clearing through forested areas is needed as the
easement/powerline corridor can be minimised; and

construction practices are very simple, leading to much quicker deployments and more rapid
construction, further reducing build costs.
The SWER networks are now mostly protected by ACRs that may be located at the tee-off of a major artery
line, or mid-line on the main feeder for the rural area with a high fire risk.
Information and pictures of typical powerline hardware and equipment used in powerlines are included in
Appendix D.
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Powerline Related Bushfire Ignition
The electrical protection of SWER powerlines is generally limited to overload and high current fault
protection. Low current faults to Earth add to the load current, and by the very nature of an earth return
system, these are particularly difficult to detect. These low current faults can cause ignition through either
sparking from impact, or heat generated from consistent tracking.

Causes of earth faults with low currents can be:

damaged, moist, dusty or polluted insulators that allow tracking across from conductor to pole;

trees or branches in contact with the powerline;

swaying powerlines under high wind conditions contacting trees or other structures;

sagging conductors at elevated temperatures contacting trees or other strutures;

fauna or vermin contacting or damaging live wires and poles concurrently; and

broken conductors contacting the ground, vegetation or earthed objects while live.
For multiphase lines the protection includes sensitive earthfault protection, and this makes it possible to
detect smaller earth fault currents. However it is still not sensitive enough to stop all fire starts. For
multiphase lines the causes of fire starts include the ones listed for SWER plus:

clashing conductors; and

dislodged conductor resting on a crossarm.
The risk of each of these ignition scenarios for SWER and multiphase powerlines can be reduced by a covered
conductor.
There are other scenarios where powerlines can contribute to bushfire ignition – however these mostly
involve plant and equipment failures. Malfunctioning fuses, transformer short circuit and earthing cables
being cut are not addressed by insulated conductors. However when an insulated conductor system is
installed all connections will also be required to be insulated.
3. DESIGN CONSIDERATIONS
The following considerations need to be addressed by the R&D project in developing a functional covered
conductor system replacement:

Cables must be manufactured and tested in line with relevant Australian Standards, or where there is
no suitable Australian Standard, an acceptable International Standard. Some relevant standards are
included in Section 4.

For a direct cable replacement option it is necessary to be able to string to the relevant stringing
chart in order to maintain clearances and minimise the requirement for additional poles. This
requires the insulation to perform similarly in terms of:
- stringing and strain during installation;
- creep over time; and
- break load.
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
Meet the required current carrying capacity and at least the same or preferably lower resistance per
kilometre. It is a requirement that when replacing SC/GZ cable, the current carrying capacity of the
replacement cable shall be at least that of the 3/2.75 SC/AL cable instead.

The variation of the co-efficient of temperature of the insulation and the conductor across the
potential operating temperature range of -10o and the maximum temperature reached with the
cable fully loaded and an ambient temperature of 48oC at noon in full sunlight and still air.

Any additional cable weight may have an impact on the adequacy of the footings and pole strengths
of termination, tee off and angle poles and will likely lead to more widespread guy/stay wire
installations and potentially lead to additional easement requirements from landholders. Additional
cable weight therefore needs to be minimised.

The impact that infrequent light snow deposits may have on the cable.

Any additional wind loading, due to a larger profile covered cable, needs to be taken into account as
it will cause additional poletip weights on intermediate timber poles that generally have very low
long term load ratings, and the effect this may have on footing strengths needs to be considered.

Development of breakaway devices that are coordinated with the cable so that the device releases
the cable before the cable breaks.

The development, where required, of suitable connections that re-establish the integrity of the
conductor insulation while also preventing ingress of water, dirt and foreign matter under the
conductor insulation.

The ability of the insulation to withstand constant contact with vegetation or an earthed metallic
object over an extended period of many days and preferably months.

Ability to withstand phase to earth voltages of 22kV due to the operation of a REFCL during an earth
fault.

The design should also consider the installation techniques that may be used to minimise customer
outages.

The work practices required to install and restore the cable after an incident and to monitor and
maintain the cable in a remote heavily vegetated and difficult terrain field situation.

The reuse of pole furniture, cable fittings and construction equipment should be a consideration
where they can be used without compromising the integrity and life of the covered conductor or the
performance requirements.

Consideration of potential transportable cable manufacturing lengths.

Consideration of integrated logistics support in relation to delivery and installation.

45 year design life which will need to consider a number of items:
- UV rating over the lifespan;
- durability in typical weather conditions in Victoria which could range from snow to salt air to
50oC ambient temperatures;
- durability in the event of lightning strikes to pole tops or conductor;
- resistance to damage by fauna and vermin such as birds and rats that could tear/chew the
insulation or covering, thus the taste of the material used must discourage animals and birds
from interfering for food or nesting purposes;
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-
non-flammable to prevent spread of fire;
resistance to flame and radiant heat from passing fires to protect the integrity of insulation
or covering;
- occasional overloads and short circuits; and
- resistance to damage from occasional forceful tree or large branch contact under high winds
and also against intermittent rubbing against tree limbs.
It is understood that some design considerations may be in conflict, resulting in a design aspect not being
fully achievable. For example the trade-off between ability for the cable to be a direct replacement for the
existing bare overhead conductors while satisfying the specified insulation electrical withstand.
As stated in the Program Guidelines the goal is to achieve a direct replacement for the existing overhead
bare conductors so that a cost effective solution can be found. However, a reasonable electrical withstand
period for the insulation must also be achieved, otherwise the electrical withstand period of the insulation
may not provide sufficient bushfire risk mitigation benefits.
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4. TECHNICAL REQUIREMENTS
Conductor Ratings
Typical technical specifications for the bare overhead 3/2.75 Aluminium Clad Steel cable that is intended to be at least met or improved on include:
Stranding
and Wire
Diameter
Number /
mm
3 / 2.75
Nominal
Overall
Diameter of
Cable
mm
CrossSectional
Area of
Cable
mm2
Approx
Mass of
Cable
Breaking
Load
Modulus of
Elasticity
GPa
Coeff. of
Linear
Expansion of
Cable
x10-6 /oC
kg/km
kN
5.9
17.82
118
22.7
DC Resistance
At 20oC
159
12.9
4.8
Continuous Current Carrying Capacity
(Amps)
At 75oC
Ω /km
5.75
Winter Night
Still Air
Summer Noon
Still Air
48
38
Typical technical specifications for the bare overhead Aluminium Conductor, Steel Reinforced (AC SR) cables that are intended to be met or improved on
include:
Cable
Stranding
and Wire
Diameter
(Al)
Number /
mm
Stranding
and Wire
Diameter
(Steel)
Number /
mm
Nominal
Overall
Diameter
of Cable
mm
CrossSectional
Area of
Cable
mm2
Approx
Mass of
Cable
Breaking
Load
Modulus
of
Elasticity
kg/km
kN
GPa
Coeff. of
Linear
Expansion
of Cable
x10-6 /oC
DC Resistance
3/4/2.5
3/2.5
4/2.5
7.5
34.4
195
24.4
136
13.9
1.59
6/1/3.0
6/3.0
1/3.0
9.0
49.5
171
14.9
83
19.3
0.677
At
At
20oC
75oC
Ω /km
Continuous Current Carrying
Capacity (Amps)
Winter
Night
Still Air
Summer
Noon
Still Air
Summer
Noon
1/m/s
2.14
91
61
129
0.91
148
98
205
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Typical technical specifications for the bare overhead All Aluminium Conductor (AAC) cable that is intended to be met or improved on include:
Cable
19/3.25
Stranding
and Wire
Diameter
(Al)
Number /
mm
Nominal
Overall
Diameter
of Cable
mm
CrossSectional
Area of
Cable
mm2
Approx
Mass of
Cable
Breaking
Load
Modulus
of
Elasticity
kg/km
kN
GPa
Coeff. of
Linear
Expansion
of Cable
x10-6 /oC
19/3.25
16.3
158
433
24.7
65
23.0
DC Resistance
At
At
o
20 C
75oC
Ω /km
0.183
0.224
Continuous Current Carrying
Capacity (Amps)
Winter
Night
Still Air
Summer
Noon
Still Air
Summer
Noon
1/m/s
373
216
465
Notes:
1. The electrical performance characteristics shown above do not take magnetic effects into consideration and are therefore only approximate.
2. The following conditions are also applied to the ratings:

conductor temperature rise above ambient of 40°C;

ambient air temperature of 35°C for summer noon or 10°C for winter night;

direct solar radiation intensity of 1000W/m2 for summer noon and zero for winter night;

diffuse solar radiation intensity of 100W/m2 for summer noon and zero for winter night;

ground reflectance of 0.2; and

emissivity and solar absorption coefficient of the conductor surface of 0.5.
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Additional Performance Requirements
The cables are required to also meet the following performance requirements and be suitable for use and
achieve the required 45 year service life with the environmental and system operating conditions listed.
Parameter
Value or Range
Insulation electrical withstand period. (Test to AS 1660.3.
Section 3.2.2 high voltage ac test at a phase to earth test
voltage of 22kV in accordance with AS3675)
Maximum multiphase operating voltage with a Rapid
Earth Fault Current Limiter (REFCL or GFN) in service.
While AS 1660.3 requires 4 hours the
withstand time is required to be many days.
22kV phase to earth on un-faulted phases.
Cable core design temperature for mechanical strength
when strung.
-10oC
Maximum ambient temperature in summer.
+48oC
Maximum pollution levels. (AS 4436)
Heavy.
Additional protective measures to be
available to enable operation in some Very
Heavy pollution areas.
Maximum wind pressure. (AS 7000)
950 pa
Direct solar radiation intensity of 1000W/m2 for summer
noon and zero for winter night.
1,000 W/m2 in summer
Operating Voltage
22 kV (12.7kV phase to earth)
Maximum continuous operating voltage
24kV (13.9kV phase to earth)
Ambient temperature and wind speed at rated current
35oC & 0.7 m/s summer
10 oC & 0.7 m/s winter
Short Circuit (SWER) with preloading of full rating in
summer
1 kA for 1 second
Short Circuit (1 phase and 3 phase) with a precondition of
full current rating in summer
Steel
2 kA for 1 second
ACSR & ACC
5kA for 1 second
Maximum short duration overload current with a
precondition of full current rating in summer all cables
150% for 3 hours
Leakage current due to contact over the outer surface
with a length of 250mm
Preferably less than 0.5 mA
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Standards
The following provides a list of standards that are applicable to covered conductors. It is not intended to be a
complete list of standards.
The standards often assume certain design parameters which may not be applicable to a proposed new
concept of covered conductor and therefore it is not to be taken as prescriptive. The proposal shall consider
the performance requirements rather than any design specific aspects in these standards.

AS 7000:2010. “Overhead line design detailed procedures”

AS 3675:2002. “Conductors – covered overhead – for working voltages 6.35/11 (12) kV to and
including 19/33(36) kV”

EN50397-1:2006. “Covered conductors for overhead lines and the related accessories - For
working voltages above 1kV ac and not exceeding 36kV ac – Part 1: Covered conductors”

EN 50397-2:2009. “Covered conductor for overhead lines and the related accessories - For rated
voltages above 1 kV ac and not exceeding 36 kV ac - Part 2: accessories for covered conductors Tests and acceptance criteria”

EN 50397-3. “Covered conductor for overhead lines and the related accessories - For rated
voltages above 1 kV ac and not exceeding 36 kV ac - Part 3: Guide to use”

AS/NZS 1429.1:2006. “Electric cables – Polymeric insulated – For working voltages 1.9/3.3 (3.6)kV
up to and including 19/33 (36) kV”

IEC 60502-1 Ed. 2.1. “Power cables with extruded insulation and their accessories for rated
voltages from 1 kV (Um = 1,2 kV) up to 30 kV (Um = 36 kV) - Part 1: Cables for rated voltages of 1
kV (Um = 1,2 kV) and 3 kV (Um = 3,6 kV)”

IEC 60502-2 Ed. 3.0. “Power cables with extruded insulation and their accessories for rated
voltages from 1 kV (Um = 1,2 kV) up to 30 kV (Um = 36 kV) - Part 2: Cables for rated voltages from
6 kV (Um = 7,2 kV) up to 30 kV (Um = 36 kV)”

IEC 60502-4 Ed. 3.0. “Power cables with extruded insulation and their accessories for rated
voltages from 1 kV (Um = 1,2 kV) up to 30 kV (Um = 36 kV) - Part 4: Test requirements on
accessories for cables with rated voltages from 6 kV (Um = 7,2 kV) up to 30 kV (Um = 36 kV)”

AS/NZS 1125:2001.(IEC 60228:2004). “Conductors in insulated electric cables and flexible cords”

AS/NZS 1660:1998. “Test methods for electric cables, cords and conductors”

AS/NZS 1660.1:1998. “Test methods for electric cables, cords and conductors - Conductors and
metallic components”

AS/NZS 1660.2.1:1998. “Test methods for electric cables, cords and conductors - Insulation,
extruded semi-conductive screens and non-metallic sheaths - Methods for general application”

AS/NZS 1660.2.2:1998. “Test methods for electric cables, cords and conductors - Insulation,
extruded semi-conductive screens and non-metallic sheaths - Methods specific to elastomeric,
XLPE and XLPVC materials”

AS/NZS 1660.2.3:1998. “Test methods for electric cables, cords and conductors - Insulation,
extruded semi-conductive screens and non-metallic sheaths”

AS/NZS 1660.3:1998. “Test methods for electrical cables, cords and conductors”.
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
ASTM G155 (Specified by AS3675 for UV tests). “Standard Practice for selecting and Characterising
Weathering Reference Material”

IEC 60468:1974. “Method for the measurement of resistivity of metallic parts”

UL 94. “Standard for Tests for Flammability of Plastic Materials for Parts in Devices and
Appliances”

AS/NZ 1391. “Methods for tensile testing of metals”

AS 3822-2002. “Test methods for bare overhead conductors”

IEEE 653 and CEI 62567 for vibration testing.

NZS/AS 1531:1991. “Conductors - Bare overhead - Aluminium and aluminium alloy”

AS/NZS 60479-1:2010 (or IEC/TS 60479-1). “Effects of current on human beings and livestock, Part
1 – General Aspects”

AS/NZS 60479-2:2010 (or IEC/TC 60479-2). “Effects of current on human beings and livestock,
Part 2 – Special Aspects”
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5. CONSTRUCTION STANDARDS
SECV
The former State Electricity Commission of Victoria (SECV) maintained a state-wide rural design standard for
open wire systems, which included standardisation of pole sizes, strengths and performance, along with
standard conductors, load capacity and stringing, with the associated standardised construction manuals.
Through the following 20 years since the SECV was dis-aggregated, many of those design standards have
remained in place in both the Powercor and AusNet Services areas, including the basis for 3/2.75 Steel
stringing. The basis for construction and maintenance of SWER, 1 Phase and 3 Phase systems remains largely
unchanged as a result.
Pole sizes and strengths – such as the common 12.5m/8kN timber intermediate pole, remain a common
standard across both Powercor and AusNet Services.
3/2.75 Steel conductor remains widespread in rural lightly loaded areas in both businesses.
Insulators, cross arms and connection devices remain relatively consistent across the State.
Stringing Charts
The SECV VX18/50 stringing chart for steel conductor is included in Appendix A.
Also included in Appendix B is a typical stringing chart for Ergon Energy where it uses the 3/2.75 Steel
conductor, known as Drawing 3014 of the Ergon Energy Distribution Design – Overhead manual. It should be
noted that Queensland stringing is less taut than in Victoria for this conductor, thus any cable that meets
Victorian stringing tensile strength will also be useful and saleable interstate, creating a much larger market
than just the Victorian industry.
The EVX18/42 D and EVX18/37 E stringing charts for the ACSR conductors and stringing chart EVX18/49 for
AAC are included in Appendix A.
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APPENDIX A – STRINGING CHARTS
Sag for Mean Equivalent Span Lengths (MES) at different conductor temperatures and tension are provided
for each of the bare overhead cables for replacement.
3/2.75 Steel Conductor Aluminium Clad. (Note: can also be used for Galvanised Steel Conductor)
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6/1 Aluminium Conductor Steel Reinforced
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3/4/2.5 Aluminium Conductor Steel Reinforced
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19/3.25 All Aluminium Conductor
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APPENDIX B – ERGON DWG 3014 STRINGING CHART
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APPENDIX C – COMMON VOLTAGE SYSTEMS
Rural powerlines across Australia are not dissimilar in construction format – each of the eastern states
commonly use the 3/2.75 Steel conductor, but do operate at different voltages, sometimes within the same
state.
It should be noted that when SWER and 1 or 3 Phase power are discussed, the reference to different voltages
between the two is a misnomer. SWER is referred to as a Phase-Ground voltage, whereas 1 and 3 Phase are
discussed as Phase-Phase voltage. There is a factor of ≈1.73 between the phase-ground and phase-phase
references, thus Victoria’s SWER is 12.7kV and Victoria’s regional distribution grid is 22kV.
Interstate the distribution voltages are usually 11kV or 33kV where SWER is established, with some 11kV
systems stepping up the SWER voltage by a factor of 2 to keep the 12.7kV SWER system voltage.
A 12.7kV insulated conductor system could be used across all eastern states potentially, meaning a large
market potentially exists for such a cable when you consider Victoria has over 28,000km of SWER while
Queensland has over 65,000km. Across Australia around 190,000km of SWER is in operation.
Victoria
The distribution grid is almost exclusively 22kV outside of inner Melbourne. All SWER systems are run at
12.7kV.
Queensland
The distribution grid varies from region to region between 11kV, 22kV and 33kV, while there are pockets of
6.6kV that are being phased out. SWER voltages are generally 12.7kV and 19.1kV.
South Australia
The distribution grid is generally 11kV with some 33kV feeders in high load areas such as the Riverland
Irrigation Zone. SWER voltages are typically 19.1kV and 6.35kV.
NSW
The distribution grid varies from region to region between 11kV, 22kV and 33kV. SWER voltages are limited
to 12.7kV and 19.1kV
Western Australia
The distribution grid is generally 22kV and 33kV with some 66kV and 132kV. SWER voltages are 12.7kV and
19.1kV.
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APPENDIX D – LINE HARDWARE AND EQUIPMENT
Poles
The typical pole strengths used are shown below. For the purposes of the replacement conductor it should
be assumed that wood poles are used.
Type
Wood
Wood
Concrete
Concrete
Strength rating
Working/Ultimate
8kN/16kN
12kN/24kN
8kN/16kN
12kN/24kN
Height
12.5m
12.5m
12.5m
12.5m
Insulators
The following drawings provide examples of the newer insulators installed on lines. There are still many older porcelain
insulators remaining on the powerlines. Information on these can be provided on request.
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Specification
Creepage Distance
Wet p.f. withstand
Impulse voltage withstand
Cantilever
Axial
AS 2947
610 mm
50 kV
150 kV
11 kN
5.5 kN
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Cross Arms
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SWER Line and Multi-Phase Line Photos
SWER line and pole with distribution transformer and fuse
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22kV three phase line with single phase (2 wire) tee off and LV subsidiary circuit.
Single phase (2 wire) line with HV fuses and pole mounted transformer.
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APPENDIX E – EXAMPLE OF VEGETATION CONTACT
Examples of a fallen tree and branch contacts with an overhead powerline.
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Falling tree test in Forest-Sax line, 110kV insulated line, Finland.
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