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UNDERGROUNDING TRANSMISSION LINES IN URBAN AREAS

APRIL 2013

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CONTENTS

01 1. ThE ISSUE

02 Why do we need transmission lines?

02 Why were the lines erected over built-up areas?

03 Can buildings still be erected under high voltage lines?

03 What is the impact of overhead transmission lines in urban areas?

04 How extensive is underbuild?

05 2. UNDERGROUNDING

08 But aren’t underground cables more reliable, and cheaper to maintain?

08 Won’t these lines be replaced over time anyway as they age?

08 Are there alternatives to undergrounding?

10 How can undergrounding (or relocation) of existing lines be funded?

10 Who are the beneficiaries?

11 3. TRANSPOwER’S vIEw

12 Our current approach

13 The future

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we have some 400 km of overhead transmission lines running through built-up areas in New Zealand cities. These are visually unattractive and can constrain what landowners do with the underlying land. So can these existing lines be undergrounded? If so, who should foot the bill?

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Transmission lines are an integral and essential part of electricity supply. They are the system’s arteries.

Most of New Zealand’s electricity comes from power stations located remote from our major cities. Much of our generation is located in the South Island, but we use the most electricity in the Upper North Island. Our high voltage transmission lines carry it from the generation plants to major substations in, and around, our cities. From there, local lines companies (like vector) distribute it to our businesses and houses.

Auckland, New Zealand’s major consumer, has nine Transpower substations: smaller cities like Gisborne have just one.

why were the lines erected over built-up areas?

With a few exceptions dating back decades, they weren’t!

However, over the years, cities have grown out and – in some cases – under transmission lines which were built years before over open land. This development under high voltage lines is called ‘underbuild.’ The photos below show two examples. The lines through South Auckland (below left) were built on open farmland, and the city boundaries have grown out to encompass them. The tower in Onehunga (below centre) was constructed in the sea bed, before reclamation brought the city out to meet it.

We do not build transmission lines over built-up areas. All new transmission lines within urban areas are placed underground.

Transmission lines in Auckland in 1963.

why DO wE NEED TRANSMISSION LINES?

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Can buildings still be erected under high voltage lines?

Since the 1950s and 1960s, when the Government built many of our transmission lines, the terms under which they occupy private land have been defined by legislation (The Electricity Act). This does not prevent underbuild.

Very recently, the Government has enacted the National Policy Statement on Electricity Transmission, which is helping us work with councils and developers to restrict further underbuild of the older transmission lines.

When we build an overhead line today, we buy easements beneath the line to ensure inappropriate development cannot occur.

Any existing dwellings are removed. So underbuild is not an issue for our newer lines, like the 400 kV line recently completed through the Waikato. For existing transmission lines, the new legislation should prevent underbuild getting any worse.

what is the impact of overhead transmission lines in urban areas?

Most people understand the need for transmission lines but, understandably, nobody wants them in their neighbourhood. For the landowner, they can restrict development. For the neighbourhood, they usually aren’t viewed as a piece of art.

As neighbourhood land values rise, these impacts increase.

Underbuild also impacts Transpower. Overhead transmission lines require ongoing maintenance. This requires ready access to towers. Access problems caused by underbuild increase the difficulty of regular maintenance, and can make major maintenance, like replacing corroded conductors (wires), extremely difficult, if it can be done safely at all.

Maintenance difficulties aside, we would prefer nobody lived beneath our lines. While we operate and maintain them well within international guidelines for electromagnetic fields, residents still raise concerns. We understand that.

UNDERGROUNDING A TRANSMISSION LINE COSTS $5-15 MILLION A kILOMETRE.

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how extensive is underbuild?

The principal areas of underbuilt urban transmission lines are shown on the map below. key areas include the west and south of Auckland, suburban Tauranga, and Christchurch, but there are pockets across the country.

The absence of underbuild in some cities reflects, in part, different topographies: Wellington City is surrounded by steep, undeveloped hills, along which the transmission arteries run. In contrast, in Auckland, all the lines must pass through the narrow, fully developed isthmus.

The historic policies of local councils are also an influence. Some councils controlled underbuild through their planning processes, while others allowed development (despite counsel against doing so).

CHRISTCHURCH

PRINCIPAL AREAS OF UNDERBUILT TRANSMISSION LINES

TAURANGA

AUCkLAND

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UNDERGROUNDING2.

Unfortunately, undergrounding is very expensive. In fact, it is prohibitively expensive on a widespread basis. As a rule of thumb, undergrounding a transmission line costs $5 to $15 million a kilometre. Overall, undergrounding our 400 km of urban lines could cost around $4 billion.

To understand why it is so expensive, we need to do some elementary engineering.

Two things are important – insulation and heat.

We insulate a transmission line so that the electricity won’t take a short cut and jump to earth – and electrocute anyone in its path (the electricity on our higher voltage lines will jump up to 2 metres through air, just as forked lightning will jump to earth).

Heat, on the other hand, is generated when we send electricity along a conductor. Feel your extension cord after it has been powering the vacuum cleaner for a while – it will be warm.

New lines are undergrounded within urban areas – clearly, a solution is to underground the existing ones too?This is technically possible and would resolve most landowners’ and neighbourhoods’ concerns!

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The cable cosTs abouT $750/meTre – 50 Times more Than The bare wire conducTor.

The diagram shows equivalent underground cable and overhead wire. The cable costs about $750/metre – up to 50 times more than the bare wire conductor.

Underground cables do not, of course, need transmission towers and other hardware, but the total equipment cost is still much lower than for underground cable.

Further, the cost of laying high voltage underground cable is high. High voltage cables have to be protected from accidental damage – not least, so people don’t get hurt or killed. They must also be located away from other services, like metal water pipes, gas lines and telecommunication cables, because of the effects of the high voltages and currents.

Usually, the roadway must be used: our two recent underground circuits from Brownhill to Pakuranga in Auckland are an example (see photo opposite). Each circuit consists of three 150 mm diameter power cables, which are laid in a 1 metre wide, 2 metre deep trench – one trench for each circuit. The trenches are then backfilled with special, heat conducting cement, before the road is resurfaced.

UNDERGROUND CABLE AND OvERhEAD CONDUCTOR

When a conductor is suspended high up on our overhead lines, it is surrounded by air, which both insulates and cools it. So the conductor can just be a bare wire, strung between insulators. These bare wire conductors are usually made of aluminium.

When transmission lines are buried in the ground, they have to be coated with insulation material (special plastics), in the same way as your electrical wiring – and your extension cord – is insulated in your house. As you can see from the diagram, this specialized insulation is thick.

Getting rid of the heat (to stop the cables overheating) is also a major problem underground, as we don’t have the cooling effect of air to carry the heat away like overhead conductors. So we use more costly metals (usually copper) which don’t heat up so much, and bigger conductors which generate less heat.

As a result, underground electricity cables, especially the very high voltages ones that we need to use, are bigger, heavier and more expensive than equivalent overhead wires.

15 cm 4 cm

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TRENCh FOR BROwNhILL TO PAKURANGA CABLES

Underground cables often need to be longer (and therefore more costly) than overhead lines: the transmission line shown below takes the direct route across the gully (as shown below), while an underground cable would need to take a longer route.

On average, we plan on an underground line being at least ten times more costly than the equivalent new overhead line.

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TRANSMISSION LINE CROSSING A GULLy

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underground cables are neiTher cheaper nor more reliable long-Term.

But aren’t underground cables more reliable, and cheaper to maintain?

Yes, cable failures are uncommon. But they do occur, and they take a couple of weeks – or longer – to fix, which can mean longer power outages for residents and businesses. For critical lines, this risk means we may need another back-up transmission line, adding to the cost!

Overhead lines have more frequent faults, but we can fix them very quickly. Cables are less susceptible to cyclones (and lightning, in most cases), but can suffer long-term damage in earthquakes, unlike overhead lines. On balance, an overhead system can be more resilient over time.

High voltage underground cables don’t cost a lot to maintain – but they don’t last forever, cannot be modified once laid, and are very expensive to replace.

Overhead lines do need to be maintained regularly, including painting the towers and renewing conductors. But, maintained properly, they will last forever.

Overall, underground cables are neither cheaper nor more reliable long-term.

won’t these lines be replaced over time anyway as they age?

No. Overhead lines are like the farmer’s wagon: many parts are replaced over time, but the wagon lives on. Properly maintained, they can last forever.

Very occasionally, older lines become redundant, often because a bigger line is required to meet increased electricity demand. Recently, an 8.2 kilometre long overhead line between Pakuranga and Penrose (in Auckland) was taken down in this way. But this is the exception.

Are there alternatives to undergrounding?

In some cases, yes. The line can be re-routed or redesigned at a much lower cost.

The case study on the next page demonstrates a successful project undertaken between Transpower and a developer. The 107 hectare Highbrook subdivision in Auckland invested $22.7 million to both move and underground existing lines a decade ago. They used a combination of undergrounding and innovative redesign and re-routing to achieve a striking outcome. The redesigned overhead line is built higher than normal, so that native trees can grow unencumbered below.

One issue is where the line can be moved to. Nobody but the affected landowner is keen to see it moved closer to their backyard.

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In August 2005, Transpower and highbrook Development Limited entered into an agreement whereby highbrook paid to underground, or realign, existing transmission lines. This was to facilitate their development of a high class business park on their land in East Tamaki, while allowing Transpower to maintain the capacity of their existing lines located on the site.

The project involved cabling 2.6 km of the Otahuhu–Penrose A and B 110 kv lines and realigning 2.6 km of the Otahuhu–Penrose C 220 kv line onto nine steel monopoles. The new lines were commissioned in May 2008. Redundant towers and conductors were removed.

The monopoles are some of the largest 220 kv double circuit monopoles installed in New Zealand. Pole 8 is the largest with a height of 48 metres, a base diameter of just under 3 metres and weighs just under 60 tonne. The monopoles were fabricated in South East China. The average cost for an installed monopole at highbrook is approximately $540,000.

The monopole option was chosen due to cost; they are cheaper to install than underground cable of equal capacity and highbrook considered monopoles to be less intrusive than a conventional lattice tower.

SOME OF THE LARGEST MONOPOLES IN NEW ZEALAND

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The lines have To run somewhere, jusT as moTorways, porTs and prisons (To name jusT some infrasTrucTure) affecT a few communiTies To serve all.

how can undergrounding (or relocation) of existing lines be funded?

This is the thorny question.

It is impossible to underground all of the existing urban transmission lines. As noted, the bill would be around $4 billion, and New Zealand simply does not have the wealth to fund that – whoever picks up the bill.

But, if more lines in urban areas are undergrounded or moved, who can or should share the cost?

The economist will say the beneficiary should bear the cost. We’ll explore that more in a moment.

Others cite fairness: “why should I have all the towers in my neighbourhood, when it is serving the leafy suburbs across the city?” That is a completely understandable view, but not one that helps us find a solution. The lines have to run somewhere, just as motorways, ports and prisons (to name just some infrastructure) affect a few communities to serve all.

who are the beneficiaries?

Individual landowners benefit directly. The value of properties hosting towers and lines increases if they are removed, due to the removal of development restrictions.

A secondary benefit is the removal of the ‘stigma’ associated with the lines for all landowners in their vicinity.

The community – the landowners, residents, retailers and visitors – are also beneficiaries to the extent that the neighbourhood is improved.

Transpower is sometimes a beneficiary through lower ongoing costs. Unfortunately, this is usually only a small part of the total cost.

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TRANSPOwER’S vIEw3.

The lines are operated well within international limits for public safety; they are legally established (and in most – not all – cases, were there before the current owner purchased the property); and they have the right to remain there indefinitely. Occasionally, we face significant one-time expenditure to maintain an overhead line. Replacing corroded wires – which might happen after 50 years – is an example. Avoiding costs such as these by undergrounding is a benefit, which we do contribute to offset the cost of the undergrounding. However, even for the most difficult task on the most difficult line, this avoided expenditure will only be a small part of the cost for a new underground line.

we support undergrounding. Economics aside, we would prefer not to be the ‘ugly duckling’ in a community. we will always attempt to help those who seek ways to lessen the impact of overhead transmission lines. however, we are rarely a material beneficiary of undergrounding the lines.

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Transpower’s income comes from electricity consumers nationwide, through their monthly electricity bill. All of our costs are subject to review by the Commerce Commission to ensure we are achieving our goal of keeping these bills as low as possible. If we spend money which is unnecessary, or for which we cannot show a benefit to the electricity consumer, we cannot include it in our charges.

Put simply, electricity users in, say, the South Island do not expect to pay increased electricity bills for underground existing lines in Auckland, when those existing lines are doing their job well.

Were we to spend the money, the cost will fall to our owner – the Government, and therefore the New Zealand taxpayer. The effect is the same as the Government funding the undergrounding directly.

Ultimately, that is a policy decision for the Government, not Transpower, and must be prioritised with other public spending.

Our current approach

Our policy is to support and encourage undergrounding or relocation of an overhead transmission line provided the beneficiary meets the costs that cannot be justified by Transpower.

Over $40 million of undergrounding has been funded in this way since 2000. Major examples are Highbrook (see earlier case study) and the undergrounding of 2.4 kilometres of line to allow development of the new Westgate development in Auckland (see photo, below).

ulTimaTely, ThaT is a policy decision for The governmenT, noT Transpower, and musT be prioriTised wiTh oTher public spending.

wESTGATE DEvELOPMENT – AUCKLAND

Almost exclusively, this undergrounding has been funded by a single landowner developing a large block of land.

Undergrounding short sections of less than a kilometre or two can seldom be justified by smaller landowners: the ‘fixed costs’ (including providing joints at each end of the cable) make small projects very expensive. So it is really only a viable option for large landholders.

For Transpower’s own projects and works, we have a policy of undergrounding any new lines required in urban areas.

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The benefiTs of undergrounding (or relocaTing) a single line is greaTesT when iT is The only line, and when land is being developed.

The future

Discrete undergrounding funded by landowners will continue. From time to time, we will remove redundant lines. Neither will address many of the existing underbuilt areas.

If a community really wants to underground existing transmission lines through their community, who could foot the bill? If the benefits do stack up for the community as a whole, one candidate is the local authority. Perhaps there are situations where this is appropriate, but the challenges in large cities like Auckland are obvious: the competition from core infrastructure needs, like transport and sewage, is high and councils face tough choices about where they spend their money.

We mentioned fairness earlier. We hear – and empathise with – the argument that the Government should (directly or by foregoing dividends from its investment in Transpower) fund part of undergrounding since the overhead lines affecting individual neighbourhoods are there for the greater good? That is a matter of policy for Government, not Transpower, but we would be remiss not to point out that this is not an argument unique to existing urban transmission lines. What about the rural landowners where transmission towers limit irrigation development? Or the landowners near the major motorway from which the noise and disturbance has grown over the years, or those near prisons, and airports – and the list goes on.

Inevitably many of the mature and developed communities most impacted are likely to be at the back of the queue in any prioritisation. The benefits of undergrounding (or relocating) a single line is greatest when it is the only line, and when land is being developed.

With new lines being undergrounded in urban areas, and with corridor management legislation in place to limit further underbuild of overhead transmission lines, the problem is at least not growing.

For existing underbuild, we are conscious we have not provided a solution: there simply isn’t an easy one. But hopefully we have left everybody better informed.

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