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Third Strategic Optioneering Report 1

September 2013

SP Mid Wales Connections Third Strategic

Optioneering Report

EXECUTIVE SUMMARYThe Mid Wales Wind Farm Connections project is a major electrical infrastructure development project, involving several wind farm developers, SPM (the local Distribution Network Operator – SP Manweb) and National Grid (the Transmission Network Operator). SPM and National Grid are progressing separate elements of the project and, in due course, following detailed pre-application consultation will be submitting separate applications for Development Consent to the Planning Inspectorate under the Planning Act 2008.

An Initial Strategic Optioneering Report (SOR) was published in March 2011, which presented SPM’s initial system option studies. Pre-application consultation is being carried out and SPM is constantly reviewing the system option studies in order to address issues arising during that process.

A Second SOR reviewed the position and served to harmonise the options around the then contracted Mid Wales connections and the network required to serve that position, ensuring compliance with SPM’s Licence obligations.

This Second SOR supported National Grid’s proposal for the extension of their 400 kV Transmission system into mid Wales, and provided for a harmonised and efficient local 132 kV collector network utilising National Grid’s then proposed hub locations at either Cefn Coch or Abermule. Subsequent to the publication of the Second SOR, National Grid selected Cefn Coch as the preferred location for the 400/132 kV substation hub.

During the past 20 years, over 100 MW of wind generation has been connected to the SPM distribution network in mid Wales. SPM is currently contracted to connect 720.6 MW of wind generation within the TAN 8 Strategic Search Areas (SSAs) B and C. The options presented in this report address those connection offers.

As the capacity of the existing network in the area is already largely utilised by the existing connected wind generation, the connection in mid Wales of SPM’s and National Grid’s contracted position will require new National Grid transmission infrastructure in the form of an additional 400 kV circuit and new 400/132 kV substation.

The wind farms vary in size from about 25 MW up to 160 MW and are dispersed over a wide area and so to collect electricity from the wind farms and transport it to the transmission system requires a combination of 33 kV and 132 kV connections. New 33 kV circuits have a typical maximum capability of about 25 MVA (depending on length), whereas single circuit wood pole 132 kV line capacities range from 89 MVA to 176 MVA in capacity. Single circuit 132 kV steel tower lines can transport up to 245 MVA, whilst double circuit tower lines can transport up to 490 MVA.

This previous SOR showed that multiple 132 kV circuit only solutions have significantly higher losses and costs when compared to a 132 kV/400 kV solution. Furthermore, a 132 kV/400 kV transmission system is considered the most efficient, coordinated and environmental design to connect the contracted wind generation in mid Wales, as is the case for bulk power transfer throughout the UK. Accordingly, 132 kV only solutions are not considered further in this report.

The evaluation set out in this Third SOR has reconsidered options to connect to Cefn Coch, taking into account developments since the previous SOR. All except two options considered are viable (i.e. they are capable of accommodating at least the contracted level of generation). However, Option NC1R is the preferred option as it meets the level of contracted generation with better use of the existing system assets, which results in both lower capital costs and losses. In addition, it does not provide capacity over and above the level required.

Based upon the evaluation criteria within this report, a preference for the NC1R option is therefore recommended. This option is considered to be the most optimal, efficient and environmentally endurable way to connect the contracted wind generation in mid Wales.

Third Strategic Optioneering Report

Contents:

SECTION 1.0: INTRODUCTION

SECTION 2.0: STAGE TWO CONSULTATION OUTCOMES

SECTION 3.0: NEEDS AND DESIGN PROCESS

SECTION 4.0: BUSINESS PROCESS

SECTION 5.0: OPTIONS EVALUATION

SECTION 6.0: CONCLUSIONS

SECTION 7.0: ABBREVIATIONS

Appendices:

OPTIONS CONSIDERED IN THE ASSESSMENT PROCESS


1.0 INTRODUCTION

Purpose1.1. This report is a development of the Second Strategic Optioneering Report (the Second SOR), which was

prepared in March 2012, and published when SP Manweb plc (under the name of SP Energy Networks) announced its preferred route corridors in July 2012. The March 2012 report outlined a number of network options and identified NC1 as the recommended design. The Second SOR noted that SP Manweb would continue to review options which meet the identified need case, i.e. the level of contracted generation.

1.2. This report presents options based on the previous NC1, NC2 and NC3 options, taking into account the various events that have occurred since the publication of the Second SOR March 2012. Details of the recommended option, NC1, were presented in the Second SOR in Table A8 and Figure A8, and these are copied in the next Section of this report (see Section 2.2). The main difference between the three options is that whereas NC1 has one 132 kV wood pole circuit between areas SSA B and SSA C (along corridor CC2). NC2 has two 132 kV wood pole circuits (one each along corridors CC1 and CC2), and NC3 has a 132 kV double circuit steel tower line along corridor CC2.

1.3. Relevant events that have occurred since the Second SOR was published include:

The publication of the Preferred Route Corridors Report of April 2012; Objections to the proposed 132 kV circuit between Llandinam and Welshpool for

connection of the Llandinam windfarm re-powering; The granting of planning consent for the proposed Legacy to Oswestry third 132 kV circuit; Feedback from the Stage Two Consultation.

1.4. Following the structure adopted in previous reports, this report first refers to the conclusions of the Second SOR of March 2012 report and accompanying reports published at the same time, and then addresses the need for new connections in mid Wales. As with the previous report, the process of option development and assessment is described and an updated range of options is described and evaluated.


2.0 STAGE TWO CONSULTATION OUTCOMES Planning Context2.1. The Second SOR March 2012 referred to the Welsh Government’s Planning Guidance Technical Advice

Note 8 (TAN 8), which was published in July 2005, and which identifies seven Strategic Search Areas (SSAs) for the development of wind energy in Wales. The SOR explained the background to TAN 8 and also that the SP Mid Wales Connections Project includes reference to the electrical infrastructure requirements for three of these SSAs: Area B (Carno North), Area C (Newtown South) and Area D (Nant-y-Moch). TAN 8 remains relevant policy and since 2005 further renewable energy policy guidance has been issued by the Welsh Government which advises on avoiding environmental impacts and providing benefits to local communities.

Regulations and Legal Requirements2.2. The Second SOR also referred to the regulatory and statutory duties that SP Manweb must comply with

in operating the network in its licensed area. These are referred to below, in this extract from the Second SOR March 2012.

EXTRACT FROM SECOND SOR MARCH 20122.6 SPEN has a statutory duty to offer terms to connect new generating stations to its distribution

system. The form which these connections might take will depend on a number of factors including the location, capacity and timing of new generating stations. In particular it should be noted that wind farms are often remote from the main centres of electricity demand and the existing distribution network. In order to connect this additional generation, reinforcement of the distribution system, including uprating and reconductoring existing lines, new overhead lines, new underground cables and new or extended substations may be required. Because of the interconnected nature and topology of the existing SPEN distribution system, system reinforcement or enhancement works may be required some distance away from the new generating stations which are to be connected.

2.7 At privatisation, and as required by its distribution licence, SPEN and the other UK DNOs implemented the Distribution Code, which is designed to permit the development, maintenance and operation of an efficient, co¬ordinated and economical system for the distribution of electricity, to facilitate competition in the generation and supply of electricity and to promote the security and efficiency of the power system as a whole. This reflects SPEN’s statutory duties under the Electricity Act 1989. It does this by providing a clear technical basis for its requirements for suitable performance from electrical equipment connected to the distribution system, and by specifying clear levels of expected performance from the distribution system on which the design of other parties’ equipment may be based or reviewed. By application of these standards, material damage to other parties’ equipment, resulting from credible events in the development, maintenance and operation of the distribution system, may be avoided. Additionally, the technical interface between SPEN and National Grid is governed by the Grid Code, whilst the commercial interface is dictated by the Connection and Use of System Code (CUSC).

2.8 In terms of the relevant legislation, Section 9(2) of the Electricity Act 1989 requires SPEN:

(a) “to develop and maintain an efficient, co-ordinated and economical system of electricity transmission; and

(b) to facilitate competition in the supply and generation of electricity.”

2.9 Section 38 and Schedule 9 of the Electricity Act requires SPEN, when formulating proposals for new lines and other works:

“(a) shall have regard to the desirability of preserving natural beauty, of conserving flora, fauna, and geological or physiographical features of special interest and of protecting sites, buildings and objects of architectural, historic or archaeological interest; and

(b) shall do what he reasonably can to mitigate any effect which the proposals would have on the natural beauty of the countryside or on any such flora, fauna, features, sites, buildings or objects”.

SP Mid Wales Connections Project8

2.3. The Second SOR March 2012 concluded that a combined transmission and distribution design with a supergrid substation at Cefn Coch was the preferred solution for the connection of the mid Wales wind farms. Having considered a number of distribution options, the Second SOR then recommended NC1 as the preferred option. This option consisted of: single and double circuit 132 kV overhead lines in TAN8 SSA B north; single circuit 132 kV overhead lines in SSA B south and SSA C; and a single circuit 132 kV overhead line between SSA B and SSA C. This design was outlined in Table A8 and illustrated in Figure A8 of the Second SOR, and followed the route corridor options of BNC1, BSC and CC2. Table A8 and Figure A8 from the Second SOR are copied below.

2.4. These conclusions of the Second SOR March 2012 then fed into the Preferred Route Corridors Report April 2012 which identified the preferred route corridors for the SP Mid Wales Connections Project as BNC1, BSC and CC1.

TABLE A8 FROM THE SECOND SOR MARCH 2012


Table A8 Scheme: Mid Wales

Option Reference Option ‘NC1’ Option Title Connect to new NG substation at Cefn Coch

Scope of Works Construct new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from a new NGT hub substation located at Cefn Coch to the north of SSA B (~8 km);

Construct two new HDWP lines (176 MVA summer rating) from a new NGT hub substation located at Cefn Coch to:

1. the south of SSA B (~5 km) 2. SSA C (~20 km)

Construct Local 132 kV hub and HDWP collector network to wind farms in respective SSAs

Evaluation Criteria Issues Economy Estimated 132 kV circuit costs: £42m;

Overall system losses lower than option ’NA1’ and ‘NA2’. Park

Discount System Compliance

System compliant;

Capacity to connect currently contracted generation; Opportunity to integrate Mid Wales hub with existing SPEN

infrastructure (both demand and generation). Park Discount

Deliverability

132 kV circuit km’s shorter than option ’NA1’ and ‘NA2’;

Minimal use of 132 kV L7 Tower lines; Route corridor options to NG Hub available;

Integration of Llandinam into SSA C at some additional cost. Park

Discount Environmental

Minimises 132 kV circuit lengths over longer distances (and therefore associated environmental effects) and makes use of existing topography and landscapes associated with the locations of the wind farms where possible. Largely avoids concatenation of overhead lines across open valley..

Park Discount

Recommendation: Take option forward.

A viable option and the lowest cost (excluding NG costs).


FIGURE A8 FROM THE SECOND SOR MARCH 2012


3.0 NEED AND DESIGN PROCESS3.1. Chapters 3 and 4 in the Second SOR March 2012 dealt with the need for new infrastructure and the

considerations taken into account in terms of the design process for new infrastructure. This section of this report updates these two areas where necessary.

NEED EXISTING NETWORK3.2. The Second SOR March 2012 set out the existing network and for the purposes of this report, Figure 2

from the 2012 report is included again below, with the addition of the, now consented, third 132 kV circuit between Legacy and Oswestry.

3.3. The 33 kV and 11 kV networks have been omitted from the above Figure for clarity. Depending upon the size of the wind farm, generation may be connected, under the Mid Wales Connection Project, at 132 kV, 33 kV or 11 kV; however, the amount of contracted generation to be connected far exceeds the capability of lower voltage networks.

PLANNED NETWORK3.4. The proposed third 132 kV circuit from Legacy to Oswestry was promoted in 2007, objected to by two

relevant local authorities in 2009, and the subject of a public inquiry in November 2012. Prior to the inquiry in July 2012 one of the local authorities, Shropshire Council, decided to withdraw its objections to the scheme and the other, Wrexham Council, decided to withdraw some of its objections.

3.5. The decision was made in May 2013 to grant consent for this third 132 kV circuit between Legacy to Oswestry, which will provide necessary reinforcement and provide supply security for the Legacy to Oswestry group.

3.6. No work further is required on the distribution network south of Oswestry as the existing 132 kV (Oswestry to Newtown and Oswestry to Welshpool) and 33 kV circuits provide sufficient capacity to meet the levels of network security as specified in Engineering Recommendation P2/6.


CONNECTION AGREEMENTS3.7. As of 1 March 2012, there were 756.3 MW of proposed generation contracted with SP Manweb in mid

Wales. Since then, one wind farm developer has withdrawn from their connection agreement, with other schemes making small changes to the levels of proposed generation. Table 1 shows the updated (as of 1 April 2013) levels of proposed generation.

Table 1: Mid Wales Wind Farms – status and capacities at 1 April 20131

Wind Farm SSA Area Num C a p a c i t y (MW) Contracted Connection?

Dyfnant Forest B (Nth) 1 78 YESRhyd Ddu/Mynydd Waun Fawr B (Nth) 2 99 YES

Llanbrynmair South B (Nth) 3 90 YES (transferred from a direct connection to NGET)

Carnedd Wen B (Nth) 4 150 YES (transferred from a direct connection to NGET)

Carno III B (Sth) 6 48 YESEsgair Cwmowen 10 47.5 NOEstyniad (Llaithddu) C 7 74.4 YESLlanbadarn Fynydd C 8 61.2 YESNeuadd Goch C 9 30 YES

Llandinam re-powering C 11 90 YES (to the existing SPM network)

Bryngydfa C 12 30 NO Bryn Blaen 15 27 NOMynydd-y-Gwynt 13 81 NO

Moel Fferm/Nant-y-Moch D 14 160 Contracted directly with NGET

TotalsContracted with SP Manweb[1] 720.6Contracted with National Grid 160Received connection offer from SP Manweb 155.5Possible future, known to SP Manweb 185.5Contracted with Central Networks 30

3.8. As of 1 April 2013 the total level of contracted generation (including Llandinam re-powering) is 720.6 MW, a decrease of 35.7 MW from the level reported in the Second SOR. This change has no impact on the current mid Wales transmission/distribution design, and the above contracted position is the level of generation on which the design and review of the options referred to below is based.

3.9. As previously stated in the Second SOR, the connection of this proposed level of generation will require significant new infrastructure to be established. The Second SOR report went on to examine the connection options available to meet the contracted capacities.

DESIGN PROCESS3.10. The Second SOR March 2012 identified five key issues affecting the design of distribution networks:

thermal conditions fault levels voltage levels security of supply losses

1 Including Llandinam re-powering


3.11. As stated in the Second SOR (Chapter 4) these issues related to overhead line design, and as referred to in that report, the proposed circuits would comprise mostly of the Heavy Duty Wood Pole design (300 sq mm Upas AAAC, 176 MVA summer rating at 75°C) and in the case of a section of the preferred BNC1 corridor, the L7 tower line design (500 sq mm Rubus AAAC, 245 MVA summer rating).

THERMAL CONDITIONS3.12. Overhead line conductors are designed for a certain operating temperature, and safe clearances between

the conductors and the ground/structures are based on this assumption. The thermal rating translates into standard seasonal current ratings. Overloading causes conductors to overheat which will increase the sag of the conductors and reduce safety clearances. Operating at a temperature greater than their design temperature could also lead to a reduction in conductor strength.

3.13. Most existing 132 kV overhead line conductors within the SP Manweb network are ACSR 175 sq mm Lynx, which has a summer rating of 389 amps (89 MVA) at 50°C. New or replacement conductors are 200 sq mm AAAC Poplar, which has a higher summer rating of 542 amps (124 MVA) at 75°C. Poplar conductors can be accommodated on either heavy duty wood pole (HDWP) or steel lattice tower construction. In certain circumstances, it is possible to place 300 sq mm AAAC Upas conductors (770 amps, 176 MVA) on new HDWP, although this has a tendency to reduce the span lengths between poles, introducing more poles per km. L4 construction steel towers can accommodate two 132 kV circuits with 300 sq mm conductors (i.e. rating of 176 MVA per circuit), whilst L7 construction steel towers can accommodate double circuits with 500 sq mm AAAC Rubus conductors, with a summer rating of 245 MVA (1071 amps per circuit).

FAULT LEVELS3.14. The SP Manweb 132 kV design fault level limit is 20 kA (4570 MVA) for three phase faults and 25 kA (5700

MVA) for single phase faults. A high fault level improves the quality of supply by reducing the magnitude of short-term voltage fluctuations, but the fault level must also be kept within the capability of the plant and switchgear, otherwise catastrophic equipment failure can result during a network fault. Therefore, the design approach is generally to keep the fault levels as high as possible, whilst also maintaining sufficient design margins relative to the plant rating.

VOLTAGE LEVELS3.15. The statutory voltage level limits at 132 kV are ±10%. This allows for a voltage gradient along the length

of a 132 kV circuit. The voltage gradient is directly related to the current flowing in the conductor and it is primarily this voltage gradient that limits the practical length of a 132 kV circuit. In fact, on a power network, particularly at the higher voltages levels, voltage drop is caused by reactive power (MVAr) flow to a much greater degree than active power (MW) flow.

3.16. Since most elements of a power system absorb reactive power, operation of a power network requires the input of reactive power, and this is mainly provided by the generators. The UK Grid Code[2] specifies the reactive power import/export levels that generators are required to be capable of delivering. Although the exact requirements depend on the size and type of generation, typically a generator must be able to deliver/absorb reactive power down to a power factor of 0.95[3]. It is the reactive power flowing in a circuit that limits the length of line that can be used without exceeding statutory voltage limits. For example the graph below shows how the voltage along a 132 kV circuit varies with distance. This example is for one circuit of a 132 kV L7 tower line at its maximum transfer capacity of 281 MVA over the range of power factors, and it shows that voltage drop/rise becomes a significant issue for a circuit longer that about 45 km.

2 http://www.nationalgrid.com/uk/Electricity/Codes/gridcode/3 Powerfactorisdefinedastheratioofrealpower(MW)toapparentpower(MVA),i.e.PF=MW/MVA.SinceMVA2=MW2+MVAr2,

at0.95powerfactorthereactivepower(MVAr)isaboutonethirdthemagnitudeoftherealpower(MW).


3.17. A larger power transfer will therefore require either multiple 132 kV circuits or a higher voltage circuit (which will have a lower effective impedance) to be utilised. The plot below shows the voltage drop for one circuit of a 400 kV L12 tower line carrying 700 MVA. This clearly shows that the circuit ‘reach’ is much longer for a 400kV circuit compared to a 132kV circuit without voltage compliance issues being experienced.

3.18. If there is an instantaneous change in power flow (for example as a result of a wind farm disconnecting itself from the network or a circuit or transformer being switched out) this will cause an instantaneous step change in voltage. Plant and equipment can be sensitive to sudden changes in voltage, therefore events that cause instantaneous changes in power flow are avoided as much as possible (for example, the wind farm ramps up and down its export in a ‘slow’ and controlled manner). Therefore, voltage step change is considered as part of the design process.


SECURITY OF SUPPLY3.19. Distribution networks in the UK are generally designed according to the security standard defined within

the ENA Engineering Recommendation P2/6 ‘Security of Supply’. The basic principle of P2/6 is based on the need to provide greater levels of supply security as the size of the group load increases. Network security is created by a combination of plant redundancy and load transfer capability. In other words, for large load groups, it should be possible to maintain supplies to customers following an outage of any single item of plant or to restore supplies by transferring the load into another load group by network switching.

3.20. However, the standard does not apply to individual (large) customers if:

(a) the customer requests a security different from that defined in P2/6 (either better or worse) and

(b) it is possible to provide the level of security that the customer requests.

LOSSES3.21. Losses occur in the circuits and transformers used within the distribution network as a result of the power

flowing through them. One of the dominant loss mechanisms is Ohmic losses, which are proportional to the circuit resistance, R, and the square of the current (I2). These are generally referred to as the ‘I squared R’ losses. The ‘R’ in any circuit is proportional to its length, therefore, the longer the circuit, the greater the losses. One way to reduce the losses for a given circuit length is to operate at a higher voltage. For example, for a given power transfer, if the voltage is increased by a factor of three (say, from 132 kV to 400 kV), the current is reduced by a factor of three and the I2R losses are reduced by a factor of nine for the same conductor size and power transfer.

3.22. As distance and the amount of energy increase it becomes more efficient to use higher voltage circuits. It is for these fundamental reasons that the transmission of large amounts of power is achieved with 275 kV / 400 kV infrastructure, rather than 132 kV or lower. This was illustrated earlier in 3.17.

UNDERGROUNDING 3.23. In terms of its approach on undergrounding, SP Manweb has a licence obligation to develop an efficient,

coordinated and economical system. An overhead line solution typically facilitates compliance with these obligations. Overhead line solutions are more economical than cable alternatives to develop, as well as providing shorter return to service times under fault conditions.

3.24. SP Manweb accepts however that the justification for undergrounding should be considered on a case by case basis. These considerations would take into account cost and system design requirements, and the specific factors involved in each particular proposal, such as areas of high technical environmental constraint and areas of the highest recognised amenity value, in accordance with the requirements of the National Policy Statement for Electricity Networks Infrastructure (EN-5).

3.25. For the SP Mid Wales Connections Project, cost estimates for wholly undergrounded options range between approximately £150m to £500m[ ]. Depending upon route conditions, the cost of an underground 132 kV circuit can typically be between £1m and £1.5m per km.

3.26. It must be recognised that the use of cable circuits within a power system introduces additional reactive power (VAr) within the network. This is due to the additional capacitance of cable circuits compared to that of an equivalent overhead line.

3.27. The long circuit routes involved with Mid Wales further exacerbate these capacitance and additional reactive power issues. To address these, additional reactive power compensation equipment is required. This increases cost, inefficiencies and footprint of the network solution. Furthermore, the introduction of high levels of reactive power into a system limits or reduces the level of maximum power transfer through a network.

3.28. In terms of high amenity value, the approach in this project has been to develop a routeing methodology with the objective of avoiding areas of highest environmental value where possible. This has resulted in route corridor options, as presented in the consultation, considered to be environmentally viable for the purposes of routeing overhead lines.

3.29. On the basis of the above, SP Manweb’s current view is that the test for undergrounding set out in National Policy Statement for Electricity Networks Infrastructure (EN-5) will not be met. As part of the application to be submitted for the SP Mid Wales Connections Project, an assessment will be made against the relevant policy set out in EN-5.

3.30. SP Manweb has not ruled out using some cable sections within the options presented. Currently, less than 10% of the SP Manweb 132 kV circuits within Wales are cable and so when comparing the costs of the initial options, a nominal amount of cable has been assumed. However, it is currently anticipated that, with careful selection of National Grid substation location in relation to outgoing circuit routes, the total circuit lengths and the amount of 132 kV cable required will be minimal.

3.31. The extent of cabling required will be guided by the outcome of more detailed environmental assessments in respect of the line design.


4.0 BUSINESS PROCESS

Background to Connection Applications4.1. As mentioned in the Second SOR, the trigger for the start of the strategic optioneering process was the

concurrent connection applications made by several developers of ‘larger’ wind farms schemes directly to National Grid early in 2007. In June 2007 National Grid held a workshop with representatives from SP Manweb, developers and other interested parties to discuss options to determine the commitment from new wind farm developers for transmission capacity in Mid Wales, TAN 8 Strategic Search Areas B, C and D.

4.2. The British Wind Energy Association (now known as RenewableUK) notified their members that there was an opportunity for developers to become part of a strategic infrastructure development project for the provision of new wind farm connections in Mid Wales.

4.3. As a result, SP Manweb co-ordinated the applications from several developers of wind farms who made concurrent applications for connection to the NGET transmission network via a new SP Manweb ‘mid Wales’ distribution network.

4.4. To date, the SP Manweb contracted capacity (as of April 2013) is 720.6 MW. Since the Second SOR, SP Manweb has made three connection offers within mid Wales totalling a further 155.5 MW of wind generation. The options however presented in this report address those connection offers only currently contracted for and accepted.

4.5. National Grid continues to undertake detailed optioneering to consider and refine the substation location and necessary associated 400 kV connection. These studies confirm the need for a new 400 kV connection from a 400 kV/132 kV substation. The location of this 400kV hub substation will be in the Cefn Coch area.

4.6. Studies carried out by National Grid continue to propose to connect to the Legacy-Ironbridge 400 kV circuit north of Shrewsbury (at Lower Frankton). The options presented in this report take this into account (further information can be found within the National Grid optioneering report).

4.7. The optioneering exercise is a continuous, ongoing process, driven by the generation connection enquires and resulting accepted connection offers. Key assumptions include:

the design of the generators being in accordance with the connection applications received (or as subsequently amended);

the contracted position (i.e. accepted connection offers); the need to maintain the appropriate level of security of supply; and need to establish a economic and efficient design to meet contracted position, whilst

ensuring future connections do not inhibit its delivery.


5.0 OPTIONS EVALUATION

Background5.1. In response to changed circumstances since completing the previous report in 2012, SP Manweb has

reviewed the options presented in the Second SOR. In the Appendix, the Table ‘Options Considered’ summarises the present situation. Since the level of contracted generation has changed very little, all of the ‘132 kV only’ options remain non-viable. Also, since National Grid has now chosen Cefn Coch as the location for the 400/132 kV substation, the options to connect to Abermule are no longer a possibility.

5.2. The remaining alternative viable options: NC1, NC2 and NC3; of which the recommended option to provide a connection for SP Manweb’s contracted mid Wales generation was NC1, are considered further in this report.

5.3. Having had regard to the findings of the Routeing Phase Two Report March 2012 and the Stage One Feedback Report March 2012, the Preferred Route Corridors Report April 2012 concluded that the preferred corridors were BNC1, BSC and CC1. The latter corridor differs from the conclusion of the Second SOR March 2012 report, which selected the CC2 option, and switches the connection to SSA C from that as shown in Appendix A8 of the Second SOR (the NC1 Option) to the more westerly corridor option as represented by CC1 in the Preferred Route Corridors Report April 2012. This is shown in the Appendix to this report in Table A1 and Figure A1 (the NC1R Option).

5.4. However, the Secretary of State’s decision in May 2013 to grant consent for the proposed Oswestry-Legacy third circuit means that, once operational, the area to the south of Oswestry in mid Wales does not require the reinforcement outlined in the Second SOR March 2012 report, which was proposed by integrating the transmission hub and the wind farm generation via the new SP Mid Wales connections into the existing networks. This means disregarding the I-NC1 option, since it is no longer justified to integrate, as was shown in Appendix A13 of the Second SOR.

5.5. Stage Two Consultation ran from July 2012 to April 2013, and Stage 2A Consultation from May 2013 to July 2013. These both followed the announcement of the preferred route corridors and the revised project to connect contracted generation only. This resulted in feedback that highlighted the concerns related to the proposed network design, given Powys County Council’s decisions in March 2012 and October 2012 to object to four of the wind farms which are part of the contracted SP Manweb connection scheme in mid Wales.

5.6. In October 2012, Powys County Council also objected to the proposed Llandinam to Welshpool 132 kV connection. The implication of this decision is taken into account in reviewing Options NC2 and NC3, which were factored into the Second SOR in order to accommodate future development. In this Third SOR they have been amended as NC2R-1, NC2R-2, NC2R-3, NC2R-4, NC2R-5, NC3R-1 and NC3R 2 respectively in order to accommodate the proposed Llandinam connection to Welshpool.

Options5.7. In evaluating the options, due regard has been given to the key criteria of developing and maintaining

an “efficient, co-ordinated and economical system of electricity transmission” as well as Schedule 9 Electricity Act 1989 environmental factors.

5.8. For the purposes of strategic optioneering, the cost estimates for individual options for contracted schemes are based on unit costs for the key elements of the option. This is sufficient to allow a broad order of relative costs to be established and compared for the options, as necessary at the strategic level, and is not intended to provide an accurate cost for each option which can only be obtained at the more detailed design stage.

5.9. Issues of system compliance and deliverability were addressed by SP Manweb’s internal System Design and Asset Engineering Departments, whilst environmental issues were advised by our internal Environmental Department and external landscape architect consultants.

5.10. Additional information on individual options is provided in the Appendix, along with diagrammatic representations.


OPTION NC1R: CONNECT TO NEW NG SUBSTATION AT CEFN COCH (FIGURE A1)5.11. This option assumes that NG will build a new Supergrid substation near Cefn Coch through which all

currently contracted Mid Wales wind farms, except for the Llandinam re-powering connection (which is proposed to connect into the local distribution network via a 132 kV line to Welshpool), will export their generation.

5.12. Corridor BNC: Connection from the substation to the wind farm areas to the north of SSA B would be via about 2 km of new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from the new NGT hub substation located at Cefn Coch. From this, the wind farms would be connected via four new HDWP lines (176 MVA summer rating) totalling about 20 km in length.

5.13. Corridors BSC and CC1: A further two new HDWP lines (176 MVA summer rating) are also required from the new NGT hub substation, located at Cefn Coch, towards the south of SSA B (~10 km) and SSA C (~35 km) – one HDWP line in corridor BSC and one HDWP line in corridor CC1.

5.14. This arrangement provides sufficient capacity to connect the currently contracted generation, and some future capacity; possibly up to about 30 MW which would be subject to operational constraints. Further generation connections would most likely require additional 132 kV circuits to the hub.

5.15. This option minimises the use of L7 Tower lines which would only be located in the BNC corridor and likely to be no more than 2 km in length, the majority of the 132 kV lines being HDWP. It has the lowest 132 kV cost to provide a connection to the contracted levels of generation. This is therefore a viable option which is able to accommodate all the contracted generation and provide capacity for some future generation. A consideration as to which of the eight options is preferred is given in the conclusions section of this document.

OPTION NC2R-1: CONNECT TO NEW NG SUBSTATION AT CEFN COCH (FIGURE A2)5.16. This option assumes that NG will build a new Supergrid substation near Cefn Coch through which currently

contracted Mid Wales wind farms and the Llandinam re-powering connection will export their generation (i.e. this option assumes that the proposed 132 kV line from Llandinam to Welshpool that is currently at Inquiry does not get consent).

5.17. Corridor BNC: Connection from the substation to the wind farm areas to the north of SSA B would be via about 2 km of new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from the new NGT hub substation located at Cefn Coch. From this, the wind farms would be connected via four new HDWP lines (176 MVA summer rating) totalling about 20 km in length. In effect, BNC would remain unchanged compared to NC1R.

5.18. Corridor BSC: About 10 km of new HDWP line (176 MVA summer rating) would also be required to the south of SSA B from the new NGT hub substation located at Cefn Coch. In effect, BSC would remain unchanged compared to NC1R.

5.19. Corridors CC1 and CC2: Two HDWP lines (176 MVA summer rating) would also be required from the new NGT hub substation, located at Cefn Coch to SSA C (~35 km and ~30 km). This is different from NC1R, which assumes only one HDWP line in corridor CC1. In this option, there would be two HDWP lines, one in each corridor.

5.20. This arrangement provides sufficient capacity to connect the currently contracted generation whilst facilitating future generation of the order of up to 100 MW.

5.21. This option minimises the use of L7 Tower lines which would only be located in the BNC corridor and likely to be no more than 2 km in length, the majority of the 132 kV lines being HDWP. Although the 132 kV circuit costs are similar to NC1R, it does not make use of existing assets and requires additional infrastructure at Cefn Coch. It also will result in greater network losses. This is viable option, in that it can accommodate the contracted generation; but it is not preferred to NC1R unless the Llandinam to Welshpool 132 kV does not get consent. A consideration as to which of the eight options is preferred is given in the conclusions section of this document.




5.23. Corridor BNC: Connection from the substation to the wind farm areas to the north of SSA B would be via about 2 km of new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from the new NGT hub substation located at Cefn Coch. From this, the wind farms would be connected via four new HDWP lines (176 MVA summer rating) totalling about 20 km in length. In effect, BNC would remain unchanged compared to NC1R and NC2R-1.

5.24. Corridor BSC: About 10 km of new HDWP line (176 MVA summer rating) would also be required to the south of SSA B from the new NGT hub substation located at Cefn Coch. In effect, BSC would remain unchanged compared to NC1R and NC2R-1.

5.25. Corridor CC1: Two HDWP lines (176 MVA summer rating) would also be required from the new NGT hub substation, located at Cefn Coch, to SSA C (~35 km each). This is different from NC1R, which assumes only one HDWP line in corridor CC1, and also from NC2R-1, which assumes one HDWP line in each corridor, CC1 and CC2. In this option, there would be two HDWP lines in corridor CC1 only.


5.27. This option minimises the use of L7 Tower lines which would only be located in the BNC corridor and likely to be no more than 2 km in length, the majority of the 132 kV lines being HDWP. Although the 132 kV circuit costs are similar to NC1R, it does not make use of existing assets and requires additional infrastructure at Cefn Coch. It also will result in greater network losses.

5.28. This is viable option, in that it can accommodate the contracted generation; but it is not preferred to NC1R. NC2R-1 would be preferable compared to NC2R 2, since the total route length of HWDP line is slightly less, and it avoids having two circuits in the one corridor. A consideration as to which of the eight options is preferred is given in the conclusions section of this document.



5.30. Corridor BNC: Connection from the substation to the wind farm areas to the north of SSA B would be via about 2 km of new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from the new NGT hub substation located at Cefn Coch. From this, the wind farms would be connected via four new HDWP lines (176 MVA summer rating) totalling about 20 km in length. In effect, BNC would remain unchanged compared to all the previous options.

5.31. Corridor BSC: About 10 km of new HDWP line (176 MVA summer rating) would also be required to the south of SSA B from the new NGT hub substation located at Cefn Coch. In effect, BSC would remain unchanged compared to all the previous options.

5.32. Corridor CC2: Two HDWP lines (176 MVA summer rating) would also be required from the new NGT hub substation, located at Cefn Coch, to SSA C (~30 km each). This is different from any of the previous options. In this option, there would be two HDWP lines in corridor CC2 and none in CC1.


5.34. This option minimises the use of L7 Tower lines which would only be located in the BNC corridor and likely to be no more than 2 km in length, the majority of the 132 kV lines being HDWP. Although the 132 kV circuit costs are similar to NC1R, it does not make use of existing assets and requires additional infrastructure at Cefn Coch. It also will result in greater network losses.


5.35. This is viable option, in that it can accommodate the contracted generation; but it is not preferred to NC1R. NC2R-1 would be preferable compared to NC2R 3, since it avoids having two circuits in the one corridor. A consideration as to which of the eight options is preferred is given in the conclusions section of this document.



5.37. Corridor BNC: Connection from the substation to the wind farm areas to the north of SSA B would be via about 2 km of new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from a new NGT hub substation located at Cefn Coch. From this, the wind farms would be connected via four new HDWP lines (176 MVA summer rating) totalling about 20 km in length. In effect, BNC would remain unchanged compared to all the previous options.

5.38. Corridor BSC: About 10 km of new HDWP line (176 MVA summer rating) would also be required to the south of SSA B from the new NGT hub substation, located at Cefn Coch. In effect, BSC would remain unchanged compared to all the previous options.

5.39. Corridor CC1: One HDWP line (176 MVA summer rating) would also be required from the new NGT hub substation, located at Cefn Coch to SSA C (~35 km). This is similar to NC1R, which also assumes only one HDWP line in corridor CC1, but this option assumes that the proposed 132 kV line from Llandinam to Welshpool does not get consent. In this option, there would be one HDWP line from SSA C.

5.40. This arrangement is not system compliant as it does not provide sufficient capacity to connect the currently contracted generation (including the Llandinam re-powering) within SSA C. In addition it also fails to make use of existing network capacity and does not facilitate any future generation.

5.41. This is not a viable option in that it cannot accommodate the contracted generation. A consideration as to which of the options is preferred is given in the conclusions section of this document.



5.43. Corridor BNC: Connection from the substation to the wind farm areas to the north of SSA B would be via about 2 km of new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from the new NGT hub substation located at Cefn Coch. From this, the wind farms would be connected via four new HDWP lines (176 MVA summer rating) totalling about 20 km in length. In effect, BNC would remain unchanged compared to all the previous options.

5.44. Corridor BSC: About 10 km of new HDWP line (176 MVA summer rating) would also be required to the south of SSA B from the new NGT hub substation located at Cefn Coch. In effect, BSC would remain unchanged compared to all the previous options.

5.45. Corridor CC2: One HDWP line (176 MVA summer rating) would also be required from the new NGT hub substation, located at Cefn Coch to SSA C (~30 km). This is similar to NC1R, which also assumes only one HDWP line (but in corridor CC1). This option assumes that the proposed 132 kV line from Llandinam to Welshpool does not get consent. In this option, there would be one HDWP line from SSA C.

5.46. This arrangement is not system compliant as it does not provide sufficient capacity to connect the currently contracted generation within SSA C. In addition it also fails to make use of existing network capacity and does not facilitate any future generation.

5.47. This is not a viable option in that it cannot accommodate the contracted generation. A consideration as to which of the options is preferred is given in the conclusions section of this document.


OPTION NC3R-1: CONNECT TO NEW NG SUBSTATION AT CEFN COCH (FIGURE A7)5.48. This option assumes that NG will build a new Supergrid substation near Cefn Coch through which all

currently contracted Mid Wales wind farms and the Llandinam re-powering connection will export their generation (i.e. this option assumes that the proposed 132kV line from Llandinam to Welshpool that is currently at Inquiry does not get consent).


5.50. Corridor BSC: About 10 km of new HDWP line (176 MVA summer rating) would also be required to the south of SSA B from the new NGT hub substation, located at Cefn Coch. In effect, BSC would remain unchanged compared to all the previous options.

5.51. Corridor CC1: Connection from the substation to the wind farm areas would be via a new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from a new NGT hub substation located at Cefn Coch to SSA C (~35 km). The route of the line would follow route corridor CC1. This is different from NC1R, which assumes only one HDWP line in corridor CC1. In this option, there would be an L7 tower line instead of a single HDWP (NC1R, NC2R-4 and NC2R-5) or two HDWP lines (NC2R-1, NC2R-2 and NC2R-3).

5.52. This arrangement provides sufficient capacity to connect the currently contracted generation including the Llandinam re-powering connection. It would also facilitate further generation in and around SSA C in excess of that provided by any of the NC1R and NC2R Options, of the order of up to 240 MW above the currently contracted level.

5.53. This option does not minimise the use of L7 Tower Lines, requiring about 35 km more than the NC1R, NC2R-1, NC2R-2 and NC2R-3 options, and as such would have worse environmental impact than these options. It provides an excess of capacity, about 140 MW more than Options, NC2R-1, NC2R-2 and NC2R-3. Although this is a viable option, in that it can accommodate the contracted generation, it provides more capacity than is required, and is more expensive than each of these other four options. In addition it fails to make use of existing network capacity. A consideration as to which of the eight options is preferred is given in the conclusions section of this document.

OPTION NC3R-2: CONNECT TO NEW NG SUBSTATION AT CEFN COCH (FIGURE A8)5.54. This option assumes that NG will build a new Supergrid substation near Cefn Coch through which all

currently contracted Mid Wales wind farms and the Llandinam re-powering connection will export their generation (i.e. this option assumes that the proposed 132 kV line from Llandinam to Welshpool that is currently at Inquiry does not get consent).


5.56. Corridor BSC: About 10 km of new HDWP line (176 MVA summer rating) would also be required to the south of SSA B from the new NGT hub substation, located at Cefn Coch. In effect, BSC would remain unchanged compared to all previous options.

5.57. Corridor CC2: Connection from the substation to the wind farm areas would be via a new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from a new NGT hub substation located at Cefn Coch to SSA C (~30 km). The route of the line would follow route corridor CC2. This is different from NC1R, which assumes one HDWP line in corridor CC1. In this option, there would be an L7 tower line instead of a single HDWP (NC1R, NC2R-4 and NC2R-5)) or two HDWP lines (NC2R-1, NC2R-2 and NC2R-3) and it would be located in corridor CC2 not CC1.

5.58. This arrangement provides sufficient capacity to connect the currently contracted generation including the Llandinam re-powering connection. It would also facilitate further generation in and around SSA C in excess of that provided by any of the NC1R and NC2R Options, of the order of up to 240 MW above the currently contracted level.


5.59. This option does not minimise the use of L7 Tower Lines requiring about 30 km more than the NC1R, NC2R-1, NC2R-2 and NC2R-3 options, and as such would have worse environmental impact than these options. It also provides an excess of capacity, about 140 MW more than Options NC2R-1, NC2R-2 and NC2R-3. Although this is a viable option, in that it can accommodate the contracted generation, it provides more capacity than is required, and is more expensive than each of these other four options. In addition it fails to make use of existing network capacity. A consideration as to which of the eight options is preferred is given in the conclusions section of this document.


6.0 CONCLUSIONS6.1. The Initial Strategic Optioneering Report (March 2011) made various assumptions regarding contracted

generation connections and future developments for Mid Wales as at March 2011. The Second Strategic Optioneering Report (Second SOR, March 2012) reviewed this position and served to harmonise the options around the contracted Mid Wales connections and the network required to serve this contracted position, ensuring compliance with SP Manweb’s Licence obligations.

6.2. The Second SOR supported National Grid’s proposal for the extension of their 400 kV Transmission system into mid Wales, and provided for a harmonised and efficient local 132 kV collector network utilising National Grid’s proposed hub locations at either Cefn Coch or Abermule. National Grid has now chosen Cefn Coch as the preferred hub location, and therefore going forward the Abermule options are no longer under consideration.

6.3. The contracted level of generation has changed very little since the Second SOR. As such the ‘132 kV only’ options considered in the Second SOR remain non-viable.

6.4. In this Third SOR a summary of the options evaluated further is provided in the Appendix. As with the previous optioneering reports, the evaluation within this report supports the ‘NC’ options as being the most appropriate network solutions to provide a connection for the current contracted position for Mid Wales. The options presented take into account early routing option investigations, but detailed route corridor studies will need to be undertaken.

6.5. The ‘NC’ options are considered to be the ones which best meet SP Manweb’s statutory obligations. They take into account the current contracted position whilst further considering the required evolution and natural progression of the design should further generation be contracted and connected to the Mid Wales hub. This represents an efficient and harmonised network design philosophy across the voltage levels.

6.6. Of the eight options considered in this SOR, option NC1R is the preferred option going forward. This option accommodates all the SP Manweb contracted generation for mid Wales with very little excess capacity. The design is able to accommodate some additional generation beyond the present contracted levels.

6.7. As a result of the network capacity within NC1R being highly utilised, up to ~95% by the contracted generation, NC1R represents an economic and efficient network and design. It is the least cost solution to connect the contracted mid Wales generation with a minimal amount of distribution network infrastructure required.

6.8. Option NC1R also makes efficient use of the existing capacity of the SP Manweb distribution network from the connection of Llandinam re-powering into Welshpool. As such no new/additional capacity at Cefn Coch would be required to accommodate Llandinam re-powering.

6.9. Option NC1R has the benefit of increasing the effective SGT capacity at Legacy as the Llandinam re-powering generation connection into Welshpool would offset demand within the group and reduce the local distribution network losses. None of the other options provide for this.

6.10. Options NC2R-1, NC2R-2, NC2R-3, NC2R-4 and NC2R-5 connect the current contracted mid Wales generation (including Llandinam re-powering), to the NGT hub at Cefn Coch. However, unlike Option NC1R, these options fail to make use of the existing distribution assets and available local capacity and so require additional infrastructure at Cefn Coch (132kV Bay and SGT) to accommodate the additional generation at Llandinam.

6.11. Options NC2R-1, NC2R-2 and NC2R-3 provide for unnecessary over capacity of the circuits to the Cefn Coch hub and are more expensive compared with the recommended option NC1R.

6.12. Options NC2R-4 and NC2R-5 do not provide sufficient capacity to connect all the currently contracted generation (including the Llandinam re-powering) within SSA C compared to the recommended option NC1R. Even if the generation to be connected were lower, they would not be preferred because they do not make use of existing network capacity and are therefore more expensive.

6.13. Rather than accommodating the Llandinam re-powering generation within the existing SP Manweb distribution network, as provided for by NC1R, Options NC2R-1, NC2R-2 and NC2R-3 will have greater network losses as a result of the Llandinam re-powering generation being coupled to the transmission hub at Cefn Coch and the 400 kV network.


6.14. NC3R-1 and NC3R-2 serve to connect the current contracted mid Wales generation (including Llandinam re-powering), to the NGT hub at Cefn Coch. Both options however utilise significantly more L7 tower line compared to the recommended option NC1R. This significant increase in L7 towers represents an additional environmental impact.

6.15. Both NC3R-1 and NC3R-2 options also provide for an unnecessary overcapacity (over 70% more) for the SP Manweb contracted mid Wales generation compared to the preferred and recommended Option NC1R which provides for a more efficient utilisation of capacity.

6.16. Options NC3R-1 and NC3R-2 would also trigger, depending on the level of generation connected, a requirement for almost twice the number of SGTs at the NGT hub at Cefn Coch due to the number of circuits. This will increase the substation infrastructure required compared to the recommended Option NC1R.

6.17. Options NC3R-1 and NC3R-2 are also more expensive than the preferred and recommended Option NC1R, and do not make use of existing network capacity.

6.18. Should the Llandinam to Welshpool 132 kV line not get consent, then, considering the NC2R options, NC2R-1 is preferred to all the others. However, the disadvantages of Option NC2R-1 against the preferred and recommended NC1R option remain valid.

6.19. Neither NC3R-1 nor NC3R-2 is preferred to the recommended Option NC1R for the reasons outlined above.

6.20. The evaluation has confirmed that, except for NC2R-4 and NC2R 5, all the ‘NC’ options provide an appropriate distribution network. The recommended option going forward is NC1R. This is because NC1R provides for the following which the other options fail to do:

Accommodates the present level of contracted generation without unnecessarily exceeding the required capacity for the generation it serves to connect

Is the least cost solution to connect the contracted mid Wales generation with a minimal amount of distribution network infrastructure required

Makes efficient use of the existing SP Manweb distribution network capacity, and provides for an effective increased SGT capacity at Legacy, from the connection of Llandinam re-powering into Welshpool

Provides for the lowest network losses Has the minimal infrastructure required to connect the contracted level of mid Wales

generation to the NGT hub at Cefn Coch.

6.21. NC1R is therefore the recommended option going forward. The Route Corridor Studies will be undertaken on this basis.


7.0 ABBREVIATIONSAAAC All Aluminium Alloy Conductor

ACSR Aluminium Conductor Steel Reinforced

BSP Bulk Supply Point

CUSC Connection and Use of System Code

DGIM Distributed Generation Incentive Mechanism

DNO Distribution Network Operator

ENA Energy Networks Association

GSP Grid Supply Point

GW Gigawatt (one thousand megawatts or 109 watts)

HDWP Heavy Duty Wood Pole

kA Kiloamp (one thousand amps)

km Kilometre

kV Kilovolt (one thousand volts)

MVA Mega Volt Amp (one million volt amps)

MVAr Mega Volt Amp reactive (one million volt amps reactive)

MW Megawatt (one million watts or 106 watts)

MWh Megawatt-hour

NG National Grid

NGET National Grid Electricity Transmission plc

SPEN ScottishPower Energy Networks

SPM ScottishPower Manweb plc

SP Manweb ScottishPower Manweb plc

SSA Strategic Search Area

SGT SuperGrid Transformer

sq mm Square millimetre

TAN Technical Advice Note

TW Terawatt (one million megawatts or 1012 watts)

TWh Terawatt-hour

WG Welsh Government (formally the Welsh Assembly Government, WAG)

Wh A unit of energy measurement (1 Wh=3600 joules)

XLPE Cross-linked Polyethylene


APPENDIX – OPTIONS CONSIDERED IN THE ASSESSMENT PROCESS

Second SOR Third SOR

Option Recommendation Consideration Comments

DN Not viable, discounted

Not required No material change in circumstances

CEN Not viable, discounted


UEN Not viable, discounted


UL1 Not viable, discounted


UL2 Not viable, discounted


EW1 Not viable, discounted


EW2 Not viable, discounted


NC1 Viable, take forward Required Reconsidered as Option NC1R taking into account changes since second SOR

NC2 Viable, take forward Required Reconsidered as Option NC2R taking into account changes since second SOR

NC3 Viable, take forward Required Reconsidered as Options NC3R-1 and NC3R-2 taking into account changes since second SOR

NA1 Viable, take forward Not required NG has rejected Abermule as the hub location

NA2 Viable, take forward Not required NG has rejected Abermule as the hub location

I-NC1 Viable, take forward Not required Supply security will now be assured by the third Legacy to Oswestry 132 kV circuit


Summary of Options Evaluated in this SOROption Description Additional Comments Option Status Summary

NC1R Connect to new NG substation at Cefn Coch, one circuit between SSAs B and C

Construct local collector network using new 132 kV double circuit L7 tower line and HDWP lines from the new NGT hub substation at Cefn Coch to the north of SSA B. Construct new HDWP lines from Cefn Coch to the south of SSA B and to SSA C (along corridor CC1)

Taken forward.A viable option and the lowest cost (excluding NG costs).The preferred option which meets the contracted generation level whilst providing some excess capacity.Makes best use of the existing network capacity and has the lowest cost of losses.

NC2R-1 Connect to new NG substation at Cefn Coch two circuits between SSAs B and C

As NC1R but with a second new HDWP line from new NGT hub substation at Cefn Coch to SSA C (along corridor CC2). This line is an alternative to the Llandinam to Welshpool 132 kV circuit shown in NC1R.

A viable option which incorporates Llandinam re-powering.Less preferable to NC1R because of additional environmental impact and does not make use of the existing 132 kV system assets. It also provides somewhat more capacity including additional substation equipment (bay and SGT) than is required, and is more expensive.

NC2R-2 Connect to new NG substation at Cefn Coch two circuits between SSAs B and C (CC1 Route)

As NC1R but with a second new HDWP line from new NGT hub substation at Cefn Coch to SSA C (along corridor CC1). This line is an alternative to the Llandinam to Welshpool 132 kV circuit shown in NC1R. Both circuits from SSA C to the new NGT hub substation are in the same CC1 corridor.


NC2R-3 Connect to new NG substation at Cefn Coch two circuits between SSAs B and C (CC2 Route)

As NC2R-2 but with both circuits from SSA C to the new NGT hub substation in the same CC2 corridor. As before, one of the lines is an alternative to the Llandinam to Welshpool 132 kV circuit shown in NC1R.


NC2R-4 Connect to new NG substation at Cefn Coch one circuit between SSAs B and C (CC1 route)

As NC1R but with without Llandinam to Welshpool 132 kV circuit (as shown in NC1R). For this arrangement, only one circuit from SSA C connects to new NGT hub substation at Cefn Coch using corridor CC1.

Not a viable option as fails to accommodate the currently contracted generation.Does not make use of existing 132 kV system assets.

NC2R-5 Connect to new NG substation at Cefn Coch one circuit between SSAs B and C (CC2 route)

As NC1R but with without Llandinam to Welshpool 132 kV circuit (as shown in NC1R). For this arrangement, only one circuit from SSA C connects to new NGT hub substation at Cefn Coch but utilises corridor CC2 rather than CC1.

Not a viable option as fails to accommodate the currently contracted generation. Does not make use of existing 132 kV system assets.

NC3R-1 Connect to new NG substation at Cefn Coch double circuit between SSAs B and C

As NC1R but with an L7 tower line from the Cefn Coch hub to SSA C instead of the HDWP line (along corridor CC1).

A viable option facilitating future generation connections.Less preferable to other options since it requires much more L7 tower line than NC1R, and provides much more capacity including additional substation equipment (bay and SGT) than is required, and is more expensive.

NC3R-2 Connect to new NG substation at Cefn Coch double circuit between SSAs B and C

As NC3R-1 but with the L7 tower line from the Cefn Coch hub to SSA C routed along corridor CC2 rather then corridor CC1.

A viable option facilitating future generation connections.Less preferable to other options since it requires much more L7 tower line than NC1R (though less than NC3R-1), and provides much more capacity including additional substation equipment (bay and SGT) than is required, and is more expensive.


Table A1

Scheme: Mid Wales

Option Reference Option NC1R Option Title Connect to new NG substation at Cefn Coch

Scope of Works Construct new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from a new NGT hub substation located at Cefn Coch to the north of SSA B (~2 km);


1. the south of SSA B (~10 km)

2. SSA C (~35 km)

Construct Local 132 kV hub and HDWP collector network to wind farms in respective SSAs (circa 20 km of HDWP line).

Evaluation Criteria Issues Economy Estimated 132 kV circuit costs: £44m;

Park

Discount

System Compliance System compliant;

Capacity to connect currently contracted generation;

Opportunity to integrate Mid Wales hub with existing SP Manweb infrastructure (both demand and generation). Park

Discount

Deliverability Minimal use of 132 kV L7 Tower lines;

Route corridor options to NG Hub available;

Park

Discount

Environmental Minimises 132 kV circuit lengths over longer distances (and therefore associated environmental effects) and makes use of existing topography and landscapes associated with the locations of the wind farms where possible. Largely avoids concatenation of overhead lines across open valley.

Park

Discount

Recommendation: Take option forward.

A viable option and the lowest cost (excluding NG costs).

The preferred option which meets the contracted generation level.


Table A2

Scheme: Mid Wales

Option Reference Option NC2R-1 Option Title Connect to new NG substation at Cefn Coch

Scope of Works Construct a new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from a new NGT hub substation located at Cefn Coch to the north of SSA B (~2 km);

Construct three new HDWP lines (176 MVA summer rating) from a new NGT hub substation located at Cefn Coch to:


2. SSA C (~30 km)

3. SSA C (~35 km)


Evaluation Criteria Issues Economical Estimated 132 kV circuit costs: £53m;

Park

Discount



Park

Discount



The second circuit between SSA B and SSA C facilitates the integration of Llandinam into SSA C.

Park

Discount

Environmental As with NC1R, however likely additional environmental effects associated with construction and operation of the additional 132kV circuit from SSA C to Cefn Coch. Park

Discount

Recommendation: A viable option which incorporates Llandinam re-powering.

Less preferable to NC1R because of additional environmental impact and does not make use of the existing 132 kV system assets. It also provides somewhat more capacity including additional substation equipment (bay and SGT) than is required, and is more expensive.


Table A3

Scheme: Mid Wales





2. SSA C (2 x ~35 km) – CC1



Park

Discount



Park

Discount




Park

Discount

Environmental As with NC1R and NC2R-1, however, likely additional environmental effects associated with construction and operation of 132kV circuits from SSA C to Cefn Coch, especially as in same CC1 corridor.

Park

Discount



For this scenario, NC2R-1 would be preferable compared to NC2R-2


Table A4

Scheme: Mid Wales





2. SSA C (2 x ~30 km) – CC2



Park

Discount



Park

Discount




Park

Discount

Environmental As with NC1R, NC2R-1 and NC2R-2 however, likely additional environmental effects associated with construction and operation of 132 kV circuits from SSA C to Cefn Coch, especially as in same CC2 corridor.

Park

Discount



For this scenario, NC2R-1 would be preferable compared to NC2R-3.


Table A5

Scheme: Mid Wales





2. SSA C (~35 km) – CC1



Park

Discount

System Compliance Non system compliance;

Insufficient capacity to connect currently contracted generation;

Park

Discount



Single circuit between SSA B and SSA C does not accommodate the integration of Llandinam into SSA C.

Park

Discount

Environmental As per NC1R.

Park

Discount

Recommendation: Not a viable option as cannot incorporate Llandinam re-powering.


Table A6

Scheme: Mid Wales





2. SSA C (~30 km) – CC2



Park

Discount

System Compliance Non system compliance;

Insufficient capacity to connect currently contracted generation;

Park

Discount



Single circuit between SSA B and SSA C does not accommodate the integration of Llandinam into SSA C.

Park

Discount

Environmental As per NC1R.

Park

Discount

Recommendation: Not a viable option as cannot incorporate Llandinam re-powering.


Table A7

Scheme: Mid Wales


Scope of Works Construct two new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from a new NGT hub substation located at Cefn Coch to:

1. the north of SSA B (~2 km)

2. SSA C (~35 km)

Construct new HDWP line (176 MVA summer rating) from a new NGT hub substation located at Cefn Coch to the south of SSA B (~10 km);



Park

Discount



Park

Discount

Deliverability Route corridor options to NG Hub available;

Integration of Llandinam into SSA C. Park

Discount

Environmental Overall offers shorter circuits lengths, however additional environmental effect arises due to a 35 km steel tower line.

Park

Discount

Recommendation: A viable option facilitating both future generation connections.

However this option is not recommended since it requires much more L7 tower line than NC1R (resulting in greater environment effect), provides more capacity than is required, and is more expensive than either NC1R .


Table A8

Scheme: Mid Wales


Scope of Works Construct two new 132 kV double circuit L7 tower line using Rubus conductor (2 x 245 MVA summer rating) from a new NGT hub substation located at Cefn Coch to:

1. the north of SSA B (~2 km)

2. SSA C (~30 km)

Construct new HDWP line (176 MVA summer rating) from a new NGT hub substation located at Cefn Coch to the south of SSA B (~10 km);



Park

Discount



Park

Discount

Deliverability Route corridor options to NG Hub available;

Integration of Llandinam into SSA C. Park

Discount

Environmental Overall offers shorter circuits lengths, however additional environmental effect arises due to 30 km steel tower line across open valley. Park

Discount

Recommendation: A viable option facilitating both future generation connections.

However this option is not recommended since it requires much more L7 tower line than NC1R (though less than NC3R-1) resulting in greater environmental effect. It provides more capacity than is required, and is more expensive than either NC1R.

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