Chapter 3: The Proposed Grid Upgrade
Need for upgrade
39. The electricity transmission system connects power stations with load and plays an important role in maintaining reliability and security of the supply of electricity.
40. Transpower maintained that to ensure the continued security and certainty of supply of electricity to Auckland, Northland and parts of Coromandel and the Waikato, the existing upper North Island Grid needed to be upgraded. Transpower further maintained that security and certainty could be achieved by a new transmission link, with substations and ancillary facilities, and by upgrading existing assets, commissioned in stages over 30 years to meet forecasted increasing electricity needs.
41. The Grid Reliability Standards (as described in Chapter 4) require the transmission system be operated so that it remains stable and capable of supplying demand in any single outage of the largest relevant item of plant that is in service at any particular time. This is often referred to as an “N-1” security requirement.
42. Transpower contended that even with all local existing and committed generation in the region operating reliably, under current security standards the existing transmission system would not be able to supply peak demand in the upper North Island in excess of 2190 MW. This is due to insufficient thermal capacity, and the potential for voltage instability at times of high system load, with consequential risk of partial or total losses of supply to Auckland and further north.
43. Transpower also contended that forecast demand beyond 2013 would exceed 2500 MW, and that, even with all local existing and committed generation in the region operating reliably, and taking account of planned interim improvements and upgrades to the existing grid, this level of demand would not be able to be supplied by the existing transmission system. Transpower maintained that demand is forecast to exceed transmission capacity by 40 MW in 2014, rising to 565 MW by 2020, levels of demand that could not reliably be supplied.
44. Transpower acknowledged that some people assert there is no supply or capacity problem, but contended that the point of deficit may change by about a year at most; and that the key areas of dispute are the best method of providing for increased supply, such as transmission, new generation, or demand-side management. In addition, Transpower also relied on the ability of the grid upgrade to “unlock” isolated renewable energy generation, which (it asserted) is almost all sourced south of Whakamaru.
45. The forecasts of demand and generation in the upper North Island that had been used by Transpower in assessing the need to provide for increased supply were also significant issues for submitters.
46. Transpower submitted that the grid upgrade is needed because the existing transmission system would not be adequate to meet demand in the short or longer term.
47. The 400-kV capable transmission link (comprising a new 400-kV capable transmission line, initially operated at 220-kV, new 220-kV cables, new and upgraded substations and ancillary facilities) is the option selected by Transpower to address the lack of capacity of the existing power system to reliably supply the upper North Island at times of peak demand.
48. Transpower urged that the RMA process should not be taken as an opportunity to re-litigate earlier decisions made by separate bodies under their specific statutory mandates. It maintained that the grid upgrade is the option it selected (mandated by the Electricity Commission) to respond to the identified problem of insufficient capacity in the existing system to reliably supply the upper North Island at times of peak demand. Transpower contended other methods for solving the supply problem which might meet the RMA tests are not relevant, as they are not being pursued by Transpower, have not been mandated by the Commission, and are not before the Board.
49. In summary, the context in which Transpower submitted the Grid Upgrade Project for the Board’s consideration by the RMA process is that it is the method, approved by the Commission, for meeting forecasted demand, in a way that would also provide transmission of electrical energy generated by renewable methods south of Whakamaru.
50. Mighty River Power supported the need for new and improved transmission for the upper North Island, contending that the National Grid must have sufficient capacity to ensure that energy generated by new wind, geothermal and small hydro plants can, at any instant, reliably be transported between where it is generated and where it is consumed.1
51. The Board will address the issues raised by the submitters. Having addressed those issues, the Board will then be able to review the need for the 400-kV capable transmission link and reach its finding on that issue.
Submitters’ cases
52. Submitters, who supported the need for the upgrade project, identified the importance of the continued reliability, diversity, security and certainty of supply, and the role these have in national well-being, investment and economic activity.
53. Supporting submissions also referred to the upgrade project facilitating new electricity generation, – including generation from renewable resources, to be connected to the grid – and efficient electricity transmission.
54. Most other submitters contended that the 400-kV capable transmission link proposed by Transpower is unnecessary.
55. The contentions, in relation to the need for the upgrade, of submitters in opposition can be summarised as:
- a) there is no need for more overhead lines because Auckland needs to save power, not demand more
- b) the demand growth projections of the Electricity Commission (2007 Statement of Opportunity – SOO) do not justify its construction
- c) the scale and capacity of this proposed 400-kV capable line is completely out of alignment with the expected requirements for transmission capacity into Auckland to meet the demand growth in the next 40 years
- d) the potential new generation capacity likely to be constructed in the Auckland region in the next 40 years has been grossly underestimated in an attempt to justify this line as one of national significance and urgency
- e) the need for this line to be built is based on out-of-date and inaccurate high-demand growth forecasts (2005 SOO)
- f) the line will reduce, rather than increase, the security of electricity supply to Auckland.
56. Dr McQueen was a submitter who included most of these contentions in his submission. Although Dr McQueen’s pre-circulated brief of evidence (on which he was cross-examined by Transpower’s counsel) focussed on health effects rather than the need for the 400-kV capable transmission link, he made extensive oral submissions to the Board on the need for the upgrade when he presented his pre-circulated brief of evidence.
57. In addressing the Board in support of his submission, Dr McQueen stated his opposition to the 400-kV capable transmission link. He continued:
The supposed justification of this line by the demand growth of Auckland has not been linked to new base load generation that will be of use in meeting Auckland demand periods that has been proposed and approved that will come on stream south of Whakamaru. So, in effect, I’m saying in that statement that this line is being built on speculation that there will be a large amount of new generation built separate to Whakamaru that will justify the use of this line. To my knowledge, there are no significant generation projects that have been proposed. So, this line is a line to nowhere, it’s a white elephant of obsolete, third world technology. This line will reduce rather than increase the security of electricity supply to Auckland. Capacity of the transmission capability, size of the pylons proposed in the 400 kV capability, will not be required in the next 40 years if reasonable assumptions on demand growth, the 2007 SOO, and reasonable estimates of key...of likely new Auckland area generation are used...2
58. He spoke about alternatives to meet the need:
There are better benefit alternatives to the proposed line available that have a much reduced environmental impact, such as more generation in the Auckland region, duplexing and re-conductoring of the Whakamaru A, B and C lines, use of HVDC transmission technology, which will be less obtrusive and easier to underground, and more extensive use of undergrounding High-voltage, alternating-current (HVAC) lines, and use of new, conventional, small scale 220-kV transmission lines...3
59. Dr McQueen then returned to demand forecasts and need:
I oppose these applications, because Transpower is falsely trying to justify the need for this line by...being built, by using out of date and inaccurate, high-demand growth forecasts, the 2005 SOO or Statement of Opportunity...4
I put this document together, probably about three weeks ago, and it was spurred by the Electricity Commission announcing its draft 2008 Statement of Opportunity, which has been released on the Electricity Commission website, and, which I’ll refer to in a little while, but the motivation for putting this document together, and for speaking to it today, was to try and give some kind of a high-level view of what the requirements are of transmission capacity into Auckland, and some sense of what the existing transmission capacity is in the upper North Island, and having sat through some of the Transpower witnesses that have talked about future demand, and so on, I was struck by how unclear and clouded those discussions were. What seemed to come across from the...from the expert witnesses of Transpower was that there’s an urgent need to get on and build this line and that this is of national significance and, if we don’t build this by 2012, you know, the world is going to come tumbling down around our shoulders. Well, if I can direct you to the Table that starts at the start of this document. What I’ve shown in this Table is the five-year forecast...5
The net additional demand, point 2 of the conclusions, the increase in 30 years of demand between 2007 to 2036 in Auckland and the North Isthmus is 1855 MW and that’s not considering any new generation, that’s just the difference in the demand growth that’s now forecast by the 2008 SOO, which has been published by the Electricity Commission. The net additional demand 8 growth increase from 2007 with Rodney and Otahuhu C built is only 1055 MW by year 2036...6
60. He next spoke about security of supply, losses and demand forecasts:
....multiple smaller circuits provide much greater security of supply and, I believe, you’re going to hear evidence later on from other people that the security of supply of the proposed Transpower 400-kV line is 18,000 times less than the security of supply of having other multiple paths of transmission. So, in other words, you’re putting all your eggs in one basket too, in one huge transmission capability basket. That, always, is going to lower the security of supply by having the risks of everything in that one basket and the requirement to have backup capable of handling that capacity, if that line should go down...7
However, there is new technology that has arisen, and the trade name for that technology is ‘HVDC Light’, and I won’t go into the details of that, that’s for other experts to discuss, but the nature of HVDC Light is, it really is designed for much lower cost implementation of high voltage DC conductors, and high voltage DC transmission lines...8
...the so-called higher losses of these composite conductors are really losses that are only going to be used a relatively small amount of the time. And again, in listening to the evidence that was presented by the Transpower witnesses, I didn’t see any quantitative analysis of these higher losses. I just saw some qualitative…qualitative pronouncements of a small power station, and so on. And, I think, that that’s been a bit misleading, in terms of presenting that, without a hard quantitative analysis of what those losses exactly are, and what percentage of the time those losses are likely to occur...9
... and part of the information that I’ve passed on yesterday and today is about the newly accepted and mandated, I guess, by the Electricity Commission, is lower estimates of demand in the Auckland region, of 1.4 to 1.5 per cent growth...demand growth rates, versus the almost 3 per cent demand growth rates that Transpower has used in its original proposal and in the amended proposal...10
61. Ms K Brennan and Mr G Copstick gave evidence on need. Cross examination by Transpower’s counsel (Mr Laing) included the following:
Laing: Thank you. Can I ask you to go to Paragraph 3 of your evidence...Page 3 sorry, Page 3, near the top of Page 3; you have a heading, ‘the line is unnecessary, because expert opinion says it will never be converted to 400 kV’. Do you see that?
Copstick: I do, yes.
Laing: And, that part of your evidence, I believe, goes over to Page 8, but could you just confirm that for me?
Copstick: Yes.
Laing: The expert opinion that you’re referring to there, is that the expert opinion, which is, again, referred to in Paragraphs 16 to 33?
Copstick: Yes, we’re largely quoting from Graham Pinnell of the Electricity Commission who was involved in the decision process up to that point.
Laing: Thank you. But, Mr Pinnell is not giving evidence before this Board of Inquiry, is he?
Copstick: No, we couldn’t get him to come.11
(Ms Brennan and Mr Copstick rely here on a minority opinion of Mr Pinnell – as a member of the Electricity Commission – in the Electricity Commission’s (majority) approval of Transpower’s 400-kV-capable amended proposal.)
Transpower’s case
62. Transpower contended that the security of sup ply issue and need for reinforcement of the transmission network into the upper North Island had been identified in 2002 and that Transpower, in its planning, used a five-to-seven-year period as the lead time to establish new transmission infrastructure.
63. Transpower reported that in October 2004 it had issued a request for further information on non-transmission options, and that the responses had revealed that there was little prospect of deferring the grid upgrade. Peak demand management (such as commissioning a special peak-demand generator) could delay the need for about 12 months, which would be insignificant in the context of the lead time for the project; and in any event Transpower has limited ability to influence that peak-demand management, or to influence willingness to invest in such a plant.
64. In October 2004, Transpower produced a report titled Security of Supply into Auckland Assessment of Alternative Solutions.12 Section 5 of that document identified non-transmission alternatives that Transpower had considered: new local generation, and new demand-side management solutions. The report summarised the contribution of each to system security; addressed availability, economic benefit, environmental impact, and timeliness; and gave summaries of the conclusions reached in respect of each. Appendix A described the generation scenarios that had been modelled.
65. In May 2005, Transpower produced a report titled Assessment of HVDC Transmission Options between Whakamaru and Auckland.65 This document identified and examined a range of high-voltage, direct-current (HVDC) options that Transpower had considered, including HVDC Light. The report’s key conclusions indicated the HVDC option that provides the highest level of asset availability and security of supply is closest to the 400-kV HVAC solution in terms of asset availability and system security, but noted that all HVDC options are more costly than 400-kV HVAC.
66. The Electricity Commission approval process included a comparative analysis, according to the Grid Investment Test (GIT) between a number of short-listed alternatives, themselves derived from a longer list of other alternatives. This analysis did not favour any one of the alternatives, all of which were assessed in detail.
67. Transpower contended that it had considered and analysed numerous potential methods of addressing security of electricity supply to Auckland for the purpose of the Electricity Commission process. Transpower also contended that environmental considerations had been part of the development and assessment of different transmission alternatives, particularly with regard to minimising the number of lines and corridors in the long term which clause 88E of the Government Policy Statement on Electricity Governance (GPS)14 requires the Commission to take into account.
68. Transpower submitted that the grid upgrade is needed by 2013 because the existing transmission system would not be adequate enough to meet demand in the short or longer term.
69. Transpower contended that non-transmission alternatives had been investigated, and that, overall, these alternatives had been found inadequate or uncertain to meet demand in the short or longer term.
70. With regard to generation development scenarios, Transpower contended that it is neither prudent nor good transmission planning to take into account uncommitted generation, and that Schedule F4 of the Electricity Governance Rules (which set the basis for the GIT) clearly refers to alternative projects that are reasonably likely to proceed. If there is no actual commitment to construct new generation then it cannot be considered as likely to proceed.
71. Although there is also debate about what is known as the ‘need date’ and the rate of demand growth, even using differing assumptions and forecasts, Transpower submitted that this may change by about a year at the most.
72. Transpower’s contentions were supported by evidence. Mr J N O Coad, acting Grid Programme Manager for Transpower, testified that at least 11 alternatives (transmission alternatives and non-transmission generation and demand-side) had been considered and analysed in the original 2005 proposal, and a further nine alternatives in the amended proposal. Mr Coad confirmed that Transpower had considered generation as an alternative solution for security of supply into Auckland, and had explored contracts with generation companies. He remarked if the generation companies chose not to invest, there would presumably be good reason why they had not done so already.15> He confirmed that the basis on which an option was considered was that it must be credible and able to be relied on.16>
73. Mr T A George, Transpower’s General Manager Grid Investment, explained that, where it is determined that projected demand for electricity is going to exceed existing transmission capacity, a process of identifying solutions begins sufficiently in advance of the need date to allow potential investments to be constructed. The process involves seeking input from industry on the needs analysis, and seeking proposals for non-transmission alternatives such as generation or demand-management options. He stated that investment in new transmission lines may have lead times of five to seven years.
74. Mr George also gave evidence that Transpower recognises and takes into account in its planning processes, the contribution that demand management and the use of local distributed generation (including renewable generation) can make to the grid to potentially defer some transmission investment.
75. Mr George gave his opinion that non-transmission alternatives have to be practicable, technically feasible, have reliability comparable to transmission investment, and be able to defer transmission investment by at least one year.
76. He stated that in preparing the original proposal, 11 options had been considered that were technically feasible to meet the need, including peaking generation (available during times of peak demand).
77. Mr George reported that the analysis and review of the Grid Upgrade Project by Transpower and the Electricity Commission had included identification of over 60 technically feasible options, including energy efficiency measures, energy substitution programmes, peaking generation plant, wind generation, tidal generation and coal or gas generation.
78. The witness also reported that some non-transmission alternatives for improving reliability and security of supply to Auckland had been adopted and are being implemented. These are improvements to substations and new substations and generation connections.
79. Mr George stated that, because electricity cannot be stored practically in the quantities required, meeting electricity demand means having sufficient capacity in the electricity supply system (generation, transmission and distribution) to meet the highest (peak) demand that may occur approximately one year in ten.
80. He also reported that Transpower is required to ensure the reliability of the transmission system. (This requirement is set out in the Electricity Governance Rules 2003).17
81. Mr D E Boyle, Transpower’s Planning and Development Manager, gave evidence about alternatives to transmission, including energy efficiency initiatives, peak demand management, and peaking generation, of which only the latter had been considered viable. The witness explained why uncommitted generation prospects had not been taken into account; and he also explained why continued growth in demand had been assumed, even if forecasts of the timing of a particular level of demand were uncertain to some extent.
82. He contended that forecast demand in excess of 2500 MW would not be able to be supplied beyond 2013 by the existing transmission system even with all local existing and committed generation in the region operating reliably, along with interim improvements and upgrades to the existing grid that are planned.
83. Mr Boyle further stated that, in 2014, the demand is forecast to exceed the transmission capability by 40 MW, growing to 565 MW by 2020, and that this is the level of demand that could not be reliably supplied.
84. Mr Boyle gave evidence that of three principal transmission alternatives that were assessed against the amended proposal, two involved augmentation of existing 220-kV transmission lines. He described features involved in comparing duplexing the Otahuhu-Whakamaru (OTA-WKM) A and B lines with conventional conductors, and duplexing the OTA-WKM A, B and C lines with high-temperature conductors.
85. An additional factor taken into account by Transpower was transmission losses that resulted from the resistance of conductors. Mr Boyle gave evidence about the way that these losses would be increased or reduced by changes in the levels of current and voltage, including comparing the losses of the four options considered.
86. He also gave evidence that Transpower had assessed conventional HVDC and HVDC Light alternative transmission methods as part of the development of the grid upgrade proposal. He described relative environmental effects of HVDC in terms of the heights of line support structures, sizes of conductor bundles, interconnections with alternating current equipment, reliability, and economics, stating that HVDC had been found to be significantly more expensive. He reported that Transpower considered HVDC to be an inappropriate solution due to high costs and risks, lack of reliability and practicability.
87. Mr George gave evidence that, in its 2005 original proposal to the Electricity Commission, Transpower had reported on 11 options, including underground cables. He gave his opinion that the use of underground cables is typically restricted to urban areas; and stated that intermediate substations are required to control voltage.
88. Mr Boyle explained that the longer the length of underground cable, the higher the probability of failure; and stated that, currently, underground transmission cables cost in the order of 10 times more on average than equivalent capacity overhead lines.
89. Mr Coad stated that, in relation to forecasts of demand, Transpower is obliged to use the Statement of Opportunities (SOO) issued by the Electricity Commission, although it has the right to offer an alternate view on that SOO.18 Similarly, Mr George identified that Transpower uses the generation scenarios that the Commission published in the SOO when assessing possible futures for grid investment,19 also with the right to offer an alternate view on that SOO.
90. In cross-examination by Ms Brennan about the apparent overcapacity of the proposed grid upgrade, Mr Boyle identified that the line would not be operated to the maximum thermal design capacity because of the need to meet the ‘N-1’ security requirement. This requires any electricity being generated or transmitted by equipment that fails to then be taken up by the other circuits supplying that demand without any of these other circuits exceeding 100 per cent of their capability.20
91. The complexity of meeting the N-1 security requirement was added to when Mr Boyle gave evidence about the loading of each circuit being governed by the laws of physics. As a result, Transpower has only a limited ability to modify the power flowing through each circuit. He identified that the natural distribution of the load across the six existing 220-kV circuits, plus the two proposed 400-kV-capable circuits, would not be in proportion to the circuits’ ratings, resulting in some circuits being underused.
92. A number of submitters queried the reliance Transpower placed on the demand forecasts in the 2005 SOO instead of the forecasts in the draft 2007 SOO. Mr Boyle explained that:
At the time of the assessment of the proposal the Electricity Commission did consider whether it would be appropriate to adopt the scenarios in the draft 2007 SOO, but determined that it would not be appropriate, part way through the process, to adopt scenarios that underlie the draft 2007 SOO. At that time, the draft 2007 SOO had yet to be consulted on, and may have changed as a result of consultation. The Commission did, in any event, include the draft 2007 demand forecasts as a sensitivity in applying the GIT to the proposal.
93. He gave his opinion that, even if the draft 2007 demand forecasts were used the need date would at best be delayed a year.
94. Mr Boyle also noted that some submitters had suggested demand growth has dropped and is trending down over time. He contended that demand is increasing but the annual rate of increase in the demand forecast is decreasing over time, resulting in a reasonably straight demand curve rather than the exponential demand curve that would be expected if an identical annual growth rate compounded year on year.
95. He noted, by way of example, that the annual growth rate in the demand forecast for central Auckland starts at 4.06 per cent in 2008 and reduces to 2.05 per cent by 2042.
96. Mr Boyle then gave evidence in response to submitters’ suggestions that the demand will never reach levels that require the change from 220-kV to 400-kV operation. He reported that the development plans are based on the 2005 SOO and noted that the demand curve in the draft 2007 SOO is flatter than the 2005 SOO demand curve (especially in the later stages of the forecast period) and that, if the draft 2007 SOO demand forecast is used, the conversion to 400 kV would be delayed by about five years.
97. He then identified that this delay may be countered with the adoption of a renewable future with a high percentage of renewables. In his opinion, with a renewable target of 90 per cent by 2025, it was probable that the Huntly coal-fired power plant would no longer be used as baseload generation, and that it was quite likely that the change from 220-kV to 400-kV operation of the line would occur earlier than forecast and in any event, by 2039.
Consideration of need
98. The Board has reviewed all the evidence bearing on whether there in a need for this 400-kV-capable transmission link.
99. The Board also heard submissions on need (including on demand forecasts), that could have been (but were not) lodged as evidence. As explained in Chapter 4, this has resulted in the Board placing less reliance on evidence given without notice as submissions.
100. In the instance of Ms Brennan and Mr Copstick relying on the opinion of Mr Pinnell, the Board does not place reliance on Mr Pinnell’s opinion because he was not called to give evidence, so the Board was not able to hear his opinion directly, nor could it be tested by cross-examination.
101. The Board accepts the evidence of Mr Boyle about Transpower’s and the Commission’s use of the 2005 SOO and the draft 2007 SOO demand forecasts and generation scenarios against which the 400-kV capable upgrade and other options were assessed.
102. The Board also notes the evidence of Mr Boyle that forecasts of the timing of a particular level of demand may be uncertain.
103. Dr McQueen’s submissions on need for the grid upgrade conflict with the submissions of Transpower. The Board has to resolve that conflict. It does so on the basis that Transpower’s submissions were supported by evidence of expert witnesses, whose statements had been published prior to the hearing in accordance with the Board’s directions, and who attended the hearing to give their evidence, and to be tested on it by cross-examination and by questions from the Board. Dr McQueen’s submissions on need for the upgrade were not supported by evidence, whether or not published in advance, nor open to testing by cross-examination. Therefore, the Board finds that the evidence supporting Transpower’s submissions is more dependable as a basis for resolving the conflict between those submissions and Dr McQueen’s.
104. The Board understands that, in relation to demand forecasts, Dr McQueen’s submissions demonstrate the uncertainty that Transpower also identified.
105. Some submitters contended that the proposed transmission line would have much greater capacity than would be needed. In that respect, the Board accepts the evidence of Messrs George and Boyle about the complexity of the power system; the requirement that it meets N-1 security; and that a line’s capacity cannot be determined simply by calculations that use theoretical ratings of individual components of the grid.
106. In summary, the Board accepts Mr Boyle’s evidence, and finds that the capacity of the proposed 400-kV-capable grid upgrade is required to meet forecast demand.
Conclusion on need for the upgrade
107. The Board finds that the 400-kV-capable grid upgrade is needed.
Original and amended proposals
108. On 30 September 2005, Transpower submitted to the Electricity Commission a grid upgrade plan for a 400-kV transmission line to Auckland. That plan was for a 400-kV line of 1200 MVA capacity per circuit from Whakamaru to the South Auckland urban boundary; 400‑kV underground cables from there to the Otahuhu Substation; and 400/220-kV interconnections at Otahuhu and Whakamaru.
109. The Commission reviewed that plan in April 2006 and issued a draft decision to decline its approval. Transpower decided to amend that plan and, at its request, the Commission suspended consideration of it.
110. In October 2006, Transpower submitted an amended proposal to the Electricity Commission which, in January 2007, gave notice of its intention to approve the amended proposal. In July 2007, the Commission made a final decision approving the amended proposal.
111. The amended proposal is a staged project in which the overhead line section would be constructed to be capable of 400-kV operation, but would initially be operated at 220 kV; the capacity of the line would be 2700 MVA per circuit (at 400 kV); the 220-kV connection point in Auckland would initially be the Pakuranga Substation; and the northern 400-kV/220-kV interconnection would be at a new transition station/substation at Brownhill Road, Whitford, from where 220-kV underground cables would connect to the Pakuranga and (eventually) Otahuhu Substations.
112. By clause 66 of the Government Policy Statement (GPS),21(as described in Chapter 4), the Electricity Commission was also required to take into account the Government’s objective to facilitate the potential contribution of renewables to the transmission system; and that the approval criteria should allow grid upgrade plans to facilitate the efficient and timely development of renewable generation resources, taking into account any difference in lead times for transmission and generation investment.
113. Transpower also maintained that the environmental effects of the grid upgrade had been considered by it and by the Electricity Commission in applying what are now identified as clauses 63, 66 and 94 of the GPS22 in considering the comparative efficiency, facilitation of renewable generation, and environmental effects of any new lines.
Outline of upgrade plan
114. By the amended project, Transpower proposes to upgrade the Upper North Island Grid by constructing a new 400-kV-capable transmission link between Whakamaru and Auckland, which would be operated at 220 kV from 2013 until its capacity is insufficient, and at 400 kV from about 2033.
115. In more detail, the upgrade would involve the following main elements:
- a) modifications to existing equipment and connections, and installing new equipment, at the Pakuranga Substation, converting it from 110-kV to 220-kV operation with a new 220‑kV air-insulated switchgear (AIS) switchyard, and commissioning the existing Otahuhu to Pakuranga 220-kV line (presently operated at 110 kV) at 220 kV
- b) modifications to existing equipment and connections, and installing new equipment, at the Otahuhu Substation, including moving the termination of the existing Otahuhu to Pakuranga line from the 110-kV bus to the 220-kV bus, and terminating the two 220-kV underground cable circuits from Brownhill into the existing Otahuhu 220-kV Substation, constructing a new 220-kV double-circuit underground cable, about 10.6-kilometres long, between the Pakuranga Substation and the proposed Brownhill Substation
- c) constructing a new 220-kV double-circuit underground cable, about 9.9-kilometres long, between the Otahuhu Substation and the proposed Brownhill Substation
- d) constructing a new substation at Brownhill Road, initially to be a transition station connecting the underground cable with Pakuranga to the start of the 400-kV-capable overhead line (to be commissioned by 2011); later, when the Otahuhu underground cable has been constructed, to be a switching station (to be commissioned by 2023); and later still when the overhead line is enlivened at 400 kV, to be a substation to transform the energy from 400 kV and 220 kV (to be commissioned by 2034). The Brownhill Substation will use gas-insulated switchgear (GIS) located in buildings
- e) constructing a double-circuit 400-kV-capable overhead line, with a capacity of 2700 MVA per circuit and about 185‑kilometres long, between Brownhill and Whakamaru, including 429 towers, insulators, triplex all-aluminium-alloy conductors, and earth wires (one of which would contain optical fibres for communication and operational control)
- f) additions to the existing substation at Whakamaru
- g) constructing a new AIS switching station at Whakamaru North, connected to the existing Whakamaru Substation, and later to be converted to a substation
- h) dismantling and removing the existing Arapuni-Pakuranga A double-circuit 110-kV line (ARI-PAK A line)
- i) ancillary activities, including accesses, fencing, safety and directional signage.
116. Although the Grid Upgrade Project has distinct components at different sites, and would be carried out in stages over a number of years, it has been developed as a single concept (including construction works, and operation and maintenance activities), with each component being integral to the overall project.
117. The works would span six districts, one city and two regions. Transpower gave notice of requirements for designations in district plans and applications for regional resource consents. As the existing Otahuhu and Pakuranga Substations are not designated, Transpower’s requirements include designation of the existing substation activities there; and as additions are proposed to the existing designated Whakamaru Substation, it requires a replacement designation of that substation.
118. The overhead line would cross about 315 properties. The designation for the line would be at least 65-metres wide, to allow for operation and maintenance of the line, and the swing of conductors. Transpower intends to acquire easements over those properties (or in some cases, to purchase the properties). The heights of the towers would vary, depending on the slope of the underlying ground and the minimum clearance required. The maximum tower height would be 70 metres, and the average height would be about 60 metres.
119. The towers would mostly be double-circuit, steel lattice towers. Four single-circuit towers are proposed at two transposition sites along the route; two single-circuit towers are proposed at Brookby Ridge to comply with a height restriction for Ardmore Airport; and monopole towers (instead of lattice construction) are proposed at Brownhill Substation, and at a crossing of Lake Karapiro.
120. The conductors would be high capacity, arranged in triplex bundles, separated by spacers; and there would be two earthwires of approximately 15 mm diametre, to protect the conductors from lightning strikes. One of the earthwires would contain optical fibres for communications for operation of the proposed line and the National Grid.
121. The underground cables are to follow separate routes from Brownhill to the Pakuranga and Otahuhu Substations. Each underground cable is to have double-circuit 220-kV cable in duplex formation, with each circuit made up of three 130–160-mm diametre cables, with associated fibre-optic communications and temperature-sensing cables. Each circuit would include buried water pipes of about 110 mm diametre for cable cooling, to be used as required later.
122. The cable routes are predominantly within roads and streets. Each cable would be buried in a trench about 1.5-metres wide and 2.2-metres deep; except that a short length of one circuit of the Pakuranga cable is to be installed in an existing cable tunnel.
123. Once the cable has been installed, Transpower intends to reduce the width of the designation to allow sufficient width for protection and maintenance.
Expected benefits
124. Transpower identified these expected benefits of the proposed upgrade:
- a) the ultimate capacity of the proposed transmission line would be 2700 MVA per circuit, maximising the use of the line corridor
- b) it would facilitate efficient transmission of energy (minimising line losses)
- c) it would promote renewable generation
- d) it would fit in with long-term strategic development of the National Grid
- e) it would promote confidence among business investors
- f) it would reduce adverse environmental effects by avoiding proliferation of transmission corridors.
125. These results would be consistent with the GPS and the New Zealand Energy Statement.
Endnotes
1. T J Densem, para 5.3.
2. Transcript 21/07/08, p 39.
3. Ibid.
11. Transcript 24/07/08, pp 2–3.
12. Published by Transpower, October 2004; produced in Common Bundle of Exhibits, Vol 1, Tab 5.
13. Published by Transpower, October 2004; produced in Common Bundle of Exhibits, Vol 1I, Tab 7.
14. Cl 88E was inserted in the GPS 2004 by the 2006 amendment. The GPS 2008 contained a corresponding provision in cl 104. The corresponding provision of the now current GPS 2009 is cl 94. See Chap 4 para [328].
17 See Chap 4, paras [329-337].
21 Formerly cl 80 of the GPS 2004, and cl 49 of the GPS 2008.
22 These clause numbers refer to the current May 2009 version of the GPS.
