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
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
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