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132kVOVERHEADLINETOMAESGWYNWINDFARM

REPORTONPLSANALYSISOFTOWERD32ANDTRIDENTWOODPOLECONNECTIONSTRUCTURES

FOR

WesternPowerDistribution

ReviewHistoryAPFP2009Reg5(2)Ref: Reg5(2)(q)

Author: AdrianLiveseyBEng(hons)

Reviewed:

Eur Ing PeterPapanastasiou B Sc(Hons)CEngMICE

Approved:

GrahamYoungBSc(Hons)CEngMICE

DocumentNumber:201006001

Issue: IssueDate:

Description

A 20/04/2010 IssuetoWPDB 17/06/2010 Staysremoved

structuresD32B&D32JC 16/07/2010 RevisedforIPC

submissionD 23/07/2010 AmendedtoreflectIPC

andWPDrequirementsE 26/07/2010 Minorcorrections

Maesgwyn Wind Farm Connection

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Copyright:LSTCThis report has been prepared by LS Transmission Consultancy Limited (LSTC) on behalf of Western Power Distribution (the Client) inconnectionwiththedetailedassessmentoftheMaesgwynproposedwindfarmconnectionandtakesintoaccounttheirparticularinstructionsandrequirements.LSTCwillnotbeliabletotheClientforanyuseofthisreportforanypurposesotherthanthoseforwhichthisreportwasproduced.This report is for theprivateand confidentialuseof theClientand shouldnotbe reproduced inwholeor inpartwithout theexpresswrittenconsentofLSTC.IfLSTCconsentstothereproductionofthisreportthenitmayonlybereproducedonceinwholeandnotpart.Thisreportisnotintendedforandshouldnotberelieduponbyanythirdpartyandnodutyofresponsibility(includinginnegligence)isacceptedbyLSTCinrelationtoanythirdparty.LSTCdisclaimsallliabilityofanynaturewhatsoevertoanysuchthirdpartyinrespectofthisreport.ThisreportisnotintendedtoconferanyrightsonanythirdpartypursuanttotheContracts(RightsofThirdParties)Act1999.ThisreportmaynotbeassignedtoanythirdpartywithouttheexpresswrittenconsentofLSTCLSTransmissionConsultancyLimitedmakesnowarranties,expressorimplied,thatcompliancewiththisdocumentwouldinitselfbesufficienttoensuresafesystemsofworkoroperation.Usersareremindedoftheirowndutiesunderhealthandsafetylegislation.


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TableofContents

1.Summary 4

2.Introduction 5

3.Maesgwyn 132 kV loading criteria 6

3.1 Line Location and configuration .................................................................. 6

3.2 Loading checks carried out ......................................................................... 6

3.3 Tower analysis methodology ...................................................................... 6

3.4 Conductor tensioning basis options ............................................................. 6

3.5 Maintenance Loads & Failure containment Loads ......................................... 7

3.6 BS EN 50341 Probabilistic Loading Criteria ................................................. 7

4.Conclusions 11

5.Glossary 12

AppendicesAppendixAPLSPoleAnalysissummaryAppendixBPLSTowerAnalysissummaryAppendixCPLSCADDscreenprintsAppendixDPoleinformation


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1. Summary 1.1 This document describes the design assessment carried out on the proposed single

circuit overhead line connection between the planned wind farm at Maesgwyn and existing tower D32. The proposed structures to be used for this connection are based on the Electricity Networks Association (ENA) 43-50 trident wood pole design using 175 ACSR Lynx as the conductor.

1.2 Section 3 of this document details the approach taken to validate the suitability of the structures, outlining the climatic and geographical conditions considered. Loading criteria have been derived from British Standard EN50341-3-9:2001 UK NNA and applied in the analysis, which has been carried out using industry standard PLS CADD software.

1.3 Our initial investigation showed that standard thickness poles of the 43-50 structure design would not be suitable for this location. Strengthened designs using various combinations of stays, stay positions and pole thicknesses where analysed until a final design for each structure was determined. The proposed 43-50 steel terminal structure also required slight modification from the original design to achieve satisfactory design capacity under the applied loading. Our assessment also indicated that crossarm ties on the existing tower D32 would need to be strengthened to accommodate the new downlead loads. Further details are included in section 4.


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2. Introduction 2.1 Western Power Distribution is proposing to install a connection between a new

substation at the new wind farm at Maesgwyn and the existing 132kV route at tower D32

2.2 The proposed structure types are based on ENA TS 43-50 trident wood pole design

with a lattice steel terminal structure. 2.3 The proposed conductor system will be single circuit 175 ACSR LYNX conductor.

The ENA TS 43 50 line design is unearthed construction. 2.4 This document defines the design criteria that has been applied, the type of

structure used, the PLS analysis and the recommendations resulting from the outcome of analysis together with necessary strengthening.

2.5 LSTC carried out a detailed survey of the line route which included positions of

existing towers D31, D32 and D33. 2.6 LSTC carried out a topographical survey of the proposed 132kV connection and a

profile was produced, ref LSTC 01-10060-05. This profile along with the survey data and wire clearance diagram LSTC 17-10060-01 were used as the basis of the PLS CADD model.

2.7 The profiles identified structures (see Appendix C for PLS CADD screen prints) that

were outside the generic design parameters for the ENA TS 43 50 technical specification and as a result further site specific analyses were proposed.

2.8 This investigation details the site specific analysis of the wood pole structures and

the connection arrangements at tower D32. The site specific loading analysis is carried out using PLS-CADD, PLS-Pole and PLS-TOWER programs.

2.9 BS50341-3-9:2001 was used for the basic wind speed and ice thickness. 2.10 Records have been requested and no information was found on the existing tower

D32. It was therefore considered prudent to adopt a conservative value of 247 N/mm2 yield stress for the mild steel grade on the PL16 D2s (D32)

2.11 For the new ENA TS 43-50 steel terminal structure values of 275 N/mm2 for mild

steel and 355 N/mm2 for high yield steel were used in the analysis.


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3. Maesgwyn 132 kV loading criteria This section outlines the loading criteria used for the proposed Maesgwyn wind farm connection.

3.1 Line Location and configuration

3.1.1 The proposed line is located in South Wales. Detailed works and access plans are

referenced 03-10060-04 & 03-10060-13 respectively. 3.1.2 The proposed conductor is 175 ACSR LYNX.

3.2 Loading checks carried out

3.2.1 Loading checks were carried to verify the strength for all the wood poles and lattice steel structures for the proposed wind farm connection.

3.2.2 Structure overloads were identified using PLS-CADD, PLS POLE and PLS-

TOWER. 3.3 Tower analysis methodology

3.3.1 Power line Systems software PLS CADD, Tower and Pole are industry standard packages for transmission line analysis. The software runs a Non-Linear Elastic analysis of the tower steelwork using BS EN 50341 part 3-9 UK NNA section 7 methodologies (based on ECCS 39). Angle member properties are calculated in accordance with BS EN 10056-1.

3.3.2 Structures were modelled in PLS Pole for wood pole structures and PLS Tower for

lattice steel towers. 3.3.3 The OPTIMAL profiles were converted into PLS CADD model and each wood pole

and steel tower structure models were then added to the PLS CADD line. 3.3.4 Site specific climatic criteria together with, where appropriate, Construction and

Maintenance loading conditions were input into the PLS CADD Model. The line was then analysed in PLS to determine the site specific applied loadings on all the structures. These loadings were then transferred to the structural analysis packages PLS Tower and PLS Pole for checking the integrity of each structure.

3.4 Conductor tensioning basis options

3.4.1 The sagging basis adopted in the PLS CADD analysis is as set out below: 3.4.1.1 Lynx sagging basis used for conductors on wood poles

20 % of UTS at an Everyday Tension of 5 Degrees Celsius 23.3kN at a temperature of Minus 20 Degrees Celsius

3.4.1.2 Lynx sagging basis used for conductors on towers


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20 % of the UTS at an Everyday Tension for 5 Degrees Celsius 25 % of the UTS at an Maximum Erection Tension for Minus 20 Degrees Celsius

3.5 Maintenance Loads & Failure containment Loads

3.5.1 Tower D32 is the only structure for this project where these conditions will apply. 3.5.2 The Maintenance case considers a load of 4905 N on each crossarm, with downleads attached. This represents the weight of equipment necessary to install semi tension insulator strings including a 132kV platform and linesmen. 3.5.3 Tower D32 also has applied load cases to simulate broken wires (failure containment). These 12 load cases each consider 1 broken wire either ahead or behind the cross arm. These do not include (a conservative approach) any reduction in conductor tension (alleviation) caused by the swing of the suspension link connecting the tension sets to the crossarm. 3.6 BS EN 50341 Probabilistic Loading Criteria

3.6.1 The following sets out the relevant site specific design criteria/inputs for determining the ultimate applied loadings. These are based on BS EN 50341 general approach requirements as set out in part 3, section 9, UK NNA: 3.6.2 Input Loading Conditions: Item BSEN50341UK

NNAref WindSpeed Highwind 22m/s 4.2.2GB.1 Wind+Ice 18.7m/s 3yrRPwithIce 14.21m/s 3yrRPnoIce 16.72m/s Kddirectionfactor 1.0forHighWind 0.85forWind+Ice 4.2.2GB.2 TerrainCategory II 4.2.2GB.3 Gcconductorgust

responsefactorCalculatedbyPLSCADD

Forallwindloadcases

BasicIcethickness(conductorsandtowers)

ro Withoutwind 55mm 4.2.3GB.1rw Withwind 5mm 4.2.4GB.1r3yr 3yearreturnIcewith

wind5x0.76=3.8 mm NGTS2.4/ENATS43

125table3.1IceDensity Towers/Conductors Withoutwind 5000N/m3

Towers/Conductors Withwind 9000N/m3 Whichevermoreonerousfortowerloadingonly.Conductoriceinpresenceofwindisalways9000N/m3

Towersonly Withwind 5000N/m3

Icethicknessconductors

rb CalculatedbyPLSCADD


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rr CalculatedbyPLSCADD

ConductorIcecapping

Forinitialinvestigation,noicecapproposed.

Icethicknessstructures

rb CalculatedbyPLSCADD

rr CalculatedbyPLSCADD

Linealtitude Sitespecific (iceandwindadjustedbyPLSCADDforeachstructure)

(maxaltitude312m)

ConductorTemperature

HighWindCases0C Ice,Wind+IceCases10CStillairnoiceBrokenWireCases 0C Wind+IceBrokenWireCases10CMaxoperating75C

ReliabilityLevelAngle/Tension

2150yearreturnperiod

v=1.1 132kVlineperipheral

4.2.11GB1

ReliabilityLevelSuspension

150yearreturnperiod

v=1.0 ConductorDragCoefficient

CalculatedbyPLSCADD

Table4.2.2(b)/GB

TowerDragCoefficient

CalculatedbyPLSCADD

4.2.2GB9

Spanlengths Sitespecific Conductorheights AutomaticallydeterminedbyPLSCADD Verticalloadings +or10% DL=1.1 DL=0.9 3.6.3 BS EN 50341 Partial Strength Factors for determining material/equipment capacity Item Foundations M=1.35(underhigh

windandwind/icecases)

M=1.60(underhighicecases)

TowerSteel M=1.10 Conductors M=1.25Towersteelworkdesign

ECCS#39


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3.6.4 PLS CADD UK NNA Criteria inputs blue selected text is inserted below.

Note that separate runs for each terrain category and reliability level and subsequent partial factor need to be carried out.


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3.6.5 PLS Criteria notes for UK NNA 3.6.5.1 Notes on inputs to Criteria/Weather Cases for EN50341-3-9:2001 UK NNA: 3.6.5.2 Input wind speed should be Kd*Vb where Kd is the wind direction factor from section 4.2.2 GB.2 and Vb is the basic wind speed from 4.2.2 GB.1 (maximum mean hourly wind speed 10m above level ground in basic open terrain category III at sea level) (4.2.2 GB.1). 3.6.5.3 Kcom (combination factor to take account of the improbability of maximum gust loading on both conductors and towers simultaneously) should be entered in the structure wind area factor column in the load case table. 3.6.5.4 Wire wind height adjust model set to 'EN50341-3-9:2001 UK NNA' applies the following:

Wind speed will be increased 10% for each 100m above sea level as per 4.2.2 GB.1

Wind speed adjusted for terrain roughness factor Kr for selected terrain category as per 4.2.2 GB.4

Wind speed multiplied by 'partial factor for desired reliability level' above including an adjustment of .8 in the presence of ice (Table 4.2.8(a)/GB.1)

Wind speed adjusted for average attach height above ground as per 4.2.2 GB.5.1 Ice thickness adjusted for wire diameter and avg. attachment elevation as per 4.2.3

GB.1.1 Ice thickness multiplied by 'partial factor for desired reliability level' above and for

shape factor (4.2.3 GB.2 and Table 4.2.8(a)/GB.1) 3.6.5.5 Wire gust response factor set to 'EN50341-3-9:2001 UK NNA' applies the following:

Wire GRF adjusted for span length, average attach height and terrain roughness using formulas from 4.2.2 GB.7

GRF further adjusted for drag coefficient as function of Reynolds number and ice thickness as per Table 4.2.2(b)/GB values for conductor locked coil ropes, spiral steel strand with more than seven wires

3.6.5.6 Structure wind load model set to 'EN50341-3-9:2001 UK NNA' applies the following:

Wind speed passed to TOWER is adjusted for ground elevation, terrain category and 'partial factor for desired reliability level'.

Structure ice thickness passed to TOWER is adjusted for structure top elevation as per 4.2.3 GB.1.1

Structure ice thickness multiplied by 'partial factor for desired reliability level' above (4.2.3 GB.2 and Table 4.2.8(a)/GB.1)

TOWER will increase wind with height logarithmically. TOWER will apply gust response factor calculated as (1+Kcom*Gb).


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TOWER: 'wind on face' with drag coefficients a function of solidity ratio and apply K wind incidence factor

4. Conclusions 4.1 For the wood pole section of the line, standard pole structures were selected in line with criteria set out in ENATS 43-50. The analysis results (see Appendix A) showed that due to the altitude of the line, the 4 intermediate single pole structures are heavily loaded or overloaded. It was therefore decided that these structures should be strengthened and pole diameters were increased. 4.2 Results of the subsequent analysis of the wood pole structures show a maximum usage of around 83% which is considered acceptable. However, it is noted that the wood pole structure with the non standard poles may require modifications to the steelwork and different fittings to attach the crossarm to the pole. This is due to the thickness of the poles at the attachment point. 4.3 The ENATS 43-50 steel terminal structure shows one horizontal member at the tower waist (see Appendix B) which is overloaded. 4.4 By replacing the original design member with a high yield steel 65x50x5, connected on the short flange and using high yield bolts, this structure no longer has any failing members under the applied probabilistic loads and a gamma V of 1.1 reliability level of 1. 4.5 At tower D32, on the side where the downleads are to be attached, the analysis indicated both the middle and bottom crossarm ties are overloaded and should be replaced (see Appendix B). 4.6 Top crossarm ties are also heavily loaded so it is recommended that ties are strengthened at all 3 crossarms prior to the downleads being attached. It will also be necessary to incorporate a means of attaching the downleads to the suspension tower crossarms which may require additional or modified plates to be installed. 4.7 There are various ways that tower D32 crossarm modification could be undertaken, however the approved method should be decided by the contractor in consultation with WPD and the CDMC which may be based on their preferred safe methods of work and subject to appropriate design checks. 4.8 The method considered in this analysis is for conductor loads to be temporarily removed from the crossarm whilst work is being undertaken. Temporary supports are then applied whilst each individual member is changed and members added and replaced, noting that only 1 crossarm can only be strengthened at any one time.


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5. Glossary Angle member: Steel members with perpendicular angles Cables: see Conductor. Conductor: That which has the property of transmitting electricity. The name given to the metallic wires strung from tower to tower to carry electric current Circuit: Consists of metal conductors, single or grouped in bundles for each of the three phases in which electricity is transmitted under an alternating current. Downleads: Downleads are conductors used to connect the overhead cables to a lower level structure. Earthwire: A wire commonly erected above the top most conductor at the tower peak for protection against lightning strikes and to earth any faults. It is connected directly to all supports. Insulators: Materials that are very poor conductors of electricity. Air exists as natural insulation around the bulk of the conductor, but at support structures, an insulator string or strings are required to provide a safe insulation gap between the live conductors and any point of earth. Lattice steel: A framework of steel angle sections with the form of their main components corresponding to a triangular lattice. PLS CADD, PLS Pole and PLS Tower are industry standard software packages produced by Power Line Systems for analysis of overhead lines, pole structures and steel lattice towers respectively. Span length: The distance from one structure to the next. Substation: Electricity generated at power stations is fed into the National Grid System through associated substations. They control the flow of power through the system by means of transformers and switchgear, with facilities for control, fault protection and communications. Topographical: The topography of an area is its surface shape and features. Towers: Overhead transmission line supports more commonly known as pylons. Wire clearance: Specified minimum clearances that must be maintained between overhead transmission line live conductors and the ground, obstacles, railway property and other power lines. Yield stress: The stress at which a material begins to permanently deform.


20/10060/01 Appendix A PLS Pole Analysis summary

Preliminary assessment:

Final assessment allowing for thicker poles and stays where necessary, in line with final profile:


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Appendix B PLS Tower Analysis summary

Tower D32 Blaw Knox PL16 D2S Tower summary

Criteria Detail Tower Type Blaw Knox PL16 D2S Extension STD Tower Number D32

Loading

Conditions

BS EN 50341-3-9 UK NNA

General Approach

High Wind (HW)

Wind Ice (WI)

Heavy Ice (HI)

Maintenance and erection (ME)

Failure Containment (FC)

Reliability Level 2 (v=1.1) Outgoing angle N/A

Maximum member

utilisation

Middle crossarm ties are up to 144%

NET section capacity in tension under

(HI)

It is recommended that the crossarm ties are strengthened


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Tower 43-50 steel terminal structure summary

Criteria DetailTowerType 4350steelterminalstructureExtension N/ATowerNumber P12

LoadingConditions BSEN5034139UKNNA

GeneralApproach

HighWind(HW)

WindIce(WI)

HeavyIce(HI)

ReliabilityLevel 2(v=1.1)Outgoingangle N/A

Maximummember

utilisation

The member show below is 156% of L/R

capacityincompressionunder(HI)


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AppendixCPLSCADDscreenprints(nottoscale)Profileview

3Dview1


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3DView2


20/10060/01 AppendixDPoleinformation


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1. Summary2. Introduction3. Maesgwyn 132 kV loading criteria3.1 Line Location and configuration3.2 Loading checks carried out3.3 Tower analysis methodology3.4 Conductor tensioning basis options3.5 Maintenance Loads & Failure containment Loads3.6 BS EN 50341 Probabilistic Loading Criteria

4. Conclusions5. GlossaryTower D32 Blaw Knox PL16 D2S Tower summaryTower 43-50 steel terminal structure summary

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