Submission for Tactical Transmission Upgrade Approval

Transcription

1 Submission for Tactical Transmission Upgrade Approval April 2005

2 Electricity Commission Submission Tactical Transmission Projects April 05 1 Executive Summary Transpower seeks approval from the Electricity Commission under Rule F-III-16 (the transitional provisions ) of the Electricity Governance Regulations 2003 ( EGRs ) for the following: 1. Approval of each of the interim grid projects set out in this submission in accordance with rule F-III-16; and 2. Approval for all actual project costs for the interim grid projects in accordance with rule F-III-17. Transpower has determined that the expenditure described in this document is reasonably prudent or necessary to meet Transpower s current transmission security standards. A summary of the tactical transmission upgrade projects included in this submission is set out on the following page. This submission is structured into the following sections: the planning process utilised by Transpower to develop the tactical transmission projects necessary to meet the Transpower s current security standards; the transmission planning assumptions used in the analysis; the types of tactical transmission projects included in the submission; a region by region summary which includes a summary of the regional network, the key planning assumptions, an identification of the constraints that will cause a breach of the transmission security standards within the next few years and the tactical transmission projects selected to increase the capacity of the transmission system. Page 2

3 Electricity Commission Submission Tactical Transmission Projects April 05 Region Project Description Budget (000's) North Isthmus Henderson - Otahuhu 1 & 2 Thermal Upgrade $2,300 Auckland Otahuhu - Penrose 5 & 6 Thermal Upgrade $700 Huntly - Otahuhu 1 Thermal Uprating $1,700 2 x 50 Mvar 110 kv Penrose Capacitors $2,400 1 x 50 Mvar 110 kv Hepburn Rd Capacitor $1,400 Bombay - Otahuhu 1 & 2 Thermal Upgrade $800 Waikato Hamilton - Waihou 1 & 2 Thermal Uprating $720 Bay of Plenty Tarukenga - Tauranga 1 Thermal Upgade $250 Wairakei - Poihipi - Whakamaru 1 Thermal Upgrade $1,650 Central North Island Tokaanu - Whakamaru 1 & 2 Thermal Upgrade $6,400 Rangipo - Wairakei 1 Thermal Upgrade $3,200 Bunnythorpe - Tokaanu 1 & 2 Thermal Upgrade $8,500 Wellington Bunnythorpe - Haywards 1 & 2 Thermal Upgrade $4,800 Nelson Marlborough 40 Mvar Stoke Capacitor Banks $1,450 Islington - Kikiwa third 220 kv circuit $32,500 New Culverden substation $5,000 New Waipara substation $7,200 Blenheim - Stoke 110 kv second circuit $20,200 West Coast Dobson - Inangahua line upgrade 66 kv to 110 kv $3,200 Second Dobson - Inangahua 110 kv circuit connection $265 Second Dobson Interconnecting transformer $2,700 Canterbury Islington 2 x 60 Mvar 220 kv Capacitor Banks $3,100 Islington - Livingstone 1 Thermal Upgrade $1,600 Islington - Tekapo B - Twizel Thermal Upgrade $3,800 Islington - Timaru - Twizel 1 & 2 Thermal Upgrade $3,800 Southbrook 38 Mvar 66 kv capacitor $1,200 Islington - Livingstone 1 Duplexing $25,800 Ashburton bussing $7,300 South Canterbury Timaru Temuka 1 & 2 Thermal Upgarde $500 Otago Southland Invercargill - Roxburgh 1 & 2 Thermal Upgrade $3,800 Total $158,235 Page 3

4 Electricity Commission Submission Tactical Transmission Projects April 05 2 Introduction This submission is based on a subset of the projects that Transpower has identified in the document titled Future of the National Grid published in December 2004 and has communicated its intent to implement to customers and stakeholders over the last two years. The tactical transmission projects have been widely communicated to customers and stakeholders over the past two years. The most significant investment proposals in terms of cost are the projects required to deliver security into the upper South Island and into Christchurch. The detailed transmission plans into Christchurch and the upper South Island have been communicated to the CEO s of lines companies and generators affected by the proposals in the South Island and have received broad support. All the projects in this submission focus on delivering sufficient transmission capacity to enable demand to be supplied within Transpower s current grid security standards. In this document Transpower s current security standards are referred to as transmission security standards ( TSS ). A copy of these standards is attached in Appendix 2 of this submission. It should be noted that Transpower s security standards are consistent with the Electricity Commission s Grid Reliability Standards (GRS) and the rules for system operation under Part C of the EGR s. In terms of timing, the focus of these tactical projects is to address short term investments that Transpower has determined are reasonably prudent or necessary to maintain satisfactory transmission capacity and security levels in accordance with the TSS, across the National Grid over the next two to three years only. These projects therefore do not address all security issues forecast to occur over the next 10 years as identified in the System Security Forecast prepared by the System Operator. In all cases, Transpower has proposed the least cost transmission upgrade alternative possible to meet the TSS. All of these projects are aimed at extracting the maximum transmission capacity possible from Transpower s existing transmission assets, an approach which is: more cost effective than the construction of new assets such as new transmission lines; and in most cases the only practical solution given the timeframes required to secure designations and property rights for new transmission corridors. This document first sets out the transmission process utilised to derive the tactical transmission upgrade programme. The tactical transmission investments are then detailed on a region by region basis. Included in the regional sections are details of the need for investment, the committed transmission project to address the need, the increase in capacity delivered by the project and the budgeted project costs. Page 4

5 Electricity Commission Submission Tactical Transmission Projects April 05 3 Grid Planning Processes 3.1 Process Outline The range of tactical transmission upgrades set out in this paper is an outcome of Transpower assessing the adequacy of the power system by applying its standard transmission planning process. The transmission planning process utilised is summarised as follows: 1. Needs Identification An assessment of the adequacy of the power system to meet the TSS was completed based on the capabilities of the existing transmission assets and likely generation dispatch scenarios across a range of demand growth forecasts. The needs identification phase concluded where and when investment is required to enable demand within a specific region to be supplied securely or to relieve core grid constraints when appropriate. 2. Alternatives Identification An identification of the range of possible transmission alternatives to address the needs identified in the previous phase was completed. 3. Selection of preferred transmission alternative An assessment of the transmission alternatives identified was conducted across a range of criteria including achieving technical, economic and environmental outcomes Scoping and Approval The preferred transmission alternatives have been scoped which includes a full technical specification of the work required and environmental and property requirements including easements and Resource Consents where necessary. All of the projects included in this submission have been approved by the Transpower Board and are at varying stages of implementation. 3.2 Transmission Planning Assumptions The following transmission planning assumptions were applied in the analysis: The existing transmission system The electricity transmission system in New Zealand mainly consists of 220 kv and 110 kv transmission lines and substations. The 220 kv transmission lines function as the main conduit of electricity in the North and South Islands. A high voltage direct current (HVDC) transmission link (including high voltage cables across the Cook Strait) form an important connection between the North and South Islands. 1 In the case of tactical transmission upgrades, Transpower has concluded that maximising the capacity of existing assets will always achieve better economic, environmental and project feasibility outcomes than the construction of new assets. In the consideration of these tactical transmission projects the range of possible means of transmission such as new lines (including HVDC and HVAC links) at varying voltage ranges was discounted due to economic, environmental reasons as well as the inability to achieve outcomes within the necessary timetables required to maintain security of the power system. Page 5

6 Electricity Commission Submission Tactical Transmission Projects April 05 The 110 kv transmission systems connect and supply the regional loads from the 220 kv core transmission grid. All existing transmission assets were assumed to be in service at times of system peak load and the transmission capacities assumed were those provided in the relevant Asset Capability Statements. Transmission Security Criteria Commonly, the level of security that a load is supplied with is denoted by (N-k). (N-k) security means that the system is in a secure state with all transmission facilities in service and in a satisfactory state following a forced outage (or contingency) of k number of transmission components, including any connected generators. Presently, the transmission system is designed to maintain supply while meeting N-1 security criterion. This means that the transmission system will operate in a satisfactory state following any single credible contingent event. These standards are consistent with: The Electricity Commission s proposed GRS The rules for system operation under Part C of the EGR s. The single contingencies considered under the N-1 criterion were: loss of a single transmission circuit loss of a single generating unit loss of a single bus section (for new transmission builds only) loss of an interconnecting transformer loss of a single reactive component, e.g. capacitor bank or SVC Additionally, where loads are relatively smaller (i.e. less than 10 MW) and the economic cost of supplying the load with (N-1) security is unjustifiably high, then (N-0) security may be used. Refer to Appendix 2 for the detailed standards. Demand Assumptions Growth in forecast demand changes from region to region. National demand is expected to grow annually on average by 2.3% for the next ten years under the medium growth scenario, and 2.8% and 1.8% under high and low growth scenarios respectively. Presently, demand is measured as the off-take from the grid exit points (GXPs) and does not include demand met by any embedded generation. Embedded generation is assumed to grow at the same rate as demand. These tactical transmission upgrades as set out in this paper are assessed against Transpower s 2005 regional demand forecasts, which are based on the Electricity Commission s 2005 energy forecast figures. It should be noted that these tactical transmission upgrades are required to meet predicted shortfalls in demand over the next 2-3 years therefore the need for tactical transmission upgrades are relatively insensitive to changes in long term demand forecasts. Page 6

7 Electricity Commission Submission Tactical Transmission Projects April 05 Generation Dispatch Assumptions The adequacy of the grid for ensuring supply security is determined taking into account generation available or committed (generation already being constructed) in each region. In a number of regions, local generation is critical to ensuring that demand can be met during times of peak demand. Generation dispatch assumptions were developed by assuming that generation will continue to be available during peak times consistent with historical performance. 3.3 Generic Tactical Transmission Project Types Transmission Line Thermal Upgrades Existing transmission lines have been designed and constructed to operate at a thermal level whereby the conductors and associated equipment can all operate safely and within statutory clearances (for transmission line conductors). Transpower has utilised aerial laser surveying technology to map the spatial details of a number of key transmission lines. This information is then used to develop a programme of remedial works on a number of transmission lines to increase their thermal capacity. This is achieved by increasing the clearance of conductors to ground as well as ensuring that the terminal equipment at each end of the transmission line is upgraded where necessary to accommodate the new required capacity. As a consequence Transpower is able to achieve substantial increases in transmission line thermal capacities for relatively low cost and low implementation risk. Capacitor Bank Installation A number of capacitor bank installation projects have been commissioned or are currently being implemented to provide additional reactive support to critical areas of the network. Voltage stability limitations are relatively commonplace across the New Zealand National Grid and capacitor bank installation provides the least cost means of increasing voltage stability limits and improving local voltage quality. It should be noted that there is a limit to the amount of capacitance that can be connected to the power system. Furthermore, the incremental benefit of capacitor banks in respect of increasing power flows diminishes as the quantity of capacitance connected to the system increases. Stringing Additional Circuits A number of Transpower s existing transmission lines were constructed as double circuit tower lines but only strung with a single circuit which was satisfactory to meet Page 7

8 Electricity Commission Submission Tactical Transmission Projects April 05 demand at that time. Two projects in the upper South Island involve installing the second circuit on the tower lines to complete the ultimate design capacity of the transmission line. As these projects represent a substantive change in the capability of the line, easements are required to be purchased as part of the overall upgrade projects. Installing Additional Conductors (Duplexing) Some of Transpower s existing lines are capable of having an additional set of conductors installed in parallel with the existing conductors. The Roxburgh-Islington line is the only example of this in the suite of projects submitted to the Commission for approval. This will provide a substantial increase in thermal capacity and to a lesser degree improve voltage stability limits. Bussing Circuits The outage of long transmission circuits is often the limiting factor in the voltage stability performance of the grid. The ability to interconnect or bus long lines at a convenient mid-point provides a low cost way of reducing the impact of a line outage and consequently increases the voltage stability limits of the overall system. The following section sets out the specific tactical transmission projects by region, for approval. Page 8

9 Electricity Commission Submission Tactical Transmission Projects April 05 4 North Isthmus Region 4.1 Introduction Existing Transmission System The North Isthmus region covers the transmission system in the upper North Island, north of and including Hepburn Road as illustrated in Figures 4.1 and 4.2. The North Isthmus region is supplied from the south by the 220 kv double circuit Henderson Otahuhu A line. Within the North Isthmus region, Northland is supplied from the south by the 220 kv double circuit Henderson - Marsden line and the 110 kv double circuit Henderson-Maungatapere line. From Maungatapere there is a double circuit 110 kv line to Kensington and a 110 kv double circuit line to Kaikohe which carries on as a 110 kv single circuit line to Kaitaia. There are also two 50 kv single circuit lines from Maungatapere to Dargaville. There are 220/110 kv interconnecting transformers at Henderson, Albany and Marsden. Figure 4-1: North Isthmus Region Figure 4-2: North Isthmus Region Schematic Page 9

10 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum demand for the North Isthmus region in 2004 was 725 MW. This is projected to increase to around 877 MW by 2010 and 1009 MW by Local generation The installed generation capacity in the region is 10 MW of geothermal generation from Ngawha. No new generation is known to be committed in the North Isthmus region for the study period ( ), therefore no new generation has been assumed in the studies. 4.2 Forecast of System Adequacy The key issues that may affect security of supply to the region over the next few years are as follows: Issue 1: Outage of either a 220 kv Henderson-Southdown or Otahuhu-Henderson Circuit Loss of a 220 kv Henderson-Southdown or Henderson-Otahuhu circuit causes thermal overloading of the remaining circuit by Demand will therefore need to be limited at times of system peak to within the ratings of the assets. 4.3 Transmission Projects The transmission projects that address the security issues identified in the Northland region are summarised in Table 4.3-1: The thermal upgrade of Otahuhu-Henderson is required to be commissioned prior to winter 2006 to enable the system to meet the TSS into the North Isthmus and Northland regions and will enable demand to be supplied without curtailment, at times of system peak load. The upgrade provides a substantial increase in capacity and will provide sufficient thermal capacity until approximately Grid Upgrade Project Pre Upgrade Capacity Post Upgrade Capacity Project Budget Commissioning Date Thermal upgrade of 220 kv Otahuhu Henderson circuits 1 & 2. (Addresses issue 1) 695/765 MVA (Sum/Win) 938 /984 MVA (Sum/Win) $2.3 million Apr 2006 Table 4.3-1: Transmission Projects for North Isthmus Region Page 10

11 Electricity Commission Submission Tactical Transmission Projects April 05 5 Auckland Region 5.1 Introduction Existing Transmission System The Auckland region covers the transmission system in the area bordered by and including Bombay in the south and Penrose and Mount Roskill in the north, as illustrated in Figures 5.1 and 5.2. The region is supplied by 220 kv and 110 kv transmission circuits from the south with interconnecting transformers located at Otahuhu and Penrose substations. Figure 5-1: Auckland Region Figure 5-2: Auckland Region Schematic Page 11

12 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum demand for the Auckland region in 2004 was 1,172 MW and is projected to increase to 1,411 MW by 2010 and 1,621 MW by Local generation Installed generation in the region comprises 114 MW of thermal co-generation at Southdown and 395 MW of thermal generation at Otahuhu. No new generation is known to be committed in the Auckland region for the study period ( ). 5.2 Forecast of System Adequacy The key issues that may affect security of supply to the region over the next few years, are as follows: Issue 1: Outage of a 220 kv Otahuhu Penrose Circuit An outage of one of the 220 kv Otahuhu Penrose circuits could overload the other remaining circuit during high demand periods by Issue 2: Outage of either a 220 kv Huntly-Otahuhu 2 or Glenbrook-Huntly Circuit Loss of either the 220 kv Huntly-Otahuhu 2 circuit or Glenbrook-Huntly circuit leads to overloading of the Huntly-Otahuhu 1 circuit when generation at Huntly is high. This may occur as early as 2005 but is more likely to constrain generation dispatch when the new station at Huntly e3p is commissioned in Issue 3: Voltage Instability Loss of a major generating unit (either Huntly or Otahuhu) or the Otahuhu Whakamaru 3 circuit could cause voltage collapse in the Auckland and the North Isthmus region. Voltage stability issues are the limiting factor on power transfer into the Auckland region and investment in reactive support is necessary to meet the TSS and to enable demand in the upper North Island to be supplied without curtailment, at times of system peak load. While there is currently sufficient operating margin with all generators in service, voltage stability limitations may cause issues as early as 2005/06, particularly in summer and under certain generator outage scenarios. It should also be noted that the condition of a number of Transpower s older capacitor installations in the area is such that they are nearing replacement criteria. 5.3 Transmission Projects The transmission projects that address the security issues identified in the Auckland region are summarised in Table Response to Issue 1 - The thermal upgrade of Otahuhu-Penrose is required to be commissioned prior to winter 2007 to meet the TSS into Penrose and the Auckland CBD and will enable demand to be supplied without curtailment, at times of system peak load. Page 12

13 Electricity Commission Submission Tactical Transmission Projects April 05 Response to Issue 2 - The thermal upgrade of Huntly-Otahuhu is required to be commissioned prior to winter 2006 and before the commissioning of Huntly e3p to enable the additional generation to be dispatched from Huntly into the upper North Island. As well as providing energy balance, this generation also assists in managing voltage stability limitations into the upper North Island. Response to Issue 3 - Voltage stability issues are the limiting factor on power transfer into the Auckland region and investment in capacitors at Penrose and Hepburn Rd are the optimal location for new capacitor banks and will be necessary to meet the TSS and to enable demand in the upper North Island to be supplied without curtailment, at times of system peak load. New capacitor banks in the Auckland area are the least cost alternative to increase the existing voltage stability limits into Auckland. Furthermore they provide contingency cover for a number of ageing capacitor bank installations in the region. Grid Upgrade Project Pre Upgrade Capacity Post Upgrade Capacity Project Budget Commissioning Date Thermal upgrade of 220 kv Otahuhu Penrose circuits 5&6 (Addresses Issue 1) 330/370 MVA (Sum/Win) 469 / 492MVA (Sum/Win) $0.7 million 2006 Thermal upgrade of 220 kv Huntly Otahuhu circuit 1 (Addresses Issue 2) 2 x 50 Mvar 110 kv shunt capacitors at Penrose substation (Addresses Issue 3) 1 x 50 Mvar 110 kv shunt capacitor at Hepburn Road sub station (Addresses Issue 3) Thermal upgrade of 110 kv Bombay - Otahuhu circuits 1 & 2 404/492 MVA (Sum/Win) NA 614/671 MVA (Sum/Win) 50 Mvar (1x 50 Mvar is a backup unit for capacitors in Auckland) $1.7 million Completed $2.4 million May 2006 NA 50 Mvar $1.4 million May /77 MVA (Sum/Win) 92/101 MVA (Sum/Win) $0.8 million May 2005 Table 5.3-1: Transmission projects in the Auckland region Page 13

14 Electricity Commission Submission Tactical Transmission Projects April 05 6 Waikato Region 6.1 Introduction Existing Transmission System The Waikato region is the area bordered by and including Whakamaru and Maraetai in the south, and Huntly and Kopu in the north, as illustrated in Figures 6.1 and 6.2. The boundary between the Waikato region and the Bay of Plenty region extends east to include Lichfield. The Waikato regional grid is comprised of 220 kv and 110 kv transmission circuits with interconnecting transformers located at Hamilton. The transmission grid in the region is used for transferring the local generation out of the region as well as to the load centres within the region. While the generation at Huntly (thermal), Whakamaru (hydro), Waipapa (hydro), and Maraetai (hydro) is connected to the 220 kv transmission system, generation at Te Awamutu (co-generation), Karapiro (hydro), Arapuni (hydro) is connected to the 110 kv transmission system. Figure 6-1: Waikato Region Figure 6-2: Waikato Transmission Schematic Page 14

15 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum demand for the Waikato region in 2004 was 544 MW and is projected to increase to around 589 MW by 2010 and 649 MW by Local Generation The installed generation capacity in the region is 1,945 MW, with an available capacity of 1,919 MW. New generation has been confirmed at Huntly (e3p 385 MW by end of 2006) and at Mokai (40 MW by 2006). However, there are a few additional investigations into the possibility of generation, each in the range of 25 MW to 500 MW. As transmission and generation are complementary, these schemes would have an impact on the transmission within the region, and into and out of the region. 6.2 Forecast of System Adequacy The key issue that may affect security of supply to the region over the next few years are as follows: Issue 1: Outage of a 110 kv Hamilton-Waihou Circuit Loss of one 110 kv Hamilton-Waihou circuit overloads the other 110 kv Hamilton Waihou circuit (during summer peak periods). These circuits have caused constraints at peak load times during 2004 and with no local generation, demand was required to be managed off the system. The level of demand management required was forecast to become a more significant in 2005 and would continue to increase year on year. 6.3 Transmission Project The transmission project that address the security issues identified in the Waikato region are summarised in Table 6.3-1: The Hamilton-Waihou project was commissioned to meet the TSS in time to ensure that demand to the Thames Valley and Coromandel could continue to be supplied without curtailment, at times of system peak load. This was commissioned prior to winter and spring peak loads expected in Grid Upgrade Project Pre Upgrade Capacity Post Upgrade Capacity Project Budget Commissioning Date Thermal upgrade of 110 kv Hamilton- Waihou circuits 1 & 2 101/123 MVA (Sum/Win) 154/168 MVA (Sum/Win) $0.72 million Completed Table 6.3-1: Transmission Project for Waikato Region Page 15

16 Electricity Commission Submission Tactical Transmission Projects April 05 7 Bay Of Plenty Region 7.1 Introduction Existing Transmission System The Bay of Plenty region is the area bordered by and including Tarukenga in the west and Wairakei in the south, as illustrated in Figures 7.1 and 7.2. It is supplied by 220 kv, 110 kv and 50 kv transmission circuits with interconnecting transformers located at Tarukenga, Kawerau and Edgecumbe. Figure 7-1: Bay of Plenty Region Figure 7-2: Bay of Plenty Region Schematic Page 16

17 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum demand for the Bay of Plenty region in 2004 was 444 MW and is projected to increase to 510 MW by 2010 and 562 MW by Local generation The total available generation in the Bay of Plenty region roughly balances the load, however, much of it has a low capacity factor and much of it is hydro that is prone to dry year issues. A result of this situation is that there are often neutral power flows into the region, but power flows can substantially change to a large net in-flow during periods of low hydro availability. Therefore, transmission constraints into the region are dependant on generation patterns as well as demand. The embedded generation from the Kaimai Hydro scheme also has an impact on transmission constraints into the Tauranga / Mt Maunganui areas. This generation is injected in to the Tauranga bus. It is a run of river scheme that varies between 14 MW and 38 MW. 14 MW is typically the minimum generation available from the scheme. 7.2 Forecast of System Adequacy The key issues that may affect security of supply to the region over the next few years are as follows: Issue 1: Outage of the 110 kv Mount Maunganui Tarukenga Circuit The outage of the 110 kv Mount Maunganui Tarukenga circuit will overload the 110 kv Tarukenga Tauranga and Poike Tauranga circuits during high demand periods. Demand is forecast to exceed transmission capacity by Issue 2: Outage of the 220 kv Ohakuri Wairakei Circuit At present, through transfer between Whakamaru and Wairakei is constrained by the outage of the Ohakuri-Wairakei circuit. Under this outage, the thermal transfer limit of the Poihipi-Whakamaru section of the Wairakei-Whakamaru circuit will be reached in about 2012/2013 under generation scenarios such as low generation from Whakamaru, Waipapa and Maraetai. 7.3 Transmission Projects The transmission projects that address the system security issues identified in the Bay of Plenty region are summarised in Table Response to Issue 1 -The thermal upgrade of Tauranga Tarukenga is required to meet the TSS into Tauranga and Mount Maunganui regions. This project is targeted to be completed in December 2005 and is necessary to ensure that demand can be supplied securely without curtailment, at times of system peak load. Response to Issue 2 - The upgrade of the Wairakei-Whakamaru-Poihipi line is required to increase the capacity of the central North Island transmission system which is a critical conduit for HVDC and central North Island power transfer to the upper North Island and the Bay of Plenty. Transpower considers that it prudent to complete this work ahead of a number of potential generation projects in the Central Page 17

18 Electricity Commission Submission Tactical Transmission Projects April 05 and Lower North Island which will drive this section of the network into constraint and limit generation dispatch flexibility. Grid Upgrade Project Thermal upgrade of 110 kv Tauranga Tarukenga circuit (Addresses issue 1) Thermal upgrade of the 220 kv Wairakei- Poihipi-Whakamaru circuit 1 (Addresses issue 2) Pre Upgrade Capacity 63/77 MVA (Sum/Win) 239/291 & 289/332 MVA (Sum/Win) Post Upgrade Capacity 76/88 MVA (Sum/Win) 421/449 MVA (Sum/Win) Project Budget Commissioning Date $0.25 million Dec 2005 $1.65 million Completed Table 7.3-1: Transmission Projects for the Bay of Plenty Region Page 18

19 Electricity Commission Submission Tactical Transmission Projects April 05 8 Central North Island Region 8.1 Introduction Existing Transmission System The Central North Island region is the area bordered by and including Mangahao and Mangamaire in the south and Ongarue in the north, as illustrated in Figures 8.1 and 8.2 below. The regional grid consists of 220 kv and 110 kv transmission circuits with interconnecting transformers located at Bunnythorpe. All of the 220 kv circuits form part of the core grid through transmission, with a strong connection to the substations. The 110 kv circuits are predominantly supplied through the 220/110 kv interconnecting transformers at Bunnythorpe, plus low capacity connections to the other regions. Figure 8-1: Central North Island Region Figure 8-2: Central North Island Region Schematic Page 19

20 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum demand for the Central North Island region in 2004 was 325 MW and this is projected to increase to 368 MW by 2010 and 394 MW by Local generation The installed hydro generation capacity in the region is 240 MW from Tokaanu, 120 MW from Rangipo and 26 MW from Mangahao, plus wind generation of 91 MW from Te Apiti and 63 MW from Tararua (embedded). No new generation is known to be committed in the Central North Island region for the study period ( ). However, there are several investigations into the possibility of major new wind farm generation in the region. 8.2 Forecast of System Adequacy The key issues that may affect security of supply to the region over the next few years are as follows: Issue 1: Outage of a 220 kv Tokaanu-Whakamaru Circuit During periods of high HVDC north flow and high Tokaanu generation an outage of one of the Tokaanu-Whakamaru circuits will result in an overload on the other and thus limit the power transfer north. After the Tokaanu-Whakamaru constraint has been alleviated, the Rangipo-Wairakei and Bunnythorpe-Tokaanu circuits will be the limiting circuits for power transmission north, followed by the Bunnythorpe Tangiwai and Tangiwai Rangipo circuits. The precise date at which these circuits become critical constraints is difficult to specify as the power flows are highly dependent on generation flows from the South Island and Taranaki. However these circuits do constrain currently and the increase in intermmittent generation from Manawatu wind farms is likely to increase the time at which these constraints limit the flow of predominantly renewable energy (South Island hydro and North Island wind) from accessing the upper North island market. On this basis, Transpower considers that these constraints should be alleviated from Tokaanu and Rangipo north by 2006 and between Bunnythorpe and Tokaanu by Transmission Projects The following projects to address the security issues in the central North Island are summarised in table 8.3.1: Response to Issue 1 - The response to this Issue requires three projects which involve the thermal upgrading of the transmission lines between Bunnythorpe, Tokaanu and Whakamaru. A substantial amount of work is required to complete these necessary upgrades due to the specific construction of these lines and Transpower does not have a pre-existing right to modify its lines. It is therefore likely to take at least two years to acquire property rights and complete the necessary work within the outage windows available. With the amount of lower North Island wind generation being planned combined with the generally high level of power flows experienced across the central North Island corridor, Transpower considered that it Page 20

21 Electricity Commission Submission Tactical Transmission Projects April 05 was prudent to initiate these projects while there are outage windows available to implement the thermal upgrades. Grid Upgrade Project Pre Upgrade Capacity Post Upgrade Capacity Project Budget Commissioning Date Thermal upgrade of 220 kv Tokaanu- Whakamaru circuits 1&2. 244/281 MVA (Sum/Win) 307/335 MVA (Sum/Win) $6.4 million Apr 2006 Thermal upgrade of Rangipo-Wairakei circuit 1 239/292 MVA (Sum/Win) 364/397 MVA (Sum/Win) $3.2 million Apr 2006 Thermal upgrade of Bunnythorpe-Tokaanu circuits 1&2 202/246 MVA (Sum/Win) 307/335 MVA (Sum/Win) $8.5 million Apr 2008 Table 8.3-1: Transmission Projects for Central North Island Region Page 21

22 Electricity Commission Submission Tactical Transmission Projects April 05 9 Taranaki & Hawkes Bay Regions 9.1 Transmission Projects No tactical transmission projects have been proposed in the Taranaki or Hawkes Bay regions. Page 22

23 Electricity Commission Submission Tactical Transmission Projects April Wellington Region 10.1 Introduction Existing Transmission System The Wellington region covers the transmission system in the lower North Island, bordered by and including Masterton and Paraparaumu in the north, as illustrated in Figures 10.1 and The regional grid consists of 220 kv and 110 kv transmission circuits with 220/110 kv interconnecting transformers located at Haywards and Wilton. The region is predominantly supplied from the HVDC link from the South Island and by four 220 kv circuits from Bunnythorpe substation to the north. Static capacitors and synchronous condensers are installed at the Haywards substation as part of the HVDC operational requirements. Figure 10-1: Wellington Region Figure 10-2: Wellington Region Schematic Page 23

24 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum forecasted demand for the Wellington region in 2004 was 626 MW and is projected to increase to 700 MW by 2010 and 776 MW by Local Generation The installed generation capacity in the region is 3.8 MW (embedded) from Hau Nui wind farm. Hau Nui will be expanded by 5 MW to 8.8 MW. No new generation is known to be committed in the Wellington region for the study period ( ). However, there are several investigations into the possibility of new wind farm generation in the region Forecast of System Adequacy The key issues that may affect security of supply to the region over the next 10 years are as follows: Issue 1: Outage of the 220 kv Bunnythorpe Haywards 3 Circuit An outage on the Bunnythorpe-Linton-Haywards circuit would cause thermal overloading of the Bunnythorpe-Haywards 1 and 2 circuits for certain network generation dispatch schedules. There is currently a HVDC runback scheme installed to prevent overloading of the Bunnythorpe-Haywards 1 and 2 circuits during high HVDC transfer for a tripping of any 220 kv circuit between Bunnythorpe and Haywards. The Bunnythorpe Haywards circuits are the transmission constraint that limits power flow southwards during typical dry years. The timing for these upgrades is dependent on the view of when the next dry year will occur. Transpower considers that these circuits should be upgraded by 2006 such that the system is capable of transferring the maximum capacity southward (including Whirinaki reserve generation) during the next dry year Transmission Project The transmission projects that address the security issues identified in the Wellington region are summarised in Table : Response to Issue 1 - The thermal upgrade of the Bunnythorpe Haywards circuits 1 and 2 is required to meet the TSS during dry years. The implementation of these projects will increase the overall transmission capacity into Wellington and will increase the quantity of North Island generation that is able to be exported to the South Island during dry years. In particular it will substantially improve the ability of the dry year reserve plant at Whirinaki to be dispatched to meet South Island demand. Grid Upgrade Project Pre Upgrade Capacity Post Upgrade Capacity Project Budget Commissioning Date Thermal upgrade of 220 kv Bunnythorpe - Haywards 1&2 circuits 202/246 MVA (Sum/Win) 307/335 MVA (Sum/Win) $4.8 million Apr 2006 Table : Transmission Project for the Wellington Region Page 24

25 Electricity Commission Submission Tactical Transmission Projects April Nelson-Marlborough Region 11.1 Introduction Existing Transmission System The Nelson-Marlborough region is the area bordered by and including Murchison in the south and west, as illustrated in Figures 11.1 and The regional grid consists of 220 kv, 110 kv and 66 kv transmission circuits with interconnecting transformers located at Kikiwa and Stoke. The region is predominantly supplied by two 220 kv circuits between Islington and Kikiwa substations. Figure 11-1: Nelson-Marlborough Region Figure 11-2: Nelson-Marlborough Region Schematic Page 25

26 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum demand for the Nelson/Marlborough region in 2004 was 190 MW. This is projected to increase to around 227 MW by 2010 and 256 MW by Local generation The installed generation capacity in the region is 32 MW from Cobb and 11 MW from Argyle. No new generation is known to be committed in the Nelson-Marlborough Region for the study period ( ). However, there are several investigations into the possibility of major generation in the range of 100 MW 200 MW Forecast of System Adequacy The key issues that may affect security of supply to the region over the next 10 years are as follows: Issue 1: Outage of a 220 kv Islington Kikiwa Circuit The entire Nelson Marlborough region and part of the West Coast is supplied mainly by two single circuit 220 kv lines from Islington to Kikiwa. The outage of one of these circuits is forecast to cause voltage stability limitations on power transfer into the Nelson Marlborough and West Coast regions during high demand periods by Issue 2: Outage of the Blenheim-Stoke or Blenheim-Kikiwa Circuit Blenheim is supplied by two 110 kv circuits. The outage of one of these circuits could cause low voltage at Blenheim at peak load times and overload either the remaining 110 kv circuit or the 220/110 kv interconnecting transformer at Kikiwa also by Transmission Projects The transmission projects that address the security issues identified in the Nelson region are summarised in Table : The range of projects to provide a secure transmission supply into the Nelson and Marlborough regions form part of an integrated plan to maintain security into the region in accordance with the TSS. The primary driver is to establish new transmission lines from Islington to Kikiwa and between Blenheim and Stoke substations. The least cost approach in both of these cases is to utilise existing double-circuit tower lines. In both of these cases Transpower does not have a preexisting right to install the additional circuit and easements will be required to secure property rights to complete the works. Response to Issue 1 - In order to release the entire circuit two side of the Islington - Kikiwa B line for 220 kv transmission it is necessary to replace both the 66 kv Culverden - Waipara circuit, and the 66 kv Islington - Ashley circuit which currently occupy one side of these towers. To do this Culverden and Waipara substations must be supplied from new 220 kv connections to be established at these locations. Page 26

27 Electricity Commission Submission Tactical Transmission Projects April 05 The third circuit between Islington and Kikiwa can then be completed by stringing the remainder of the second side of the existing tower line. Response to Issue 2 - This project is to string the second circuit on the existing 110 kv double circuit towers between Stoke and Blenheim to complete a total of three transmission circuits supplying Blenheim substation. Grid Upgrade Project 40 Mvar capacitor banks at Stoke substation. (Addresses issue 1 in short term) String 220 kv circuit between Islington and Kikiwa utilising existing tower line including easements Establishment of a new 220/33/66 kv supply at Culverden Establishment of a new 220/66 kv interconnection at Waipara String 110 kv circuit to Blenheim utilising existing tower line including easements Notes Pre Upgrade Capacity NA NA NA NA NA Post Upgrade Capacity Increase the power transmission into the region by 30 MW. Increase the power transmission capacity into the region to 320 MW. 2 x 30 MVA transformers 2 x 80 MVA transformers Increase the power transmission capacity into Blenheim to 130 MW. Project Budget Commissioning Date $1.45 million Apr 2005 $32.5 million May 2006 $5.0 million May 2006 $7.2 million May 2006 $20.2 million May 2006 Table : Transmission Projects for the Nelson Marlborough region. 1. See regional plan in Appendix 1 for details on pre and post upgrade capacities into the upper South island. 2. The project budgets for the third circuit between Islington and Kikiwa and Blenheim and Stoke contain substantial provisional sums for foundation work. These total $7.7 million and $4.6 million respectively. The exact extent of foundation work required remains uncertain and will only become clear once the construction phase of the project commences and existing foundations are excavated. Page 27

28 Electricity Commission Submission Tactical Transmission Projects April West Coast Region 12.1 Introduction Existing Transmission System The West Coast region is the area bordered in the north by the Inangahua 110/66kV interconnecting transformer and in the south by Arthur s Pass, as illustrated in Figures 12.1 and 12.2 below. The region is supplied by two 66 kv circuits from the Islington substation via Coleridge and by the interconnecting bank at Inangahua. Static capacitors are installed at Greymouth, Hokitika and within the distribution network to improve the network voltage and voltage stability performance. Figure 12-1: West Coast Region Figure 12-2: West Coast Region Schematic Page 28

29 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum load demand for the West Coast region in 2004 was 43 MW. The demand due to underlying load growth is projected to increase to around 50 MW by 2010 and 53 MW by However, predicted block load increases will increase the projected demand to approximately 65 MW by Local generation There is a small amount of local generation at Kumara (10 MW) and Arnold (3 MW). No new generation is known to be committed in the West Coast Region for the study period ( ). However, there are several investigations into the possibility of major generation in the range of 50 MW 200 MW Forecast of System Adequacy The key issues that may affect security of supply to the region over the next 10 years are as follows: Issue: 1 Outage of a Coleridge-Otira or Dobson-Inangahua Circuit The West Coast is fed from the south by two circuits (considered as a single contingency risk because of the configuration of the circuits) between Coleridge and Otira. The West Coast is fed from the north by a single circuit from Inangahua to Dobson. An outage of the circuits from the north or south will leave the West Coast with limited supply and low voltages. Issue: 2 Outage of either Dobson-Greymouth or Greymouth-Kumara Circuit There is only one circuit between Dobson and Greymouth and between Greymouth and Kumara. An outage of either of these circuits leaves the West Coast fed from either the north or south. In high load periods this results in low voltages and voltage instability. The interconnecting transformer at Inangahua is also overloaded Transmission Projects The transmission projects that address the security issues identified in the West Coast region are summarised in Table : Response to Issues 1 and 2 - Conversion of the existing line between Dobson and Inangahua from 66 kv to 110 kv operation and associated 110/66 kv transformation at Dobson will increase the capacity of supply to the Greymouth-Dobson area and improve voltage stability and quality during line outage conditions. A second circuit is being constructed by Westpower to improve transmission security and capacity into the region. Transpower is required to install a second 110/66 kv interconnector to connect this new line to the existing 66 kv supply system. Page 29

30 Electricity Commission Submission Tactical Transmission Projects April 05 Grid Upgrade Project Convert the Dobson Inangahua circuit from 66 kv operation to 110 kv and a new 110/66 kv interconnecting transformer at Dobson Connection of second Dobson Inangahua 110 kv circuit Second Dobson- Inangahua 110/66 kv interconnecting transformer at Dobson, (Second 110 kv circuit constructed by Westpower) Pre Upgrade Capacity 33/41 MVA (Sum/Win) N Security Post Upgrade Capacity 56/68 MVA (Sum/Win) N security Project Budget Commissioning Date $3.2 million Aug 2005 NA NA 0.26 million Apr MVA $2.7 million Apr 2007 Table : Transmission Projects for the West Coast Region Page 30

31 Electricity Commission Submission Tactical Transmission Projects April Canterbury Region 13.1 Introduction Existing Transmission System The Canterbury region is the area bordered by and including Ashburton in the south, Coleridge and Castle Hill in the west and Kaikoura in the north, as illustrated in Figures 13.1 and The regional grid consists of 220 kv and 66 kv transmission circuits with interconnecting transformers located at Bromley, and Islington. The region is predominantly supplied by four 220 kv circuits between Islington and the Waitaki Valley. Figure 13-1: Canterbury Region Figure 13-2: Canterbury Region Schematic Page 31

32 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum demand forecast for the Canterbury region in 2004 was 700 MW. This is projected to increase to around 852 MW by 2010 and 960 MW by Local generation The installed generation capacity in the region is 45 MW from Coleridge. No new generation is known to be committed in the Canterbury region for the study period ( ) Forecast of System Adequacy The key security issues that may affect security of supply to the region over the next 10 years are as follows: Issue 1: Outage of an Islington-Twizel 220 kv Circuit There are four 220 kv circuits into Islington from the Waitaki Valley, one from Livingston and three from Twizel. If one of the Islington-Twizel circuits is out of service it may cause voltage instability or thermal overloading in the region. The worst single contingency is the loss of Ashburton-Timaru-Twizel circuit. This is forecast to lead to voltage stability problems from 2005 and thermal overloading from Both of these issues will constrain the ability of the transmission system to supply demand to the Canterbury and upper South Island regions. Issue 2: Outage of the Ashley-Islington 66 kv circuit The North Canterbury region is supplied by three 66 kv circuits from Islington, one is terminated at Ashley and the other two at Southbrook. In an Ashley-Islington outage the voltage in the North Canterbury region is low, particularly at the northern Grid Exit Points (Kaikoura, Culverden and Waipara) Transmission Projects The transmission projects that address the security issues identified in the Canterbury region are summarised in Table : Response to issue 1 - Installation of an additional 120 Mvar of capacitors at Islington will ensure that satisfactory voltage stability limits can be maintained and will enable demand to be supplied without curtailment for a further two to three years from 2005 in the Canterbury region and the north of the South Island. Following the installation of capacitors at Islington, bussing the Twizel to Islington circuits at Ashburton to minimise the effect of a line outage condition will further increase the voltage stability limits of the system from 2007/08 out until approximately 2012 depending on demand growth. Substantial thermal upgrading of the existing 220 kv lines to the south of Christchurch is also required to extend the capacity of the core grid to meet the growth in demand in the Canterbury region. This involves four individual projects which have to be scheduled to make sure of outage windows which allow each of the circuits to be taken out in turn to allow the Page 32

33 Electricity Commission Submission Tactical Transmission Projects April 05 up-grading work to be carried out. The most significant project is the duplexing of the Islington-Livingstone 220 kv circuit which will effectively double its thermal capability. The three other projects include: Thermal upgrading of the 220 kv Livingstone to Islington circuit. Thermal upgrading of the 220 kv Twizel to Islington circuit via Tekapo B. Thermal upgrading of the 220 kv Twizel to Islington circuit via Timaru. All of these projects taken together will defer the need for the anticipated augmentation of the Canterbury region at 400 kv. The first project is required to be commissioned prior to winter 2005 to ensure that there is sufficient thermal capacity to transfer power into Christchurch. The remaining projects are required to be commissioned in 2006 and 2007 respectively in order to keep ahead of demand growth. Response to Issue 2 - This issue will be resolved by construction of 220/66 kv injection points at Culverden and Waipara which are included elsewhere as a part of the project to provide a third 220 kv circuit from Islington to Kikiwa and the installation of capacitors at Southbrook substation. Grid Upgrade Project Islington 220 kv capacitor banks to increase voltage stability limits into Canterbury and North Thermal upgrade of 220 kv Islington-Livingstone circuit Thermal upgrade of 220 kv Islington-Tekapo B- Twizel circuit to enable sufficient capacity for Islington Livingston duplexing Thermal upgrade of 220 kv Islington-Timaru- Twizel circuit 1 & 2 to enable sufficient capacity for Islington Livingston duplexing Southbrook 66 kv capacitor bank to increase voltage stability limits Duplexing of Islington- Livingstone 220 kv circuit. Bussing of Christchurch Twizel Line A at Ashburton substation Pre Upgrade Capacity Post Upgrade Capacity Project Budget NA 2 x 60 Mvar $3.1 million 202/247 MVA (Sum/Win) 404/493 (Sum/Win) 478/583 (Sum/Win) 307/335 MVA (Sum/Win) 523/591 MVA (Sum/Win) 619/699 MVA (Sum/Win) $1.6 million $3.8 million $3.8 million NA 38 Mvar $1.2 million 202/246 (Sum/Win) Commissioning Date Apr 2005 Apr 2005 Dec 2005 Dec 2005 Dec /492 MVA $ 25.8 million May 2007 NA NA $7.3 million May 2008 Table : Transmission Projects for the Canterbury Region Page 33

34 Electricity Commission Submission Tactical Transmission Projects April South Canterbury Region 14.1 Introduction Existing Transmission System The South Canterbury region covers the transmission system in the area bordered by and including Tekapo A and Temuka in the north and Livingstone and Oamaru in the south, as illustrated in Figures 14.1 and The region is supplied by 220 kv and 110 kv transmission circuits with interconnecting transformers at Timaru and Waitaki. The 110 kv network is normally operated split at Studholme creating two radial feeds: the Timaru 220/110 kv interconnecting transformer banks supplying Albury, Tekapo A and Temuka; the Waitaki 220/110 kv interconnecting transformer banks supplying Studholme and Oamaru. Figure 14-1: South Canterbury Region Figure 14-2: South Canterbury Region Schematic Page 34

35 Electricity Commission Submission Tactical Transmission Projects April 05 Demand Forecast The maximum demand for the South Canterbury region in 2004 was 91 MW and this is projected to increase to around 128 MW by 2010 and 134 MW by Local Generation This region contributes a major portion of the generation in the South Island feeding the 220 kv network from the Tekapo B (160 MW), Ohau (688 MW) and Waitaki Valley (865 MW) generation stations. A small amount of local generation at Tekapo A (25 MW) and embedded generation at Opuha (7 MW) feeds the 110 kv network supplied from the Timaru 220/110 kv interconnecting banks. No new generation is known to be committed in the South Canterbury region for the period Forecast of System Adequacy The key issues that may affect security of supply to the region over the next 10 years are as follows: Issue 1: Outage of a Temuka-Timaru 110 kv circuit Loss of the one Temuka-Timaru 110kV circuit can cause overloading of the remaining circuit Transmission Project The transmission project that address the security issues identified in the South Canterbury region are summarised in Table : Response to Issue 1 - The thermal upgrade of the Temuka Timaru circuits is required to supply demand to Temuka which is forecast to exceed the firm capacity of the transmission line by winter Grid Upgrade Project Thermal upgrade of 110 kv Temuka- Timaru circuits 1 & 2 Pre Upgrade Capacity 48/56 MVA (Sum/Win) Post Upgrade Capacity 69/76 MVA (Sum/Win) Project Budget Commissioning Date $0.5 million Aug 2005 Table Transmission Projects for South Canterbury Region 15 Otago Southland Region 15.1 Introduction Existing Transmission System The Otago-Southland region covers the grid in the southern part of the South Island, bordered by and including Naseby and Cromwell in the north, as illustrated in Figures 15.1 and The regional grid consists of 220 kv and 110 kv transmission circuits with interconnecting transformers located at Cromwell, Halfway Bush, Roxburgh and Invercargill. Page 35

36 Electricity Commission Submission Tactical Transmission Projects April 05 Figure 15-1: Otago-Southland Region Figure 15-2: Otago-Southland Region Schematic Demand Forecast The maximum demand forecast for the Otago-Southland region in 2004 was 1,012 MW. This is projected to increase to around 1,051 MW by 2010 and 1,087 MW by This is assuming no increase in the base load at Tiwai (610 MW) or other block load increases in Southland. Local generation The installed generation capacity in the region is 710 MW from Manapouri, 320 MW from Roxburgh, 432 MW from Clyde and 72 MW from Waipori. Page 36

37 Electricity Commission Submission Tactical Transmission Projects April 05 No new generation is known to be committed in the Otago-Southland Region for the study period ( ). However, there are several investigations into the possibility of major generation in the Southland area. As transmission and generation are complementary, all these schemes would have an impact on transmission in the region Forecast of System Adequacy The key issues that may affect security of supply to the region over the next 10 years are as follows: Issue 1: Outage of an Invercargill-Roxburgh 220 kv Circuit The transfer within the Southland region, between the Clutha Valley and the large load at Tiwai, is predominantly via the 220 kv Invercargill-Roxburgh circuits. In times of low Manapouri generation the remaining circuit may overload during an Invercargill-Roxburgh outage. The security of supply is generally managed by constraining on the generation at Manapouri. The timing of this issue is related to hydrological conditions in the lower South Island and the constraint is therefore likely to become an issue again during the next dry year. As with the dry year constraints into Wellington, Transpower considers that the timing of the project should be 2005 such that this risk is mitigated prior to the next dry year Transmission Project The transmission projects that address the system adequacy issues identified in the Otago Southland region are summarised in Table : Response to issue 1 - The issue of possible thermal overloading of an Invercargill to Roxburgh line is most efficiently resolved by upgrading the thermal capability of both circuits of this line. Grid Upgrade Project 220 kv Invercargill- Roxburgh 1&2 circuits thermal upgrade Pre Upgrade Capacity 2 x 241/295 MVA (Sum/Win) Post Upgrade Capacity 2 x 347/382 MVA (Sum/Win) Project Budget Commissioning Date $3.8 million Apr 2005 Table : Transmission Projects for Otago-Southland Region Page 37

38 APPENDIX 1: NELSON MARLBOROUGH REGIONAL PLAN Page i

39 Nelson-Marlborough Regional Transmission Plan Updated: 19/04/05 NELSON-MARLBOROUGH REGIONAL TRANSMISSION PLAN 2004 April, 2005 C:\WINNT\Profiles\carmodyt\Desktop\appendix-a.doc Page- 1 -

40 Nelson-Marlborough Regional Transmission Plan Updated: 19/04/05 Executive Summary The System Security Forecast and other planning studies undertaken by Transpower have identified a number of security issues for this region over the next ten years. These largely revolve around voltage stability, thermal capacity, supply security and supply capacity. If these issues are not addressed by investment in transmission or generation, then demand curtailment may be required at times of peak demand. For its part as the transmission owner, Transpower is initiating the following projects now: Project name Completion Date Cost Estimate Stoke capacitor bank March 2005 $1.5m 220 kv Islington Kikiwa third circuit May 2006 $32.5m Culverden 220 kv connection May 2006 $5m Waipara 220 kv connection May 2006 $7m 110kV third circuit to Blenheim May 2006 $20.2m Summary of Committed projects in the Nelson / Marlborough region As well as these projects, Transpower is also considering the need for the following future projects. These projects are possible only at this stage, but provide an indication of the type of work that might be required in the future dependant on demand and generation growth in the region: Project name Completion Date Cost Estimate 220/110 kv second transformer at Stoke June 2007 $ 4 m 220 kv bus security upgrade at Kikiwa 2008 $ 8 m Summary of Recommended projects in the Nelson / Marlborough region C:\WINNT\Profiles\carmodyt\Desktop\appendix-a.doc Page- 2 -

41 Nelson-Marlborough Regional Transmission Plan Updated: 19/04/05 Project name 110/33 kv supply transformer capacity upgrade at Blenheim Additional 220/33 kv supply transformer at Stoke Kikiwa Waimangaroa new circuit Possible Completion Date 2013 Not known Within 5 years Summary of Possible projects in the Nelson / Marlborough region C:\WINNT\Profiles\carmodyt\Desktop\appendix-a.doc Page- 3 -

42 Nelson-Marlborough Regional Transmission Plan Updated: 19/04/05 1. Introduction 1.1 Existing Transmission System The Nelson-Marlborough region is the area bordered by and including Murchison in the south and west as shown in Figure 1.1. The regional grid consists of 220 kv, 110 kv and 66 kv transmission circuits with interconnecting transformers located at Kikiwa and Stoke. The region is predominantly supplied by two 220 kv circuits between Islington and Kikiwa substations. There is also a small amount of local generation at Cobb (32 MW) and Argyle (11 MW). Reactive power support in the Nelson-Marlborough region is located at Stoke and Blenheim substations in the form of static capacitor banks and a synchronous condenser. Reactive power support at Stoke consists of 20 Mvar static capacitors and a -5/+10 Mvar synchronous condenser. At Blenheim, 20.4 Mvar static capacitors provide the reactive power support. The regional network used in the analysis is the network as at 30 June Figure 1.1: Nelson - Marlborough Region C:\WINNT\Profiles\carmodyt\Desktop\appendix-a.doc Page- 4 -