What Cable Required For New Home Construction In Australia?

Since its release in June this year, the new Wiring Rules have sparked discussion throughout the electrical industry. The new requirements for installing wiring systems (cables) and the different protection methods have been at the centre of the debate.

At a recent information night, a NECA member, who is often involved in installing wiring systems (cables) below raised floors in data centres and other similar installations, expressed serious concerns about the impact of the new requirements on his work. The standard imposes a range of new requirements on installing wiring systems (cables) that are likely to be disturbed or damaged. 

Installation requirements for customer cabling

This industry-standard explains the installation and maintenance practices that you must follow. It covers the requirements for fixed or concealed cabling or equipment that is connected or is intended to be connected to a telecommunications network. The industry standard AS/CA S009 2020 was published on 20 August 2020. An 18 month transition period commenced on 20 August 2020, during which time the AS/CA S009 2013 industry standard can still be used.

FAQs About Cable Wiring System

A wiring system can be defined as a group of more conductors, cables or busbars, and all parts used to secure them in position. It also includes any mechanical protection that is provided for the conductor. The first concept that we need to understand is that the installation method will determine the classification of the wiring system. It will be either a "Wiring system likely to be disturbed" or a wiring system requiring "protection against mechanical damage".

Wiring Systems requiring protection against mechanical damage are generally cables installed in hollow walls, walls with plasterboard or similar material on either side of the wall studs. When wiring systems (cables) are installed in locations where they may reasonably be expected to be subjected to mechanical damage, you are required to provide adequate protection. This can be done by one or any combination of the following:

  • Mechanical characteristics of the wiring system
  • Location selected
  • Provision of additional local or general mechanical protection 

If additional mechanical protection is selected, appendix H of AS/NZS 3000:2018 provides an explanation of the WS classification system and practical information about what is needed to comply with each classification. Now 'What is a WS classification?' you may ask. Well, it has been around for some time and comes from another Australian Standard specifying fire and mechanical protection ratings for wiring systems.

 

There are some specific methods of installing wiring systems where the Wiring Rules provide additional guidance or requirements, such as;

  • Wiring systems near building surfaces - Wiring systems that are fixed in position by fasteners, or held in position by thermal insulation, or by passing through an opening in a structural member concealed within 50 mm from the surface of a wall, floor, ceiling or roof.
    • Exception: This requirement need not apply to wiring systems that can move freely to a point not less than 50 mm from the surface in the event of a nail or screw penetrating the cavity at the location of the wiring system.
  • Wiring systems near roofing material - wiring systems passing through a structural member or are fixed in position, within 50 mm from the face of the supporting member to which the lining or roofing material is attached.

If you're looking at rewiring your home, one of the biggest factors is cost. Of course, rewiring a home is not cheap. But it's essential for the safety of your family. After all, more than 40% of residential fires in Australia are associated with electrical faults or failures caused by degraded wiring or overloading the system. Rewiring a home can involve anything from fixing up a few dodgy outlets to replacing all the wires throughout your home.

You might just be covering the essentials or thinking of the future and setting your house up for complete home automation. Since rewiring jobs are so varied, it's impossible to put a simple price tag on the project. But on average, you can expect to spend between $3,500 and $8000 to rewire a medium-sized home. This guide looks at the different factors that will impact the cost of your home rewiring and answer all those other questions you might have. So click on a section below, and let's get started.

There's no pretending rewiring a house isn't a big job. It involves pulling out all the old electrical wires and replacing them with newer, safer ones. If you're lucky, a sparky can access the wiring from outside the house or without needing to damage existing walls. Sometimes, they might have to do some damage - by removing the cladding or drilling through timber - that will be fixed up and cost out as part of the project. A home rewiring might involve replacing the wires. It will likely include additional upgrades: new sockets, power points, switches, or a new switchboard.

Underground Power Cables: Costs And Benefits

It would cost up to $50 billion to underground all of Australia's existing overhead power lines. This figure has been conservatively calculated after discussing the issue with executives in many distribution systems, and it is based on precise calculations made in specific areas. Nevertheless, it is a considerable investment, similar to the current total investment in the nation's power generation and transmission systems. Still, the benefits are considerable even in dollars and cents if this cost can be faced. In countries with a shortage of land, it is sometimes attractive to bury high voltage lines. For example, in the Philippines, the easement sale on which overhead lines have been built has yielded enough money to bury them and make a profit.

In most Australian states, underground power delivery is compulsory in new, outer suburban subdivisions, which has impacted recent years. It is estimated that between 150 000 and 200 000 new homes are connected to underground power supplies each year throughout Australia. Over many decades, this will result in a significant proportion of the national housing stock having an underground connection. Paradoxically, the aesthetically pleasing and technically desirable option of underground power will be in place in the outer suburbs. At the same time, highly valued neighbourhoods close to central city areas are much less likely to benefit. This is because underground distribution systems almost universally serve central city areas. Still, there are many near-city suburbs where this has not occurred, nor is it likely to.

There have been exceptions in inner high-value suburbs, where wealthy local authorities with relatively low debt levels have introduced their schemes-sometimes attempting to retrieve some of the costs from householders, sometimes simply adding it to the rates. Without political and community will, however, it is unlikely that older established areas will be transformed on a large scale in the foreseeable future. Moreover, some transmission authorities point out that even when inner suburban areas are 'gentrified', the piecemeal manner in which this takes place precludes any neighbourhood-wide effort to sink lines. Nevertheless, utility engineers point out that if a proper assessment of maintenance and depreciation of overhead lines, the argument for underground cabling becomes more attractive.

The sinking of high voltage transmission lines presents special challenges, with the costs likely to be five or ten times (in places even 13 times) the cost of overhead high voltage transmission. Therefore, it is not surprising that only a tiny percentage of 66 kilovolts (kV) and above lines are underground throughout Australia. In the case of the lowest voltage category in this range, there are 24 500 kilometres of overhead lines, but only 156 kilometres are buried. Even in the most advanced classification, the 110 kV lines, only 4.6% of 3670 kilometres of lineage (178 kilometres) is buried. The proportion of underground cable in the 132, 220, 275, 330 and 500 kv classifications is even lower.

The following discussion embraces many issues associated with undergrounding, namely cost, safety, technical problems, ways in which some communities have removed overhead wiring, and environmental matters.

Major Issues

  • Few people disagree with the proposition that the sinking of electricity cables below ground makes a street or an area more attractive, but implementing such an improvement on a national scale is a formidable challenge. It seems unlikely to be addressed in the foreseeable future.
  • Less than 7 per cent of Australian homes are served by underground power. This figure conceals the paradox that big areas in outer suburbs have this amenity. At the same time, unsightly overhead wiring remains in older suburbs, although some of these older suburbs are close to city centres and attract premium property values.
  • Efforts to increase the area served by underground power vary across Australia. In most States, underground power connection is compulsory in newly developing outer suburban subdivisions. Still, in general, it can be said that there is a little political will to do more.
  • At first glance, a proposal to have underground power conduits shared with cable TV and other telecommunications would seem attractive-even more so with the growing Australia-wide resentment of television cables being strung along street poles and the increasing anger of local governments constituents at this unsightly 'invasion'.
  • However, the advocates of underground power throughout Australia are wary and even opposed to any quick embrace of cable TV. They see the issues as so complex that they are likely to delay the sinking of electricity power lines. Engineers point out that these complexities are such that the sharing option has not been widely debated.

Issues

Traffic Hazard

what cable required for new home construction in australia (2)Safety and aesthetics have been a major driving force for increasing the proportion of underground power. For example, in 1993, there were 743 motor vehicle accidents involving power and Telstra poles in Western Australia, six of them fatal. The South East Queensland Electricity Corporation has estimated that traffic accidents in which cars have hit poles cost $45 million a year. This takes no account of the human cost. However, one executive pointed out that because utilities almost always recover the cost of such damage from drivers' insurance companies, the safety aspect of overhead power has attracted little attention throughout Australia.

Tree Hazard

Other safety concerns include the dangers of electrocution when trees are being pruned (there have been several such fatalities in recent months), the danger from falling wires and problems due to storms. The hazards presented by the current power-on-pole systems are immense and increase as householders demand greener suburbs. During storms, a major problem is damage to overhead lines caused by falling trees. The resultant chaos is irritating to householders and industry and highly expensive to repair. Unfortunately, the fragility of our distribution networks in the face of such forces is rarely recognised by householders. Only when a major disruption occurs is there a renewed clamour for underground power.

In May 1994, which severely affected the whole distribution network throughout the southwest of Western Australia, led to a new drive by the State Government to push ahead with underground power. The storm knocked out a vast part of the suburban and near country distribution system, which in some cases took many days to repair. Trees accounted for more than 80% of the physical damage.

The 1994 storm, and to a lesser extent Cyclone Alby sometime earlier, demonstrated the inevitability of power cuts when power is distributed on poles in such a sprawling area with an ever-present threat of tree damage. As a result, about 300 000 customers in Perth, nearly half the total, were without electricity for more than 24 hours. A few were not reconnected until eight days after the storm. However, it needs to be remembered that this storm was not as severe as the tropical cyclones which affect Northern Australia and that the population of the southwest of Western Australia is less than 1.5 million people.

Trees, debris, and the wind itself knocked out 200 of 450 high voltage feeders. Around 850 distribution transformers were also put out of service, including 310 sections of high voltage distribution lines and 430 street mains. There was also damage to 1800 customer service leads-lines that ran into homes. In more than 2000 locations, trees fell or were blown onto wires. About 800 power poles fell or were leaning at the storm's end.

There was widespread criticism of how the State utility, Western Power, reacted to the crisis. A formal inquiry concluded that more could be done to handle such massive disruptions in future, but the dedication of Western Power's repair crews throughout that storm was widely recognised. Similar comments could apply to the disruptions that occurred during the wild storms in Sydney during January 1991.

The Costs Of Sinking Power Lines In An Inner Suburb

The Perth inner suburb of Subiaco has carried out an ambitious program of burying power lines. The program has been a great success, particularly because many of the streets are narrow (10 metres), and the removal of poles has greatly improved their appearance. The City of Subiaco is believed to be the only local authority in Australia to underground without subsidy or charges to individual householders. It chose not to impose charges on property owners because of possible conflict between those who agreed to pay and those who did not. Subiaco found that by removing unsightly poles and improving the alignment of footpaths and roads, it increased average property values by $10 000 per lot on properties valued at $200 000 to $300 000. A similar figure is estimated for other parts of Australia. This seems a reasonable return on the $3000 to $4000 per house required for sinking power lines, especially when the intangible benefits are added.

Subiaco's program began 14 years ago, and by the middle of 1997, some 35% of the suburb's streets will be free of overhead power lines. The council has spent $5.8 million over the past nine years, with a peak of $1 million in the last financial year. While annual budgets for the project will fall in the immediate future, it is hoped that the suburb will be free of overhead lines by the year, 2010-though council officers admit that this may be optimistic. One benefit that all householders with overhead lines will recognise is that the wanton cutting of street trees to provide clearance from overhead lines is no longer necessary. Trees can be allowed to develop their natural shape. In some areas, the heavier foliage reduces the benefits of street lighting. Still, the Subiaco City Council has introduced careful lower pruning and installed more lighting was necessary to alleviate this problem. Protection methods for wiring systems requiring protection against mechanical damage

Where protection of a wiring system is required, the wiring system must be protected by an RCD with a maximum rated operating residual current of 30 mA. Alternatively, it can be provided with an earthed metallic armouring, screen, covering or enclosure, allowing a short circuit protective device to operate under fault conditions. The other possibility is to provide adequate mechanical protection at a minimum of WSX3 to prevent damage.

 

The most common protection method used by our industry, particularly for circuits up to 32A and in domestic installations, is the installation of an RCD. This method is difficult to apply to consumer mains and subdomains. One of the other protection methods will be required unless you protect the submarine with a Type "S" RCD which are expensive and not readily available. The other forms of protection can be harder to achieve, especially in existing homes where alterations are being carried out. New homes aren't as difficult. 

what cable required for new home construction in australia (3)You may use a metallic armouring, screen, covering or enclosure. If less than 2mm in thickness, these must be earthed so that the short circuit protective device will operate under fault conditions. You may elect to use a steel conduit or anaconda earthed with an appropriate earth clip as recommended by the manufacturer. Steel sheeting suitable earthed if less than 2mm thick across the studs can also be used. An option that will be infrequently used is providing adequate mechanical protection at a minimum of WSX3 to prevent damage. 

  • WSX3 is a substantial rating and requires the wiring system (cables) to be Provided with medium-duty protection against damage, meeting the requirements of the appropriate tests of AS/NZS 3013.
  • Any wiring system (cables) with additional 2.0 mm sheet steel coverage with a maximum unsupported width of 100 mm.
  • Or you may use any WSX2 systems with an additional 1.6 mm sheet steel coverage and unsupported width not exceeding 100 mm.
  • Another option is to use galvanised medium tubes complying with AS 1074 or very heavy-duty conduits complying with AS/NZS 2053 or AS/NZS 61386.

Mind-blowing stuff. However, this option may need to be used, especially in medical installations, consumer mains or subdomains.

Conclusion:

A Quick reminder for Wiring systems installed vertically. Where wiring systems are installed vertically, they must be installed to avoid damage to any part of the wiring system. You must ensure that damage isn't caused by the wiring system's weight or by the support or fixings used to secure it. This can be achieved by providing additional supports for cables enclosed in a vertically installed wiring enclosure. Cable supports need to be provided at intervals not exceeding 8 m or according to the cable manufacturer's recommendations. Remember, cables installed vertically also need to comply with the wiring systems requiring protection against mechanical damage.

 

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