electricity act 1989 (sections 36, 37, 62(3) & schedule 8

Electricity Act 1989 (Sections 36, 37, 62(3) & Schedule 8) Town and

Country Planning Act 1990 (Section 90) and the Electricity Generating

Stations and Overhead Lines (Inquiries Procedure)(England and Wales)

Rules 2007

Application by SP Manweb PLC, dated 2 December 2009 for consent

under Section 37 of the Electricity Act 1989 to install and keep installed a

132kV overhead electric line connection from the proposed Llandinam

Wind Farm to Welshpool Substation (the “Application”)

Proof of Evidence

Of

Eric Paalman

On

Engineering Project Design

SPM/ENGINEERING/POE/PAALMAN/003A

1 QUALIFICATIONS AND EXPERIENCE 1

2 SCOPE OF EVIDENCE 2

3 THE PROPOSED LLANDINAM SCHEME 3

4 UNDERGROUNDING 14

5 SELECTION OF WOOD POLE DESIGN (CONSIDERATION OF TRIDENT AND HDWP TECHNOLOGY) 16

6 TECHNICAL AND COST CHARACTERISTICS OF CONNECTION ALTERNATIVES. 22

7 CONCLUSIONS 32

1

1. QUALIFICATIONS AND EXPERIENCE

1.1 I graduated in 2004 from John Moore‟s University with a BEng in

Electrical Plant Engineering. Since July 2011 I have been employed as

a Lead Design Engineer in the Asset Strategy section for Scottish

Power Energy Networks ("SPEN"). I am part of a team that is

responsible for 132kV design to deliver investment projects to ensure

that the electrical connectivity, equipment layout and technical

specifications are appropriate to meet the needs identified for SP

Manweb plc's ("SP Manweb") electrical networks.

1.2 As a Lead Design Engineer for SPEN I am also responsible for

ensuring that investment projects are designed appropriately to meet

SP Manweb‟s licence obligations and are done so in a cost effective

manner. In my previous role at SPEN, as a System Design Engineer, I

was responsible for the preparation of investment projects to develop

and maintain the network infrastructure and connectivity.

1.3 I have worked in the electricity supply industry since 1992 and in that

time I have held numerous positions from overhead linesman to senior

engineer. The roles have involved design, construction, operation and

maintenance activities on electrical network equipment at all voltages

from 230 Volts up to 132kV.

1.4 I confirm the opinions set out in this proof of evidence which I have

prepared and provide for this inquiry are my own truly held professional

opinions.

2

2. SCOPE OF EVIDENCE

2.1 In December 2009, SP Manweb applied for consent under section 37 of

the Electricity Act 1989 (CD/COM/023) to construct a single circuit

132kV Heavy Duty Wood Pole (“HDWP”) overhead line between the

Llandinam Repowering Wind Farm substation and Welshpool Grid

substation (the "Llandinam Scheme"). My proof of evidence describes

how the engineering design of the Llandinam Scheme takes account of

the technical requirements of the electricity distribution system,

customer requirements and the costs of the connection.

2.2 Section 3 provides a summary of the engineering design and the key

components of the Llandinam Scheme.

2.3 Section 4 discusses part undergrounding of the Llandinam Scheme.

2.4 Section 5 addresses the selection of the overhead line design.

2.5 Section 6 discusses the technical and cost characteristics of alternative

connection options.

2.6 Section 7 sets out my conclusions.

2.7 I have reviewed the objections to the Llandinam Scheme. Some

objectors have commented on engineering design matters (such as

undergrounding and the selection of the overhead line design). My

proof addresses these comments.

3

3. THE PROPOSED LLANDINAM SCHEME

Introduction

3.1 Dr Beddoes (SPM/NETWORK/POE/BEDDOES/001A) describes the

need for a circuit that is capable of carrying 90MVA at 132kV between

the Llandinam Repowering Wind Farm substation and Welshpool Grid

substation.

3.2 Having regard to all SP Manweb‟s statutory duties and licence

obligations, an overhead line solution typically facilitates compliance

with these various requirements.

3.3 To minimise the environmental effects of overhead lines, consideration

is given to the type of support to be used, the overhead line route,

balancing technical requirements with SP Manweb's licence obligations

and other aspects of the design of an overhead line

3.4 While 132kV circuits were previously supported by steel lattice towers

(pylons) or steel portal design structures (similar to goal posts), the

lighter conductors and availability of „post‟-type freestanding insulators

has made it possible to utilise a single circuit wood pole design. The

shorter span lengths of the pole supports, compared to lattice pylons,

result in lower profiles and this, combined with careful routeing, can

lessen the visual impact of a line. A height comparison of typical wood

pole structures, pylons, and a wind turbine is shown in Appendix 1

Comparison of relative electrical infrastructures.

3.5 The proposed wood pole overhead line design supports the

requirements as set out by Dr Beddoes

(SPM/NETWORK/POE/BEDDOES/001A). In section 5 I carefully

consider the use of two woodpole overhead line designs: Trident and

HDWP.

3.6 The Trident design specification is described in ENA technical

specification 43-50 issue 1 & 2 132kV Single Circuit Overhead Lines on

Wood Poles (Appendix 2). The HDWP design specification is set out in

4

OHL-03-132 issue 2 Technical Guidance for the Design and Analysis of

SP 132kV Single Cct, 4-Wire Heavy Duty Wood Pole OHL (c/w

underslung OPGW Earthwire) (Appendix 3). This guidance is in

accordance with BS EN 50341 Parts 1-3:2001 Overhead electrical lines

exceeding AC 45 kV; ENA-TS 43-8 Issue 3, 2004 (with respect to safety

clearances) and as required under the Electrical Safety, Quality and

Continuity Regulations 2002 (CD/SPM/LEG/01).

Engineering specification of the overhead line

3.7 The Llandinam Scheme primarily comprises the installation of a 132kV

single circuit overhead line between Welshpool Grid substation and the

proposed Llandinam Repowering Wind Farm substation. The

connection comprises (for the majority of its length) of an overhead line

on wood pole supports with a short cable section at the termination at

Welshpool Grid substation.

3.8 The wood pole overheadline support structures have to carry a single

circuit containing three phase conductors (these are what are

commonly known as the "wires" on an overhead line). Depending upon

the ground conditions at the Llandinam Repowering Wind Farm

substation an additional aerial earth wire may have to be incorporated

within the overhead line construction. The justification for this earth wire

is described in section 5.

3.9 The three phase conductors are made of an aluminium alloy whilst the

earth conductor is made of aluminium alloy with steel reinforcement in

the centre. The primary circuit conductors have an overall diameter of

20mm whilst the earth conductor has a diameter of 14mm.

3.10 The woodpole structures are designed to support bare overhead

metallic conductors. The current HDWP design can support a conductor

with a cross sectional area of either 300mm2 (referred to as “Upas”) or

200mm2 (referred to as “Poplar”). The Trident design, as described in

ENA technical specification 43-50 issue 1 & 2 132kV Single Circuit

Overhead Lines on Wood Poles (Appendix 2), can support 200mm2

5

Poplar. In this instance a 200mm2 conductor is proposed, providing a

summer rating of 124MVA which is sufficient to meet the design

connection requirement of 90MVA. Both wood pole designs, Trident

and HDWP, can support this Poplar conductor.

3.11 There is need for a fibre optic communication circuit between

Welshpool Grid substation and the proposed Llandinam Repowering

Wind Farm substation. To protect the overhead line and high voltage

equipment at the wind farm substation, a reliable communication circuit

is required between Welshpool Grid and Llandinam Repowering Wind

Farm substation. This communication circuit transfers essential system

information such as measurements and operational conditions of the

switchgear to the distribution network operator. The most economic

method to provide a communication circuit is to integrate a fibre optic

circuit with the proposed overhead line. This can either be achieved by

installing a fibre optic circuit within the earthed conductor or live phase

conductor.

3.12 The line is approximately 34.3km in length and has to be supported on

wood pole support structures containing galvanised steelwork bracings

onto which the insulators and conductors are fitted.

3.13 At the Welshpool Grid substation, the overhead line terminates onto a

cable supporting structure (cable sealing ends) from where a 50m

section of cable provides the connection to the existing 132kV network.

The woodpole cable sealing end structure consists of 4 wood poles with

steel galvanised bracings on the top that support the conductors and

surge arresters. Typically, 4 stays are needed to support each

structure. At Llandinam Repowering Wind Farm substation the

overhead line terminates via overhead conductors into the customer's

substation compound.

3.14 The minimum ground safety clearance distance for a 132kV overhead

line is 6.7m (including the lower earth wire). The overhead line is

designed to ensure that this distance is maintained at all times and in all

6

conditions. For example, in winter the conductors may be subject to

severe ice and wind loadings and in summer hotter weather may cause

the conductors to expand and sag lower. The line is also designed to

take account of varying ground levels, height and topography (slopes

and gradients).

3.15 Span lengths are optimised to achieve sympathetic pole placements

and pole heights have been minimised whilst maintaining statutory

ground clearance. The detail of the different wood pole structure

configurations are provided in Mr Livingston‟s evidence

(SPM/CONSTRUCTION/POE/LIVINGSTON/004A).

3.16 The line supports comprise of timber poles varying in length from 11.5m

to 16m with galvanised steelwork bracings onto which the insulators

and conductors are fitted. The pole heights referred to in Appendix 04b

pole schedule (Volume 3a of the Updated ES (CD/SPM/ES/01)) are the

actual pole lengths. Taking into account that the nominal depth of the

poles is 2.5m and the steel bracings and insulators add typically 2.3m to

the length, the net result is that the actual conductor height above

ground (at pole positions) is about 0.2m less than the pole length

referred to.

3.17 The span length or distance between supports depends on similar

criteria to the line height and varies from 31m to 137m, with an average

span of approximately 90m between supports.

Engineering specification of the underground section

3.18 Miss Berry describes the National Policy Statement (NPS) for Electricity

Networks Infrastructure (EN-5) (CD/COM/003) in her evidence

(SPM/PLANNING/POE/BERRY/011A) and how it applies to Llandinam

Scheme. NPS EN-5 contains guidance on the approach which should

be taken in assessing the merits of an underground cable option as a

full or partial alternative to an overhead line solution

7

3.19 There exists a physical constraint associated with achieving entry to the

substation site at the Welshpool end of the route. The construction of

overhead lines requires a relatively wide hazard free zone. For this

reason, where there are multiple lines needing to access a limited area

and to allow safe segregation of electrical assets in and around

substations, it is often necessary to provide cable sections to connect

the switchgear to the overhead lines.

3.20 The short section of cable (50m) terminating at Welshpool will be

achieved by installing 3 single 800mm2 Aluminium Cross-Linked

Polyethylene (XLPE) insulation cables. The dimension of the cable

trench is typically 1 meter wide and 1 meter deep and may vary

depending on whether the installation is either laid direct or ducted and

if the cables are installed in road, verge or field. In the case of the

Llandinam Scheme, the trench would be excavated between Welshpool

Grid substation and the overhead line termination in the field opposite

the substation. The trench would be backfilled and reinstated after the

cable has been installed.

3.21 The engineering specification of the underground cable section is in

accordance with CAB-03-031 Issue 2 Single core power cables with

extruded insulation and associated accessories for 132kV (Um = 145

kV) networks (Appendix 4).

Engineering specification of the Substation

3.22 At Welshpool Grid substation the 132kV compound has to be extended

to accommodate 132kV electrical equipment such as disconnectors,

circuit breaker, cable termination structures and surge arresters.

3.23 At the Llandinam Repowering Wind Farm substation a new 132kV

compound is to be constructed to accommodate SP Manweb‟s 132kV

equipment such as disconnectors, circuit breaker, metering equipment,

overhead line termination structures and surge arresters.

8

3.24 The engineering specification for the substation works is in accordance

with Part 2 Balance of Plant – Generic Document (Appendix 5). This

guidance is in accordance with BS 7354:1990 Design of High Voltage

open terminal stations (Appendix 6) and NGTS 2.1 issue 5 Substations

(Appendix 7).

Routeing the overhead line

3.25 While SP Manweb‟s internal environmental planning team and external

consultants have a good understanding of the engineering aspects of

the required electrical connection, regular dialogue is maintained with

the engineering design team throughout the route selection and

environmental planning process. This enables any engineering

constraints which may not have been fully appreciated to be brought to

light as may be required and factored in to the routeing process. The

environmental planning and routeing details are further described in

Miss Berry‟s evidence (SPM/PLANNING/POE/BERRY/011A) and is

also described in the Review of Needs Case and Alternatives section

4.1 (Volume 5 of the Updated ES (CD/SPM/ES/01)) (the “Alternatives

Paper”).

3.26 Guidance on routeing an overhead line is provided by the „Holford

Rules‟ (CD/SPM/GUID/01). Rule 3 assists in minimising the number

and angle of line deviations (in other words, minimising the number of

times that the line has to change direction), which also serves to reduce

costs. In addition, it is necessary to be careful not to propose the

construction of assets in a location where other parties‟ infrastructure

operations would compromise operational or safety requirements for SP

Manweb's assets or vice versa. It is also necessary to seek to avoid

areas where lines might introduce significant hazards to the leisure and

commercial activities being carried out there.

3.27 Clearly there are limits to the physical dimensions of the obstacles that

can be overcome by overhead lines due to the strength of the materials

and the technically viable solutions which are available within a design

9

specification. Wood pole line supports become relatively expensive and

difficult to source when extra long or unusually stout wood poles are

required. This in effect provides a height constraint and in turn has a

bearing on the span lengths. The average span length for the proposed

design of the Llandinam Scheme is 90m. The maximum span for the

Llandinam Scheme is 137m utilising the HDWP design. Whilst an

occasional high pole or a long span necessitating extensions to the

existing pole top steelwork can sometimes be accommodated, as part

of an economical design solutions these exceptions must generally be

minimised.

3.28 It is also economically and technically desirable to minimise the number

of transitions from overhead to underground assets. Apart from the

cost, these transitions can be problematic when investigating faults in

an electrical circuit with multiple cable sections. For practical purposes,

overhead lines can be quickly re-energised after a fault clearance as

typically no permanent damage would be sustained. By contrast, an

underground cable will need to be repaired before it is possible to

successfully re-energising it.

3.29 To facilitate the above, in 2008, SP Manweb engaged an external

overhead line design consultancy LS Transmission Consultancy Ltd

("LSTC") to consider initial high level designs based on the route option.

LSTC developed an optimised design in August 2009 as part of the

Application in December 2009. In response to comments received

following statutory consultee feedback, further revisions were

undertaken and Revision F was produced as an Addendum to the ES in

December 2010. The resulting overhead line design has been

developed as an iterative approach and is aligned within the 100m

corridor identified by the environmental routeing study.

3.30 Further revisions were undertaken in response to landowner and local

people comments and the line was further revised (Revision G) in June

2011 to reduce likely environmental impacts. A further revision, Line

Revision G(1), is referred to in the Updated ES (CD/SPM/ES/01). This

10

revision is noted as showing the indicative line route that has been

assessed in that document. This revision takes into account alterations

made in response to statutory consultee comments and landowner

feedback. Revision G(1) sits within the Revision F corridor applied for

by SP Manweb pursuant to the Application.

3.31 In Revision G(1) of the overhead line design there are no significant

engineering constraints identified along the route as defined.

Capital and operational costs

Capital costs

3.32 Until a construction contract has been awarded, the exact cost of a

project is unknown. Decisions on which options are to be promoted and

constructed are, therefore, based upon robust estimates informed by

recent purchasing and project experience.

3.33 For an HDWP overhead line, the base estimate used by SP Manweb in

September 2013 prices is £340,000 per km erected. This value takes

into account the installation of several overhead angle support

structures and assumes an almost straight overhead line route. This

value excludes additional costs such as scaffolding over roads, legal

costs, wayleaving etc.

3.34 SP Manweb estimates overall cable (ie underground line) cost at

approximately £1,100,000 per km installed in arable or unmade ground

with an uplift to £1,300,000 per km in the case of made ground, for

example, within a roadway. These are typical costs, not taking into

account underlying rock formations and terrain difficulties.

3.35 It must be kept in mind that these costs are in respect of normal

engineering installations. When considering additional transitions

between overhead lines and underground cables the length of cable at

shorter distances becomes less significant with the cost being

dominated by the relatively expensive terminal structures. These

terminal structures support the overhead line and underground cable

11

termination. When terminating overhead lines onto underground

cables, surge protection to protect the underground cable has to be

installed and adds to the cost. Typical cost for a cable termination

structure is £220,000 and for a section of overhead line to be

undergrounded two termination structures are needed.

3.36 The costs of the Llandinam Scheme connection to Welshpool Grid is

referred to as the „Llandinam Scheme Cost‟ (“LSC”), this is an

estimated cost between £21m - £24m and is based on a new

approximately 35km 132kV overhead line plus associated substation

works.

Operational costs

3.37 Overhead lines are subject to weather and other environmental

interference. Typically, following an instance such as wind borne

material causing a short circuit, the circuit will automatically trip to clear

the fault and the material will fall away clear of the line. This is referred

to as a transient fault. In such circumstances, it would be possible to

successfully put the line into service almost immediately following the

fault.

3.38 The national fault incident rate for overhead line is 0.4 permanent faults

per 100km per year which would give rise to a theoretical fault rate of

one every 7 years for a 35km overhead line. Typical fault repair cost to

restore a grounded conductor is approximately £20,000 per incident.

The repair time for an overhead line is generally measured within hours

or a few days as access is easier and spares are generally more

available. The estimated lifetime maintenance cost for the overhead line

is estimated at (very roughly) £70,000. In the UK, it is unusual for

natural causes to bring down a 132kV overhead line and they have

given reliable service over many years.

3.39 In relation to underground cables, service performance is reliable

provided that third party interference can be prevented. This is achieved

through providing additional mechanical protection at installation.

12

Nevertheless, ensuring that a cable is not compromised while in service

is not economically viable for extensive networks. From time to time,

activities along the route take place which result in damage that can

take several years to come to light. Underground cable faults invariably

lead to permanent damage. A 132kV underground cable fault can take

several days to locate using specialist equipment and several weeks

will then be required to arrange sufficient excavation and to install a

repair section. During all of this time the network is depleted and in this

case customer supply interrupted. It may be that the excavations and

repair activities result in significant disruption to other parties where, for

example, excavations are required in the highway or agricultural land.

3.40 From information contained within the National Fault and Interruption

Reporting Scheme (NAFIRS) 2011/2012 (Appendix 8) the national

incidence rate for 132kV cables is 3.2 faults per year per 100km of

cable installed. For the proposed design, 50m of cable at Welshpool

Grid, this could theoretically result in a frequency of one fault in 600

years. It is not economical to repair this short section of cable and in

case of a fault the 50m of cable will be replaced in its entirety at an

estimated cost of £125,000. The estimated lifetime maintenance cost

for this short section of cable is estimated at (very roughly) £5,000. This

is in contrast to a lifetime maintenance cost estimated in excess of (very

roughly) £20,000,000 if the whole section of the proposed route

between Welshpool and Llandinam is to be undergrounded (based

upon an estimated fault repair cost of £800,000).

3.41 In addition, more time would be needed for the repair as this could be

up to several weeks from the fault occurrence to the return to service,

dependent on the fault location and the availability of spare cable and

jointing accessories.

3.42 A further difficulty is introduced when a circuit has several transitions

between overhead and underground. When such a circuit faults, it must

be ascertained whether the fault is overhead or underground and,

should the circuit have permanent damage, then the task of locating the

13

fault becomes extended. An overhead line which has significant

underground sections is not therefore able to be treated in the same

fashion as one which is mainly overhead. It is therefore considered

industry best practice to minimise the number of transitions in

distribution circuits.

3.43 Maintenance of the line is mainly based on routine inspections either by

foot or by helicopter patrol. As the HDWP is a robust design, the

structures are unlikely to require significant maintenance throughout

their lives. The poles, conductors and insulators have an anticipated life

expectancy of 63 years, 54 years and 45 years respectively. Vegetation

management will be undertaken as part of an ongoing inspection

regime.

3.44 The short section of cable connected at Welshpool Grid will be subject

to regular inspection of the above ground terminations but otherwise

should require nominal maintenance. The short length of cable section

(50m) should ensure the likelihood for a cable fault is significantly

reduced.

14

4. UNDERGROUNDING

4.1 Miss Berry describes in her evidence

(SPM/PLANNING/POE/BERRY/011A) NPS EN-5 (CD/COM/003) and

how it applies to SP Manweb‟s 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 this obligation. Overhead line solutions are more

economical than cable alternatives to develop, as well as providing

shorter return to service times under fault conditions.

4.2 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 NPS

EN-5 and SP Manweb's statutory environmental duties under the

Electricity Act 1989 (CD/COM/023).

4.3 One section, the A483 near Old Neuadd Bank to Cae-betin Wood, has

been considered for undergrounding due to the "serious concerns" that

arise in relation to this section (as described in the Alternatives Paper

(Volume 5 of the Updated ES (CD/SPM/ES/01)).

4.4 In the event of placing a section underground, SP Manweb would utilise

local roads which generally follow the same direction as the overhead

line route. The potential underground solution for the Old Neuadd Bank

to Cae-betin Wood section of the Llandinam Scheme is illustrated in

Figure 4.1: Location of Potential Underground cabling of Appendix 05a

to the Updated ES (Volume 3a) (CD/SPM/ES/01).

4.5 This route would be likely to follow a route along the track/byway to the

west of the B4335 (Sheep Pen) and then along the B4335 before

turning into a track which runs along the northern foot slopes of Kerry

Hill to join the proposed route near to Cae-betin Wood.

15

4.6 Installing a cable along this route is technically feasible and it is

assumed that a trench can be excavated without encountering

significant rock formations. This assumption has been used for costing

this underground cable section. Excavating a trench in rock is likely to

double or treble the installation costs.

4.7 The net additional capital cost of this route which extends to over 8.5km

would be approximately £8.2m.

4.8 As explained in the Appraisal of the Llandinam Scheme against

National Policy Statement for Electricity Networks Infrastructure (NPS

EN-5) (the "NPS EN-5 Paper") (Appendix 05a to the Updated ES

(Volume 3a) (CD/SPM/ES/01)), SP Manweb considers that there would

be limited benefits to undergrounding in this location as the landscape

is not a nationally designated landscape and not close to residential

areas. In addition, the "serious concerns" identified would remain even

if the Llandinam Scheme were undergrounded in the Old Neuadd Bank

to Cae-betin Wood section, due to the cumulative impacts of nearby

windfarms on that same area.

4.9 SP Manweb has estimated the costs of undergrounding at this section,

including an estimate (very roughly) of the lifetime maintenance cost,

and identified the combination of the capital cost and the estimated

lifetime cost to be in the region of an additional £13.6m, which is over

half the cost of the total scheme as an overhead line. This figure could

increase to approximately £20m if rock formations are encountered.

For the reasons given in NPS EN-5 Paper (Appendix 05a to the

Updated ES (Volume 3a) (CD/SPM/ES/01)), SP Manweb‟s view is that

undergrounding in the context of the Llandinam Scheme is not justified.

16

5. SELECTION OF WOOD POLE DESIGN (CONSIDERATION OF

TRIDENT AND HDWP TECHNOLOGY)

5.1 Based on the outcome of the network design studies performed by Dr

Beddoes (SPM/NETWORK/POE/BEDDOES/001A), it is proposed to

install a wood pole overhead line (rather than a steel lattice tower line)

between Welshpool and Llandinam Repowering Wind Farm substation.

5.2 Initially two wood pole options were considered, Trident and HDWP.

This is also described in the Alternatives Paper (Volume 5 of the

Updated ES (CD/SPM/ES/01)).

HDWP

5.3 The wood poles carry a single circuit containing three phase conductors

with an under slung aerial earth wire. The three phase conductors are

made of an aluminium alloy; the earth conductor is aluminium with steel

reinforcement and contains a fibre optic circuit. This earthwire

incorporates a fibre optic cable for protection signalling and

communication purposes known as Optical Ground Wire (OPGW). The

primary circuit conductors have an overall diameter of 20mm whilst the

earth conductor has a diameter of 14mm.

5.4 The engineering specification of the overhead line is in accordance with

the OHL-03-132 Issue 2 Technical Guidance for the Design and

Analysis of SP 132kV Single Cct, 4-Wire Heavy Duty Wood Pole OHL

(Appendix 3). Typical design sketches showing construction details are

shown in Appendix B of that document (Design Sketches).

Trident

5.5 The wood poles carry a single circuit containing three phase

conductors. There is no earth wire with this design and the Trident

design is therefore referred to as unearthed. The three phase

conductors are made of an aluminium alloy. The primary circuit

conductors have an overall diameter of 20mm.

17

5.6 Existing wood pole overhead lines are primarily build at low level

altitude and intermediate supports can be single pole support

structures. Design support structures are calculated taking into account

environmental conditions such as wind and ice loading. These factors

are influenced by altitude. For the Trident design, support structures

above 250m sea level are typically dual pole wood support structures.

In the case of the Llandinam Scheme, if it could be designed to ENA TS

43-50 (Trident), the last 13km towards the windfarm, from Cefn Gwyn

including the section adjacent to the Kerry ridge, would likely be

constructed with dual pole wood pole structures. This is important as

many objectors to date have just focussed on the single pole structure

of the Trident series of poles.

Need for an earth wire

5.7 I have already explained the need to protect the overhead line and high

voltage equipment at the Llandinam Repowering Wind Farm substation

by the provision of a reliable communication circuit between the

Welshpool Grid and Llandinam Repowering Wind Farm substation.

5.8 Although two options were initially identified, Trident and HDWP, the

unearthed Trident design in 2009 and 2010 was not capable of carrying

a protection communication circuit. HDWP has a separate earth wire,

designed to carry fault current, but which can also be used to carry an

additional protection communication circuit. HDWP was therefore

selected and formed the basis of the Application. This HDWP design

was assessed in the December 2009 ES (CD/SPM/ES/02) and the

December 2010 Addendum (CD/SPM/ES/03). Objectors in December

2013 have raised a question querying whether an initial proposal for

what they term “single T-pylons” was unilaterally changed by SP

Manweb to be HDWP. I assume that this reference to “single T-pylons”

is a reference to single Trident wood pole structures. Paragraphs 5.9 to

5.21 below respond to the selection of HDWP in place of Trident.

18

5.9 In response to the Application more generally, objectors have over a

number of months and years suggested that in the event of the need for

the connection being demonstrated, then SP Manweb should consider

whether the line design could be changed to the unearthed Trident

design. They argue that the Trident design has potentially less

environmental impact due to its lighter construction and potentially

longer span lengths.

5.10 Subsequent improvements in overhead line conductor technology have

led to a conductor that can carry an integrated protection

communication circuit. Optical fibres are incorporated in the design of

the phase conductor. This conductor design is known as Optical Phase

Conductor (“OPPC”). Therefore a Trident pole can now carry a

communication circuit. As a result, SP Manweb has considered the use

of the Trident design again as part of the Updated ES (CD/SPM/ES/01).

5.11 An electrical fault at a substation can cause very high current to flow.

This current is trying to find the path of least resistance back to its

source. In an unearthed design (Trident) all this current has to find its

way back to the source via the general mass of earth which in effect is a

return conductor, and thus relies upon the general make up of the

ground. The resistivity of the ground determines how easy it is for this

current to flow. A low resistivity indicates a material that readily allows

the movement of electric current.

5.12 When a current flows through a resistance a voltage is set up. When

high voltage equipment faults and current flows to the general mass of

earth a fault develops (earth fault). The magnitude of this earth fault

current is dictated by the amount of energy that is available at the point

of the fault and the resistance in the earth return path. The earth fault

current is highest at the point of the fault and declines with distance

from this source. A voltage (potential) is created in the ground

surrounding the point of fault and the ground rises in potential

compared to a remote earth (ie. a voltage difference may be present at

the ground where the fault occurs compared with a point some distance

19

away which is at a different potential; general mass of earth is to be

taken at 0 Volt). This voltage is commonly referred to as Rise Of Earth

Potential (“ROEP”).

5.13 The ROEP may be so high that a person could be injured due to the

voltage developed between the position on the ground of his or her two

feet (“step potential”), or between the ground on which the person is

standing whilst touching a metal object (“touch potential”). Any

conducting object in contact with the surrounding substation ground,

such as telephone wires, fences, or metallic piping, may also be

energised at the ground potential in the substation. This transferred

potential is a hazard to people and equipment outside the substation

(“transfer potential”).

5.14 An earth fault at a substation supplied via an unearthed design,

combined with highly resistive ground at the substation, can result in a

very high ROEP. At Llandinam Repowering Wind Farm substation

measurements show that the resistivity of the ground is very high. The

prospective earth fault current combined with this highly resistive

ground causes an extremely high ROEP.

5.15 The substation and associated equipment can be designed to ensure

there are no dangerous touch or step potentials for personnel within, or

at, the boundary of the substation compound. To ensure that no

members of the public are subjected to dangerous voltages, the

substation area may have to be increased to ensure all dangerous

voltages are controlled within the substation compound.

5.16 The location of the point of connection, the Llandinam Repowering

Wind Farm substation, has been identified by the customer. The

customer has made a plot of land available of approximately 35m by

100m. The substation compound that contains the 132kV and 33kV

switchgear is about 30m by 45m. The immediate area surrounding the

land made available by the customer is uniform and the resistivity of the

20

ground is unlikely to vary - resulting in no significant increase, or

reduction, in the ROEP.

5.17 For the Trident design the extent of the substation compound (the

controlled area) would have to be so large to overcome ROEP issues

that it would be impracticable to safeguard the public, since the

compound would encompass third party buildings. It may not be

possible to control the touch and step potentials if the substation

compound overlaps these third party buildings and therefore may

present a hazard to third parties.

5.18 SP Manweb has a duty to design and operate installations that

minimise the ROEP and hence eliminate dangerous touch and step

potentials. There are no practical solutions to significantly reduce

ground impedance values to reduce the ROEP to acceptable limits

around the substation, nor would it be practical to establish a large

exclusion zone from the perimeter of the main substation earth system

(and, in any event, the efficacy of such an exclusion zone is dubious: it

could be deliberately breached). As a result, the use of a Trident

overhead line design cannot be recommended on the grounds of public

safety.

5.19 The high resistivity of the ground at the Llandinam Repowering Wind

Farm substation and the resulting ROEP confirmed the need to

incorporate an earth conductor within the proposed overhead line

design. An earthed construction ensures that in case of an earth fault

not all the fault current is flowing through the ground and part of it will

flow through the earth return conductor back to its source. There is

therefore less current flowing to earth and the inherent local ROEP has

been lowered, reducing the area subjected to high ROEP values.

5.20 The proposed earthed HDWP line ensures that the ROEP is

significantly reduced to an acceptable level and the area surrounding

the substation compound is safe for the public. The perimeter fence

enclosing the substation compound ensures the substation compound

21

is controlled as far as is reasonable practicable. The earthing system, a

buried copper mesh embedded within the substation, is designed so

there is no danger to personnel from touch or step potentials. The

positioning of the perimeter fence has been designed to ensure there is

no danger to public adjacent to, and outside, the perimeter fence.

5.21 In conclusion, it is recommended that the HDWP design for the

overhead line is progressed as the most appropriate design to meet the

earthing needs for the connection within acceptable safe limits.

22

6. TECHNICAL AND COST CHARACTERISTICS OF CONNECTION ALTERNATIVES.

Estimate of cost for the Llandinam Scheme and combined with the

SP Mid Wales Connections Project.

6.1 The alternatives listed below were considered in the Alternatives Paper

(Volume 5 of the Updated ES (CD/SPM/ES/01)) and Dr Beddoes' proof

of evidence (SPM/NETWORK/POE/BEDDOES/001A). This section

should be read alongside Dr Beddoes evidence (section 6). I deal here

with the technical and cost implications only of the alternatives

proposed.

6.2 The estimated costs of the alternatives have been compared against

the LSC (identified above as between £21 – 24m) or, where the

alternative involves a connection through the currently proposed SP Mid

Wales Connections Project, against a combined cost for the Llandinam

Scheme with the SP Mid Wales Connections Project in so far as it

relates to the CC1 corridor of that scheme. This later scenario is termed

the "status quo" in the Alternatives paper (Volume 5 of the Updated ES

(CD/SPM/ES/01)).

6.3 The combined costs of the Llandinam Scheme and the SP Mid Wales

Connections Project is referred to as the (LS/MWC). The LS/MWC is

estimated to amount to between £48m to £52m.

Technical and cost considerations of accommodating a connection on existing 33kV customer connection using current 33kV infrastructure.

6.4 Dr Beddoes concludes (SPM/NETWORK/POE/BEDDOES/001A) that

the connection of any additional generation at the Llandinam

Repowering Wind Farm substation, using the existing 33kV customer

connection, cannot be accommodated on the current 33kV network

infrastructure. As such, the costs of this alternative are not considered.

Technical and cost considerations of accommodating a

connection on existing 33kV customer connection using current

and new 33kV infrastructure – Newtown Grid.

23

6.5 An alternative means to connect 90MVA of embedded generation at the

Llandinam Repowering Wind Farm substation is by installing a new

33kV circuit between the Wind Farm and Newtown Grid.

6.6 In order to connect the Llandinam Repowering Wind Farm at 33kV into

the nearest 132kV network at Newtown (a distance of 12km) an

additional five new 33kV circuits would be required based upon a circuit

capacity of 20MVA each.

6.7 This would result in a total of 60km (5 x 12km) of new 33kV overhead

lines running in parallel through the Severn Valley or 5 new 33kV cable

circuits installed in roads and verges.

6.8 It would be very difficult to construct 5 overhead lines running in parallel

taking into account the necessary spacing between them. Typically a

distance of 12 meters is required between the lines and a similar

distance outside the lines, which results in a 70 meter corridor.

6.9 33kV circuits that are installed underground close together have to take

account of mutual heating effect of the ground surrounding the cables.

Typical spacing of 500mm between circuits would apply and result in

having to excavate one or two wide trenches in road or verge.

6.10 The Newtown Grid substation compound would need to be increased in

size to accommodate the new circuits and associated switchgear, which

in turn would require additional land and necessary permissions. The

current grid transformer at Newtown Grid Substation would need to be

changed as its power rating would be exceeded.

6.11 Several existing 33kV circuits in the Newtown / Welshpool area would

also need to be replaced as they would exceed their thermal capability.

6.12 As discussed in Dr Beddoes' evidence

(SPM/NETWORK/POE/BEDDOES/001A), the majority of the 132kV

overhead line between Newtown and Oswestry Grid (referred to as the

BU circuit) would need to be reinforced.

24

6.13 The existing conductor is not capable of carrying the required current

and requires upgrading to 300 mm2 Upas. This is not an option with the

current conductor supporting structures that are not capable of

supporting the 300mm2 Upas conductor. The only practicable solution

would be an offline rebuild in parallel with the existing circuit. The

rebuild will have to be capable of supporting a 300mm2 Upas conductor.

This would either be a new woodpole line or a steel lattice tower line.

6.14 The total estimated cost of this alternative is £30.5m above the LSC

defined in section 3.36.

6.15 Taking into account the above and the introduction of additional 33kV

circuits to provide capacity, this option is not considered to be a feasible

technical design solution which meets the needs of the current and

future network, and does not demonstrate the maintenance of an

efficient, co-ordinated and economical system of electricity distribution.


connection on existing 132kV network – Newtown Grid.

6.16 Newtown Grid (12km from Llandinam) is the nearest 132kV connection

point to the Llandinam Repowering Wind Farm.

6.17 As discussed in Dr Beddoes' evidence

(SPM/NETWORK/POE/BEDDOES/001A) and section 6.13 above, the

majority of the 132kV BU circuit would need to be rebuilt to

accommodate the generation power flows on the 132kV network.

6.18 The Newtown Grid substation compound would need to be increased in

size to accommodate equipment such as disconnectors, circuit breaker,

cable termination structures and surge arresters. The extension of

Newtown Grid substation would require additional land and necessary

permissions.

6.19 This alternative is not considered efficient and would cost £9.8m above

the LSC.

25

6.20 The introduction of additional generation onto the Newtown Grid 132kV

BU circuit is therefore not considered a feasible technical design

solution which meets the needs of the current and future network. It

does not demonstrate the maintenance of an efficient, co-ordinated and

economical system of electricity distribution.


connection on existing 132kV network – Carno Grid / Circuit.

6.21 Given that a connection within the local 33kV network and a 132kV

connection at Newtown is not viable, the next nearest 132kV connection

point is Carno Grid. Carno Grid substation is 15km from Llandinam

Repowering Wind Farm and connected at 132kV to Oswestry Grid via

the 132kV line referred to as the MB line, the nearest point to the

Carno 132kV circuit is 12km.

6.22 Reinforcement / rebuilding of the MB circuit has been considered, but

additional upstream 132kV circuit reinforcement as described in 6.13 of

this paper (132kV Oswestry to Newtown circuit) would also be

necessary in order to accommodate any additional generation to the

Carno MB 132kV circuit. A new overhead line of approximately 83km

would have to be constructed.

6.23 For the reasons set out above, this alternative is not considered efficient

at a cost of £22.4m above the LSC.

6.24 The introduction of additional generation onto the Carno 132kV MB

circuit is therefore not considered a feasible technical design solution

which would meet the needs of the current and future network. It does

not demonstrate the maintenance of an efficient, co-ordinated and

economical system of electricity distribution.


connection on existing 132kV network – Welshpool Grid via an

underground cable.

26

6.25 An alternative to the proposed overhead line would be to install an

underground cable between Welshpool Grid and Llandinam

Repowering Wind Farm substation.

6.26 The underground cable would have to be installed in roadways or in

verges and the route would comprise approximately 40km of

underground cable buried at a depth of about 1m in a trench of about

1m wide.

6.27 The capital costs for this alternative would be £38.8m above the LSC -

based on new cable (40km) plus associated substation works. SP

Manweb considers that, as the cost would be a multiple of the LSC, this

would not be an economical means of providing the required

connection.

Alternative network 400kV infeeds

6.28 The nearest 400kV connection from Llandinam Repowering Wind Farm

would be north west of Shrewsbury, approximately 55km in distance.

Such a long connection at 400kV would be more expensive than the

shorter Llandinam Scheme connected at 132kV.

6.29 The proposed Llandinam to Welshpool 132kV connection makes more

efficient use of the existing and available local Distribution Network

capacity.

Alternative network 400kV infeeds – Mid Wales

6.30 As discussed in the Alternatives paper (Volume 5 of the Updated ES

(CD/SPM/ES/01)) at section 6.1, National Grid has committed to the

provision of a Grid Entry Point (GEP) in Mid Wales in order to provide a

connection for the proposed Mid Wales wind farms that are being

connected by SP Manweb via the SP Mid Wales Connections Project.

6.31 The location of the GEP as Cefn Coch was only confirmed last year

with a more detailed announcement on the draft route and substation

site location within Cefn Coch announced very recently. In considering

27

whether the SP Mid Wales Connections Project would provide a

suitable 132kV connection for the Llandinam Repowering Wind Farm,

SP Manweb has noted that the distance from the Llandinam

Repowering Wind Farm to the proposed GEP substation is no different

to that of the Llandinam Scheme.

6.32 However, the integration of the Llandinam Repowering Wind Farm into

the GEP substation would necessitate, due to existing contracted Mid

Wales generation, the installation of an additional 132kV circuit between

the GEP substation and SSA C (wood pole or steel tower line) to

ensure that suitable circuit capacity is provided.

6.33 The following alternatives to connect the Llandinam Repowering Wind

Farm via the SP Mid Wales Connections Project have been considered

and should be read alongside the Alternatives Paper (Volume 5 of the

Updated ES (CD/SPM/ES/01)) and section 6 of Dr Beddoes' proof of

evidence (SPM/NETWORK/POE/BEDDOES/001A).

Alternative 4a (two 132kV HDWP overhead lines, one in CC1 and a

second line in CC2):

6.34 The alternative overhead line construction for both circuits is HDWP,

the second circuit would be strung with 200mm2 Poplar conductor.

6.35 This connection would require an additional Supergrid transformer and

a new 132kV bay comprising of disconnectors, circuitbreaker, surge

arresters, associated busbar supports and protection equipment.

6.36 The total estimated costs for this alternative would be £6m above the

LS/MWC.

Alternative 4b (two 132kV HDWP overhead lines in CC1):



28




6.39 The total estimated costs of this scheme would be £8.2m above the

LS/MWC.

Alternative 4c (two 132kV HDWP overhead lines in CC2):






6.42 The total estimated costs of this option would be £3.9m above the

LS/MWC.

Alternative 4d (a double circuit steel tower pylon) in CC1:

6.43 The alternative overhead line construction for the Llandinam

Repowering Wind Farm is based upon a steel lattice L4 tower

construction strung with 300mm2 Upas conductor. This conductor type

is the smallest conductor size taking into account other connected

parties on the shared tower line (all parties share both circuits on one

double circuit tower line).

6.44 The connection would require an additional Supergrid transformer and a

new 132kV bay comprising of disconnectors, circuitbreaker, surge


6.45 In terms of costs, the total estimated costs of this option would be

£6.7m above the LS/MWC. For Celt Power the estimated Llandinam

apportioned cost is in the order of 75% of the LSC.

Alternative 4e (a double circuit steel tower pylon) in CC2):

29


Repowering Wind Farm is based upon a steel lattice L4 tower

construction strung with 300mm2 Upas conductor. This conductor type

is the smallest conductor size taking into account other connected

parties on the shared tower line (all parties share both circuits on one

double circuit tower line).




6.48 The total costs of this alternative would be £0.7m above the LS/MWC.

For Celt Power the estimated Llandinam apportioned cost is in the order

of 70% of the LSC.

6.49 In response to comments from statutory consultees, SP Manweb has

considered two additional alternatives, 4f and 4g, these being

alternatives introduced on the basis of a presumed reduction in the level

of generation in SSA C to that which could be accommodated in a

single 132kV connection using 300mm2 Upas conductor (rating of

176MVA). These options are described in section 6.4 of the Alternatives

Paper (Volume 5 of the Updated ES (CD/SPM/ES/01)).

Alternative 4f (a connection provided by a 132kV HDWP overhead

line in CC1 able to carry 176MVA of generation capacity):


Repowering Wind Farm substation is HDWP strung with 300mm2 Upas

conductor.

6.51 The Llandinam connection, including other contracted parties to the Mid

Wales hub is included within the cost estimate for the SP Mid Wales

Connections Project.

6.52 The total costs of this option would be £24m less than the LS/MWC as

generation would be capped such that only one 132kV overhead line

would be provided. For Celt Power the estimated apportioned

30

Llandinam Repowering Wind Farm project connection cost is in the

order of 60% of the LSC.

Alternative 4g (as alternative 4f but in CC2):

6.53 The proposed overhead line construction for the Llandinam Repowering

Wind Farm substation is HDWP strung with 300mm2 Upas conductor.

6.54 The Llandinam connection, including other contracted parties to the Mid

Wales hub is included within the cost estimate for the SP Mid Wales

Connections Project.

6.55 The total costs of this option would be £26m less than the LS/MWC as

generation would be capped such that only one 132kV overhead line

would be provided. For Celt Power the estimated apportioned

Llandinam Repowering Wind Farm project connection cost is in the

order of 55% of the LSC.

6.56 From an engineering design and a costs perspective, the Llandinam

Scheme is the preferred option.

6.57 A summary of the costs of the alternative options is shown below in Table 1.

31

Accommodate on existing network £,000,000

33kV

Current and new 33kV infrastructure – Newtown Grid 30.5 Above LSC132kV

Newtown Grid 9.8 Above LSC

Carno Grid / Circuit 22.4 Above LSCWelshpool Grid via an underground cable 38.8 Above LSCAlternative network 400kV infeeds – Mid Wales

Alternative 4a 6 Above LS/MWC

Alternative 4b 8.2 Above LS/MWC

Alternative 4c 3.9 Above LS/MWC

Alternative 4d 6.7 Above LS/MWC

Alternative 4e 0.7 Above LS/MWC

Alternative 4f 24 Below* LS/MWC

Alternative 4g 26 Below* LS/MWC

Table 1 summary of the costs of the alternative options.

*Assumes not all contracted generation associated with the SP Mid Wales

Connection Project is consented

32

7. CONCLUSIONS

7.1 I have described how SP Manweb has approached the development of

its proposal for a 132kV wood pole overhead line between the proposed

Llandinam Repowering Wind Farm substation and Welshpool Grid.

7.2 I have explained the engineering requirements and variation in costs for

the alternatives listed compared to the Llandinam Scheme and (where

relevant) the combined costs of the Llandinam Scheme and the SP Mid

Wales Connections Project.

7.3 I have highlighted that undergrounding small sections of overhead line

could give rise to unwarranted adverse impacts both on operational

performance and construction costs.

7.4 Following representations on the project, SP Manweb has been asked

to consider the use of a Trident design rather than the HDWP design to

further mitigate environmental impacts. In section 5 of this paper I have

explained the technical reasoning behind the decision to maintain the

HDWP design, due to the need for an aerial earth connection that limits

the ROEP at the proposed Llandinam Repowering Wind Farm

substation.

7.5 There are no practical solutions to significantly reduce the ground

impedance values to reduce the ROEP to acceptable limits around the

proposed Llandinam Repowering Wind Farm substation, nor would it be

practical to establish and maintain an exclusion zone from the perimeter

of the main substation earth mat. As a result, use of the Trident design

for all or part of the route cannot be recommended on the grounds of

safety.

7.6 To limit the ROEP to manageable levels the overhead line arrangement

must be of an earthed design.

7.7 HDWP is an earthed design and ensures that SP Manweb adheres to

its licence obligation to develop a safe, efficient, coordinated and

economical system.

33

7.8 From an engineering design and a costs perspective, the proposed

connection utilising HDWP between Welshpool Grid and the proposed

Llandinam Repowering Wind Farm, is the preferred option.

electricity act 1989 (sections 36, 37, 62(3) & schedule 8

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